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HIRDLSSPARC Applications and Development Status

John GilleUniversity of Colorado and NCAR

John BarnettOxford University

Alyn Lambert, David Edwards, Christopher PalmerMichael Dials, Chris Halvorson, Eric Johnson, Wayne Rudolf

Ken Stone, Bob Wells, John Whitney, Douglas Woodard

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HIRDLS Scientific Goals

The primary goals of the High Resolution Dynamics Limb Sounder (HIRDLS) experiment are to acquire data with which to investigate

1) the recovery of the ozone layer following the phase-out of some halogen-containing chemicals;

2) the role of the upper troposphere and lower stratosphere (UT/LS) in climate; and

3) the chemistry of the upper troposphere.

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Recovery of the Ozone Layer

• Stratospheric chlorine is predicted to decrease as a result of the Montreal Protocol and subsequent agreements

• Chlorine abundances are decreasing in the troposphere, and now, in the stratosphere

• The recovery of the ozone layer with decreasing Cl will be complicated by the lower temperatures in the lower stratosphere, due to greenhouse effects as well as the reduction in ozone itself

• HIRDLS, and the Aura spacecraft, will fly during the unique period near the maximum loading of stratospheric chlorine. It will be important to acquire a record of atmospheric composition and behavior during this singular period.

• One of the goals of HIRDLS is to document this period in the atmosphere, and use these data to understand ozone chemistry and radiative effects in this unique period.

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Stratospheric Chlorine

1.0

2.0

3.0

EE

SC

(p

pb

)

1960 1980 2000 2020 2040 2060

CH3Cl

CH3Br(N)

CFCs

CH3CCl3CCl4

HCFCsHalons

CH3Br(A) A3

Growth of stratospheric chlorine according to various scenariosFigure 1

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• The structure and behavior of the atmosphere around the tropopause are now known to be more complex than previously thought.

• Exchange of material between the troposphere and the stratosphere takes place not only through ascent through the tropical tropopause, but also through transports along isentropic surfaces that cross the tropopause. These transports include those of radiatively active (e.g. CO2, H2O, CH4, etc.) and chemically active (N2O, CFC11, CFC12, H2O, etc.) gases that directly or indirectly influence the earth’s radiative balance.

• Many of these transports are on finer scales than have been observed before. In addition, there are other features which lead to the formation of fine scale filaments.

• One of HIRDLS’ goals is to observe these small-scale transports and subsequent mixing, and to clarify their effects in the climate system.

The Role of the UT/LS in Climate

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Transport Features Observed by HIRDLS

Figure 2(from J. Holton/UGAMP)

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Stratosphere-troposphere exchange on small scales

Passive tracers on the 320 K isentrope.Coloured air is stratospheric, blank is tropospheric

Figure 3[From Appenzeller et al. [1995]]

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UT/LS Chemistry

• HIRDLS measurements will extend down into the lower stratosphere and upper troposphere when clouds are not too optically thick.

• Trace species in this region are rapidly transported over long distances.

• HIRDLS will obtain measurements of: O3, H2O, and HNO3, CFC11, CFC12, CH4, N20 and aerosols.

• These data will greatly augment knowledge of composition and transports at these levels.

Temperature <50 km 0.4 K precision 1 K absolute

>50 km 1 K precision 2 K absolute

Constituents O3, H2O, CH4, H2O, HNO3, NO2, N2O5, 1-5% precision

ClONO2, CF2Cl2, CFCl3, Aerosol 5-10% absoluteGeopotential height gradient 20 metres/500 km (vertical/horizontal)(Equivalent 60oN geostrophic wind) (3 m s-1)Coverage:

Horizontal - global 90oS to 90oN (must include polar night)Vertical - upper troposphere to mesopause (8-80 km)Temporal - long-term, continuous (5 years unbroken)

Resolution:Horizontal - profile spacing of 5o latitude x 5o longitude (approx 500 km)Vertical - 1-1.25 km

Temporal - complete field in 12 hours

Summary of Measurement Requirements

The LIMB Scanning Technique

Infrared radiance emitted by the earth’s atmosphere,

seen at the limb, is measured as a function of relative

altitude

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Spectral Locations of the HIRDLS Channels

Figure 5

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Examples of Calculated Radiance Profiles

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Driving Requirements on Accuracy and Precision

Retrieval based on N (h). This leads to the most stringent requirements: Radiance Accuracy 1%

(temperature channels 0.5%), Random noise1-12 x 10-4 Wm-2 sr-1 (channel dependent)

Sample spacing Accuracy 0.25%,random error of 1 arcsec (1 ).

Requirements are divided between - encoder on the scan mirror (motion relative to optical bench), and - gyroscope on the optical bench (motion of bench in inertial space).

HIRDLS Alternative Global Mode Sub-Tangent Point

Figure 6

HIRDLS Boresight Tangent Point Latitudes and Longitudes in the Alternative Global Mode

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HIRDLS Instrument Consists of 9 Subsystems

HIRDLS Instrument Consists of 9 Subsystems

TELESCOPE SUBSYSTEM (TSS)

INSTRUMENT TELESCOPE AND RELATED ELECTRONICS UNITS

SUN-SHIELD SUBSYSTEM (SSH)

STRUCTURAL THERMAL SUBSYSTEM (STH)

PRIMARY STRUCTURAL SUPPORT AND ENVIRONMENTAL ENCLOSURE FOR ELECTRONIC UNITS AND TELESCOPE

GYRO SUBSYSTEM (GSS)

PROVIDES PRECISION BASE MOTION DISTURBANCE DATA

COOLER SUBSYSTEM (CSS)

PROVIDES ACTIVE CRYO-COOLING FOR THE INSTRUMENT DETECTOR ARRAY

POWER SUBSYSTEM (PSS)

PROVIDES BASIC POWER CONVERSION AND SWITCHING

DETECTOR SUBSYSTEM (DSS)

MULTI-CHANNEL INFRARED RADIOMETRIC DETECTOR ARRAY AND DEWAR ASSEMBLY

IN-FLIGHT CALIBRATION SUBSYSTEM (IFC)

OPTICAL ITEMS AND ELECTRONICS TO ENABLE RADIOMETRIC CALIBRATION DURING FLIGHT OPERATIONS.

INSTRUMENT PROCESSING SUBSYSTEM (IPS)

SIGNAL AND DATA PROCESSING TO SUPPORT MISSION SCIENCE OPERATIONS AND HOUSEKEEPING FUNCTIONS

•UK•US

Figure 7

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INSTRUMENT SUBSYSTEMS - EXPLODED VIEWFixed Sunshield

(STH)

Sunshield-Door(SSH)

Space-View ApertureAssembly

(SSH)

Vibration Isolators(TSS)

Power Converter Unit(PSS)

Inst. Processor Unit(IPS)

Signal ProcessingUnit(IPS)

Black Body Assembly(IFC)

Black BodyElectronics Unit

(IFC)

Baseplate(STH)

Cooler Radiator Panelwith Compressors & Displacer

(CSS)

Flexible Vacuum Enclosure(CSS)

Cooler Control Unit(CSS)

S-Link(CSS)

Gyro Mechanical Unit(GSS)

Encoder Electronics Assy.(TSS)

TelescopeElectronics Unit

(TSS)

Detector Dewar(DSS)

Optical Bench Assy.with Shroud

(TSS)

Gyro Electronics Unit(GSS)

External ConnectorBulkhead

LEGENDSTH

SSH

TSS

DSS

GSS

CSS

IFC

PSS

IPS

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Optical SchematicOptical Schematic

ScanMirror

PrimaryMirror

SecondaryMirror

Fold

Ge Lens#1

Ge Lens#2

SystemAperture

Stop

Field Stop #2&

Warm FilterAssembly

Chopper

Radiation Trap

PrimaryDiffraction

Baffle(PDB)

Space ViewRelay Mirror

Space ViewAperture Stop

Space ViewField Stop

SpaceViewPort

In-flightCalibratorBlack Body

DSS

IntermediateLyot Stop

CalibratorMirror

FixedSunshade

LensAssembly

AlbedoShield

SunshieldDoor

FieldStop #1

ChopperMechanical Unit

SunshieldDoor

Aperture

"Hot Dog"Aperture

Out-of-Field Baffle

TelescopeSubsystem

Structural Ther-mal Subsystem

Cold FilterAssembly

Figure 8

18Figure 9

19Figure 10

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Structure Thermal Subsystem Status

Dummy MLI on Flight Structure in MMS Clean Room

Figure 11

21Monochromator turretSeismic isolator

Clean room and vacuum chamber Chamber optical bench

HIRDLS Calibration Facility

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True Temperature WaveTrue Temperature Wave Retrieved Temperature WaveRetrieved Temperature Wave

Verification of 1 KM Resolution

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.

PRECISIONMIXINGRATIO

(%)TEMP

(K)

1 .25

3 .5

5 1.

10

15

20

40

60

80

TEMP

O3

H O2

CH4

N O2

NO2

N O2 5

HNO3

CFCl3

CF Cl2 2Aerosol

PSC

CloudTops

HIRDLS CAPABILITIES

Effects

LocationsNO2ClO

Figure 12

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Summary

• HIRDLS is a powerful and flexible instrument for the global measurement from the upper troposphere into the mesosphere of

Temperature, 10 trace species and aerosols

• New features are:

– Fine spacing of measured profiles in the longitudinal direction (<500km)

– High vertical resolution (<2 km vertical wavelength)

– Ability to sound the upper troposphere and low stratosphere (UT/LS) regions

– Measurement of many species with a range of chemical lifetimes

– 5-6 year instrument life

• Standard data will provide long-term detailed data and important insights into:

– Evolution of the ozone layer

– Climate processes, especially in the tropopause region

– Upper troposphere chemistry

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Additional information on HIRDLS can be found at the HIRDLS website,

http://www.eos.ucar.edu/hirdls/home.html.