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ACTIVE

VH-ARA Data Set

Final Report

Peter Isaac and Jörg Hacker

1 August 2007

Airborne Research Australia / Finders University

P.O. Box 335

Salisbury South, 5106

Australia

ARA Technical Report No. ??-2007

Table of Contents 1 INTRODUCTION ..........................................................................................................................3 2 OVERVIEW OF FLIGHTS ..........................................................................................................4

2.1 GENERAL...................................................................................................................................4 2.2 FLIGHTS ....................................................................................................................................4 2.3 STANDARD AIRCRAFT CONFIGURATION....................................................................................7 2.4 FERRY/LIDAR AIRCRAFT CONFIGURATION............................................................................10

3 FLIGHT DETAILS ......................................................................................................................13 3.1 11/11/2005 : TE01 ..................................................................................................................13 3.2 13/11/2005 : TE02 ..................................................................................................................16 3.3 15/11/2005 : AE03..................................................................................................................19 3.4 16/11/2005 : AE04..................................................................................................................22 3.5 27/11/2005 : TE05 ..................................................................................................................25 3.6 30/11/2005 : AE06..................................................................................................................27 3.7 1/12/2005 : AE07....................................................................................................................30 3.8 3/12/2005 : AE08....................................................................................................................33 3.9 4/12/2005 : AE09....................................................................................................................35 3.10 5/12/2005 : AE10....................................................................................................................37 3.11 6/12/2005 : AE11....................................................................................................................39 3.12 8/12/2005 : AE12....................................................................................................................41 3.13 9/12/2005 : AE13....................................................................................................................43 3.14 10/12/2005 : SE14...................................................................................................................45 3.15 11/12/2005 : FE15...................................................................................................................47 3.16 17/01/2006 : FE16...................................................................................................................49 3.17 20/01/2006 : AE17..................................................................................................................51 3.18 22/01/2006 : AE18..................................................................................................................53 3.19 23/01/2006 : AE19..................................................................................................................55 3.20 25/01/2006 : AE20..................................................................................................................57 3.21 27/01/2006 : AE21..................................................................................................................59 3.22 31/01/2006 : LE22 ..................................................................................................................61 3.23 01/02/2006 : LE23 ..................................................................................................................63 3.24 03/02/2006 : SE24...................................................................................................................65 3.25 06/02/2006 : AE25..................................................................................................................67 3.26 08/02/2006 : AE26..................................................................................................................69 3.27 10/02/2006 : AE27..................................................................................................................71 3.28 12/02/2006 : AE28..................................................................................................................73 3.29 13/02/2006 : AE29..................................................................................................................75 3.30 14/02/2006 : AE30..................................................................................................................77 3.31 15/02/2006 : TE31 ..................................................................................................................79 3.32 16/02/2006 : FE32...................................................................................................................81

4 DESCRIPTION OF DATA SET .................................................................................................83 4.1 FILE FORMAT ..........................................................................................................................83 4.2 DATA QUALITY FLAG..............................................................................................................87

5 KNOWN PROBLEMS.................................................................................................................89 5.1 SYNTHESIS OF DYNAMIC PRESSURE USING ANGLE OF ATTACK..............................................89 5.2 SYNTHESIS OF DYNAMIC PRESSURE USING AIRCRAFT GROUND SPEED ..................................92 5.3 PROCEDURE FOR FILLING GAPS IN DATA ................................................................................94 5.4 NOISE IN STATIC PRESSURE AND TEMPERATURE.....................................................................96 5.5 ROSEMOUNT TEMPERATURE SENSOR DE-ICE HEATERS ..........................................................97

6 COMPARISON WITH OTHER DATA.....................................................................................99 6.1 DARWIN GROUND-BASED DATA .............................................................................................99 6.2 DARWIN RADIOSONDE DATA ................................................................................................100 6.3 INTER-COMPARISON FLIGHTS WITH DCALM........................................................................103

7 ACKNOWLEDGMENTS..........................................................................................................106

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1 Introduction The Aerosol and Chemical Transport in Tropical Convection (ACTIVE) experiment held field campaigns based in Darwin in November/December 2005 and January/February 2006. The Airborne Research Australia (ARA) high altitude research aircraft, the Grob G520T Egret (call sign VH-ARA), was used in both of these campaigns. This report and the companion Appendix have been written to act as a guide to the data set provided by ARA to the University of Manchester. The data set comprises all of the data recorded on the aircraft data loggers during the ACTIVE field campaigns.

The Egret was configured to carry a wide range of aerosol, cloud particle and air chemistry instrumentation along with a suite of air state instruments for measuring pressure, air temperature and the three components of the ambient wind field. This report describes the instrumentation carried by the Egret, gives a brief description of each flight and describes the data set obtained from the instruments mounted on the Egret whose output was recorded by the aircraft data loggers.

Section 2 presents an overview of the flights performed by VH-ARA and provides a general description of the instrumentation and aircraft data logger configuration for the flights.

Section 3 gives a more detailed description of each flight. The basic flight details and any special circumstances are given, followed by a description of the instrumentation and data logger set up for each flight. This is followed by a detailed description of the flight pattern for each flight and a plot of the flight track overlaid on an outline map of the Darwin area. Each flight is dealt with in a separate subsection.

Section 4 describes the data set provided to the University of Manchester. The names of the files, their contents and formats are given in separate subsections. To aid interpretation of the data, each data field has been assigned a data quality flag during processing and these are defined in the last subsection of Section 4.

A number of problems with the data were identified during the field campaigns and during the subsequent processing of the final data set. Section 5 describes these problems and provides details of the methods used to identify and remove affected data. The techniques used to replace missing dynamic pressure data, caused by ice forming in the pitot tube or by leaks in the associated tubing, are given. The method used to fill gaps in the data due to logger failures or due to the reject of contaminated data is also described in detail.

Section 6 presents the results from comparisons of the data from VH-ARA with data from the Darwin automatic weather station, the Darwin radiosondes and from the National Environmental Research Council (NERC) Dornier 228 (call sign D-CALM). The inter-comparison data is used to validate the air temperature and wind data from the VH-ARA data set.

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2 Overview of Flights

2.1 General

The data set from VH-ARA for the ACTIVE campaign consists of 32 flights, 15 in 2005 and 17 in 2006. The flights have been numbered consecutively from 01 to 32 and given a two letter prefix that designates the type of flight (A for science flight, F for ferry flight, S for survey flight and T for test flight) and the aircraft (E for Egret).

Of the 32 flights, 4 were dedicated test flights. The first 2, TE01 and TE02 in 2005, were to test the general set up of the aircraft and the NOX and SP2 instruments.

The third test flight, TE05, was flown following the propeller repair. Oil streaks were found on the aircraft canopy after flight AE04 on 16/11/2005 and these were traced to a failed start lock on the propeller. A replacement start lock was sourced from the aircraft manufacturer (Grob Aerospace AG) and installed on 26/11/2005.

The fourth, TE31, was a calibration flight at the end of the 2006 campaign. During this flight, the aircraft performed a series of specific manoeuvres designed to yield correction factors and calibrations for the temperature (Ta), static pressure (ps), dynamic pressure (qc) and the angle of sideslip (β) and attack (α) measurements. The manoeuvres were performed at nominal altitudes of 10,000' and 30,000'.

Three of the flights were ferry flights from Darwin to Adelaide (FE15 and FE32) or from Adelaide to Darwin (FE16). A gas chromatograph was installed on the aircraft for these ferry flights along with instruments for measuring pressure and temperature.

The remaining 25 flights were science flights in the vicinity of Darwin. Twenty-three of these flights (AE03, AE04, AE06 - SE14, AE17 - AE21, SE24 - AE30) carried either an instrument for measuring NOX concentration (NOX u-bay) or black carbon aerosol (SP2 u-bay). Two of these 23 flights were survey flights (SE14 and SE24) which were performed to characterise background conditions in relatively clear air.

For the remaining 2 of the 25 flights science flights (LE22 and LE23), the aircraft carried an ozone-detecting LIDAR in place of the NOX or SP2 u-bays.

The aircraft configurations, in terms of instrumentation and data logging, used for the ACTIVE flights fall into two broad categories: standard and ferry/LIDAR. The standard configuration was used for all test and science flights excluding the LIDAR flights. The ferry/LIDAR configuration was used, naturally, for the ferry and LIDAR flights. The configurations are described in Sections ? and ?.

2.2 Flights

Table 2.1 and Table 2.2 summarise the VH-ARA flights for the 2005 and 2006 campaigns respectively.

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Date Flight Take Land Type FR RR ps Ta qc UV TDL1 TDL2 TSI1 TSI2 Comments 11/11 TE01 06:44 09:45 Test 20 20 P P P P N N N N NOX u-bay, loggers stopped repeatedly 13/11 TE02 05:51 07:18 Test 20 20 P P P P N N N N SP2 u-bay, loggers stopped repeatedly 15/11 AE03 06:16 07:59 HA1 20 20 P P P P N N N N loggers stopped repeatedly 16/11 AE04 06:28 09:47 HC1 20 20 P P P P N N N N loggers stopped repeatedly, qc bad after 07:58 27/11 TE05 06:42 08:10 Test 20 20 Y Y Y Y Y Y N N SP2 u-bay 30/11 AE06 04:14 08:11 HC1 20 20 P P P P P P N P loggers stopped repeatedly 01/12 AE07 05:01 08:34 HA1 20 20 P P P P P P N P loggers stopped repeatedly, qc bad after 06:17 03/12 AE08 06:17 09:45 HC1 1 1 Y Y P P Y Y Y Y qc bad after 07:13 04/12 AE09 06:51 09:42 HA1 1 1 Y Y Y Y Y Y Y Y 05/12 AE10 06:04 08:27 HC1 1 1 Y Y Y Y Y Y Y Y inter-comparison with DCALM 06/12 AE11 04:39 09:07 HA1 1 1 Y Y P P N Y Y Y qc bad after 05:40, no TANS until 06:56 08/12 AE12 03:51 08:03 HC2 1 1 Y Y Y Y Y Y Y Y 09/12 AE13 04:25 08:07 HA1 1 1 Y Y N Y Y Y Y Y qc bad for entire flight 10/12 SE14 01:53 04:47 HA2 1 1 Y Y Y Y Y Y Y Y 11/12 FE15 23:55 06:05 Ferry 1 1 Y Y N N N Y N N Darwin to Parafield

Table 2.1: Summary of flights for the 2005 ACTIVE campaign. 1) HA flights had the SP2 u-bay fitted; HC flights had the NOX u-bay fitted. 2) HA1 and HC1 flights were through cirrus; HA2 and HC2 flights were survey flights in clear air. 3) FR is the Fuselage REMlet (CR-2, TE-49C O3, TSIs); RR is the Right-wing REMlet (pressures, temperatures, winds), 20 means data is at 20 Hz, 1 means that data is at 1 Hz. 4) "Y" means data is available for entire flight; "N" means data is not available. 5) "P" indicates partial data is available, missing ps, Ta data have been interpolated using the GPS altitude, missing qc data has been synthesised from the pressure difference across the angle of attack ports when available or from ground speed.

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Date Flight Take Land Type FR RR ps Ta qc UV TDL1 TDL2 TSI1 TSI2 Comments 17/01 FE16 23:13 06:47 Ferry 20 N Y Y N N N Y N N Parafield to Darwin 20/01 AE17 06:47 09:05 MA1 20 1 Y Y P Y Y Y A A qc bad after 07:21 22/01 AE18 07:05 10:05 MC1 20 1 Y Y P Y Y Y Y Y qc bad after 08:01 23/01 AE19 02:55 06:35 MC2 20 1 Y Y Y Y Y Y Y Y 25/01 AE20 05:20 09:35 MA2 20 1 Y Y Y Y Y Y Y Y 27/01 AE21 05:40 09:35 MA2 20 20 Y Y Y Y Y Y Y Y 31/01 LE22 10:51 13:23 LIDAR 20 N Y Y N N Y Y N N 01/02 LE23 10:55 14:12 LIDAR 20 N Y Y N N Y Y N N 03/02 SE24 05:12 09:10 MA2 20 20 Y Y Y Y Y Y Y Y 06/02 AE25 06:17 09:10 MA1 20 20 Y Y N Y Y Y Y Y qc data bad for whole flight 08/02 AE26 08:08 10:50 MC1 20 20 Y Y N P Y Y N N qc data bad for whole flight, gaps in TANS

data, TSIs not plugged in 10/02 AE27 07:12 11:00 MC1 20 20 Y Y N Y Y Y Y Y qc data bad or whole flight 12/02 AE28 07:48 09:52 MA1 20 20 Y Y Y Y Y Y Y Y 13/02 AE29 05:55 10:12 MA1 20 20 Y Y N P Y Y Y Y qc data bad for whole flight, gaps in TANS

data 14/02 AE30 02:44 05:22 MI 20 20 Y Y Y Y Y Y Y Y inter-comparison with DCALM 15/02 TE31 02:48 06:32 Test 20 20 Y Y Y Y Y Y Y Y calibration flight 18/02 FE32 23:19 06:17 Ferry 20 N Y Y N N Y Y N N Darwin to Parafield

Table 2.2: Summary of flights for the 2006 ACTIVE campaign. 1) MA flights had the SP2 u-bay fitted; MC flights had the NOX u-bay fitted. 2) MA1 and MC1 flights were through cirrus; MA2 and MC2 flights were survey flights in clear air. 3) FR is the Fuselage REMlet, RR is the Right-wing REMlet, 20 means data is at 20 Hz and 1 means that data is at 1 Hz. 4) "P" indicates partial data is available, missing ps, Ta data have been interpolated using the GPS altitude, missing qc data has been synthesised from the pressure difference across the angle of attack ports when available or from ground speed.

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2.3 Standard Aircraft Configuration

2.3.1 Instrumentation

Table 2.3 lists the quantities recorded by the data logging system on VH-ARA, the sensors used to measure these and their location on the aircraft for the standard configuration flights. "Standard" configuration flights were TE01 to AE14 inclusive (2005), AE17 to AE21 and SE24 to TE31 inclusive (2006).

Quantity Sensor Location Pressure ports Rosemount 858 5-hole probe at tip of 2.5m mast mounted

to right pylon Static pressure Rosemount1201 right pylon Dynamic pressure Rosemount 1221 right pylon Angle of attack Rosemount 1221 right pylon Angle of side slip Rosemount 1221 right pylon Air temperature Rosemount 102 de-iced right pylon Aircraft position Novatel GPS fuselage behind rear cabin Aircraft velocity Novatel GPS fuselage behind rear cabin Aircraft attitude Trimble TANS fuselage behind rear cabin Water vapour Closed path TDL hygrometer right gear pod Open path TDL hygrometer right gear pod Buck Research CR-2 rear fuselage compartment Ozone Thermo Electron TE-49C rear fuselage compartment Condensation particles

2 x TSI-3010 u-bay

Table 2.3: Summary of instrumentation recorded by the VH-ARA data logging system during the standard configuration flights (see text for details).

The open path TDL (TE05 onwards) required information on the pressure and temperature in real-time during the flight in order to calculate its internal calibration coefficients. The original method of supplying this information from the aircraft logging system was via a digital-to-analogue converter that accepted a serial data stream from the aircraft display computer and fed an analogue output to the TDL.

This method was abandoned when it proved to be inoperable during testing of the system between AE04 and TE05. In its place, the analogue signal from the Rosemount pressure and temperature sensors was fed direct to the TDL for TE05. Examination of the data after the flight showed that the pressure recorded by the TDL was approximately 20 hPa lower than that recorded by the aircraft data logger. This was due to a combination of low input impedance for the TDL analogue input and a slow rise time for the Rosemount pressure sensor after the TDL input impedance became high when the TDL analogue inputs were sampled. This meant that the pressure signal was still recovering for being loaded down when the TDL sampled the pressure input.

The direct analogue connection between the TDL and the Rosemount pressure and temperature sensors was removed for AE06 pending the construction of an electronic

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buffer to prevent loading of the pressure sensor output. For AE07, the pressure and temperature for the open path TDL were set internally at constant values of 190 hPa and -53 C respectively.

An instrumentation amplifier was placed between the Rosemount pressure and temperature sensor and the TDL analogue inputs before flight AE08. As a result, the aircraft and TDL pressures agree to within approximately 1 hPa when the aircraft is on the ground before take-off and after landing. However, at the maximum altitude of the TDL pressure reads approximately 20 hPa higher than the pressure recorded by the aircraft. This was due to the use of a voltage divider on the output of the instrumentation amplifier that was also being loaded down by the low input impedance of the TDL analogue input. The voltage divider was removed before flight AE09. Note that the pressures recorded by the TDL differ from those recorded by the aircraft data logger and given in the final data set. The values from the aircraft data logger have been corrected for an observed offset of 4.6 hPa (comparison with Darwin AWS data) and low-pass filtered with a cut-off frequency of 0.2 Hz.

2.3.2 Data Logging

The data logging system employed for the standard configuration flights consisted of two remote analogue-to-digital converters (REMlets), two data loggers and a display computer. One REMlet was installed in the pylon mounted beneath the right wing and the second was installed in the rear fuselage compartment. The right pylon REMlet sampled the Rosemount pressure and temperature sensors. The fuselage REMlet sampled the CR-2 frost point hygrometer, the TE-49C O3 instrument, the TSI analogue outputs and the aircraft radio transmitter status (2 VHF channels and 1 UHF channel).

The two data loggers were located in the rear fuselage compartment, one on the left-hand side of the aircraft and the other on the right. Data logger serial number (S/N) 03 was installed in the right hand location and S/N 04 was installed in the left-hand location for flights TE01 to AE04 inclusive. The location of the loggers was swapped between flights AE04 and TE05 in an unsuccessful effort to prevent the repeated loss of the analogue data stream from the REMlets that occurred on flights TE01 to AE04 (see below). From TE05 onwards, S/N 03 was in the left-hand location and S/N 04 was in the right hand location. The display computer was mounted in the rear cabin and drove an LCD display positioned over the aircraft instrument panel in front of the mission scientist.

There were a number of changes to the data logging for the standard configuration flights during the ACTIVE campaign. The changes were made in an effort to isolate and remove the cause for the repeated loss of analogue data from the REMlets that occurred for flights TE01 to AE07 inclusive. The chronological order of the changes is given in the following paragraphs

The original configuration of the data logging system, used for flights TE01 to AE04, had the REMlet, Novatel GPS, Novatel 1 pulse-per-second (PPS) and TANS GPS data recorded on the right fuselage logger. The left fuselage logger was dedicated to the TSI and TDL serial data streams. The left and right data loggers both recorded the 1 PPS signal from their internal GPS cards to provide a means for synchronising the time stamp given to the incoming data by each logger. A 20 Hz pulse generated by

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the right fuselage logger from the internal 1 PPS timing signal was used to trigger the REMlets in this configuration.

The analogue data streams from the REMlets repeatedly halted during flights TE01 to AE04 with this configuration. The only recourse available to the mission scientist during these flights was to cycle power to the loggers and REMlets in an attempt to restart the logging system. The system halted after each restart with no apparent pattern in the time before failure.

The data logging system was tested on the ground between flights AE04 and TE05. This showed that both data loggers were halting after processing a random number of 1 PPS timing signals from their internal GPS units. The logging programme was then modified to disable the reading of the internal GPS time and the Novatel GPS data stream was routed to both right and left loggers. The recording of the Novatel GPS data by both loggers provided the means to synchronise the time stamp given to incoming data by each logger. The REMlets continued to be triggered by a 20 Hz pulse sent by the right hand data logger.

This configuration (internal GPS disabled, Novatel GPS data routed to both loggers, REMlets triggered at 20 Hz) was used for flights TE05 to AE07 inclusive. Both loggers ran without interruption for the relatively short test flight (TE05) but the loss of the analogue data stream from the REMlets occurred again on flights AE06 and AE07. The left-hand data logger appears to have run continuously for these flights.

A further attempt to fix the problem with the right hand data logger and REMlets was made on 2/12/2005 between flights AE07 and AE08. The data logger and REMlets were linked via the 20 Hz trigger pulse in the configurations described above. This meant that it was not possible to decide if the loss of analogue data was caused by a problem with the logger (eg loss of trigger pulse) or with the REMlets (eg loss of response to a trigger pulse). In an attempt to resolve this ambiguity, the 20 Hz trigger pulse for the REMlets was disabled and replaced by the Novatel GPS 1 PPS. This modification also required a change to the data logger configuration so that incoming data from the REMlets were read as generic serial data streams. The size of the data packet expected from the REMlets, required when the data is read as a generic serial stream, was initially set to 64 bytes.

This configuration (internal GPS disabled, Novatel GPS data to both loggers, REMlets triggered by Novatel 1 PPS) was used for flight AE08. The modifications to the logger configuration meant that the logger operation could not be checked during this flight. However, both loggers were found to be running when checked after parking in the hangar at the conclusion of flight AE08 and the REMlet data was still being received by the right logger. Examination of the REMlet data recorded by the right hand logger showed that the packet size of 64 bytes was 1 byte too small, causing a byte shift in the raw data. This was corrected in subsequent processing and all data from AE08 were recovered.

The right hand data logger configuration was changed to specify the correct REMlet data packet size of 65 bytes before flight AE09 and this data logger configuration was used up to and including flight FE15.

The reason for the loss of analogue data was traced to the use of a component in the data loggers that was different from the one specified by Airborne Research Australia. The problem was identified and fixed while the aircraft was in Adelaide between the 2005 and 2006 field campaigns.

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On return to Darwin, the fuselage REMlet (CR-2, TE-49C O3, analogue TSI, radio markers) was triggered by the 20 Hz pulse sent from the right hand data logger but the right wing REMlet was still triggered by the Novatel GPS 1 PPS. This was discovered after flight AE20 and the correct triggering of the right wing REMlet by the 20 Hz pulse from the logger was reintroduced from AE21 onwards. As a result, there are 20 Hz data for the analogue channels sampled by the fuselage REMlet (CR-2, TE-49C O3, analogue TSIs and radio markers) for all flights in 2006. However, the analogue data from the right wing REMlet (pressures and temperature) is only available at 1 Hz for flights AE17 to AE20. The pressure and temperature data is available at 20 Hz for flights AE21 and SE24 to FE32 inclusive.

2.4 Ferry/LIDAR Aircraft Configuration

2.4.1 Instrumentation

Table 2.4 lists the quantities recorded by the data logging system on VH-ARA, the sensors used to measure these and their location on the aircraft for the ferry and LIDAR configuration flights. Ferry and LIDAR configuration flights were FE15 (2005), FE16, LE22, LE23 and FE32 (2006).

FE15 differed from other ferry/LIDAR configuration flights in that the right pylon was mounted on the aircraft for this flight. This means that FE15 used the same static pressure sensor as used for the standard configuration flights and that the static pressure and air temperature data were sampled by the right wing REMlet.

The right pylon and the associated pressure sensors were not mounted on the aircraft for flights FE16, LE22, LE23 and FE32. An alternate pressure sensor, mounted inside the rear fuselage compartment, was used to measure static pressure for these flights. The manufacturer's calibration was not available for this pressure sensor. A calibration was inferred from the "standard" configuration sensor via the chamber pressure measurement of the CR-2 frost point hygrometer as follows. First, a calibration for the CR-2 chamber pressure was obtained by least-squares fit of the CR-2 pressure output voltage against the static pressure for all flights with the right pylon fitted to the aircraft. This calibration of the CR-2 chamber pressure was then transferred to the static pressure sensor used on the ferry and LIDAR flights.

Temperature was measured using the same Rosemount 102 de-iced sensor as for the "standard" configuration flights but the sensor was mounted on the left-hand side of the u-bay with the associated electronics in the rear fuselage compartment.

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Quantity Sensor Location Static pressure Rosemount1201 rear fuselage compartment

(FE15 used right pylon) Air temperature Rosemount 102 de-iced rear fuselage compartment

(FE15 used right pylon) Aircraft position Novatel GPS fuselage behind rear cabin Aircraft velocity Novatel GPS fuselage behind rear cabin Aircraft attitude Trimble TANS fuselage behind rear cabin Water vapour Closed path TDL hygrometer right gear pod (not used for

FE15 or FE16) Open path TDL hygrometer right gear pod Buck Research CR-2 rear fuselage compartment

(LIDAR flights only) Ozone Thermo Electron TE-49C rear fuselage compartment

(LIDAR flights only)

Table 2.4: Summary of instrumentation recorded by the VH-ARA data logging system during the ferry and LIDAR configuration flights (see text for details).

The open path TDL was supplied with analogue signals for static pressure and temperature as described in Section 2.3.1.

2.4.2 Data Logging

The data logging system employed for the ferry/LIDAR configuration flights consisted of one (FE16, LE22, LE23 and FE32) or two (FE15) remote analogue-to-digital converters (REMlets), two data loggers and a display computer.

For FE15, one REMlet was installed in the pylon mounted beneath the right wing and the second was installed in the rear fuselage compartment. The right pylon REMlet sampled the Rosemount pressure and temperature sensors. The fuselage REMlet sampled the aircraft radio transmitter status (2 VHF channels and 1 UHF channel). Note that the CR-2 frost point hygrometer, the TE-49C O3 instrument and the TSI analogue outputs were sampled as well but the instruments were not fitted to the aircraft.

For FE16, LE22, LE23 and FE32, the REMlet was installed in the rear fuselage compartment. This REMlet sampled the Rosemount static pressure and temperature sensors and the radio markers on flights FE16, LE22, LE23 and FE32. The CR-2 and TE-49C O3 instruments were also sampled on flights LE22 and LE23.

The two data loggers were located in the rear fuselage compartment, S/N 03 on the left-hand side of the aircraft and S/N 04 on the right. The display computer was mounted in the rear cabin and drove an LCD display positioned over the aircraft instrument panel in front of the mission scientist.

This data logger configuration used for flights AE09 to SE14 (internal GPS disabled, Novatel GPS data to both loggers, REMlets triggered by Novatel 1 PPS) was used for flight FE15. The use of the same configuration as the standard flights means that the data from flight FE15 can be processed using the same techniques as used for flights AE08 to SE14.

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For flights FE16, LE22, LE23 and FE32, the data loggers were configured to disable the internal GPS timing, the Novatel GPS data stream was fed to both loggers and the fuselage REMlet was triggered by a 20 Hz pulse derived from the right hand logger.

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3 Flight Details 3.1 11/11/2005 : TE01

3.1.1 General

This was the first test flight of VH-ARA in Darwin. The NOX u-bay was fitted to the aircraft. Logger S/N 03 was in the right fuselage position and S/N 04 was in the left fuselage position.

Take-off was approximately 06:44 UTC, landing at approximately 09:45 UTC. The mission scientist was Jörg Hacker.

3.1.2 Instrumentation and Data Logging

The NOX u-bay was flown with both TSI instruments in place. The standard aircraft configuration consisting of the right pylon, Rosemount boom, Novatel GPS and TANS GPS was used.

The right wing and fuselage REMlets (remote analogue to digital converters) were triggered by a 20 Hz sample pulse from the right fuselage data logger. The REMlet, Novatel GPS and TANS GPS data were recorded on the right fuselage logger. The digital data from TDL1, TSI1 and TS2 were recorded on the left fuselage logger. The right and left fuselage data loggers both recorded the 1 second timing pulse from their internal GPS systems to provide a means for synchronising the time stamp assigned to the various data streams by the loggers.

Both loggers and REMlets stopped repeatedly during the flight. For example, the right fuselage data logger was restarted 6 times during the flight but there are 17 gaps longer than 5 secs in the analogue data from the right wing (temperatures and pressures). The left fuselage data logger stopped completely after 4,250 seconds, about one third of the flight, and there is no data (digital TDL and TSI) from this logger for the remainder of the flight. The gaps in the data caused by the failure of the right fuselage data logger have been filled using different methods depending on the data type. No attempt has been made to fill gaps in the data from the left fuselage data logger.

Gaps in the Novatel GPS position data were filled by extracting the required values from the aircraft position recorded in the OziExplorer track file. Gaps in the Novatel GPS velocity data were filled by differentiating the position data obtained from the OziExplorer track file. Gaps in the temperature and pressure data were filled as follows. First, the decreases in temperature and pressure with height were calculated using all available data. The change in temperature or pressure from the last good measurement was then calculated using these lapse rates and the change in aircraft altitude from the Novatel GPS data. The values used to fill the gaps in Ta and ps were then calculated by adding the running integral of the temperature and pressure changes to the last good measurement. The difference between the last value calculated for the gap and the first good measurement of the next data block is recorded and used to characterise the uncertainty of the method. A linear correction is then applied to the values used to fill the gaps to remove any discontinuity between

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the end of the gap and the start of the next data block. Details of the method and the uncertainty in the values used to fill the gaps are discussed in Section 5.

The pressure altitude begins to deviate from the GPS altitude at 09:42:10 UTC. The aircraft was on descent into Darwin at an altitude of 400 m at this time. The problem is due to erroneous static pressure data, probably caused by water in the static port or pressure line. There are no other known problems with the meteorological data at this time other than those associated with the gaps caused by the logger failures.

There is digital data for TDL1, TSI1 and TSI2 for the first third of the flight. There is no data for TDL2. The digital data for TSI1 and TSI2, which appear to be diagnostic messages rather than measurements, are scrambled because the wrong serial port configuration was specified in the data logger initialisation file.

3.1.3 Flight Track

After taking off from Darwin airport to the north, the aircraft tracked northeast before turning northwest and continuing to climb, crossing the coast over Lee Point at 2,000 m. The aircraft then tracked west to a point 8 km northwest of Charles Point before tracking northwest and climbing to 11,900 m at a point 156 km west-northwest of Darwin. From here the aircraft turned southeast until intersecting latitude 12° 20'. The aircraft then completed three east/west oriented transects along this latitude at 12,600, 13,500 and 14,400 m. At the end of the last transect from west to east the aircraft began a spiral descent 25 km northwest of Darwin before tracking west of Darwin and landing from the southeast.

A plot of the flight track is shown in Figure 3.1.

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4 14.

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.9 0.0

129.5 130 130.5 131Longitude

-13

-12.5

-12

-11.5

Latitude

+ C a p e D o n

+ Darwin

+ G a r d e n P o in t+ M o u n t B u n d y+ P o in t S t u a r t

ACTIVE ARA TE01 20051111 06:31-09:45 UTC

Figure 3.1: Flight track for TE01 on 11/11/2005. Arrows indicate the direction of the aircraft track. Numbers to the left of the aircraft track are the seconds since 0000 UTC in increments of 300 secs. Numbers to the right of the aircraft track are the aircraft altitude in km.

15

3.2 13/11/2005 : TE02

3.2.1 General

This was the second test flight of VH-ARA in Darwin. The SP2 u-bay was fitted to the aircraft. Logger S/N 03 was in the right fuselage position and S/N 04 was in the left fuselage position.



The NOX u-bay was flown and the standard aircraft configuration consisting of the right pylon, Rosemount boom, Novatel GPS and TANS GPS was used.

The right wing and fuselage REMlets (remote analogue to digital converters) were triggered by a 20 Hz sample pulse from the right fuselage data logger. The REMlet, Novatel GPS and TANS GPS data were recorded on the right fuselage logger. The digital data from TDL1, TSI1 and TS2 were recorded on the left fuselage logger. The right and left fuselage data loggers both recorded the 1 second timing pulse from their internal GPS systems to provide a means for synchronising the time stamp assigned to the various data streams by the loggers.

Both loggers and REMlets stopped repeatedly during the flight. The right fuselage data logger was restarted 5 times during the flight. The left fuselage data logger stopped completely after 103 seconds, before the aircraft had taken off. The gaps in the data caused by the failure of the right fuselage data logger have been filled using different methods depending on the data type. No attempt has been made to fill gaps in the data from the left fuselage data logger.

Gaps in the Novatel GPS position data were filled by extracting the required values from the aircraft position recorded in the OziExplorer track file. Gaps in the Novatel GPS velocity data were filled by differentiating the position data obtained from the OziExplorer track file. Gaps in the temperature and pressure data were filled as follows. First, the decreases in temperature and pressure with height were calculated using all available data. The change in temperature or pressure from the last good measurement was then calculated using these lapse rates and the change in aircraft altitude from the Novatel GPS data. The values used to fill the gaps in Ta and ps were then calculated by adding the running integral of the temperature and pressure changes to the last good measurement. The difference between the last value calculated for the gap and the first good measurement of the next data block is recorded and used to characterise the uncertainty of the method. A linear correction is then applied to the values used to fill the gaps to remove any discontinuity between the end of the gap and the start of the next data block. Details of the method and the uncertainty in the values used to fill the gaps are discussed in Section 5.

There are no known problems with the meteorological data at this time other than those associated with the gaps caused by the logger failures.

16

There is digital data for TDL1, TSI1 and TSI2 for the first 100 seconds of the flight (aircraft still in the hangar). There is no data for TDL2. The digital data for TSI1 and TSI2, which appear to be diagnostic messages rather than measurements, are scrambled because the wrong serial port configuration was specified in the data logger initialisation file.

3.2.3 Flight Track

After take-off, the aircraft tracked west-northwest and climbed to an altitude of 6,500 m at 87 km from Darwin. The aircraft then tracked east-northeast climbing to an altitude of 12,100 m at a point 17.5 km east of Cape Gambier before turning northeast and continuing to climb slowly, reaching 12,600 m over Soldier Point on Melville Island. From here, the aircraft completed a right turn and descended southwest back towards Darwin, landing from the southeast.


17

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.4

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-12.5

-12

-11.5

Latitude

+ C a p e D o n

+ Darwin

+ Garden Point

+ M o u n t B u n d y+ P o in t S t u a r t

ACTIVE ARA TE02 20051113 05:46-07:24 UTC


18

3.3 15/11/2005 : AE03

3.3.1 General

This was the first science flight (HA1) of VH-ARA in Darwin. The SP2 u-bay was fitted to the aircraft. Logger S/N 03 was in the right fuselage position and S/N 04 was in the left fuselage position. The flight was finished early because Hector did not develop.



The SP2 u-bay was flown and the standard aircraft configuration consisting of the right pylon, Rosemount boom, Novatel GPS and TANS GPS was used.

The right wing and fuselage REMlets (remote analogue to digital converters) were triggered by a 20 Hz sample pulse from the right fuselage data logger. The REMlet, Novatel GPS and TANS GPS data were recorded on the right fuselage logger. The digital data from TDL1 were recorded on the left fuselage logger. The right and left fuselage data loggers both recorded the 1 second timing pulse from their internal GPS systems to provide a means for synchronising the time stamp assigned to the various data streams by the loggers.

Both loggers and REMlets stopped repeatedly during the flight. The right fuselage data logger was restarted twice times during the flight. The left fuselage data logger stopped completely after 746 seconds, before the aircraft had taken off. The gaps in the data caused by the failure of the right fuselage data logger have been filled using different methods depending on the data type. No attempt has been made to fill gaps in the data from the left fuselage data logger.



19

There is digital data for TDL1 for the first 746 seconds of the flight (aircraft taxiing before take-off). There is no data for TDL2, TSI1 and TSI2.

3.3.3 Flight Track

After take-off, the aircraft tracked northeast and climbed to 8,200 m at a point 27 km south of Cape Keith. The aircraft then turned to the west and continued to climb reaching 12,800 m over the southern coast of Bathurst Island. From here, the aircraft tracked east over the southern coasts of Bathurst and Melville Islands climbing to a maximum altitude of 13,800 m north of Cape Gambier. The aircraft then descended to 13,000 m at a point 26 km southeast of Cape Keith before completing a right turn and descending into Darwin from the northeast and landing from the southeast.


20

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-12.8

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-12.6

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-12.4

-12.3

-12.2

-12.1

-12

-11.9

-11.8

-11.7

-11.6

-11.5

Latitude

+ C a p e D o n

+ Darwin


ACTIVE ARA AE03 20051115 06:08-08:02 UTC

Figure 3.3: Flight track for AE03 on 15/11/2005. Arrows indicate the direction of the aircraft track. Numbers to the left of the aircraft track are the seconds since 0000 UTC in increments of 300 secs. Numbers to the right of the aircraft track are the aircraft altitude in km.

21

3.4 16/11/2005 : AE04

3.4.1 General

This was a science flight (HC1) with the NOX u-bay fitted to the aircraft. Logger S/N 03 was in the right fuselage position and S/N 04 was in the left fuselage position. Oil streaks were found on the canopy after the flight. These were traced to a failed start lock in the propeller and the aircraft did not fly again until 27/11/2005.




The right wing and fuselage REMlets (remote analogue to digital converters) were triggered by a 20 Hz sample pulse from the right fuselage data logger. The REMlet, Novatel GPS and TANS GPS data were recorded on the right fuselage logger. The digital data from TDL1 were recorded on the left fuselage logger. The right and left fuselage data loggers both recorded the 1 second timing pulse from their internal GPS systems to provide a means for synchronising the time stamp assigned to the various data streams by the loggers.

Both loggers and REMlets stopped repeatedly during the flight. The right fuselage data logger was restarted eleven times during the flight. The left fuselage data logger stopped completely after 668 seconds, before the aircraft had taken off. The gaps in the data caused by the failure of the right fuselage data logger have been filled using different methods depending on the data type. No attempt has been made to fill gaps in the data from the left fuselage data logger.


The dynamic pressure data is unreliable from time 07:59:10 UTC due to ice forming in the pitot tube of the Rosemount 5-hole probe. The missing dynamic pressure data

22

has been synthesised from the pressure difference across the angle of attack ports on the 5-hole probe. The errors associated with this approach are discussed in Section 5.

There is no data for the CR2 frost point hygrometer for this flight.

There is data for TDL1 for the first 668 seconds of the flight (aircraft taxiing before take-off). There is no data for TDL2 and no data (analogue or serial) for TSI1 and TSI2.

3.4.3 Flight Track

After take-off, the aircraft tracked northeast, climbed to an altitude of 9,300 m 19 km south of Cape Keith and then tracked west while continuing to climb to 12,900 m 27 km northwest of Cape Gambier. From here the aircraft began a run to the southwest at 13,200 m climbing to 13,800 m at the end of the transect 113 km west of Darwin. The aircraft then began a right turn onto the reverse heading and completed a run to the northeast at 12,800 m ending 29 km northwest of Cape Gambier. From here the aircraft stepped 29 km to the southeast and began a run from Cape Gambier to the southwest at 13,800 m descending to 13,200 m at the end of the transect 72 km west of Darwin. After a left procedure turn the aircraft returned on the reverse heading at 13,200 m to a point 32 km southwest of Cape Gambier. From here the aircraft stepped 29 km northwest back to the original track and completed another northeast to southwest transect at 13,200 m from Buchanan Island to a point due south of Cape Fourcroy. The aircraft then tracked northwest to southeast over the Beagle Gulf at 13,200 m before descending to the west over Cape Hotham and landing into Darwin from the southeast.


23

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6

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12.

9

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2

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2

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3

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8

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8

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9

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2

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0.3

130 130.5 131 131.5Longitude

-13

-12.5

-12

-11.5

Latitude

+ C a p e D o n

+ Darwin

+ Garden Point


ACTIVE ARA AE04 20051116 06:19-09:47 UTC


24

3.5 27/11/2005 : TE05

3.5.1 General

This was a test flight (HC1) after the propeller repair with the SP2 u-bay fitted to the aircraft. Logger S/N 03 was swapped from the right fuselage position to the left fuselage and S/N 04 was swapped to the right fuselage position. This was done after checks on the ground suggested that S/N 04 was more reliable than S/N 03.

The general flight pattern consisted of an ascent to altitude from Darwin over Van Diemen Gulf to the Cobourg Peninsula followed by a short return leg at altitude back towards Darwin and descent into Darwin.

Take-off was approximately 06:42 UTC, landing at approximately 08:10 UTC. The mission scientist was Peter Isaac.



The right wing and fuselage REMlets (remote analogue to digital converters) were triggered by a 20 Hz sample pulse from the right fuselage data logger. The REMlet, Novatel GPS and TANS GPS data were recorded on the right fuselage logger. The Novatel GPS, TDL1, TDL2, TSI1 and TSI2 data were recorded on the left fuselage logger. The Novatel GPS data (including the 1 PPS timing pulse) were fed to both data loggers for this flight to allow the two loggers to be synchronised and to provide timing for the various data streams. Both loggers operated throughout the flight.

There are no known problems with the meteorological data at this time but there is no TANS GPS attitude data. As a result, there is no wind data for this flight.

There is data for TDL1 and TDL2 for the flight. The serial data for TSI1 and TSI2, which appear to be diagnostic messages rather than measurements, are scrambled because the wrong serial port configuration was specified in the data logger initialisation file. The analogue data for TSI1 and TSI2 appear correct.

3.5.3 Flight Track

After take-off the aircraft tracked northeast over Cape Hotham climbing to an altitude of 12,800 m at a point 55 km east of Cape Don. The aircraft then completed a left turn onto the reverse heading and climbed 13,200 m while tracking southwest back towards Darwin. The descent into Darwin for landing began 15 km northeast of Cape Hotham with the aircraft landing from the southeast.


25

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5.5

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0.0

131 131.5 132Longitude

-12.5

-12

-11.5

-11

Latitude

+ Cape Don

+ Darwin


ACTIVE ARA TE05 20051127 06:39-08:14 UTC


26

3.6 30/11/2005 : AE06

3.6.1 General

This was a science flight (HC1) with the NOX u-bay fitted to the aircraft.

The flight pattern consisted of 7 transects oriented southeast to northwest over Dundas Strait. The first 4 of these transects roughly followed the line joining Soldier Point and Point Jahleel on Melville Island. The remaining 3 of these runs extended northwest from Cape Don on the Cobourg Peninsula. After these, the aircraft competed 3 runs oriented northeast to southwest over the Dundas Strait. The third of these transects extended along the southeastern coast of Melville Island.




The right wing and fuselage REMlets (remote analogue to digital converters) were triggered by a 20 Hz sample pulse from the right fuselage data logger. The REMlet, Novatel GPS and TANS GPS data were recorded on the right fuselage logger. The Novatel GPS, TDL1, TDL2, TSI1 and TSI2 data were recorded on the left fuselage logger. The Novatel GPS data (including the 1 PPS timing pulse) were fed to both data loggers for this flight to allow the two loggers to be synchronised and to provide timing for the various data streams.

Both loggers and REMlets stopped repeatedly during the flight. The right fuselage data logger was restarted five times during the flight and the left fuselage data logger was restarted twice. The right wing REMlet data (temperature and pressures) stops at a time of 27594 (seconds into UTC day). The gaps in the data caused by the failure of the right fuselage data logger have been filled using different methods depending on the data type, see below for a description of these methods. No attempt has been made to fill gaps in the data from the left fuselage data logger.


27



There is serial data for TDL1, TDL2, TSI1 and TSI2. The serial TSI1 data are diagnostic messages.

3.6.3 Flight Track

After take-off, the aircraft tracked northeast and climbed to 10,000 m due east of Soldier Point on Melville Island before continuing to track north-northwest and climbing to 11,200 m 20 km northwest of Cape Don. From here the aircraft tracked southeast to a point 19 km west-southwest at an altitude of 11,600 m. The aircraft then began a southeast to northwest transect at 11,600 m to a point 12 km northwest of Point Jahleel before executing a left turn for a reverse heading run from northwest to southeast at 12,600 m to a point 28 km due south of Cape Don. The aircraft then completed two right turns while climbing to an altitude 13,300 m and began a southeast to northwest transect to a point 43 km northwest of Point Jahleel ending at 13,600 m altitude. The aircraft then completed a right turn onto the reverse heading for a northwest to southeast transect at 14,100 m to a point 33 km south of Cape Don. It then stepped 30 km to the northeast to begin another southeast to northwest transect from 11 km east-southeast of Cape Don to 23 km north of Point Jahleel. Here, the aircraft completed a left turn onto the reverse heading and completed a northwest to southeast transect at 13,300 m ending 8 km southeast of Cape Don. The aircraft then completed a descending right turn and began another southeast to northwest transect at 12,500 m starting 4 km east of Cape Don and ending 48 km northwest of Cape Don.

The aircraft then completed a wide right turn and climbed to 12,800 m before starting a series of three transects oriented northeast to southwest over the Dundas Strait. The first of these transects was at 12,800 m. The second was 11 km to the southeast of the first transect at 12,900 m and the third followed the first northeast to southwest transect at 12,900 m. The third transect continued at 12,900 m to a point 26 km northeast of Cape Gambier from where the aircraft descended into Darwin over East Vernon Island and landed from the southeast.


28

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9

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12.

6

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1.0 0

.2 0.0


-12.5

-12

-11.5

-11

Latitude

+ Cape Don

+ Darwin


ACTIVE ARA AE06 20051130 04:07-08:18 UTC


29

3.7 1/12/2005 : AE07

3.7.1 General

This was a science flight (HA1) with the SP2 u-bay fitted to the aircraft.

The general flight pattern consisted of 3 east-west transects across the eastern half of Melville Island followed by 3 north-south transects centred over Point Judd on the northern coast of Melville Island.




The right wing and fuselage REMlets (remote analogue to digital converters) were triggered by a 20 Hz sample pulse from the right fuselage data logger. The REMlet, Novatel GPS and TANS GPS data were recorded on the right fuselage logger. The Novatel GPS, TDL1, TDL2, TSI1 and TSI2 data were recorded on the left fuselage logger. The Novatel GPS data (including the 1 PPS timing pulse) were fed to both data loggers for this flight to allow the two loggers to be synchronised and to provide timing for the various data streams.

Both loggers and REMlets stopped repeatedly during the flight. The right fuselage data logger was restarted eleven times during the flight and the left fuselage data logger was restarted once. The right wing REMlet data (temperature and pressures) stopped providing continuous data at a time of 05:45:23 UTC, 45 minutes after take-off. After this time, there are only 8 seconds of useable data before the right fuselage logger stopped completely at a time of 08:28:23 UTC with the aircraft at 1000 m on approach into Darwin for landing. The left fuselage data logger provided data for the entire flight with the exception of one gap of 850 seconds duration at a time of 05:39:59 UTC. The gaps in the data caused by the failure of the right fuselage data logger have been filled using different methods depending on the data type. No attempt has been made to fill gaps in the data from the left fuselage data logger.


30


The dynamic pressure data is unreliable from time 06:18:06 UTC due to ice forming in the pitot tube of the Rosemount 5-hole probe. The missing dynamic pressure data has been synthesised from the pressure difference across the angle of attack ports on the 5-hole probe. The errors associated with this approach are discussed in Section 5.

There is serial data for TDL1, TDL2, TSI1 and TSI2. The serial TSI1 data are diagnostic messages.

3.7.3 Flight Track

After take-off, the aircraft tracked to the northeast and climbed to an altitude of 12,000 m 40 km east of Cape Keith. The aircraft then tracked west until due south of Cape Keith before turning north and tracking in a generally northwest direction until 4 km south of Point Judd at 12,600 m. The aircraft then completed 3 east/west transects across the eastern half of Melville Island. The first transect started 4 km south of Point Judd and ended over Shark Bay northwest of the township of Millkapiti. The second transect began immediately north of Millkapiti at 13,200 m and continued to 6 km north of Soldier Point. The third transect began over Cobham Bay 10 km east of Cape Keith at 13,800 m and ended 37 km southeast of Millkapiti. From here, the aircraft tracked north, crossing the coast of Melville Island at Radford Point and continuing for a further 16 km before turning west and completing a loose figure of eight manoeuvre and descending to 13,200 m. The aircraft then proceeded to a point 11 km north of Point Judd and began a series of 3 transects oriented north-south. The first transect began 11 km north of Point Judd and ended 38 km south of the same point at 13,200 m. The second transect began 46 km south of Point Judd at 12,600 m and to a point 36 km north of Point Judd. The aircraft then turned right and climbed to 14,000 m to commence the third transect from the same point 36 km north of Point Judd and continued at altitudes up to 14,100 m until 25 km north-east of Cape Gambier. From here, the aircraft descended rapidly towards Darwin from the north and landed from the southeast.


31

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5

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14.1

12.5

9.4

6.4

2.3

130.5 131 131.5 132Longitude

-12.5

-12

-11.5

-11

Latitude

+ Cape Don

+ Darwin

+ Garden Point


ACTIVE ARA AE07 20051201 04:55-08:28 UTC


32

3.8 3/12/2005 : AE08

3.8.1 General

This was a science (HC1) flight with the NOX u-bay fitted to the aircraft.

This was the first flight with the REMlets triggered by the 1 PPS from the Novatel GPS and with the REMlet data logged as a generic data stream. This configuration was tried in an attempt to overcome the loss of analogue data that had repeatedly occurred on previous flights. The system worked and the fuselage and right wing REMlets operated for the entire flight. The nominal data rate for all analogue channels is 1 Hz due to the use of the Novatel GPS 1PPS to trigger the REMlets.

The length of the analogue data packet was incorrectly specified in the logger configuration files as 64 bytes (2 bytes each for 32 channels) instead of the actual length of 65 bytes (label byte containing "T" followed by 2 bytes each for 32 channels). The locations of the bytes for each channel are shifted within the packet as a result. A small utility programme has been written to correct the raw logger files for the byte shift and this allows the data from this flight to be processed in the same manner as all other flights.

The take-off was approximately 06:17 UTC and the landing at approximately 09:45 UTC. The mission scientist was Peter Isaac.



The Novatel GPS data and 1 PPS were fed to both data loggers for this flight to provide timing for the various data streams. The analog sample pulse (20 Hz) on the right fuselage logger was fed into a spare serial port and assigned the label "l" (lower case "L"). This label occurs regularly in the raw logger files with a time step of 50 ± 0 ms and has been used to provide the time tag for those analogue packets where the time tag was corrupted due to the incorrectly specified packet length.


There is analogue and serial data for both TSI1 and TSI2 and serial data for both TDL1 and TDL2.

3.8.3 Flight Track

After take-off, the aircraft departed Darwin to the northwest and climbed to an altitude of 12,000 to the south-southeast of Cape Fourcroy. The aircraft then completed four north/south transects over the eastern end of Bathurst Island at 12,000, 12,580, 13,200 and 13,800 m. The fourth transect was truncated with the aircraft

33

overhead Lubra Point when the aircraft turned to a westerly heading and descended to 12,700 m at a point west-southwest of Cape Fourcroy. The aircraft then turned to an east-northeasterly heading and began a transect across Bathurst Island from Point Fawcett to Peaked Hill at the western edge of Melville Island while descending from 12,700 m to 11,780 m. The transect was ended overhead Peaked Hill and the aircraft turned to a reverse heading and crossed back to the southern coast of Bathurst Island at 11,700 m before commencing the descent into Darwin for landing.


22200

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12.0

12.0

12.0

12.4

12.6

12.6

12.6

12.6

12.6

12.9

13.2

13.2

13.2

13.2

13.2

13.5

13.8

13.8

13.8

13.

8

12.

9 12.6

12.1

11.9

11.7

11.7

10.3

9.1

6.7

2.8

0.9 0

.1 0.0


-12.5

-12

-11.5

-11

Latitude

+ C a p e D o n

+ Darwin

+ Garden Point


ACTIVE ARA AE08 20051203 06:08-09:50 UTC


34

3.9 4/12/2005 : AE09

3.9.1 General

This was a science (HA1) flight with the SP2 u-bay fitted to the aircraft.

The REMlets were triggered by the Novatel 1 PPS and recorded on the right fuselage logger as a generic data stream with a packet size of 65 bytes. This was essentially the same configuration as AE08 except that the analogue packet size was correctly specified in the logger configuration file. The raw V60 files do not need to be corrected for byte shifting. The nominal data rate for all analogue channels is 1 Hz due to the use of the Novatel GPS 1PPS to trigger the REMlets.



The SP2 u-bay was flown with both TSI instruments in place. The standard aircraft configuration consisting of the right pylon, Rosemount boom, Novatel GPS and TANS GPS was used.

The Novatel GPS data and 1 PPS were fed to both data loggers for this flight to provide timing for the various data streams. The analog sample pulse (20 Hz) on the right fuselage logger was fed into a spare serial port and assigned the label "l" (lower case "L"). This label occurs regularly in the raw logger files with a time step of 50 ± 0 ms and has been used to provide the time tag for those analogue packets where the time tag was corrupted due to the incorrectly specified packet length.

There are no known problems with the meteorological data at this time.


3.9.3 Flight Track

After take-off, the aircraft departed Darwin to the northeast to a point 9 km northeast of Cape Hotham before turning west-northwest and climbing to an altitude of 10,650 south of Buchanan Island. From here, the aircraft completed two east/west transects along the southern coast of Bathurst Island at altitudes of 10,650 m (east to west) and 11,300 m (west to east). The western end of the run was approximately 15 km west of Cape Fourcroy at 129° 53.5'. The aircraft then stepped 19 km to the south and completed two more east/west transects at altitudes of 11,300 m (east to west) and 11,960 m (west to east) using the same longitude as the western end of the transect. The west/east transect was terminated early and the aircraft headed southwest and climbed to 12,600 m before commencing a southwest to northeast run from a point 50 km south of Cape Fourcroy to a point 20 km southwest of Buchanan Island. The aircraft then descended into Darwin from the northwest.


35

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0

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0

2760

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10.

7

10.

6

10.

6 11.

1

11.6

11.6

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11.3

11.3 11.

3

11.

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11.

3

11.

3

12.0

12.0

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12.0

12.3

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6

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12.6

12.1

8.2

3.3

0.5

0.1


-12.5

-12

-11.5

Latitude

+ C a p e D o n

+ Darwin

+ Garden Point


ACTIVE ARA AE09 20051204 06:43-09:44 UTC


36

3.10 5/12/2005 : AE10

3.10.1 General

This was a combined inter-comparison flight between the Egret and the Dornier and Egret science flight (HC1) with the NOX u-bay fitted to the aircraft.





There are no known problems with the meteorological data at this time.


3.10.3 Flight Track

After take-off, the aircraft departed Darwin to the northeast, climbed to an altitude of 4,200 m and continued to the rendezvous point 27 km northeast of Cape Hotham. The two aircraft then flew in close proximity along a northerly heading over Dundas Strait for approximately 125 km at an altitude of 4,500 m to a point 60 km north-northwest of Cape Don. The aircraft turned at this point onto a south-southwest heading and proceeded back towards Cape Fleeming on Melville Island, breaking off the close proximity flight after 47 km at a point 29 km west-northwest of Cape Don.

The Egret then headed east ascending over the Cobourg Peninsula to 11,600 m at a point 60 km east of Cape Don before tracking south and climbing to 12,500 m 52 km northeast of Point Stuart. The aircraft then tracked west-southwest back towards Darwin reaching a maximum altitude of 13,100 m when 12 km west of Point Stuart before descending into Darwin from the east-northeast.


37

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-12

-11.5

-11

Latitude

+ Cape Don

+ D a r w in+ G a r d e n P o in t+ M o u n t B u n d y+ P o in t S t u a r t

ACTIVE ARA AE10 20051205 05:56-08:32 UTC


38

3.11 6/12/2005 : AE11

3.11.1 General

This was a science flight (HA1) with the SP2 u-bay fitted to the aircraft.



3.11.2 Instrumentation and Data Processing



There is no TANS (GPS attitude) data for the first half of the flight from take-off to 06:56:17 UTC. The most likely cause was a drop out in GPS signal shortly before the aircraft took off and the TANS did not recover from this until half way through the flight.

As a result of these problems, the wind speed and direction data are unreliable up to 06:56:18 UTC and from this time until the end of the flight the winds have been calculated using qc synthesised from Δpz.

There is analogue and serial data for both TSI1 and TSI2 and serial data for TDL2. There is no data for TDL1 (closed path) for this flight.

3.11.3 Flight Track

After take-off, the aircraft departed Darwin to the northwest and climbed to 12,300 m at a point 13 km west of Cape Fourcroy at the southwestern tip of Bathurst Island. The aircraft then completed 7 transects over the same track at altitudes of 12,300, 12,900, 13,500, 14,100, 14,700, 13,800, 12,900 m. The transect followed the line east from 15 km west of Cape Fourcroy to Buchanan Island (85 km) then southeast to a point overhead East Vernon Island (55 km). Alternate transects were flown in the reverse direction. The aircraft commenced descent into Darwin at the end of the 7th transect (west to east), approaching from the north and landing from the east-southeast.


39

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9

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9

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9

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9

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0

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8

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8

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12.9

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12.9

11.2

6.2

1.9

1.0 0

.2


-12.5

-12

-11.5

Latitude

+ C a p e D o n

+ Darwin

+ Garden Point


ACTIVE ARA AE11 20051206 04:33-09:09 UTC


40

3.12 8/12/2005 : AE12

3.12.1 General

This was a science flight (HC2, survey) with the NOX u-bay fitted to the aircraft. After the survey section of the flight, the aircraft completed by three short passes over the eastern edge of Melville Island through the cirrus outflow from a system over the Cobourg Peninsula.


Take-off was shortly before 03:51 UTC. The data logger file starts shortly after take-off when the aircraft was already at an altitude of approximately 430 m. Landing was at approximately 08:03 UTC. The mission scientist was Peter Isaac.



There are no known problems with the meteorological data at this stage.

There is analogue and serial data for both TSI1 and TSI2 and serial data for TDL1 and TDL2.

3.12.3 Flight Track

After take-off, the aircraft departed Darwin to the southwest to a point 15 km north-northeast of Point Blaze. From here the aircraft headed west-southwest and climbed to a maximum altitude of 14,100 m at 13° 14.3'S and 128°E. The aircraft then headed north along longitude 128°E descending from 14,100 m to 12,500 m at latitude 12° 30'S where the aircraft turned east-northeast and descended to 12,000 m at longitude 128° 41'E. The aircraft then turned north and continued descending to 11,400 m at latitude 12° 5'S before tracking east back towards Darwin at 12,300 m. At 5 km north of North West Vernon Island the aircraft turned north and crossed Melville Island at 12,300 m to a point 30 km north of Lethbridge Bay before tracking to the west, reversing and tracking east to a point 25 km north-east of Cape Fleeming. From here the aircraft completed 3 north/south transects at altitudes of 14,500, 14,100 and 13,350 m at longitudes of approximately 131° 25', 131° 20' and 131° 17' respectively. At the end of the third transect the aircraft descended into Darwin from the north.


41

13500

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8.4

9.8

10.

9

11.

9

12.

6

13.

1

13.

5

13.

9

14.

1 14.1

12.9

12.6

12.4

12.1

12.0

11.4

11.3

11.5

11.8

12.3

12.3

12.3

12.3

12.3

12. 3

12.3

12.3

12.3

12.3

12.

6

13.

1 13.5

13.6

14.1

14.3

14.5

14.5

14.5 14.1

14.0

13.2

12.9

11.5

6.7

2.3

0.3

0.0

128 128.5 129 129.5 130 130.5 131 131.5Longitude

-13.5

-13

-12.5

-12

-11.5

-11

-10.5

Latitude

+ C a p e D o n

+ Darwin

+ Garden Point

+ Mount Bundy

+ P o in t S t u a r t

ACTIVE ARA AE12 20051208 03:40-08:09 UTC


42

3.13 9/12/2005 : AE13

3.13.1 General

This was a science flight (HA1) with the SP2 u-bay fitted to the aircraft. The flight track consisted of north/south passes through a cirrus outflow west of Bathurst Island.


Take-off was shortly before 04:25 UTC, landing was at approximately 08:07 UTC. The mission scientist was Peter Isaac.



The dynamic pressure measurement failed shortly after take-off due to ice forming in the pitot tube of the Rosemount 5-hole probe. The missing dynamic pressure data has been synthesised from the pressure difference across the angle of attack ports on the 5-hole probe. The errors associated with this approach are discussed in Section 5.


3.13.3 Flight Track

After take-off, the aircraft departed Darwin to the northwest and climbed to an altitude of 10,300 m 53 km west-northwest before tracking east-northeast then northwest to a point 100 km north-northwest at 13,200 m. From here, the aircraft completed four north/south transects along longitudes 129° 45'E, 129° 38'E, 129° 19'E and 129° 4'E at altitudes of 13,200, 12,900, 13,200 and 12,300 m. At the northern extent of the fourth transect the aircraft turned east and stepped back to a longitude of 129° 22'E before turning south again for a partial transect at 12,000 m. This transect ended at a latitude of 11° 25'S from where the aircraft tracked approximately southeast then east at 12,000 m until over Kanunga Point on the western coast of Bathurst Island. The aircraft then descended, initially heading east and then to the southeast, before landing into Darwin from the southeast.


43

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1620

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.5

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6.5

7.9

9.2

10.3

11.2

12.0

12.5

13.0

13.2

13.2

13.2

13.2

13.2

13.2

12.9

12.9

12.9

12.9 1

2.9

13.2

13.2

13.2

13.2

12.6

12.6

12.3

12.0

12.0

12.0

12.0

12.0

12.0

12.0

12.0

12.0

9.4

6.7

4.1

1.7

1.0

0.2

0.0

0.0

129 129.5 130 130.5 131Longitude

-12.5

-12

-11.5

-11

Latitude

+ C a p e D o n+ D a r w in

+ Garden Point


ACTIVE ARA AE13 20051209 04:16-08:15 UTC


44

3.14 10/12/2005 : SE14

3.14.1 General

This was a survey flight (HA2) with the SP2 u-bay fitted to the aircraft. The flight track consisted of a long west to east transect over Bathurst and Melville Islands continuing across the Van Diemen Gulf and over the Cobourg Peninsula.







3.14.3 Flight Track

After take-off, the aircraft departed Darwin to the northwest and climbed to an altitude of 10,100 m 36 km west of Cape Fourcroy before turning northeast and climbing to 12,100 m 16 km west of Rocky Point. From here the aircraft tracked east along the 11° 30'S parallel over Bathurst and Melville Islands, the Van Diemen Gulf and Cobourg Peninsula at altitudes between 12,900 and 13,500 m. The eastern end of the transect was 50 km east of North Goulburn Island where the aircraft turned to a west-southwest heading and tracked back to Darwin at 12,300 m. The aircraft commenced descent into Darwin from about 22 km northeast of Point Stuart and landed from the southeast.


45

6300

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690072

00750078

00810084

00

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.5 4.3 5

.9 7.5 8

.9 10.1 11.2

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130 130.5 131 131.5 132 132.5 133 133.5 134Longitude

-14

-13.5

-13

-12.5

-12

-11.5

-11

-10.5

-10

Latitude

+ Cape Don

+ Darwin

+ Garden Point

+ Mount Bundy

+ Point Stuart

ACTIVE ARA SE14 20051210 01:40-04:52 UTC

Figure 3.14: Flight track for SE14 on 10/12/2005. Arrows indicate the direction of the aircraft track. Numbers to the left of the aircraft track are the seconds since 0000 UTC in increments of 300 secs. Numbers to the right of the aircraft track are the aircraft altitude in km.

46

3.15 11/12/2005 : FE15

3.15.1 General

This was the ferry flight from Darwin back to Parafield at the end of the 2005 field campaign. The aircraft was equipped with the gas chromatograph, the open path TDL (TDL2) and the right pylon housing the Rosemount pressure transducers and the Rosemount 102 temperature sensor. The inlet port on the static pressure sensor was left disconnected so as to measure the static pressure inside the right pylon fairing. This is expected to be approximately equal to the true static pressure and was to be used, along with the temperature, to calculate the air density for use when interpreting the gas chromatograph data.


Take-off was at 10/12/2005 23:55 UTC, landing was after 11/12/2005 06:05 UTC. The mission scientist was Rudi Gaissmaier.


The analogue data is restricted to static pressure and temperature. There is no other data from the Rosemount mast and there is no data for the CR-2 frost point hygrometer or for the TE-49C O3 sensor.

There is serial data for TDL2 only. TDL1 and the TSIs were not installed on the aircraft for this flight.

There are several problems with the data for this flight. First, the TANS data stops at about 03:20 UTC and there is very limited data from the TANS after this time.

Second, both loggers (left and right fuselage) stopped shortly before 04:15 UTC and started again at 04:55 UTC, a gap of approximately 40 minutes. The gaps in the static pressure and temperature data have been filled using the interpolation approach adopted for flights TE01 to AE07.

Third, the analogue data from both the right wing and fuselage REMlets are offset by one channel from 04:55 UTC onwards. For example, the data for channel 1 of the right wing REMlet (temperature, Ta) appears in the byte location for channel 2 (pressure difference across the side slip ports, py) in the raw files from the logger from 04:55 UTC onwards. The offset in channel location is corrected during data processing for this flight.

Finally, both loggers stopped at 06:05 UTC with the aircraft at 7 km altitude on descent into Parafield. The loggers did not restart.

47

3.15.3 Flight Track

After take-off from Darwin, the aircraft tracked southeast to Parafield passing overhead Tindale and Alice Springs. A plot of the flight track is shown in Figure 3.15.

86400 87000 87600 88200 88800 8940090000

9060091200918009240093000936009420094800954009600096600972009780098400 99000

99600 100200 100800 101400 102000 102600 103200 103800 104400 105000 105600 106200 106800107400 108000

1.7 5.0 8.2 10.6 12.2 13.2 13.2 13.3 13.3 13.3 13.9 13.8 13.8 13.8 13.9 13.9 13.8 13.8 13.8 13.8 13.8

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125 130 135 140 145Longitude

-30

-25

-20

-15

Latitude

+ C a p e D o n+ D a r w in+ G a r d e n P o in t+ M o u n t B u n d y+ P o in t S t u a r t

ACTIVE ARA FE15 20051211 23:50-06:04 UTC

Figure 3.15: Flight track for FE15 on 11/12/2005. Arrows indicate the direction of the aircraft track. Numbers to the left of the aircraft track are the seconds since 0000 UTC in increments of 300 secs. Numbers to the right of the aircraft track are the aircraft altitude in km.

48

3.16 17/01/2006 : FE16

3.16.1 General

This was the ferry flight from Parafield to Darwin at the start of the 2006 field campaign. The aircraft was equipped with the open path TDL (TDL2) and the Rosemount static pressure and temperature sensors. The right pylon and associated instruments (angles of attack and sideslip, dynamic pressure) were not mounted on the aircraft for this ferry flight.

Take-off was at 16/01/2006 23:13 UTC, landing at 17/01/2006 06:47 UTC. Ed Dumas was the mission scientist.


The right pylon and mast were not mounted on the aircraft for this ferry flight. Instead, the static pressure sensor was mounted in the fuselage compartment behind the cabin and the temperature sensor was mounted on the u-bay with the associated electronics in the fuselage compartment. The static pressure sensor was not the same unit that was used for the standard ACTIVE flights (TE01 to FE15, AE17 to AE21 and SE24 to TE31 inclusive).

The aircraft configuration used for the ferry flight meant that some major changes were required to the data processing.

First, there is no measurement of dynamic pressure because the right pylon and mast were not mounted on the aircraft. Dynamic pressure is needed to calculate the correction to the measured temperature to account for heating as the airflow decelerates through the sensor housing. The correction is between 4 and 6 C at the typical cruising speed and altitudes of VH-ARA.

To improve the accuracy of the temperature correction, dynamic pressure has been estimated by assuming the aircraft's true airspeed is equal in magnitude to the vector difference between the ambient wind speed and direction and the ground speed and track of the aircraft. The ambient wind speed and direction at the aircraft altitude are approximated as the average of the data from the 05Z and 11Z Darwin radiosondes. The error associated with this approximation is expected to be tolerable, for the purposes of correcting the temperature, when the aircraft is within 100 to 200 km of Darwin.

Second, a calibration was not available for the static pressure sensor used on this, and subsequent, flights when the right pylon was not mounted. The calibration of this sensor was inferred from the standard sensor via the chamber pressure measurement of the CR-2 frost point hygrometer. A calibration for the CR-2 chamber pressure was obtained by least-squares fit of the CR-2 pressure output voltage to the static pressure for all flights with the right pylon fitted to the aircraft. The calibration of the CR-2 chamber pressure was then transferred to the static pressure sensor used on the ferry and LIDAR flights.

Third, the fuselage REMlet sampled the static pressure and temperature on channels 13 and 14 respectively.

49

Finally, the data logging system of VH-ARA was modified during the break between the 2005 and 2006 phases of the field campaign to overcome the loss of analogue data that occurred in flights TE01 to AE07 inclusive. The modifications meant that the REMlets could again be triggered by the loggers at 20 Hz rather than at 1 Hz by the Novatel 1 PPS. As a result, data from the fuselage REMlet (static pressure and temperature) are available at 20 Hz for this flight.

3.16.3 Flight Track

After take-off, the aircraft tracked northwest to Darwin passing overhead Alice Springs and Tindale. A plot of the flight track is shown in Figure 3.16.

8400

084

600

85200858008640087000876008820088800894009000090600912009180092400930009360094200948009540096000966009720097800

984009900099600

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103800104400105000105600106200106800107400108000108600109200109800

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00

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.0

125 130 135 140 145Longitude

-30

-25

-20

-15

Latitude


ACTIVE ARA FE16 20060117 23:13-06:47 UTC


50

3.17 20/01/2006 : AE17

3.17.1 General

This was a science flight (MA1) with the SP2 u-bay fitted to the aircraft. The flight track consisted of two transects south of Bathurst and Melville Islands oriented east/west followed by a west to east pass over the islands.

Take-off was shortly after 06:47 UTC, landing was at approximately 09:05 UTC. The mission scientist was Ed Dumas.



The data logging system of VH-ARA was modified during the break between the 2005 and 2006 phases of the field campaign to overcome the loss of analogue data when the aircraft was as altitude that occurred in flights TE01 to AE07 inclusive. After the modifications to the data logger at Parafield, the triggering of the fuselage REMlet was switched from the Novatel 1 PPS to the 20 Hz pulse stream from the data logger but the triggering for the right-wing REMlet was not changed and remained from the Novatel 1 PPS. As a result, there are 20 Hz analogue data from the fuselage REMlet (TE-49C O3, CR-2, analogue TSI) but only 1 Hz analogue data from the right-wing REMlet (temperatures and pressures).

The dynamic pressure measurement is unreliable after time 07:21:40 UTC due to ice forming in the pitot tube of the Rosemount 5-hole probe. The missing dynamic pressure data has been synthesised from the pressure difference across the angle of attack ports on the 5-hole probe. The errors associated with this approach are discussed in Section 5.

There is analogue data for both TSI instruments. The data logger ports dedicated to the serial data streams from the TSIs and TDLs were incorrectly initialised due to an error in the logger configuration file. The serial data from both TDLs has been recovered from the raw logger files but not the serial data from the TSIs.

3.17.3 Flight Track

After take-off from Darwin, the aircraft tracked to the northwest and climbed to an altitude of 10,700 m at a point 55 km west of Cape Fourcroy before tracking back to a point 26 km southwest of Cape Fourcroy. The aircraft then completed transects at 10,700 m (west to east) and 11,700 m (east to west) over Beagle Gulf and Clarence Strait. The eastern most extent of the runs was approximately 30 km east-northeast of Cape Hotham. At the end of the second transect the aircraft tracked north to begin a west/east pass over Bathurst and Melville Islands at 11,700 m but turned south after encountering moderate turbulence 25 km northwest of Cape Fourcroy. The west to east transect over the islands was started between Capes Fourcroy and Helveticus with the aircraft turning north after approximately 30 km and continuing the transect along

51

the 11° 30'S parallel. The transect was terminated 30 km west of Cape Keith and the aircraft descended into Darwin from the north before landing from the southeast.


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Latitude

+ C a p e D o n

+ Darwin

+ Garden Point


ACTIVE ARA AE17 20060120 05:31-09:06 UTC


52

3.18 22/01/2006 : AE18

3.18.1 General

This was a science flight (MC1) with the NOX u-bay fitted to the aircraft. The flight track consisted of three long transects oriented southwest to northeast between Point Blaze and Darwin.





The dynamic pressure measurement is unreliable after time 08:01:40 UTC due to ice forming in the pitot tube of the Rosemount 5-hole probe. The missing dynamic pressure data has been synthesised from the pressure difference across the angle of attack ports on the 5-hole probe. The errors associated with this approach are discussed in Section 5.


3.18.3 Flight Track

After take-off from Darwin, the aircraft headed northeast over Gunn Point before turning south and climbing to 10,700 m over the town of Batchelor, 73 km south-southeast of Darwin. From here the aircraft tracked west towards the coast and climbed to 11,300 m crossing the coast just south of Point Blaze. The aircraft then completed three transects between Point Blaze and Darwin at altitudes of 12,000 m (southwest to northeast), 12,300 m (northeast to southwest) and 13,500 m (southwest to northeast). The aircraft turned north at the end of the third transect and began descending into Darwin passing over Gunn Point, tracking to the east of Darwin and landing from the southeast.


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+ C a p e D o n

+ Darwin


ACTIVE ARA AE18 20060122 06:51-10:10 UTC


54

3.19 23/01/2006 : AE19

3.19.1 General

This was a science flight (MC2) with the NOX u-bay fitted to the aircraft. The flight track consisted of two long transects oriented northeast to southwest and two shorter transects oriented north to south over the Timor Sea to the west of Darwin between Point Blaze and Darwin.

Take-off was shortly after 02:55 UTC, landing was at approximately 06:35 UTC. The mission scientist was Ed Dumas.






3.19.3 Flight Track

After take-off from Darwin, the aircraft headed north-northwest over Melville Island climbing to an altitude of 10,800 m over Cape van Diemen before turning south-southwest and climbing to an altitude of 12,800 m over the centre of Bathurst Island. From here the aircraft commenced two transects oriented northeast to southwest at altitudes of 12,900 (northeast to southwest) and 13,500 m (southwest to northeast). The southwestern end of these transects was a point 74 km west of Cape Scott. After the second transect the aircraft commenced two north-south runs at altitudes of 13,500 (north to south) and 12,900 m (south to north). The second transect (south to north) was terminated early at a point 94 km west of Darwin from where the aircraft descended into Darwin from the west and landed from the northwest.


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129 129.5 130 130.5 131Longitude

-13.5

-13

-12.5

-12

-11.5

Latitude

+ C a p e D o n

+ Darwin

+ Garden Point


ACTIVE ARA AE19 20060123 02:51-06:35 UTC


56

3.20 25/01/2006 : AE20

3.20.1 General

This was a science flight (MA2) with the SP2 u-bay fitted to the aircraft. The flight track consisted of five long transects oriented southwest to northeast from west of Point Blaze, overhead Darwin to Cape Hotham.

Take-off was shortly before 05:20 UTC, landing was at approximately 09:35 UTC. The mission scientist was Ed Dumas.






3.20.3 Flight Track

After take-off from Darwin, the aircraft headed west-northwest and climbed to an altitude of 10,900 m at a point 48 km southwest of Cape Fourcroy before turning south-southeast and continuing to climb to 12,000 m at 5 km west of Point Blaze. The aircraft then completed five transects between Point Blaze and Cape Hotham overflying Darwin on each run. Transects were flown at 12,000 (southwest to northeast), 12,600 (northeast to southwest), 13,200 (southwest to northeast), 13,800 (northeast to southwest) and 14,450 m (southwest to northeast). The final transect was terminated 25 km southwest of Cape Hotham from where the aircraft descended to the south before landing into Darwin from the southeast.


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-13

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-12

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Latitude

+ C a p e D o n

+ Darwin

+ G a r d e n P o in t

+ Mount Bundy

+ P o in t S t u a r t

ACTIVE ARA AE20 20060125 05:12-09:36 UTC


58

3.21 27/01/2006 : AE21

3.21.1 General

This was a science flight (MA2) with the SP2 u-bay fitted to the aircraft. The flight track consisted of five transects oriented west to east and centred over Darwin.

Take-off was approximately 05:40 UTC, landing was at 09:35 UTC. The mission scientist was Peter Isaac.



The triggering of the right-wing REMlet was changed from the Novatel 1 PPS to the 20 Hz pulse stream from the data logger before this flight. As a result, there is 20 Hz analogue data from both the fuselage REMlet (TE-49C O3, CR-2, analogue TSI) and the right-wing REMlet (temperatures and pressures).



3.21.3 Flight Track

After take-off from Darwin, the aircraft headed northwest and climbed to an altitude of 10,700 m at a point 22 km southwest of Cape Fourcroy before turning southeast and continuing to climb to 11,600 m at the western end of the transect 67 km west of Darwin. The aircraft then completed five transects oriented west to east over Darwin at altitudes of 11,600, 12,300, 12,600, 13,200 and 13,800 m. Eastern ends of the runs were at 131° 42.3'E, 132° 10.2'E and 132° 2.5'E. At the end of the fifth transect the aircraft headed west and descended towards Darwin landing from the southeast.


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-13

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Latitude

+ Cape Don

+ Darwin

+ Garden Point

+ Mount Bundy

+ Point Stuart

ACTIVE ARA AE21 20060127 05:31-09:34 UTC


60

3.22 31/01/2006 : LE22

3.22.1 General

This was a science flight with the LIDAR u-bay fitted to the aircraft. The flight track consisted of a gradual ascent north of Darwin over Melville Island followed by a north to south pass at altitude to the west of Darwin.

Take-off was approximately 10:51 UTC, landing was at 13:23 UTC. The mission scientist was Jörg Hacker.


The right pylon and mast were not mounted on the aircraft for this flight. Instead, the static pressure sensor was mounted in the fuselage compartment behind the cabin and the temperature sensor was mounted on the LIDAR u-bay with the associated electronics in the fuselage compartment. The static pressure sensor was not the same unit that was used for the standard ACTIVE flights (TE01 to FE15, AE17 to AE21 and SE24 to TE31 inclusive). All analogue data were sampled at 20 Hz by the fuselage REMlet.

The aircraft configuration used for this flight meant that some major changes were required to the data processing.





There is serial data for both TDL1 and TDL2.

61

3.22.3 Flight Track

After take-off, the aircraft climbed to the north-northeast and crossed over Melville Island reaching an altitude of 11,500 m 47 m north of Point Jahleel. From here the aircraft tracked back to the coast of Melville Island before turning west and climbing to 13,200 m over Apsley Strait and turning south. The aircraft then tracked to a point 130 km south of Darwin climbing slowly to 13,900 m. The aircraft then turned north and began descending into Darwin before landing from the southeast. A plot of the flight track is shown in Figure 3.22.

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-13.5

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Latitude

+ Cape Don

+ Darwin

+ Garden Point

+ Mount Bundy

+ Point Stuart

ACTIVE ARA LE22 20060131 10:43-13:30 UTC

Figure 3.22: Flight track for LE22 on 31/01/2006. Arrows indicate the direction of the aircraft track. Numbers to the left of the aircraft track are the times in UTC in increments of 300 secs. Numbers to the right of the aircraft track are the aircraft altitude in km.

62

3.23 01/02/2006 : LE23

3.23.1 General

This was a science flight with the LIDAR u-bay fitted to the aircraft. The flight track consisted of a gradual ascent east of Darwin followed by a return at altitude to overhead Darwin then a long transect south of Darwin before a gradual descent back for landing.

Take-off was approximately 10:55 UTC, landing was at 14:12 UTC. The mission scientist was Jörg Hacker.


The right pylon and mast were not mounted on the aircraft for this flight. Instead, the static pressure sensor was mounted in the fuselage compartment behind the cabin and the temperature sensor was mounted on the LIDAR u-bay with the associated electronics in the fuselage compartment. The static pressure sensor was not the same unit that was used for the standard ACTIVE flights (TE01 to FE15, AE17 to AE21 and SE24 to TE31 inclusive). All analogue data were sampled at 20 Hz by the fuselage REMlet.

The aircraft configuration used for this flight meant that some major changes were required to the data processing.





63

There is serial data for both TDL1 and TDL2.

3.23.3 Flight Track

After take-off, the aircraft climbed to the east of Darwin detouring south of the Point Stuart radiosonde site before reaching 13,100 m 227 km east of Darwin. From here the aircraft tracked west and climbed to 13,900 m overhead Darwin before turning south. The aircraft then tracked south at 13,900 m to -15 S before turning east along this latitude for 100 km to intersect the 132 E meridian about 65 km southwest of Katherine. The aircraft then turned north and continued along 132 E until abeam Katherine and then began a slow descent into Darwin landing from the southeast. A plot of the flight track is shown in Figure 3.23.

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Latitude

+ C a p e D o n+ D a r w in+ G a r d e n P o in t

+ Mount Bundy

+ Point Stuart

ACTIVE ARA LE23 20060201 09:53-14:17 UTC

Figure 3.23: Flight track for LE23 on 01/02/2006. Arrows indicate the direction of the aircraft track. Numbers to the left of the aircraft track are the times in UTC in increments of 300 secs. Numbers to the right of the aircraft track are the aircraft altitude in km.

64

3.24 03/02/2006 : SE24

3.24.1 General

This was a survey flight (MA2) with the SP2 u-bay fitted to the aircraft. The flight track consisted of a long transect northeast from Darwin and return.

Take-off was at 05:12 UTC and landing was at 09:10 UTC. The mission scientist was Peter Isaac.

3.24.2 Instrumentation and Data Set

The SP2 u-bay was flown with both TSI instruments in place. The standard aircraft configuration consisting of the right pylon, Rosemount boom, Novatel GPS and TANS GPS was used. There is 20 Hz analogue data from both the fuselage REMlet (TE-49C O3, CR-2, analogue TSI) and the right-wing REMlet (temperatures and pressures).



3.24.3 Flight Track

After take-off from Darwin, the aircraft headed northwest and climbed to an altitude of 11,000 m at a point 37 km west of Cape Fourcroy before turning southeast and continuing to climb to 12,600 m. Over Darwin the aircraft turned northeast and began the outward leg of the survey flight at 12,600 m climbing to 12,900 m as it crossed the southeast coast of Melville Island. The aircraft began to climb before reaching the end of the outward leg reaching 13,400 m before commencing the turn onto the reverse leg at a point 455 km north-east of Darwin. The inward leg from this point back to Darwin was completed at an altitude of 13,800 m. The aircraft then commenced a spiral descent over Darwin before landing from the southeast.


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-12.5

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-9

Latitude

+ Cape Don

+ D a r w in

+ Garden Point


ACTIVE ARA SE24 20060203 05:01-09:10 UTC

Figure 3.24: Flight track for SE24 on 03/02/2006. Arrows indicate the direction of the aircraft track. Numbers to the left of the aircraft track are the seconds since 0000 UTC in increments of 300 secs. Numbers to the right of the aircraft track are the aircraft altitude in km.

66

3.25 06/02/2006 : AE25

3.25.1 General

This was a science flight (MA1) with the SP2 u-bay fitted to the aircraft. The flight track consisted of three transects oriented east/west along the northern coast of Melville and Bathurst Islands.

Take-off was at 06:17 UTC and landing was at 09:10 UTC. The mission scientist was Jörg Hacker.



The dynamic pressure measurement on this flight averaged approximately 10 hPa compared to approximately 18 to 20 hPa on previous flights with good quality qc data. This was probably due to a leak in the pitot pressure line from the Rosemount 5-hole probe. Dynamic pressure for this flight has been synthesised from the pressure difference across the angle of attack ports on the 5-hole probe. The errors associated with this approach are discussed in Section 5.


3.25.3 Flight Track

After take-off from Darwin, the aircraft headed northeast and climbed to an altitude of 9,800 m 43 km south of Cape Don before turning northwest and continuing to climb to 12,400 m 34 km north of Cape Fleeming. From here the aircraft tracked south to 9 km southeast of Cape Fleeming and then turned west for the first transect east to west across the northern coasts of Melville and Bathurst Islands at 12,900 m. The first transect ended 31 km west of Deception Point on the north coast of Bathurst Island. The aircraft then stepped 11 km north for the second transect from west to east at 12,900 m to a point 12 km north-west of Radford Point before turning and completing the third transect from east to west at 13,500 m. The third transect ended 69 km west of Cape Van Diemen from where the aircraft tracked south-east back towards Darwin climbing to 14,100 m 10 km north of Cape Helveticus before descending into Darwin from the northwest passing between Lee Point and Darwin and landing into Darwin from the southeast.


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130 130.5 131 131.5Longitude

-12.5

-12

-11.5

-11

Latitude

+ C a p e D o n

+ Darwin

+ Garden Point


ACTIVE ARA AE25 20060206 06:10-09:09 UTC


68

3.26 08/02/2006 : AE26

3.26.1 General

This was a science flight (MC1) with the NOX u-bay fitted to the aircraft. The flight track consisted of two north/south transects and two east/west transects over Bathurst and Melville Islands.



The NOX u-bay was flown with both TSI instruments in place. The standard aircraft configuration consisting of the right pylon, Rosemount boom, Novatel GPS and TANS GPS was used. There is 20 Hz analogue data from both the fuselage REMlet (TE-49C O3, CR-2, analogue TSI) and the right-wing REMlet (temperatures and pressures).

The dynamic pressure measurement on this flight averaged approximately 10 hPa compared to approximately 18 to 20 hPa on previous flights with good quality qc data. This was probably due to a leak in the pitot pressure line from the Rosemount 5-hole probe. Dynamic pressure for this flight has been synthesised from the pressure difference across the angle of attack ports on the 5-hole probe. The errors associated with this approach are discussed in Section 5.

In addition to the unreliable qc data there are several gaps in the aircraft attitude data from the TANS GPS system, especially towards the end of the flight. The lack of direct qc measurements and the lack of TANS data contribute to the poor quality of the wind data in the last quarter of this flight.

There is no analogue or serial data for TSI1 and TSI2 for this flight. This is because the TSI data cable was inadvertently left unplugged when the NOX u-bay was mated to the fuselage prior to the flight. There is serial data for both TDL1 and TDL2. The data for TDL2 stops at 09:55 UTC, 55 minutes before the end of the flight.

3.26.3 Flight Track

After take-off from Darwin, the aircraft headed northwest and climbed to an altitude of 10,600 m at a point 41 km west of Cape Fourcroy before tracking to the east-southeast and continuing to climb to 12,900 m immediately south of Lubra Point on the southern coast of Bathurst Island. From here the aircraft tracked north across the centre of Bathurst Island to Brace Point then turned west and climbed to 13,900 m before commencing a west to east transect across Bathurst and Melville Islands along the 11° 30'S parallel. The eastern most extent of the run was 26 km south of Smoky Point where the aircraft turned onto the reverse track after climbing to 14,500 m. The east to west transect along the 11° 30'S parallel ended at Rocky Point and the aircraft turned northeast climbing over Cape Van Diemen to Purumpenelli Point before beginning a north to south transect across Melville Island reaching an altitude of 15,100 m, the highest achieved during the ACTIVE campaign. The north to south

69

transect ended 25 km south-southwest of Buchanan Island from where the aircraft turned east and descended into Darwin from the northeast before landing from the southeast.


2880

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-12.5

-12

-11.5

-11

Latitude

+ C a p e D o n

+ Darwin

+ Garden Point


ACTIVE ARA AE26 20060208 07:56-10:49 UTC


70

3.27 10/02/2006 : AE27

3.27.1 General

This was a science flight (MC1) with the NOX u-bay fitted to the aircraft. The flight track consisted of five west/east transects across the southern half of Bathurst and Melville Islands.



The NOX u-bay was flown with both TSI instruments in place. The standard aircraft configuration consisting of the right pylon, Rosemount boom, Novatel GPS and TANS GPS was used. There is 20 Hz analogue data from both the fuselage REMlet (TE-49C O3, CR-2, analogue TSI) and the right-wing REMlet (temperatures and pressures).

The dynamic pressure measurements averaged approximately 14 hPa for the most of this flight compared to approximately 18 to 20 hPa on previous flights with good quality qc data. This was probably due to a leak in the pitot pressure line from the Rosemount 5-hole probe. In addition, the final 30 minutes of qc data suggest that the pitot tube became blocked by ice towards the end of the flight. Dynamic pressure for this flight has been synthesised from the pressure difference across the angle of attack ports on the 5-hole probe. The errors associated with this approach are discussed in Section 5.


3.27.3 Flight Track

After take-off from Darwin, the aircraft headed northwest and climbed to an altitude of 10,900 m at a point 42 km west of Cape Fourcroy. The aircraft then turned east and continued to climb before beginning a west to east transect across the southern half of Bathurst and Melville Islands along the 11° 45'S parallel at an altitude of 12,300 m. The eastern most point of this run was 14 km west of Conder Point. The aircraft then returned along the same latitude at 12,900 m to the 129°E meridian (112 km west of Cape Fourcroy) before turning back onto an easterly heading and completing another transect at 13,500 m. This second west to east transect ended above the township of Pickertaramoor on Melville Island and the aircraft turned back to a westerly heading for another transect to the west at 14,100 m which ended at 129° 27'E (48 km west of Cape Fourcroy). The aircraft then headed east again for the fifth transect starting at 12,900 m but descending to 12,300 m for most of the leg. At the completion of this transect the aircraft descended south towards Darwin and landed from the southeast.


71

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0.5129 129.5 130 130.5 131

Longitude

-13

-12.5

-12

-11.5

-11

Latitude

+ C a p e D o n

+ Darwin

+ Garden Point


ACTIVE ARA AE27 20060210 07:06-10:59 UTC


72

3.28 12/02/2006 : AE28

3.28.1 General

This was a science flight (MA1) with the SP2 u-bay fitted to the aircraft.

The original intent was to fly through a cirrus outflow to the southwest of Darwin but the de-icing on the engine air intake did not turn on with the aircraft at altitude. This meant the aircraft was unable to fly into cirrus because of the possibility of encountering icing conditions with a malfunctioning engine air intake de-ice system. The flight plan was amended to a circumnavigation of the outflow instead of transects through it.





There is analogue data for both TSI1 and TSI2 but both instruments show very similar outputs. This implies the two TSIs were set to the same particle size range instead of the configuration used on previous flights where they were set to different size ranges. The serial data for TSI1 and TSI2 consists of diagnostic messages. There is serial data for both TDL1 and TDL2.

3.28.3 Flight Track

After take-off from Darwin, the aircraft headed northwest and climbed to an altitude of 6,700 m at a point 24 km south-south-east of Cape Fourcroy before turning onto the reverse track and climbing to an altitude of 11,300 m above Darwin. From here the aircraft turned north before tracking southwest to Talc Head. The aircraft then entered a holding pattern while the problem with the engine inlet de-ice heater was diagnosed and an amended operation plan discussed with ACTIVE base. The aircraft continued to the west-southwest to a point 62 km southwest of Darwin then turned north and began a circumnavigation of the cirrus outflow at an altitude of 11,400 m. The ellipsoid track described by the circumnavigation was 42 km wide in the west-east direction (minor axis) and 58 km wide in the north-south direction (major axis). The ellipsoid was approximately centred on the southern tip of Indian Island in Bynoe Harbour, 54 km southwest of Darwin. The circumnavigation was ended when the outbound track was encountered and the aircraft turned east and completed a short (40 km) transect upwind of the convective system at 11,400 m. The aircraft then descended into Darwin from the south and landed from the southeast.

73


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130 130.1 130.2 130.3 130.4 130.5 130.6 130.7 130.8 130.9 131 131.1 131.2Longitude

-13

-12.9

-12.8

-12.7

-12.6

-12.5

-12.4

-12.3

-12.2

-12.1

-12

Latitude

+ C a p e D o n

+ Darwin


ACTIVE ARA AE28 20060212 07:46-09:56 UTC


74

3.29 13/02/2006 : AE29

3.29.1 General

This was a science flight (MA1) with the SP2 u-bay fitted to the aircraft. The flight track consisted of six transects oriented northwest to southeast through a cirrus outflow west of the Cobourg Peninsula.




The dynamic pressure measurement averaged approximately 10 hPa for the most of this flight compared to approximately 18 to 20 hPa on previous flights with good quality qc data. This was probably due to a leak in the pitot pressure line from the Rosemount 5-hole probe. Dynamic pressure for this flight has been synthesised from the pressure difference across the angle of attack ports on the 5-hole probe. The errors associated with this approach are discussed in Section 5.

There are several gaps in the aircraft attitude data from the TANS in the last quarter of this flight. The gaps occur at times 08:55:50 UTC (duration 202 s), 09:06:06 UTC (126 s), 09:09:49 UTC (19 s), 09:10:39 UTC (14 s), 09:11:28 UTC (13 s), 09:11:43 UTC (38 s), 09:13:02 UTC (237 s), 09:17:03 UTC (15 s), 09:17:29 UTC (737 s) and 09:30:43 UTC (85 s). There is also the usual gap in TANS data during the aircraft descent.


3.29.3 Flight Track

After take-off from Darwin, the aircraft headed northeast and climbed to an altitude of 10,800 m at a point 37 km southeast of Cape Don before turning northwest and continuing to climb to an altitude of 12,300 m 40 km north-northwest of Cape Don. The aircraft then tracked south to 11 km west of Cape Don and began the second transect from the north-northwest to the south-southeast at 12,300 m ending the transect 21 km northeast of Point Stuart. From here the aircraft tracked west to a point 24 km north of Point Stuart and began the third transect from the south-southeast to the north-northwest at 13,200 m. The third transect ended 12 km southeast of Cape Fleeming and the aircraft then tracked east-northeast to 44 km

75

northeast of Cape Don and began a longitudinal pass to the southwest at 13,800 m turning to a westerly heading when 5 km west of Soldier Point. The aircraft continued along the 11° 30'S parallel to a point 46 km west of Soldier Point before tracking northwest to begin the fourth transect from 12 km southwest of Cape Fleeming. The fourth transect was flown at 13,800 m and ended 34 km northwest of Point Stuart. The aircraft then executed a procedural turn and commenced the fifth transect from this point northwest to 65 km northwest of Cape Fleeming at 14,400 m. From here the aircraft tracked west and began the sixth transect from 71 km northwest of Cape Fleeming to a point 87 km east-southeast of Darwin at 13,200 m. The aircraft then descended into Darwin and landed from the southeast.


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9

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.0

130.5 131 131.5 132Longitude

-12.5

-12

-11.5

-11

Latitude

+ Cape Don

+ Darwin

+ G a r d e n P o in t+ M o u n t B u n d y

+ Point Stuart

ACTIVE ARA AE29 20060213 05:45-10:11 UTC


76

3.30 14/02/2006 : AE30

3.30.1 General

This was an inter-comparison flight between the Egret and the Dornier with the SP2 u-bay fitted to the Egret. The flight track consisted of six legs to the west and north of Melville Island flown in close proximity with the Dornier.






3.30.3 Flight Track

After take-off from Darwin, the aircraft headed northwest initially before tracking northeast and climbing to 3,100 m. The aircraft rendezvoused over Van Diemen Gulf at a point 28 km northeast of Cape Hotham. From here the aircraft tracked north for 72 km over Cape Keith to 6 km east of Cape Fleeming before turning west and continuing for 93 km west over Point Jahleel. At the western most end of this run, 20 km east of Cape Van Diemen, the aircraft descended north onto the reverse heading and tracked back towards Point Jahleel at 2,100 m. At 8 km north-west of Point Jahleel, the aircraft tracked southeast for 70 km to a point 23 km southeast of Solder Point where the aircraft turned onto the reverse heading and descended to 1,000 m. At this altitude, the aircraft tracked to the northwest across Melville Island to Smokey Point where they descended to the south and tracked south-southeast across Melville Island at 100 m to a point 24 km west of Cape Keith. The aircraft then tracked south-southwest toward Darwin at 100 m and landed from the southeast.


77

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130.4 130.5 130.6 130.7 130.8 130.9 131 131.1 131.2 131.3 131.4 131.5 131.6 131.7 131.8Longitude

-12.4

-12.3

-12.2

-12.1

-12

-11.9

-11.8

-11.7

-11.6

-11.5

-11.4

-11.3

-11.2

-11.1

Latitude


ACTIVE ARA AE30 20060214 02:30-05:23 UTC


78

3.31 15/02/2006 : TE31

3.31.1 General

This was a calibration flight for the Egret with the SP2 u-bay fitted to the aircraft. The flight track consisted of a series of short runs over the Van Diemen Gulf northeast of Cape Hotham.






3.31.3 Flight Track

After take-off from Darwin, the aircraft headed northeast over the Van Diemen Gulf. The calibration runs took place in the centre of the triangle formed by Cape Hotham, Point Stuart and Cape Keith. Calibration runs consisted of reverse heading legs flown directly into and out of the wind at 3,300 m and 9,700 m. The runs were performed at the lowest, typical and highest airspeeds. In addition, runs at both altitudes were performed with pilot induced pitch and drift oscillations. The final calibration pattern was a wind square performed at 9,700 m after which the aircraft descended into Darwin from the northeast and landed from the southeast.


79

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130.8 130.9 131 131.1 131.2 131.3 131.4 131.5 131.6 131.7 131.8 131.9 132Longitude

-12.6

-12.5

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-12

-11.9

-11.8

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-11.6

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Latitude

+ C a p e D o n

+ Darwin


ACTIVE ARA TE31 20060215 02:36-06:32 UTC


80

3.32 16/02/2006 : FE32

3.32.1 General

This was the ferry flight from Darwin to Parafield at the end of the 2006 field campaign. The aircraft was equipped with the closed and open path TDLs (TDL1 and TDL2) and the Rosemount static pressure and temperature sensors. The right pylon and associated instruments (angles of attack and sideslip, dynamic pressure) were not mounted on the aircraft for this ferry flight.

Take-off was at 17/02/2006 23:19 UTC, landing shortly after 18/02/2006 06:17 UTC. The mission scientist was Rudi Gaissmaier.


The right pylon and mast were not mounted on the aircraft for this ferry flight. Instead, the static pressure sensor was mounted in the fuselage compartment behind the cabin and the temperature sensor was mounted on the u-bay with the associated electronics in the fuselage compartment. The static pressure sensor was not the same unit that was used for the standard ACTIVE flights (TE01 to FE15, AE17 to AE21 and SE24 to TE31 inclusive). All analogue data were sampled at 20 Hz by the fuselage REMlet.

The aircraft configuration used for the ferry flight meant that some major changes were required to the data processing.




81


There is serial data for TDL1 and TDL2.

3.32.3 Flight Track

After take-off from Darwin, the aircraft tracked southeast to Parafield passing overhead Tindale and Alice Springs. A plot of the flight track is shown in Figure 3.32.

8400084600 85200 85800 86400 87000 87600

88200888008940090000906009120091800924009300093600942009480095400960009660097200 97800 98400 99000 99600 100200 100800 101400 102000 102600 103200 103800 104400 105000 105600 106200 106800 107400 108000 108600

0.2 3.7 7.1 9.9 11.7 12.9 13.5 13.5 14.3 14.4 14.4 14.4 14.4 14.4 14.4 14.4 14.4 14.4 14.4 14.4 14.4 14.4 14.4

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ACTIVE ARA FE32 20060218 23:15-06:17 UTC


82

4 Description of Data Set 4.1 File Format

4.1.1 General

The data set for VH-ARA is provided as up to 11 ASCII data files for each flight. The number of files may sometimes be less than 11 because some instruments were not flown for all aircraft configurations used during ACTIVE.

All files follow the same naming convention with the file name consisting of four parts.

The first part consists of the aircraft call sign (ARA) and identifies the source of the data.

The second part consists of a date string in the format YYYYMMDD where YYYY is the year, MM is the month and DD is the day of the month. This is the date on which the flight occurred.

The third part of the file name consists of a four-letter flight designation in the format FEKK. 'F' (one of 'A', 'F', 'L', 'T' or 'S') designates the type of flight, 'E' identifies the data as coming from the Egret and KK is the sequential number of the flight (01 to 32).

The flight designation letters, 'A', 'F', 'L', 'T' or 'S', identify ACTIVE, ferry, LIDAR, test or survey flights respectively.

The fourth part of the file name describes the type of data in the file, as shown in Table 4.1 below.

Name Data AIRDATA Pressure, airspeed, air temperature ATT Aircraft attitude DLR O3, frost point temperature GPS Aircraft position, velocity TDL1 Closed path TDL TDL2 Open path TDL TSI1 TSI1 digital data TSI2 TSI2 digital data TSI TSI1 and TSI2 analogue data TX Aircraft radio transmit marker WIND Wind speed, direction

Table 4.1: File names and data types.

All files have the file extension DAT. An example of a complete file name is ARA_20051203_AE08_AIRDATA.DAT, which contains the air state data (temperature and pressures) for flight AE08 on the 3rd December 2005.

83

4.1.2 Aircraft Position and Velocity Data

The aircraft position and velocity data measured by the Novatel GPS are contained in the file ARA_YYYYMMDD_FEKK_GPS where YYYY is the year, MM is the month, DD is the day of the month and FEKK is the flight designation. The column headers, contents and units are described in Table 4.2.

Col Header Units Description 1 SInDay s Seconds into UTC day 2 Nlat deg Latitude of aircraft 3 Nlon deg Longitude of aircraft 4 Nalt m Altitude of aircraft 5 Ntrk deg Aircraft track 6 Ngs ms-1 Aircraft ground speed 7 Nw ms-1 Aircraft vertical velocity component 8 Flag - Data quality flag

Table 4.2: Description of the GPS position and velocity data file.

4.1.3 Aircraft Attitude Data

The aircraft attitude data measured by the Trimble Advanced Navigation System (TANS) GPS are contained in the file ARA_YYYYMMDD_FEKK_ATT where YYYY is the year, MM is the month, DD is the day of the month and FEKK is the flight designation. The column headers, contents and units are described in Table 4.3.

Col Header Units Description 1 SInDay s Seconds into UTC day 2 Tpch deg Pitch 3 Trll deg Roll 4 Thdg deg Heading (true) 5 Tprt degs-1 Pitch rate 6 Trrt degs-1 Roll rate 7 Tyrt degs-1 Yaw rate 8 Flag - Data quality flag

Table 4.3: Description of the GPS attitude data file.

4.1.4 Meteorological Data (Air State)

The air state data are contained in the file ARA_YYYYMMDD_FEKK_AirData where YYYY is the year, MM is the month, DD is the day of the month and FEKK is the flight designation. The column headers, contents and units are described in Table 4.4.

84

Col Header Units Description 1 SInDay s Seconds into UTC day 2 ps hPa Static pressure 3 psNR hPa Static pressure (Noise Removed) 4 qc hPa Dynamic pressure 5 tas ms-1 True airspeed 6 taNR C Air temperature, corrected (Noise Removed) 7 ta C Air temperature, corrected 8 tar C Air temperature, raw 9 Flag - Data quality flag

Table 4.4: Description of the air state data file.

4.1.5 Meteorological Data (Wind)

The wind data are contained in the file ARA_YYYYMMDD_FEKK_Wind where YYYY is the year, MM is the month, DD is the day of the month and FEKK is the flight designation. The column headers, contents and units are described in Table 4.5.

Col Header Units Description 1 SInDay s Seconds into UTC day 2 uair ms-1 U wind component (positive east) 3 vair ms-1 V wind component (positive north) 4 wair ms-1 W wind component (positive up) 5 ff ms-1 Wind speed 6 dd ms-1 Wind direction 7 Flag - Data quality flag

Table 4.5: Description of the wind data file.

4.1.6 O3 and Frost Point Data

The O3 and frost point temperature data are contained in the file ARA_YYYYMMDD_FEKK_DLR where YYYY is the year, MM is the month, DD is the day of the month and FEKK is the flight designation. The column headers, contents and units are described in Table 4.6.

85

Col Header Units Description 1 SInDay s Seconds into UTC day 2 o3DLR V O3 concentration 3 fpCR2 V Frost point temperature 4 pCR2 V Frost point sensor pressure 5 balCR2 V Frost point sensor balance 6 ctrCR2 V Frost point sensor control 7 DLRo3a V O3 additional analogue channel 8 DLRo3b V O3 additional analogue channel 9 DLRo3c V O3 additional analogue channel 10 Flag - Data quality flag

Table 4.6: Description of the TE-49C O3 and CR-2 frost point data file.

4.1.7 TDL Data

The TDL data are contained in two files, ARA_YYYYMMDD_FEKK_TDL1 and ARA_YYYYMMDD_FEKK_TDL2, where YYYY is the year, MM is the month, DD is the day of the month and FEKK is the flight designation. Data from the closed path TDL are in the TDL1.DAT file and data from the open path instrument are in the TDL2.DAT file. The column headers, contents and units of both files are described in Table 4.7 and Table 4.8.

Col Header Units Description 1 SInDay s Seconds into UTC day 2 TDL1a V 1st field in TDL1 data packet 3 TDL1b V 2nd field in TDL1 data packet 4 TDL1c V 3rd field in TDL1 data packet 5 TDL1d V 4th field in TDL1 data packet 6 TDL1e V 5th field in TDL1 data packet 7 TDL1f V 6th field in TDL1 data packet 8 TDL1g V 7th field in TDL1 data packet 9 Flag - Data quality flag

Table 4.7: Description of the TDL1 data file.

Col Header Units Description 1 SInDay s Seconds into UTC day 2 TDL2a V 1st field in TDL2 data packet 3 TDL2b V 2nd field in TDL2 data packet 4 TDL2c V 3rd field in TDL2 data packet 5 TDL2d V 4th field in TDL2 data packet 6 TDL2e V 5th field in TDL2 data packet 7 TDL2f V 6th field in TDL2 data packet 8 TDL2g V 7th field in TDL2 data packet 9 TDL2h V 8th field in TDL2 data packet 10 TDL2i V 9th field in TDL2 data packet 11 Flag - Data quality flag

Table 4.8: Description of the TDL2 data file.

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4.1.8 TSI Data

The TSI data were recorded as both analogue and digital signals.

Two analogue signals from each TSI were measured on four channels of the fuselage REMlet and this data is contained in the file ARA_YYYYMMDD_FEKK_TSI, where YYYY is the year, MM is the month, DD is the day of the month and FEKK is the flight designation. The column headers, contents and units are described in Table 4.9.

The digital data are contained in two files, ARA_YYYYMMDD_FEKK_TSI1 and ARA_YYYYMMDD_FEKK_TSI2, where YYYY is the year, MM is the month, DD is the day of the month and FEKK is the flight designation. The column headers, contents and units of both files are described in Table 4.10 and Table 4.11.

Col Header Units Description 1 SInDay s Seconds into UTC day 2 TSIa V 1st channel of analogue TSI data 3 TSIb V 2nd channel of analogue TSI data 4 TSIc V 3rd channel of analogue TSI data 5 TSId V 4th channel of analogue TSI data 6 Flag - Data quality flag

Table 4.9: Description of the TSI analogue data file.

Col Header Units Description 1 SInDay s Seconds into UTC day 2 TSI1 Counts TSI1 counts 3 Flag - Data quality flag

Table 4.10: Description of the TSI1 digital data file.

Col Header Units Description 1 SInDay s Seconds into UTC day 2 TSI2 Counts TSI2 counts 3 Flag - Data quality flag

Table 4.11: Description of the TSI2 digital data file.

4.2 Data Quality Flag

A data quality flag consisting of a digit for each data column in the file has been added as the final column in all of the data files. The first digit of the data quality flag represents the second column in the file, the second digit of the data quality flag represents the third column in the file and so on. The possible values of the data quality flag digits are listed in the table below. The values have been allocated on the basis of severity with the most severe problems being assigned the highest value. When two or more problems affect the same data field, such as qc synthesised from Δpz and roll outside the acceptance limits, the maximum of the flag values is assigned to the appropriate digit of the data quality flag.

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Flag Quantity Dependents Cause 0 - - No known problems. 1 qc tas, ias, Ta

uair, vair, ff, dd qc synthesised from Δpz.

2 qc tas, ias, Ta uair, vair, ff, dd

qc outside limits (qc < 5 hPa or qc > 40 hPa).

3 Pitch, roll heading

uair, vair, ff, dd Pitch, roll or heading outside limits.

4 Tar tas, Ta uair, vair, ff, dd

Temperature outside limits (Ta < -75 C or Ta > 35 C).

5 Pitch, roll, heading

uair, vair, ff, dd TANS data interpolated over gap.

5 Pitch, roll and yaw rate

uair, vair, ff, dd TANS data interpolated over gap.

5 Nlat, Nlon Nalt

uair, vair, ff, dd Novatel GPS position data interpolated over gap.

5 Ngs, Ntrk Nw

uair, vair, ff, dd Novatel GPS velocity data interpolated over gap.

5 ps, qc, Tar etc

uair, vair, ff, dd Air state data interpolated over gap

5 o3, fpCR2 etc

- O3, CR-2 etc interpolated over gap

6 Pitch, roll, heading

uair, vair, ff, dd No TANS data for flight.

7 ps, Tar ps, qc, tas, Ta, Tar, uair, vair, ff, dd

No meteorological data due to failure of the data logger, static pressure and temperature interpolated using GPS altitude.

Table 4.12: Data quality flag values, the quantities that trigger the value, the data dependent on these quantities and the cause of the degradation in data quality.

Flight AE08 on 03/12/2005 provides several examples of the use of the data quality flag. The pitot tube became blocked by ice at a time (seconds into the UTC day) of 26001 and from this time onwards the data quality flag in the AirData.Dat file is set to "0011110". The occurrence of the flag value "1" indicates that the dynamic pressure has been synthesised from the pressure difference across the angle of attack ports. The sequence of digits indicates that this problem affects the data in the fourth, fifth, sixth and seventh columns in the file and that the data in the eighth column is not affected. The data in each column of the AirData.Dat file are defined in Table 4.4 and this shows that the synthesised qc affects qc, tas, and Ta. Note that the raw temperature (eighth column) is not affected and has the data quality flag value of zero. The wind speed components also depend on qc and the qc data quality flag is propagated into the Wind.Dat file where periods of synthesised qc are indicated by data quality flag values of "11111".

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5 Known Problems 5.1 Synthesis of Dynamic Pressure Using Angle of Attack

5.1.1 General

Measurements of the dynamic pressure for flights AE08, AE11, AE13 and AE18 are missing due to water freezing in the pitot tube of the Rosemount 5-hole probe. In addition to these flights, the qc values for flights AE25, AE26, AE27, AE29 and AE30 are smaller than expected, probably due to leaks in the pneumatic line from the pitot port on the 5-hole probe to the dynamic pressure sensor. From AE19 onwards, the Quiklok connector in this line was disconnected before each flight so that compressed air could be blown down the pitot line in an effort to prevent further loss of qc data due to water freezing in the pressure line. It is possible that the pressure line was not fully inserted into the Quiklok connector after purging the lines prior to the above flights, causing a small leak and consequent loss of qc signal.

5.1.2 Relationship Between qc and pz

Data from flights with good qc measurements show a very strong correlation between the dynamic pressure and the pressure difference across the angle of attack ports on the Rosemount 5-hole probe, pz. The reason for the high correlation and the nature of the relationship between qc and pz can be explained as follows.

The lift equation can be written:

( )L cL C q Aα= 1

L is the lift force acting on the aircraft, CL(α) is the lift coefficient of the wing, qc is the dynamic pressure and A is the wing area. The wing area of the Egret is 39.7 m2 and the lift force in straight and level flight is equal to the aircraft mass divided by the acceleration due to gravity (approximately 47000/9.8=479.6 N for VH-ARA).

The lift coefficient for the wing is a function of the angle of attack α, which is itself a linear function of the pressure difference across the angle of attack ports, pz. A method of estimating qc from pz can be found by combining the lift equation with empirical relationships between the lift coefficient and the angle of attack and between the angle of attack and pz.

The relationship between the angle of attack and pz has been determined from the calibration flights:

0.158 0.033z

c

pq

α = − 2

In Equation 2, pz is the pressure difference across the angle of attack ports, qc is the dynamic pressure and α is the angle of attack in radians.

The lift coefficient for the Egret as a function of the angle of attack can be estimated by inverting Equation 1 and using data from the calibration flight where straight and

89

level runs were performed at several airspeeds. Changing the airspeed varies both qc and the angle of attack. This process yields the following relation:

( ) 6.81 0.86LC α α= + 3

The general relationship between CL and α is non-linear and Equation 3 only applies to a small range of α between -4.25 and -1.0 º. Angles of attack outside this range were rarely encountered during the data collection phase of the ACTIVE flights.

Combining Equations 1, 2 and 3 leads to:

1.0760.636

zc

L pqA

−=

A 4

Substituting the values for L and A then gives:

1.69 18.8c zq p= − + 5

Equation 5 shows that the relationship between qc and pz is expected to be linear. Note that the coefficients in Equation 5 have been derived using the maximum weight of the aircraft (4700 kg) instead of the actual weight of the aircraft at the time the data were collected and are therefore approximations. The real coefficients need to be determined empirically.

Figure 5.1 shows qc as a function of pz for all flights where the qc data were known to be of good quality. The data are block averages over 10 seconds. This has been done to reduce the number of points in the analysis and to reduce the scatter by averaging out the uncorrelated turbulent fluctuations in qc and pz. In addition, data from the descent back into Darwin has been rejected because these were usually performed with the aircraft in a high drag configuration (full flaps and undercarriage out). The empirical relationships between CL and α and between α and pz derived from the calibration flight data will not apply to this flight regime.

90

0

5

10

15

20

25

30

35

40

-20 -15 -10 -5 0 5

pz (hPa)

q c (hP

a)

Figure 5.1: Dynamic pressure qc as a function of the pressure difference across the angle of attack ports on the 5-hole probe pz for flights AE09, AE10, AE12, SE14, AE17, AE19, AE20, AE21, SE24, AE27, AE28 and TE31. The linear best fit given by Equation 6 is shown as the black line.

The linear best fit to the data in Figure 5.1 is given by: 21.48 14.0, 0.982c zq p r= − + = 6

The pressure difference across the angle of attack ports is available for all flights where qc is missing due to ice blocking the pitot tube (AE08, AE11, AE13 and AE18). It is also available for all flights where qc data is compromised by leaks in the pneumatic line (AE25, AE26, AE27, AE29 and AE30). The dynamic pressure for these flights has been synthesised using Equation 6.

5.1.3 Uncertainties Associated with qc Synthesised From pz

The air temperature (Ta), wind speed (WS) and wind direction (WD) all depend on the dynamic pressure and uncertainties in qc will result in errors in these quantities. The errors can be estimated by comparing Ta, WS and WD calculated using the measured and synthesised qc for those flights where the qc data are of good quality.

91

0.00

0.05

0.10

0.15

0.20

0.25

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

Temperature difference (C)

Freq

uenc

y

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

-3.0 -2.0 -1.0 0.0 1.0 2.0 3.0

Dynamic Pressure difference (hPa)

Freq

uenc

y

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

-10 -8 -6 -4 -2 0 2 4 6 8 10Speed difference (m/s)

Freq

uenc

y

0.000.050.100.150.200.250.300.350.400.450.50

-180 -90 0 90 180Direction difference (deg)

Freq

uenc

y

Figure 5.2: Histograms of the difference between measured and synthesised dynamic pressure and of the difference between air temperature, wind speed and wind direction calculated using measured and synthesised dynamic pressure.

Figure 5.2 shows histograms of the difference between measured and synthesised qc and of the difference between air temperature, wind speed and wind direction calculated using measured and synthesised qc for all flights with good data for both qc and pz. For dynamic pressure, 95% of the synthesised values are within ±1 hPa of the observed value. This in turn leads to 99% of the temperatures calculated using the synthesised dynamic pressure being within ±0.5 C of the temperature calculated using the observed dynamic pressure. For wind speed, 90% of the wind speeds calculated using the synthesised dynamic pressure are within ±2 ms-1 of the wind speed calculated using the observed dynamic pressure. For wind direction, 90% of the wind directions calculated using the synthesised dynamic pressure are within ±20 º of the wind direction calculated using the observed dynamic pressure.

5.2 Synthesis of Dynamic Pressure Using Aircraft Ground Speed

Neither dynamic pressure nor the pressure difference across the angle of attack ports are available for the ferry (FE15, FE16 and FE32) and LIDAR (LE22 and LE23) flights. For these flights, dynamic pressure is synthesised from the aircraft ground speed after correction for the ambient wind speed and direction.

Ambient wind can be measured from aircraft as the vector difference between the aircraft's velocity with respect to the ground and the aircraft's velocity with respect to the air:

92

GS TAS= −U U U 7

UGS is the aircraft ground velocity, UTAS is the aircraft velocity through the air and U is the ambient wind velocity.

Inverting this equation and using an estimate of the ambient wind velocity allows the aircraft velocity through the air, the magnitude of which is true airspeed, to be calculated. The dynamic pressure can then be calculated from the true airspeed as follows:

( )

2,

,

3.496

2

1

a a m TAS

a a m

c s

T T U c

P T T

q p Pγ

γ−

= −

=

= −

p

8

Ta,m is the measured total temperature, UTAS is the aircraft true airspeed calculated from the ground speed and the ambient wind speed and direction, cp is the specific heat at constant pressure and ps is the static pressure.

The ambient wind speed and direction at the aircraft position have been estimated by averaging the u and v components of the wind velocity from the 05Z and 11Z Darwin radiosondes. The average components were then interpolated onto the aircraft altitude and subtracted from the aircraft ground speed components to form a synthesised true airspeed data series. This process represents the largest source of error in synthesising dynamic pressure from the aircraft ground speed since the average of the wind velocity from the 05Z and 11Z Darwin radiosondes may not be a reliable estimate of the ambient wind at the aircraft location. The approximation will hold better for the LIDAR flights in the vicinity of Darwin than for the ferry flights.

Histograms of the difference between measured and synthesised qc and of the difference between air temperature calculated using measured and synthesised qc for flight AE21 are shown in Figure 5.3.

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

-3.0 -2.0 -1.0 0.0 1.0 2.0 3.0

Dynamic Pressure difference (hPa)

Freq

uenc

y

0.00

0.05

0.10

0.15

0.20

0.25

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

Temperature difference (C)

Freq

uenc

y

Figure 5.3: Histograms of the difference between measured and synthesised dynamic pressure and of the difference between air temperature calculated using measured and synthesised dynamic pressure for flight AE21.

There is a bias of 0.6 hPa (synthesised qc greater than measured) in the qc comparison. This is because the average of the 05Z and 11Z winds from the Darwin sondes over-

93

estimates the winds at the aircraft location for this particular flight. The bias in qc leads to a 0.15 C bias in the temperature comparison (synthesised less than observed). 77% of the synthesised qc values are within ±1 hPa of the measured values and 95% of the temperatures calculated with the synthesised qc are within ±0.5 C of the temperature calculated using the measured qc.

5.3 Procedure for Filling Gaps in Data

The loss of the analogue data streams during flights TE01 to AE07 inclusive causes gaps in the static pressure and temperature data. The missing data has been filled with interpolated values using the aircraft altitude from the Novatel GPS and the measured variation of pressure and temperature with altitude.

The repeated halting of the data loggers and the cycling of power in an attempt to restart the loggers and the REMlets resulted in gaps in all data for flights TE01 to AE07. There are 34 such gaps longer than 5 secs: 7 in TE01, 4 in TE02, 2 in AE03, 12 in AE04, 6 in AE06 and 3 in AE07. The duration of the gaps ranges from 29 to 7477 secs.

The first step in filling the gaps in the pressure and temperature data is to fill the gaps in the missing Novatel GPS data.

The OziExplorer programme was used during each flight to provide the mission scientist with a display of the aircraft position overlaid on a map of the Darwin area. To this end, the Novatel GPS data stream was supplied to the display computer in the rear cabin and the position information from this data stream was logged to a file on the display computer by the OziExplorer programme. This provided an independent source of Novatel GPS data for those times when there were gaps in the Novatel data recorded by the aircraft loggers.

For flights TE01 to AE07 inclusive, the OziExplorer track file is read during processing of the aircraft data and the position information in the track file is used to fill the gaps in the position data from the aircraft logger. The OziExplorer track data are conditioned before use by removing duplicate records and converting the UTC time stamp of the OziExplorer data to an equivalent logger time stamp. The aircraft position data from the OziExplorer file are then differentiated in time to provide the aircraft ground speed and track. Data associated with ground speeds less than 5 ms-1 or greater than 150 ms-1 are then rejected before differentiating the ground speed to obtain the aircraft acceleration. Data associated with aircraft accelerations greater in magnitude than ±1 ms-2 are then replaced using linear interpolation. Finally, the aircraft ground speed and vertical velocity component are low-pass filtered with a cut-off frequency of 0.05 Hz.

Gap filling of the Novatel data stream from the aircraft logger was done by inserting the conditioned aircraft latitude, longitude and altitude from the OziExplorer track file into the gaps in the logger data. The continuous aircraft position data was then differentiated to provide the data needed to fill the gaps in the aircraft velocity data stream from the Novatel GPS.

Gaps in the aircraft pitch and roll data from the TANS were filled by linear interpolation between the values immediately before and after the gap. The missing heading data was replaced with the aircraft track data.

94

Once gaps had been removed from the aircraft position data stream, the gaps in the static pressure and temperature were filled by interpolation using the aircraft altitude from the GPS data stream and the measured lapse rates for pressure and temperature. First, the lapse rates were calculated by averaging all good static pressure and temperature data from each flight into 50 m altitude bins and differentiating the results with respect to height. The lapse rates were then interpolated onto the gap-filled aircraft altitude data.

Gaps in the static pressure and temperature data were then filled as follows.

First, an initial value at the start of each gap was found by fitting a quadratic to the last 10 good data points before the beginning of the gap. A similar process was used to find the final value using the first 10 good points after the gap. This was done to reduce the effect of spurious points immediately before or after the gap.

Once the initial and final values had been determined, the altitude change between successive points in the gap was found by differencing the aircraft altitude data. The altitude change was then multiplied by the lapse rates to get the pressure and temperature changes caused by changes in the aircraft altitude during the gap. The values for filling the gaps in pressure and temperature were then obtained by adding the running sum of the changes to the initial values at the start of the gap.

Small differences between the local lapse rate and that calculated from the good data for the entire flight resulted in small differences between the last value interpolated over the gap and the final value as calculated above. These differences seldom exceeded 0.5 C for temperature and 1 hPa for pressure when the gaps occurred while the aircraft was in straight and level flight, see Figure 5.4.

-6

-4

-2

0

2

4

6

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33Gap Index

Ta D

iffer

ence

(C)

0

2000

4000

6000

8000

10000

12000

14000

16000

Alti

tude

rang

e (m

)

Ta difference

ps difference

Altitude range

Figure 5.4: Difference between the last interpolated value and the first good value after the gap for air temperature (black, solid diamonds) and static pressure (black, open triangles). Also plotted is the range in aircraft altitude during the gap (grey, solid squares).

For all cases where the range in aircraft altitude during the gap is less than 200 m (straight and level flight), the average difference in temperature between the last interpolated point and the first good point is 0.05 ± 0.44 C. The average difference in pressure is -0.09 ± 0.64 hPa for the same data. Uncertainties are ± 1σ.

The difference between the last interpolated point and the first good point after the gap is useful because it represents likely error in the interpolated values. However,

95

sudden jumps in the pressure and temperature at the end of the gaps are undesirable. In the final data set, the difference between the last interpolated point of the gap and the first good point after the gap is forced to 0. This is done by calculating the trend in temperature or pressure, as a function of time, from the last good point before the gap to the first good point after the gap and forcing the interpolated values used to fill the gap to follow this trend.

5.4 Noise in Static Pressure and Temperature

The static pressure and temperature data for the 2006 flights (FE16 to AE21, SE24 to FE32) is contaminated by noise. The noise takes the form of a regular dip in both pressure and temperature values. The dips last for approximately 50 to 60 secs and are repeated every 150 to 160 secs. The dips have a magnitude of approximately 0.6 hPa for pressure and 0.25 C for temperature. It is possible that the noise also contaminates other analogue data channels but if this is so, it is not as evident as the contamination of static pressure and temperature.

The noise is not present in the 2005 data nor is it present in the data from the LIDAR flights, LE22 and LE23. It is most likely that the noise is due to a ground loop within the aircraft wiring and that the changes in signal levels are caused by power to an instrument or aircraft heater being cycled on and off.

163.2

163.4

163.6

163.8

164.0

164.2

164.4

164.6

164.8

27000 28000 29000 30000 31000Time (seconds after 00:00 UTC)

Pres

sure

(hPa

)

Static pressure (rejected)

Static pressure (noise)

-64.5

-64.0

-63.5

-63.0

-62.5

-62.0

-61.5

27000 28000 29000 30000 31000Time (seconds after 00:00 UTC)

Tem

pera

ture

(C)

Temperature (rejected)

Temperature (noise)

Figure 5.5: Time series of static pressure (top panel) and temperature (bottom panel) for a straight and level segment of SE24. The data contaminated with the noise is shown with grey lines, data with the noise rejected is shown with black lines.

96

Figure 5.5 shows a time series of static pressure (top panel) and temperature (bottom panel) for a segment of straight and level flight from SE24. Grey lines are data contaminated with the noise and black lines represent data where the noise has been rejected.

The traditional approach of low-pass filtering the data to remove the noise gives undesirable results because of the long duration of the noise dips (50 to 60 secs) compared to their return period (150 to 160 secs). An alternative approach was adopted that first identified the noise dips in the static pressure data, flagged these as unreliable data and then used the same interpolation scheme as described in Section 5.3 to replace the contaminated data.

The noise dips were identified in the static pressure data by high-pass filtering the data with a cut-off frequency of 0.005 Hz, finding all excursions of this high-pass filtered signal below -0.1 hPa and flagging these periods, plus an extra 15 seconds either side, as unreliable data. An interpolation scheme based on the measured lapse rates of pressure and temperature and the aircraft altitude from the GPS was then used to replace the contaminated data. The interpolation scheme is very effective at rejecting the noise contamination but because it affects such a large proportion of the data, both the noise-contaminated and noise-rejected data are included in the final data set to give the user the choice of which data to use. The cautious recommendation of this report is that the noise-rejected static pressure and temperature are the most appropriate data for further analysis. However, it is stressed that the noise-rejected data has not been exhaustively checked and it is left to the user to determine the most appropriate data for their particular application.

5.5 Rosemount Temperature Sensor De-ice Heaters

An initial comparison of the air temperature data from VH-ARA with temperatures from the Darwin radiosonde (see Section 6) showed a large bias of approximately 2 C (VH-ARA temperatures less than sonde data) for flights AE17 to AE21 and SE24. Furthermore, an examination of the data from flight AE25 showed a sudden increase in temperature of approximately 2.3 C during a straight and level flight segment. The temperature rise is roughly exponential in shape and occurs over approximately 100 seconds, a distance of 10 km at the typical true airspeed of VH-ARA. This feature suggests the aircraft flew through a horizontal temperature gradient of 0.23 C per km, which seems unlikely at an altitude of 13 km. The size and shape of this feature are similar to that expected if power were applied to the Rosemount temperature sensor de-ice heaters during flight, see Figure 5.6.

97

-58.5

-58.0

-57.5

-57.0

-56.5

-56.0

-55.5

-55.0

07:50 07:51 07:52 07:53 07:54 07:55UTC

Tem

pera

ture

(C)

12900

12910

12920

12930

12940

12950

Alti

tude

(m)

Temperature

Altitude

Figure 5.6: Time series of temperature (black) and altitude (grey) for the temperature rise feature during a straight and level segment of AE25 described above.

The most plausible explanation for this feature in the temperature data for AE25 is that the power was turned on to the Rosemount temperature sensor de-ice heaters at approximately 07:51:35 UTC. This hypothesis was checked by comparing the temperatures from VH-ARA for AE25 with those from the Darwin radiosondes but without applying the correction for the error caused by the de-ice heaters to data collected before 07:51:35 UTC. Data collected after 07:55:00 is corrected for the error due to the de-ice heaters and data between these two times is replaced with values linearly interpolated between these end points.

Processing the temperature data from VH-ARA for AE25 in this manner reduces the bias in the comparison with the Darwin radiosonde data from 1.6 C to 0.4 C. The reduction of the bias to a value close to 0 supports the hypothesis that power was applied to the de-ice heaters part way through this flight.

The switching of power to the de-ice heaters fitted to the instruments on VH-ARA was done by the mission scientist using a switch in the rear cabin. An indicator light next to the switch illuminated when the heater power was switched on. However, it appears that there was an additional circuit breaker on the power distribution board in the belly of VH-ARA and that this was mistakenly left disconnected for flights AE17 to SE24. In this case, turning the heater power on using the switch in the rear cabin would cause the indicator light to illuminate but would not result in power being applied to the instrument heaters.

The final data set has been processed with the following assumptions. First, the de-ice heaters operated correctly for all flights in 2005. Second, the de-ice heaters did not have power applied to them for flights FE16 to SE24. Third, power was applied to the de-ice heaters part way through AE25. Fourth, the de-ice heaters operated correctly for flights AE26 to FE32.

98

6 Comparison with Other Data 6.1 Darwin Ground-based Data

The aircraft pressure and temperature data has been compared to the Darwin automatic weather station (AWS) to identify any offsets in the aircraft data. The comparison used aircraft data from the take-off and landing roll (ie wheels on the ground) when the aircraft was moving at speeds between 5 and 40 ms-1. These data segments are of short duration, only several seconds, compared to the averaging time of the Darwin AWS data, 30 minutes. This will lead to a large amount of scatter in the comparison but offsets are still expected to be apparent.

-5-4-3-2-10

12345

TE01 AE03 TE05 AE07 AE09 AE11 AE13 AE17 AE19 AE21 AE25 AE27 AE29 TE31

Flight

ps(Y

PDN

) - p

s(AR

A) (h

Pa)

TO

L

Mean

-5-4-3-2-10

12345

TE01 AE03 TE05 AE07 AE09 AE11 AE13 AE17 AE19 AE21 AE25 AE27 AE29 TE31

Flight

Ta(Y

PDN

) - T

a(AR

A) (C

)

TO

L

Mean

Figure 6.1: Difference between the pressure (top panel) and temperature (bottom panel) from the Darwin automatic weather station (YPDN) and VH-ARA (ARA) during the take-off and landing roll of each flight. The dotted line marks the mean difference.

The comparison in Figure 6.1 shows no significant evidence of the offsets changing with time. The average differences from these comparisons, -1.6 hPa for pressure and 0.4 C for temperature, have been subtracted from the aircraft data to remove the observed bias.

99

6.2 Darwin Radiosonde Data

6.2.1 General

A detailed comparison between the temperature, wind speed and wind direction data from VH-ARA and the Darwin radiosondes has been performed for the ascent phase of each flight and for the straight and level segments of each flight. Splitting the comparison into two parts, ascent and level, was done to check the effect of the dependence of aircraft temperature on angle of attack that was observed during the calibration flight (TE31).

For the ascent comparison, the aircraft and radiosonde data were averaged over 10 hPa bins before subtracting the aircraft data from the radiosonde data. The final value plotted is the average of the differences across all of the 10 hPa bins. The number of bins averaged was about 80 for most flights.

For the level flight comparison, the aircraft data were averaged over each straight and level segment before subtracting this from the radiosonde data for the pressure level closest to the aircraft data. The final value plotted is the average of the differences for each of the level segments. The number of level segments was typically 3 or 4 for most flights.

Data from the 05Z and 11Z Darwin radiosondes has been used. The majority of the aircraft flights took place between these times. The difference between the 05Z and 11Z radiosonde data is used to illustrate the temporal variability of the data and to place differences between the aircraft and radiosonde data in context.

6.2.2 Temperature

Figure 6.2 shows the results of the temperature comparison. The average difference over all flights for both the ascent and level data is 0.0 ± 0.8 C. The average difference between the 05Z and 11Z radiosonde data is 0.0 ± 0.9 C. The range and variability of the difference between aircraft and radiosonde data is similar to that between the 05Z and 11Z sonde data.

An initial comparison showed that the aircraft temperatures were 0.6 C lower on average than the Darwin radiosonde data for both the ascent and level data. This is in addition to the 0.4 C offset found between the aircraft and Darwin AWS temperature, which had been applied to the data prior to the initial radiosonde comparison. The total offset for the radiosonde comparison is therefore 1.0 C and this amount has been added to the temperatures from VH-ARA for the final data set.

100

DWN-ARA : Level

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

TE01 AE03 TE05 AE07 AE09 AE11 AE13 FE15 AE17 AE19 AE21 LE23 AE25 AE27 AE29 TE31

Flight

Ta D

iffer

ence

(C)

05Z-ARA

11Z-ARA

05Z-11Z

DWN-ARA : Ascent

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0


Flight

Ta D

iffer

ence

(C)

05Z-ARA

11Z-ARA

05Z-11Z

Figure 6.2: Difference between the temperature measured by the Darwin radiosondes (05Z and 11Z) and VH-ARA for level flight segments (top panel) and for the ascent phase of each flight (bottom panel). The 05Z-ARA difference is plotted as black squares and the 11Z-ARA difference is plotted as grey squares. Also plotted is the difference between the 05Z and 11Z Darwin radiosonde data (grey diamonds and dotted lines). Error bars are one standard deviation about the mean.

The most likely explanation for the additional 0.6 C offset found in the radiosonde comparison is error in the values used for the recovery factor and the de-ice heater correction of the Rosemount 102 temperature sensor. The Rosemount 102 manual gives a range of ±50 % for the recovery factor and ±1 C for the de-ice heater correction for the typical flight conditions during ACTIVE. The observed offset lies within these uncertainties.

6.2.3 Wind speed

Figure 6.3 shows the results of the wind speed comparison. The average difference over all flights for both the ascent and level data is 0.3 ± 2.7 ms-1. The average difference between the 05Z and 11Z Darwin radiosonde data is -0.5 ± 2.7 ms-1.

101

DWN-ARA : Level

-10.0

-8.0

-6.0

-4.0

-2.0

0.0

2.0

4.0

6.0

8.0

10.0


Flight

WS

Diff

eren

ce (m

/s)

05Z-ARA

11Z-ARA

05Z-11Z

DWN-ARA : Ascent

-10.0

-8.0

-6.0

-4.0

-2.0

0.0

2.0

4.0

6.0

8.0

10.0


Flight

WS

Diff

eren

ce (m

/s)

05Z-ARA

11Z-ARA

05Z-11Z

Figure 6.3: Difference between the wind speed measured by the Darwin radiosondes (05Z and 11Z) and VH-ARA for the level flight segment (top panel) and for the ascent phase of each flight (bottom panel). The 05Z-ARA difference is plotted as black squares and the 11Z-ARA difference is plotted as grey squares. Also plotted is the difference between the 05Z and 11Z Darwin radiosonde data (grey diamonds and dotted lines). Error bars are one standard deviation about the mean.

The wind speed comparison shows no significant bias between the aircraft and radiosonde data. This is an important result because the wind speed calculated from the aircraft data is very sensitive to the true airspeed and hence the dynamic pressure. The lack of bias in this comparison provides confirmation of the method used to synthesise the dynamic pressure for those flights when direct measurements were unreliable.

6.2.4 Wind direction

Figure 6.4 shows the results of the wind direction comparison. The average difference over all flights for both the ascent and level data is -2 ± 40 º. The average difference between the 05Z and 11Z Darwin radiosonde data is 2 ± 50 º.

102

DWN-ARA : Level

-100

-80

-60

-40

-20

0

20

40

60

80

100


Flight

WD

Diff

eren

ce (d

eg)

05Z-ARA

11Z-ARA

05Z-11Z

DWN-ARA : Ascent

-100

-80

-60

-40

-20

0

20

40

60

80

100


Flight

WD

Diff

eren

ce (d

eg)

05Z-ARA

11Z-ARA

05Z-11Z

Figure 6.4: Difference between the wind direction measured by the Darwin radiosondes (05Z and 11Z) and VH-ARA for the level flight segment (top panel) and for the ascent phase of each flight (bottom panel). The 05Z-ARA difference is plotted as black squares and the 11Z-ARA difference is plotted as grey squares. Also plotted is the difference between the 05Z and 11Z Darwin radiosonde data (grey diamonds and dotted lines). Error bars are one standard deviation about the mean.

The wind direction comparison shows no significant bias between the aircraft and radiosonde data. The large scatter for level data is due to the nature of the comparison. Values from the aircraft are averages along the level segments of each flight. The level segments were typically of the order of 100 km in length. In contrast, the wind direction from the sonde is an instantaneous measurement as the sonde passes through the same pressure level as the aircraft flight segments.

6.3 Inter-comparison Flights with DCALM

Two inter-comparison flights were performed with VH-ARA and DCALM in close proximity, AE10 and AE30. This section presents the results of inter-comparison, see Figure 6.5.

The close proximity flight for AE10 lasted for 36 minutes and was conducted over Van Diemen Gulf and Dundas Strait at an altitude of 4,500 m. The close proximity flight for AE30 lasted 110 minutes and was conducted over Van Diemen Gulf, Dundas Strait, the Arafura Sea (immediately north of Melville Island) and over Melville Island at altitudes of 3,000, 2,100 and 950 m. It is convenient to group the

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data from both flights together and treat then as a single set of in proximity data for four altitudes: 4,500, 3,000, 2,100 and 950 m.

0 0.2 0.4 0.6 0.8Elapsed Time (HH.hh)

0

5

10

15

20

25

Tem

pera

ture

(C)

ARA DCALM


0

4

8

12

16

Win

d sp

eed

(m/s

)


8012016080

120160

80120160

80120160

Win

d di

rect

ion

(deg

)

4500m

3000m

2100m

950m

950m

2100m4500m

3000m

4500m

3000m

2100m

950m

Figure 6.5: Inter-comparison of temperature, wind speed and wind direction for the in proximity flights of VH-ARA (black) and DCALM (grey) at 4,500, 3,000, 2,100 and 950 m.

The averages of the VH-ARA data and of the difference between the VH-ARA and DCALM data for all altitudes are shown in Table 6.1.

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Altitude Ta C

Ta Diff C

WS ms-1

WS Diff ms-1

WD degrees

WD Diff degrees

4,500 4.0 ± 0.3 1.0 ± 0.1 5.9 ± 0.4 -0.3 ± 0.7 113 ± 12 4 ± 7 3,000 10.2 ± 0.3 1.3 ± 0.1 11.8 ± 0.6 -0.5 ± 0.4 89 ± 4 0 ± 4 2,100 15.7 ± 0.3 1.2 ± 0.1 8.8 ± 0.5 -0.8 ± 0.9 101 ± 4 18 ± 26 950 22.6 ± 0.4 1.2 ± 0.1 3.8 ± 1.1 0.2 ± 0.7 91 ± 25 3 ± 19 Mean 1.2 ± 0.2 -0.3 ± 0.7 5 ± 17

Table 6.1: Average temperature (Ta), wind speed (WS) and wind direction (WD) from VH-ARA and the difference (DCALM-ARA) in temperature (Ta Diff), wind speed (WS Diff) and wind direction (WD Diff) for the in proximity flights at 4,500, 3,000, 2,100 and 950 m. Uncertainties are one standard deviation.

The temperatures measured by DCALM are 1.2 ± 0.2 C higher than those measured by VH-ARA. Comparison of the in proximity data with the Darwin 05Z and 11Z radiosonde data shows that, for this subset of data, the temperatures from DCALM are 0.9 C higher than the Darwin radiosonde values and the temperatures from VH-ARA are 0.3 C lower than the Darwin radiosonde values. The comparison results suggest that the temperatures from DCALM are approximately 1 C too high but a detailed comparison similar to that performed for VH-ARA is needed to confirm this figure.

There is no significant difference between the wind speed and direction data from VH-ARA and DCALM. However, the data plotted in Figure 6.5 has some interesting features. There is a sudden change in both the wind speed and wind direction in the data from DCALM about mid-way through the in proximity flight at 2,100 m. This corresponds to a change in aircraft heading from easterly to southeasterly. The average difference between the aircraft heading data from DCALM and VH-ARA also increases from approximately 0 to about 6 º at this time. There are changes in the aircraft heading during the 4,500, 3,000 and 950 m in proximity flights as well but these do not seem to effect the wind speed and direction from DCALM in the same manner. The intermittent differences between the wind speed and wind direction data from VH-ARA and DCALM suggest that there are still some inconsistencies in the data sets from VH-ARA and DCALM.

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7 Acknowledgments The authors would like to acknowledge the critical role played by Rudi Gaissmaier in preparing VH-ARA before the field campaigns and in maintaining the aircraft under difficult conditions, as well as acting as ground support crew, while the field campaigns were in progress. Sometimes the use of cliches is justified. This work would not have been possible without his unstinting efforts.

We would also like to thank the pilots, Captains Alf Jonas and Gabriel Kalotay, for their contribution to this project. It was a pleasure to fly with them and we would do so again.

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