DOT/FAA/NR-92/4

Project ReportATC-188

The Terminal Doppler Weather Radar (TDWR)

Moving Target Simulator (MTS)at Orlando, Florida

W. H. Drury

J. M. Frankovich

20 August 1992

Lincoln Laboratory MASSACHUSETTS INSTITUTE OF TECHNOLOGY

LEXINGTON, MASSACHUSETTS

Prepared for the Federal Aviation Administration, Washington, D.C. 20591

This document is available to the public through

the National Technical Information Service, Springfield, VA 22161

This document is disseminated under the sponsorship of the Department of Transportation in the interest of information exchange. The United States Government assumes no liability for its contents or use thereof.

TECHNICAL REPORT STANDARD TITLE PAGE

1. Report No. 2. Government Accession No. 3. Recipient's Catalog No.

ATe-188 DOTIFAAlNR-92/4

4. Title and Subtitle 5. Report DateThe Terminal Doppler Weather Radar (TDWR) Moving Target 20 Au~st 1992

Simulator (MTS) at Orlando, Florida 6. Performing Organization Code

7. Author(s) 8. Performing Organization Report No.

William H. Drury, John M. Frankovich ATC-188

9. Performing Organization Name and Address 10. Work Unit No. (TRAIS)

Lincoln Laboratory, MITP.O. Box 73 11. Contract or Grant No.Lexington, MA 02173-9108 DTFA-0 1-89-Z-02033

12. Sponsoring Agency Name and Address 13. Type of Report and Period CoveredDepartment of Transportation Project ReportFederal Aviation AdministrationSystems Research and Development Service 14. Sponsoring Agency CodeWashington, DC 20591

15. Supplementary Notes

This report is based on studies performed at Lincoln Laboratory, a center for research operated by Massachusetts Institute ofTechnology under Air Force Contract FI9628-90-C-0002.

16. Abstract

Monitoring the performance of Doppler weather radars presents special problems since target returns cannot beverified by reference to other systems (e.g., as ASR-9 aircraft reports can be compared with beacon replies). TheTerminal Doppler Weather Radar (TDWR) system includes a Moving Target Simulator (MTS) which provides a pointtarget equivalent to a 50 dBZ reflectivity weather return with an apparent radial velocity of 5 mis.

This report describes the installation and initial operational results for a prototype MTS using the TDWR testbedradar in Orlando, FL. Procedures were developed for improved aiming of the MTS, using azimuth and elevationadjustments, which are recommended to be incorporated in the production MTS installation procedure. Initial dataanalyses indicate that the MTS returns from a typical radio tower would be useful for integrity monitoring in fair weatherusing typical TDWR filters. The use of the MTS when high-reflectivity weather or anomalous propagation (AP) is presentneeds further study.

17. Key Words 18. Distribution Statement

Moving Target Simulators (MTS) TDWRThis document is available to the public through the

Lucas Aerospace Bell SouthNational Technical Information Service,

Raytheon OrlandoSpringfield, VA 22161.

19. Security Class if. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price

Unclassified Unclassified 35

FORM DOT F 1700.7 (8-72) Reproduction of completed page authorized

ABSTRACT

Monitoring the performance of Doppler weather radars presents special problemssince target returns cannot be verified by reference to other systems (e.g., as ASR-9aircraft reports can be compared with beacon replies). The Terminal Doppler WeatherRadar (TDWR) system includes a Moving Target Simulator (MTS) which provides apoint target equivalent to a 50 dBZ reflectivity weather return with an apparent radialvelocity of 5 m/s.

This report describes the installation and initial operational results for a prototypeMTS using the TDWR testbed radar in Orlando, FL. Procedures were developed forimproved aiming of the MTS, using azimuth and elevation adjustments, which arerecommended to be incorporated in the production MTS installation procedure. Initialdata analyses indicate that the MTS returns from a typical radio tower would be useful forintegrity monitoring in fair weather using typical TDWR filters. The use of the MTSwhen high-reflectivity weather or anomalous propagation (AP) is present needs furtherstudy.

iii

ACKNOWLEDGMENTS

The authors would like to express appreciation to Lucas Aerospace and Raytheon fortheir help in obtaining the prototype unit of the MTS for use by Lincoln Laboratory. Theauthors also would like to thank Skip Copeland for his work with Bell South Mobility toobtain a lease for space on their tower in Taft, Florida and a subcontract for the MTSinstallation. Maurice Couture developed the modifications for the addition of an opticaltelescope and for adjusting the elevation of the MTS on the tower. Nat Fischer, MarkIsaminger, Ben Stevens, Sen Lee, and Leonie Henshaw provided valuable help incollecting and analyzing the MTS data.

v

TABLE OF CONTENTS

SectiOD

Abstract

Acknowledgments

List of Illustrations

1. TIlE lDWR MOVING TARGET SIMULATOR AT ORLANDO

A. Introduction

B. Installation in Orlando

C. Processing MTS Returns

1. Initial Results

MCO Control Tower

Bell South Tower

2. Parametric Effects

D. Conclusions

LIST OF ABBREVIATIONS

Vll

iii

v

ix

1

1

2

6

6

6

7

7

23

25

LIST OF ILLUSTRATIONS

Fia:ure

1. Schematic of moving target simulator assembly.

2. Modifications being made to adjust the elevation angleof the antenna.

3. MTS mounting bracket, vertical portion.

4. Aluminum bracket, 1 of 4.

5. MTS being hoisted to the 170-foot-high tower.

6. MTS on tower.

7. SP SOP plots of Bell South tower.

8. PSP A-scope plot of Bell South tower. Signal power in rangewith antenna pointing at MTS.

9. MTS reflectivity PPI scan.

10. MTS velocity PPI scan.

11. MTS reflectivity RHI scan.

12. MTS velocity RHI scan.

13. Status monitor display.

14. MTS PPI scan data [(gate 81) three-degree elevation,1114 PRF, five degree per second scan rate)].

15. MTS PPI scan data - expanded.

16. MTS PPI spectral data.

IX

1

34

5

5

6

8

10

13

15

17

19

21

21

22

22

1. THE TDWR MOVING TARGET SIMULATOR AT ORLANDO

A. Introduction

The Moving Target Simulator (MTS) is a test target mounted on a local tower suchthat the Tenninal Doppler Weather Radar (TDWR) scans past it at least once per volumescan (five minutes). It is positioned from 2 to 20 kilometers from the radar, andpreferably in the hazardous weather coverage sector.

The MTS (figure 1) consists of a 36-inch diameter antenna with a small boxcontaining microwave and electronic circuitry mounted behind it. The antennabeamwidth of the MTS antenna is three degrees. The only active (power consuming)component in the box is a digital phase shifter used for frequency translation. Thetransmitted C-band pulse from the TDWR is received, translated upwards in frequency by187 Hz, attenuated to a predetermined threshold, and then re-radiated back to the radar.The attenuator is normally adjusted to provide a return signal equivalent to a 50 dBZreflectivity at the TDWR site. The frequency translation causes the return at the TDWRto appear as a target moving away from the radar with a velocity of 5 meters per second(rn/s).

MTS ASSEMBLYWEIGHT: 55 1bsPOWER RF.QU: 10 watts

u5 VAC

36"

Fini8h: In accordance with KIL-F-I4072. paintedwith TT-E-489. high gl088 aviation white117875 in accordance with FED-STD-595.

Figure 1. Schematic ofmoving target simulator assembly (drawing by Lucas Aerospace.Hopkinton. MA).

1

The MTS unit weighs 55 pounds and consumes 10 watts at 115 volts AC. Themanufacturer is Lucas Aerospace of Hopkinton, MA. The unit under test at Orlando isthe prototype version of the units that Lucas is supplying to Raytheon for installation atall the TDWR sites. This unit is identical to the production units in all respects except forthe arrangement and certification of some of the components in the electronics box.

Radar meteorologists currently evaluate the integrity of a Doppler radar (i.e.,NEXRAD) by observing the return from "clear air"· in the presence of a known uniformwind field. In an unmanned system such as TDWR, this subjective evaluation is notpractical. The MTS will verify radar transmitted power to within ±1 dB and velocityprocessing to within ±1 mis, provided that the MTS return is at least 10 dB greater thanthe radar return from the tower on which it is mounted and that there is no significantweather occurring along the path between the TDWR and the MTS or at second tripreturn distances.

The proposed algorithm for use of the MTS selects and evaluates the frequencytranslated return from the device whenever the TDWR antenna scans past it. Anadditional internal test procedure at the TDWR verifies the integrity of the entire radarsystem, with the exception of the waveguide and antenna assemblies, by using built-inhardware test capabilities. (A sample of the transmitted pulse is delayed for severalmicroseconds and then injected into the receiver for evaluation.) Although the MTSalgorithm provides a test of the complete system, it is subject to local meteorologicalconditions and can on occasion give a false indication of failure. Therefore, a failurealarm will be given only when both the internal test signal and the MTS so indicate.

B. Installation in Orlando

An initial temporary installation of the MTS was made on the air traffic control towerat the Orlando International Airport (MeG) in order to check out the mounting andoperational procedures. Two modifications to the MTS were necessary in order tocomplete this installation and test. To aim the antenna accurately, an optical telescopewas mounted on a section of channel stock bolted to the electronics package. Afteradjustment, the channel stock was left in place and the telescope removed. It was alsonoted that the elevation adjustment was very difficult because of static friction. This wasovercome by adding a lead screw in the elevation adjustment hardware such that theadjustment could be made smoothly. Both of these modifications can be seen in figure 2.The end of the screw appears just behind the channel bar. It is strongly suggested thatthese two modifications be applied to all production MTS units.

The vertical component of the MTS mounting bracket is shown in figure 3. Note thatthere are four holes for attaching hardware, permitting attachment to either a horizontal orvertical member. Figure 4 shows an aluminum bracket (l of 4) fabricated by LincolnLaboratory. When used in pairs, these brackets will accommodate a round towerstructure component between three and five inches in diameter. Figure 2 shows theposition of the upper pair of brackets. In this photo, the lower set has not yet beenmounted.

• "Clear air" is defined subjectively as containing no perceptible contaminants.

2

Figure 2. Modifications being made to adjust the elevation angle olthe antenna.

The fmal operational installation was accomplished on 2 December 1991. The MTSwas bolted to a Rohn self-supporting tower owned by Bell South Mobility in north Taft,Florida. This tower is located approximately 6 Ian west of Mea and 11 km northwest ofthe TDWR site. The MTS was lifted to the 170-foot level on the tower where it wasbolted to one of the upright legs of the structure. Figure 5 shows this process, and figure6 shows the MTS being bolted in place. After aiming, the telescope was again removedand a power cord was connected. A surge protector made by Transtector was installedbetween the power plug and the utility outlet at the base of the tower

The MTS is located exactly at an azimuth of 339.7 degrees from the TDWR. Theradar feedhom is 137 feet above mean sea level (AMSL), the MTS is 265 feet AMSL,and the distance between them (range) is 11.075 kilometers. Using a 4/3 earthapproximation at that distance reduces the apparent height of the MTS to 240 feet AMSL.The radar thus must point at an elevation angle of 0.16 degrees to center the radiatedbeam on the MTS.

3

18.00~

~ 1 I~ 0.18A

11.12 60°

f-r 8.50 M0.50-

I II I

-$-----------Ef)-

VI I.... I I ..otII I,.. I ~

"'Il...otI

--~ R - - f-----r-------------1---~r 1.00

• I I

B=r -~-7'~f-- -- f- - -1-- ---- ---- -+-----1 6.000 8.00

t ~---I I

~ ----L-------------J---f--- ....

/ ; 3.00..... r ..otI

I t I~ I I • "'Il1/4 V ....., I I I I

-r-$--r---------Ef)- .OPANDRFACE ~ I I I

~I . I ISEE NOTE 6

J t2PLCS. THIS SIDE - 1.00 TYP f;:;'"0~

2.00 TYP ~~

5.500 1.50 -

NO WELD TeoTIOMSU

Figure 3. MTS mounting bracket. vertical portion (drawing by Lucas Aerospace. Hopkinton. MA).

k 6" >II I I f I.1

__ 1__ L_

I - - +- - -' -I __ ..., __ ...1-_

I 1---- -4- - 2t"I __ L __ I_

I I

1I II I

I

i 0 .E[r/I

1

7t" ----------~Figure 4. Aluminum bracket. 1 of4.

5/8"hole

Figure 5. MTS being hoisted to the 170{00t-high tower.

5

------------

Figure 6. MTS on tower.

C. Processing MTS Returns

1. Initial Results

MCO Control Tower

The attenuator in the MTS was adjusted for minimum attenuation in order to have asstrong a return as possible for test purposes. (In the final configuration, the MTSadjustable attenuator should have enough range to provide an equivalent 50 dBZ targetreturn at the lDWR when the MTS is located at any range between 2 km and 20 km.)With the TDWR antenna pointed directly at the MTS (spotlighted), a spectral analysis ofthe returned signal was performed using a fast Fourier transform software package,known as the Single Gate Processor (SGP) program, that runs on the original FL-2C SPand DAA computers. The return from the MTS appeared as a five-meter-per-second

6

moving target, as expected, but the return from the control tower was some 20 dB higherthan that from the MTS. Therefore, when scanning the IDWR antenna past the MTS, thetower return completely masked the return from the MTS, and the antenna scanningportion of the test was not possible while the MTS was mounted on the Mea controltower.

BeU South Tower

Before installation of the MTS the IDWR return from the Bell South Tower wasmeasured at approximately 30 dB lower than the return from the Mea control tower.With the minimal setting of the MTS attenuator and a range of about 11 kIn, the MTSreturn was expected to be 5.1 dB stronger than the 50 dBZ expected at 20 kIn. In actualfact, the MTS return is almost evenly split between two range bins in the receiverdigitizing system, causing each bin to present a return that is 3 dB lower than would beexpected if the return were centered in a single bin. The result is that the reflectivityreturn seen by the radar is between 52 and 53 dBZ, with zero attenuation inserted fromthe internal attenuator.

2. Parametric Effects

The four photos in figure 7 are outputs from the SGP program with the antenna pointingat the MTS at the Taft site. Figure 7 (a) is the return from the Bell South tower beforeinstallation of the MTS, and 7 (b) is the same signal processed through a clutter rejectionfilter. Figure 7 (c) is the return from the MTS and the tower combination, while figure7 (d) is the same signal processed through a clutter filter.

Additional results are shown on the plots in figure 8 using an A-Scope presentationprogram that runs in the new Programmable Signal Processor (PSP). Figure 8 (a) is thesignal power in range with the antenna pointing at the MTS. The target return straddlesgates 81 and 82. Figure 8 (b) is the same return calibrated in dBZ, while figure 8 (c) isthe velocity in meters per second. The PRF in these measurements is approximately1000, and the antenna elevation is 0.2 degrees. No clutter filter was used in thisprocessing. Since the reflectivity of the radio tower is close to that of the MTS return, thepulse-pair processing yielded a velocity value of about 4 mls.

There are two real-time indications from the pulse-pair processed moment data thatboth the radar and the MTS are working properly when the IDWR antenna scans past theMTS. The first is when the color displays are adjusted for moderate resolution(5 dB/color in reflectivity and 2 dB/color in velocity) and the clutter filters are enabled.The MTS then shows up in both the reflectivity and velocity presentations each time theantenna scans past it. Figures 9 and 10 are examples of these presentations in PPI mode,and figures 11 and 12 in RHI mode. The PPI scan at 0.3 degrees elevation and the RHI at339.6 degrees azimuth are intended to produce maximum values. The reflectivity appearsas 55-60 dBZ and the velocity as 4-6 m/s due to quantization effects.

The second real-time output is a report on one of the status screens each time theMTS is viewed by the radar. Figure 13 shows these reports for a scan strategy thatconsists of alternating PPI scans at 0.3 degrees and 0.5 degrees on a clear day. Note thatthe reflectivity (DZ) and velocity (V) are extremely consistent for each elevation. At anelevation of 0.3 degrees the MTS return is between 52 and 53 dBZ.

7

+SOdBZ

-40 dBZ

+16 MIS o

(a) UnfilteredTower alone

-16 MIS

+SOdBZ

-40 dBZ

+16 MIS o(b) FilteredTower alone

-16 MIS

Figure 7. SP SGP plots ofBell South tower.

8

+70dBZ

-20 dBZ

+10 MIS o -10 MIS

+70dBZ

-20 dBZ

(c) UnfilteredTower plus MTS

+10 MIS o -10 MIS

(d) FilteredTower plus MTS

Figure 7. (Continued)

9

Using various scan rates and PRFs, raw I and Q data were collected from the analog­to-digital converters for analysis at several elevations during antenna scans past the MTS.Figures 14 through 16 show plots of some of this data when the scan rate of the antennawas 5 degrees per second and the PRF was 1114. Figure 14 is the signal power of thereturn in range gate 81 over a 20-degree scan past the MTS, and figure 15 is an expandedview, four degrees wide, that is centered on the target. The MTS modulation can be seenclearly even when the FL-2C antenna is several degrees off from the MTS, whenever theambient signal is more than 60 dB below the principal peale This presumably reflects thesidelobe response of the IDWR antenna. In figure 16 a spectral analysis of a single one­second data window centered on the MTS shows the peak: in the MTS return at 187 Hz,along with the DC return from the Bell South tower and surrounding stationary objects.The MTS return is about 5 dB lower than these zero velocity returns.

()( AKisX VAKisX Format) (DEFAULTS)(SINGLE)®(HALT)(CLEAR)~(WRITE)~~(QUIT)

Al 339.6 EI 0.2 Radial 2995 Time 15:30:05 PRF 1000.,. ,

100.0 I • I I I f I I I

-------~-------~-------~-------~-------~-------~------ •• -------.----_.- ••• ---- +------- ----.--I I I I I • I I II • I I I I I I I I

• I I I I t I I • I90.0 I I • • • I I t I I

-------~-------~-------~--- --- - ----~-------.-------.-------.-------.---- - +------- -------• I t I II I 1 I'I I. I I

• I I 'I I I-~-- -- ~--- ---~--- r-------.-------.-------.-- _, ,, ,, ,

(a) Range(gate, km)

Figure 8. PSP A-scope plot ofBell South tower. Signal power in range with antenna pointing at MTS.

10

(XAxisXVAXISX Format) (OEFAULTS)(SINGLE)®( HAlT)( CLEAR)~(\lIRITE)@®~~

Az 339.6 EI 0.2 Ra.dlal 4263 Time 15:32:12 PRF 1000,,,

~~~----~-------~-------}-------~-------~-------~-------f-------~-------~-------~-------~-------I I , I I I I I I'

, I I I I t I I I'I I I I I I I I • I

~~~----~-------~-------~-------~-------~-------~-------:------_:------_.----- :-------._------

t-------t-------. .. ,

-- -------.-------

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-----~-------._-, ,, ,, ,, ,, . ,.. -----r-------r-------r--, , .

------.-------.-------.---, , ,7 :75 :839 '10 2 '11 4

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-- -------r-------,,,, ,---~-------.-------.-------.-------._------.-------, "I I

:V :~ :n :~ :~ :~'14 '27 '39 '52 '64 '77

,,, , ,40 O· I I

-~-----~_._----~-------;--, , ,, , ., , ,~~~----~-------~-------~--

-~~o _,,'8'02

Range (gate, km)

(b) Return signal calibrated in dBZ.

(x AxisXVAxisX Format) (OEFAUlTS)(SINGLE)®( HAlT)(CLEAR)~(\lIRITE)~~~

Az 339.6 EI 0.2 Radial 5765 Time 15:34:42 PRF 1000

9.0: : , : • : : I • : •

-------r-------r-------r-------r-------r-------r-------~-------~-------~-------~-------T-----8 I • , • I I • • I I I

-----r-------r-------r-------r-------r-------r-------r-------r-------r-------r-------r----7 • I , I I • I I I I

-----~-------~-------~-------~-------~-------~-------t------ ~-------~-------~-------~----I I • I I I • I 1 I I

-----~-------~-------~-------~-------~-------~-------.------, -------.-------.-------.----I • I • I • tI • I I • I' ., I-----r-------r-------r-------r-------r-------r-------T------. -------T-------T-------T---- -• , I • I • t I I I

-----~-------~-------~-------}-------~-------}-------t------ -------t-------f-------f----I I I I , I I • I I

--~-------~-------~-------~-------~-------~-------~------ ------_._-----_._------~----

L~ _ --~-------~-------~-------~- ~-------~-------i---___ _ ~-------~-------~-----.~-- --~-------~-------~-------~-------~-------~-------~----- - -------f-------~-------~----"~--- ' , -~- -.~'-----.,!_-_J .~.------'-/_l,--1.0: • • : ~ : I • I

-------~-------~-------~-------~-------~-------~-------.-------. ------.---- - .-------.--------2.0: : : : : : : : :-------r-------r-------r-------r-------r-------r-------T-------y-------T---- - ~-------T--------3.0 I , I , , I I I , I I

~:~~~~~t~~~~~~~t~~~~~~~t~~~~~~~t~~~~~~~t~~~~~~~t~~~~~~~t~~~~~~~t~~~~~~~t~~~~JJ t~~~~~~~t~~~~~~~~.o: : : : : : : : : : :-------p-------p-------p-------p-------p-------p-------.-------.-------.-------.-------.--------6.0: : : : : : : : : : :-------r-------r-------r-------r-------r-------r-------T-------T-------T-------T-------T--------7.0' , , • t • I , I • I

-------~-------~-------~-------~-------~-------~-------t-------t-------~-------~-------t--------e.O' • t I I I • I I • ,

-------~-------~-------.-------.-------~-------~-------.-------.-------.-------.-------.--------9.0: : : : : : : : : : :. ---- --~.;--- _.~- ----:;-;; --- -- ~~~ -- ---~f; --. --~. ----~----':r;,- ----~~; ----~;_... =rf; -_ ..

Range (gate, km)

(c) Velocity in meters per second.

Figure 8. (Continued)

11

ti.e: 91/12/02 16:58:10 .3 degrees330

..

bad

Figure 9. MTS reflectivity PPI scan.

•

ti.e: 91/12/02 16:58:10 .3 degrees330

Figure 10. MTS velocity PPI scan.

.....-....J

MTS

bad 5 dllZ 10 dBZ 15 dBZ 20 dBZ 30 dBZ 3S dBZ 40 dBZ 4S dBZ 50 dBZ SS dBZ 60 dBZ 6S dBZ

Figure 11. MTS reflectivity RHI scan.

•

MTS

bad

Figure 12. MTS velocity RHI scan.

09:30:24 BASEDATA: (MTS_XRAD) MTS report: AZ=339.5 EL= 0.3 DZ= 52.5 V= -5.009:30:25 BASEDATA: (MTS_XRAD) MTS report: AZ=339.5 EL= 0.5 DZ= 46.0 V= -5.009:30:27 BASEDATA: (MTS_XRAD) MTS report: AZ=339.5 EL= 0.3 DZ= 52.5 V= -5.109:30:37 BASEDATA: (MTS_XRAD) MTS report: AZ=339.5 EL= 0.5 DZ= 45.5 V= -5.009:30:41 BASEDATA: (MTS_XRAD) MTS report: AZ=339.5 EL= 0.3 DZ= 52.5 V= -5.009:30:53 BASEDATA: (MTS_XRAD) MTS report: AZ=339.5 EL= 0.5 DZ= 46.0 V= -5.009:30:57 BASEDATA: (MTS_XRAD) MTS report: AZ=339.5 EL= 0.3 DZ= 52.0 V= -5.109:31:08 BASEDATA: (MTS_XRAD) MTS report: AZ=339.5 EL= 0.5 DZ= 45.5 V= -5.009:31:13 BASEDATA: (MTS_XRAD) MTS report: AZ=339.5 EL= 0.3 DZ= 52.5 V= -5.009:31:24 BASEDATA: (MTS_XRAD) MTS report: AZ=339.5 EL= 0.5 DZ= 45.5 V= -5.009:31:28 BASEDATA: (MTS_XRAD) MTS report: AZ=339.5 EL= 0.3 DZ= 52.5 V= -5.109:31:40 BASEDATA: (MTS_XRAD) MTS report: AZ=339.5 EL= 0.5 DZ= 45.5 V= -5.009:31:44 BASEDATA: (MTS_XRAD) MTS report: AZ=339.5 EL= 0.3 DZ= 52.0 V= -5.009:31:56 BASEDATA: (MTS_XRAD) MTS report: AZ=339.5 EL= 0.5 DZ= 46.0 V= -5.009:32:00 BASEDATA: (MTS_XRAD) MTS report: AZ=339.5 EL= 0.3 DZ= 52.5 V= -5.109:32:11 BASEDATA: (MTS_XRAD) MTS report: AZ=339.5 EL= 0.5 DZ= 46.0 V= -5.0

Figure 13. SttUUS monitor display.

208027·1

80

60

40iii'~II: 20w

~ 0Q...Jc:( -20ZC)

en -40

--60

-80

MTS1114s.003

-100332.5 335 337.5 340 342.5 345 347.5 350 352.5

AZIMUTH (deg)

Figure 14. MTS PPI scan data [(gate 81) three-degree elevation. 1114 PRF,five degree per secondscan rate)].

21

I I I I I I I I

208027-3

I

-60 -

-80 - MTS1114s.003

-

--100 I

337 337.5

I

338

I I

338.5 339

I

339.5

I I

340 340.5

I

341

I

341.5 342

120

AZIMUTH (deg)

Figure 15. MTS PPI scan data - expanded.

208027-2

100

iii"~ 80a:w::o 60Q.

40

20

MTS1114s.003 SPECTRUM

o-600 -500 --400 -300 -200 -1 00 0 100 200 300 400 500 600

FREQUENCY (Hz)

Figure 16. MTS PPI spectral data.

22

•

D. Conclusions

The MTS prototype unit produces a radar return that simulates a target moving awayfrom the radar at a rate of 5 m/s when there is a clear weather path between the TDWRand the MTS. The specifications require that the return can be adjusted at the MTS toproduce a 50 dBZ return at any range between 2 km and 20 km. In order to meet thisspecification, the prototype unit should have been able to produce a 55 dBZ return withthe attenuator adjusted to zero at the 11.2 km range. This unit produced somewhat lessthan 53 dBZ, indicating that either the MTS had excess loss or that the TDWR testbedwas out of calibration. Further tests will be conducted to resolve the issue.

As configured, the MTS gave accurate returns when the size of the mounting towerwas considered. The unit has shown excellent reliability and stability. A series ofalgorithms will be tested to determine if the MTS return can be used to provideinformation concerning the weather conditions along the propagation path or at the MTSposition.

23

AMSLAPDAADZIandQMeaMTSPPIPRFPSPRHISGPSPTDWRV

LIST OF ABBREVIATIONS

Above Mean Sea LevelAnomalous PropagationData Acquisition and AnalysisReflectivityIn Phase and QuadratureOrlando International AirportMoving Target SimulatorPlan Position IndicatorPulse Repetition FrequencyProgrammable Signal ProcessorRange Height IndicatorSingle-Gate ProcessorSignal ProcessorTerminal Doppler Weather RadarVelocity

25