range instrumentation radars

I. Introduction

Range Instrumentation Radars

JOSH T. NESSMITH, Senior Member, IEEERCA Government Systems DivisionMoorestown, NJ 08057

Abstract

The history of range instrumentation radars begins at the end of

World War 11, with the SCR-584 radar. Since then, the use of in-

strumentation radars on ranges all over the globe has expanded

greatly to gather metric performance data on aircraft, projectiles,

missiles, and satellites.

In this paper, key subsystem-level and system-level developments

during the past decade are reviewed, including pulse-Doppler, digital

range systems, calibration techniques, computer usage, and dual-

frequency systems. Recently developed instrumentation radars

from domestic and foreign sources are described as are three unique

high-power large-aperture systems used for satellite and ballistic-

missile measurements. The paper concludes by examining the likely

requirements for instrumentation radars of the future.

Range instrumentation radars are the prime source ofmetric data for both noncooperative and cooperative targetson the world ranges [1] . In general, these radars are de-ployed over geographic areas configured for the support ofresearch, development, test, and evaluation of space andweapon systems and components. In the United States,most radars are on national ranges that are designed to sup-port the test needs of a wide variety of users. Much thesame type of range can be found in other countries. Radarssupporting such ranges may be at remote locations such as1) Ascension Island to support the Eastern Test Range, 2)Africa and Australia to support NASA missions, 3) KwajaleinAtoll to support both the Kwajalein Missile Range and theSpace and Missile Test Center's Western Test Range, or 4)shipborne to support missions at any range. An idea of theglobal dispersal of range instrumentation radars currentlyin use can be gleaned from Fig. 1I

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Manuscript received May 13, 1976; revised August 23, 1976. Copy-right 1976 by The Institute of Electrical and Electronics Engineers,Inc.

This paper was presented at ELECTRO '76, Boston, Mass., May11-14. A version of it appears in the ELECTRO '76 ProfessionalProgranm

In 1961 Barton [2] reviewed the steps from the WorldWar II SCR-584 through the AN/FPS-16 and indicated thecharacteristics expected in the AN/FPQ-6 (Fig. 2). In addi-tion he discussed the pros and cons of pulse radar for instru-mentation as well as performance and sources of error. Alsocovered were technology areas under development thatappeared to offer a potential for performance improvement,including pulse-Doppler and digital ranging systems. In1963 he reviewed improvements that had been made inrange and accuracy, including the techniques that offereda basis for growth in the next decade [31 .

The content of these two papers is still pertinent; yetmuch progress has been made in the meantime. This paperbriefly reviews that progress.

IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS VOL. AES-12, NO. 6 NOVEMBER 1976756

I. Key Radar Developments

Although there have been many developments at thecomponent level in range instrumentation radars, this paperaddresses only those key system-level developments thatthe author feels have enhanced the ability to obtain accuratemetric data. The reader interested in tracking-radar tech-niques at the component level is referred to Dunn et al. [4].

A. Pulse Doppler

The use of pulse Doppler in instrumentation radarsstarted with demonstrations on the AN/FPS-16 (XN-3) in1958. The first operational use was with the TRADEX [5]radar in 1962 for Doppler resolution. It was designed toseparate closely spaced targets (spaced within 1 jus in rangeresolution) whose Doppler velocity difference was greaterthan 5 ft/s. The tracking loops for the three monopulsechannels were closed through the fine-line Doppler-trackingfilters in each loop. It also provided a highly precise mea-surement of radial velocity-approaching 0.03 ft/s for aballistic path and 1 ft/s for an accelerating target. Otherrange instrumentation radars were modified for this latterpurpose, and the change became known as the coherentsignal processor (CSP) modification. The tracking loopsfor the monopulse channels were closed through the gross-spectrum receiver in normal fashion without the use of fine-line filters. Results of using the CSP on satellites are dis-cussed in Section I1-C. Results for ICBM tracking are givenin [6].

Mitchell et al. [7] and Sparks and Stevens [8] have re-ported in detail on the design and performance of such apulse-Doppler system to be used for tracking in the presenceof ground clutter. One of the specific problems they ex-amined involved automatic detection, acquisition, and trackof a high-speed artillery projectile in the presence of groundclutter. A goal was established to complete the detectionand acquisition process in less than 1 s. The radar had toacquire a signal 30 dB below the clutter and once acquired,track at a signal-to-clutter ratio of -37 dB.

The implementation was a modification of an AN/MPS-36 radar, whose measured precision in angle was better than0.1 mil rms and whose measured precision in range was 3yd rms-with a 20-dB signal-to-noise ratio. The Dopplerprecision was measured as 0.1 ft/s rms. The system modifi-cations included:

1) Filter the in-phase (I) and quadrature (Q) componentsof the received signal with a recursive digital bandpass filterto remove most clutter information-essentially a movingtarget indicator (MTI) operation.

2) Perform a fast Fourier transform (FFT) on the filteredI and Q information in order to detect the target.

3) Add tracking receivers with multiple-pole fine-linefilters for the angle and range channels, clutter guard gates,and automatic pulse repetition frequency (PRF) switching-all in order to acquire and skin-track unambiguously in thepresence of clutter.

Fig. 2. AN/FPS-16 (XN-1) with AN/FPQ-6 in background. Afterthis photograph was taken the original AN/FPS-16 was transferred .to NRL Chesapeake Bay Annex where it is still in service. TheAN/FPQ-6, built 14 years ago, is still the standard for radar angularprecision. (Courtesy RCA)

4) Use the radar computer to achieve automatic designa-tion, detection, acquisition, and mode changes in order tomeet reaction times.

In tests of the radar, 19 projectiles were fired and 18 wereautomatically acquired and tracked despite signal-to-clutterratios ranging from -20 to -35 dB.

B. Digital Range Systems

The evolution from the electromechanical range systemsof yesteryear to today's digital range tracker has been amajor step in eliminating cyclic errors caused by resolversand gears in the electromechanical system. Completelyelectronic, the digital range tracker avoids the inertia ofmechanical elements, thus affording lower acquisition timesand minimized velocity-lag error when tracking acceleratingtargets. The digital range tracker provides fine granularityof output data, capability for instantaneous digital designa-tion of target range, and high slew rates. The all-digitalrange-tracking servo eliminates the practical limitations andthe constant need for adjustments associated with analogcomponents in the range-tracking servo loop. Velocitycoast capability is significantly improved because velocityinformation can be stored indefinitely as a binary numberwithout the scaling errors (drift) and decay characteristicsassociated with analog integrators.

Early digital systems obtained their range granularitythrough the use of a master clock coupled with a tappeddelay line. A more recent concept utilizes a precisiondigital interpolator [9] that provides a granularity of lessthan a foot, thereby minimizing the associated error. Theinterpolator depends on two precise clocks, a master clockand a second used as a vernier. Typical digital range systemcharacteristics are described in Section III.

C. Calibration

AngularAccuracy: Accurate calibration of a radar to

NESSMITH: RANGE INSTRUMENTATION RADARS 757

remove systematic errors is a fundamental step in obtainingits maximum accuracy. The removal of noise errors by dataprocessing is a second step. Considerable effort has beendevoted to improving the state of the art in both. On-axistracking [10], [11] represents a significant advance in ob-taining the highest angular accuracy from a radar system.This technique had its beginning in the 1960's, and is nowin use in various forms at a number of installations. Theintent of on-axis tracking is, as the name implies, to keepthe target being tracked in the center of the beam or on thenull axis of the error pattern by minimizing errors in thesystem by means of the following techniques: 1) premissioncalibration to reduce systematic error, 2) the use of datascreening, trend analysis, and estimation to reduce dynamicerrors, and 3) the use of appropriate coordinate systems tominimize the errors in the estimation and pointing process.A secondary benefit of such an approach to improving theaccuracy in real time is that by keeping the target on axis,the coupling between the error channels (including crosspolarization and system nonlinearities) is minimized. (Coup-ling errors are not amenable to postmission correction.)

The use of 120-in focal-length boresight telescopes (witha resolution of approximately 4 arc-seconds) on the eleva-tion axis arm permits the calibration of the optical axeswith respect to a star field. Data from 50 of a catalog of600 stars are used to correct for errors such as 1) azimuthbias, 2) elevation bias, 3) mislevel, 4) azimuth skew, 5)droop, and 6) nonorthogonality.

The pattern of stars is chosen so that one group showsonly mislevel, another group only droop, etc. To reducethe time for the calibration process, star field positions arestored in the radar computer. The radar is automaticallydesignated by the computer, and any difference betweenthe star position and the cross hairs in the trunnion-mountedtelescope is then stored into the computer file for on-line orpostmission correction.

The result of the star calibration is a set of values relatingthe optical axes to the antenna-pedestal mechanical axes.The next step is to determine the position of the RF axes.Some factors, such as pedestal mislevel, encoder errors, andpedestal nonorthogonality can be assumed to be the same

as for the optical systems; but azimuth skew and droop are

normally different. A satellite optically visible in the bore-sight telescope is tracked with the RF beam of the radar to

determine the differences between the position as measuredby the optics and by RF. The resultant data are stored as a

function of azimuth and elevation to be used for furthercorrections. Of course at a lower elevation angle the differ-ence in atmospheric refraction must be taken into account

between the RF and optical frequencies.The basic limit on the results of such a calibration pro-

cess is the stability of the pedestal, errors in the boresighttelescope, and the accuracy of the atmospheric and iono-spheric corrections. A practical limitation is weather, whichcan prevent the star observations. A backup method fordetermining the vertical axis is a precise leveling sensor

(that must be accurate to 1 or 2 arc-seconds) mounted on

the pedestal and calibrated from the star track data to

remove error due to local gravitational anomalies. A single-point backup for a particular azimuth and elevation is theboresight tower [121. The star data can be used to deter-mine the position of boresight tower targets and to calculateand remove multipath errors associated with use of thesetargets. The calibration process has been automated so thatit can be accomplished in less than an hour with residualerrors of less than one-tenth of a mil with reference to thestars.A functional representation of the on-axis filtering and

pointing system is given in Fig. 3. Data derived duringcalibration are used to remove systematic errors and toyield the measured target position, i.e., the state vector[RkAkEk] T. A coordinate transformation is made so thefiltering can be performed in target coordinates. Eitherbefore or immediately after the transformation, data areavailable to the user who wants raw (unfiltered) data. Whenthis target position is compared to the predicted position,an error is derived. A trend check of this error can be madeto discover if a lag error is building up and if the bandwidthof the filters should be increased, thereby providing essenti-ally an adaptive bandwidth control. In parallel, there is anoption to do initial editing on the error. For example, ifan estimate of the standard deviation of the differencebetween measured and predicted values is made, data whichproduce differences significantly greater than that whichwould have been produced by the assumed random processcan be rejected. This tacitly makes the assumption thatthere is a priori knowledge that the target has limitedacceleration capabilities. Another form of screening datais to reject data obtained during a signal fade [10] . Herethe wavefront is distorted much as in multipath (as notedby Iloward [131 ) and can produce angular errors even withhigh signal-to-noise ratios.

It is desirable that the narrowband data filter approachzero bandwidth so as to produce a predicted state vectorwith very low noise for driving the antenna. Since theknowledge of the trajectory may be developed over a longperiod with some classes of targets, such as an unpoweredsatellite that adheres closely to a trajectory with knownequations of motion, it is relatively simple to furnish a

prediction, even with the lag induced by the effective lowbandwidth filter, that will put the RF axis on the target.For accelerating targets, the problem is somewhat more

complicated and the demands on the filter design becomegreater.

Hoffman-Heyden [14] has given results of measurementsperformed at AFETR utilizing on-axis tracking. For a non-

powered target such as the Echo satellite on an arc from50 to 1750 in elevation, the values for the dispersion ofresiduals for a series of tracks over a 2-month period are

given as

range:azimuth:elevation:

11-18 ft0.025-0.075 mil0.040-0.090 mil.

For a series of powered missile tracks with beacon operation,the residual range of values was

IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS NOVEMBER 1976758

I WIDEBAND POINTING SYSTEM

Zk+ 1,k

Fig. 3. Functional diagram of on-axis tracking loops.

range:azimuth:elevation:

4.4-5.9 ft0.06-0.15 mil0.060-0.16 mil*

For aircraft beacon tracks, the standard deviation was foundto be 0.20 mil in azimuth and 0.31 mil in elevation, bothwithout editing of data.

To a large extent the results speak for themselves. Thecalibration process has been developed to a high level ofautomaticity through the use of computer control and isundergoing further refinement. The filtering/estimationprocess is still under investigation, particularly for accelerat-ing targets. The filters being considered range from simplea, , to high-order Kalman [15] -[17]. Pollock, who wasresponsible for much of the earlier work, has recently givena much more detailed overview of the concepts and processknown as on-axis tracking in [18].

Ranging Accuracy: The GEOS-B C-Band Radar SystemProject [19] under NASA-Wallops Station had test objec-tives that included the determination of the absolute ac-curacy of instrumentation radar systems and the develop-ment of refined methods of calibrating these systems. Be-ginning in 1968 with evaluations using radars at the NASA-Wallops Station and continuing into late 1969 when aworldwide network of 18 radars was used, a set of experi-ments was performed using the GEOS-B satellite orbit forestablishing a reference.

Initially, Wallops Station experiments demonstratedautotracking noise levels of 1 m in range and 10-15 arc-seconds (0.05-0.075 mil) in angle for the AN/FPQ-6, and

1.5 m in range and 20-25 arc-seconds (0.1-0.125 mil) inangle for the AN/FPS-16. A comparison was then made atthe Wallops Station in the Wallops Island Co-location Experi-ment (WICE) program of the radars, an Army SECOR Station,Navy TRANET Station, and several geodetic camera systemsusing the Goddard laser as the range standard. GEOS-Bhad a C-band transponder aboard and was tracked a totalof 109 passes with the Wallops AN/FPQ-6, 18 of themsimultaneously with the Goddard laser. The AN/FPQ-6agreed with the laser measurements within 2 m. Both theradar and laser were compared with orbital solutions de-termined solely from observations by a worldwide opticalnetwork [20]. Over a 5a-day span, the optical orbital fitwas 4.7 arc-seconds rms. The mean residuals, when com-pared to this optical orbit, were 1.6 m for the radar and0.6 m for the laser. (An overall comparison for all GEOSobservation systems has been given by Berbert [211 .)

When these data were compared to other like radarsthroughout the worldwide network, it was determinedthat each of the radars gave similar performance whenaligned according to established calibration procedures.The radars proved accurate to within 2 m. Another outputof these tests demonstrated that when data were comparedbetween stations, it was possible to resolve timing errorsof individual stations to within 2 or 3 ms. Also establishedwere network interradar distances within North Americato within ±10 m or better and between 10 and 20 m forthe rest of the world. It was found insofar as the radarswere concerned that short arc (less than one satellite rev-olution of the Earth) orbital solutions were adequate for

NESSMITH: RANGE INSTRUMENTATION RADARS

NARROWBAND DATA FILTER

759

determining precision, but long arcs (up to 2 days in length)were required for accuracy assessment.

The AN/FPQ-6 radar had a CSP modification [22] thatpermitted fime-line spectrum tracking either in a skin orcoherent beacon mode. In WICE Test 73, an AN/FPS-16radar in beacon mode was used to generate a referenceorbit, with the AN/FPQ-6 performing both range and CSPtracking in skin mode. This test showed that integratedDoppler ranges of a precision of 1 cm or better were obtain-able with the CSP. Later tests in 1975 using the AN/FPQ-6CSP and a Vega coherent transponder in the GEOS-C satellitewith 20 separate short-arc tracks gave an orbital range ratebias of 0.255 cm/s rms. The orbital fit was within 1 cm/srmns, and the data precision was better than 0.5 cm/s.

Calibration of radars has been a challenge from the begin-ning, and although the on-axis tracking and GEOS radarprograms have established standards for calibration of radarsystems, it is expected that efforts such as these will continuewith no one method satisfying all. Many instrumentationradars do not require the accuracy achievable with thesetechniques nor do they have the power level to track satel-lites to establish range bias or optical-to-RF axis alignmentover the entire hemisphere. However, the newer level-indicator sensors for antenna pedestals, the highly stabledigital ranging systenms, extensive data now available on bore-sight tower tests [12], and the use of computers to disciplinethe calibration process and to provide real-time data correc-ton and/or on-axis tracking offer to each radar a potentiallyhigher level of performance.

D. Computers

Instead of being a peripheral that involves only the dataoutput of a range instrumentation radar, the computer isnow an integrated radar subsystem. Major functions thatcan be controlled by the computer include

elevation and azimuth controlrange controlservo bandwidth controlmode controlacquisition process and controltiming controlconstant false alarm rateautomatic gain controlantenna scanbeacon frequency searchdata report and displays.

Although some systems use the computer simply as a con-trol device, others are using the computer to close the servo

loops in the system. Examples include

range (position and rate)azimuth (position and rate)elevation (position and rate)frequencygainconstant false alarm rate.

The increasing computational capability and decreasing costof general-purpose computers, coupled with advances in filtertheory, have provided major advances in range instrumenta-tion radar capability. Implementation of more sophisticatedfiltering and adaptive control algorithms is feasible, as demon-strated by the calibration and filtering techniques describedearlier.

The use of the computer in the calibration process pro-vides means for reducing human errors. As an example, whenthe radar is controlled by the computer, it can be programmedto refuse to go into operation until an ordered calibrationprocess is performed and corrections for such factors as tilt.bias, skew, gain, and error slopes are determined by theoperator and entered into storage. If the values did not fallwithin preset limits, the entry would be rejected and nofurther steps could be taken until corrected. A further stepwould be to remove the operator from the calibration loopentirely, with outputs from ser )ors being entered directly inthe computer and the operator perfornming only maintenanceor corrective functions. Suclh calibration processes providethe discipline that can save time and reduce the potential foroperator error.

The more powerful minicomputers are currently beingused in those instrumentation radars that use the computeras an integrated subsystem, though a few utilize large general-purpose machines. The microcomputer is now beginningto enter as a potential competitor to the mini, initially inthe control function. However, development is being carriedon toward expanding its use in the data handling functionwitl the prime objective of off-loading the central computer.Consideration is being given to such1 functions as coordinatecoinversions wlhich are hiighly repetitious and are a majorfactor in the CPU load in the central machine.

As yet, neither the large-scale machine nor the mnini ormicrocomputers are used to any large extent in signal pro-cessing functions where very high speeds are essential. Cur-rent developments in high-speed programmable processorsmay make them a potential candidate for such roles.

E. Dual-Frequency Systems

In systems tests that require metric data in the presenceof jamming, i.e., in a simulated tactical environment, a rangeinstrumentaion radar could be jammed since it is usuallynot designed to work in such an environment. One of theapproaches currently under development to resolve theproblem is the dual-frequency radar witl tracking capabilityat both frequencies so that if an entire band is jammed, a

switch to a new band could potentially eliminate the prob-lem without loss of data. Although at least one range in-struImentation radar has a dual-frequency tracking capability(Altair, discussed in Section IIl), most dual-frequency radarscan track on only one of their two frequencies at a time.A combination of X- and Ka-band operation is currently

being considered with performance expected as follows:


_ _ _ v %RiNz~~_ ~~

Fig. 4. Tracking laser mounted on AN/MPS-36 radar. (Courtesy RCA)WE ..- & _

antenna gainbeamwidthpeak powerangle precision (S/N= 20

dB)range precision (S/N= 20

dB)maximum instrumented

rangerange for S/N = 20 dB

on 1 m2 targetpulsewidthPRF (selectable)

Fig. 5. ST858 radar [241. (Courtesy Marconi, Ltd.)frequency

X-band Ka-band

42 dB 55 dB tations in angle-tracking precision were due to noise in the18 mil 5 mil pedestal, servo, drive system, and the angle encoders. As of250 kW 100 kW this time there are two laser range and angle trackers inte-

grated with radars, giving a dual-frequency capability. There0.1 mil rms 0.1 mil rms are approximately 15 independent laser trackers being used

for range instrumentation at the present time.2.0 yd rms 2.0 yd rms

512 kyd 512 kyd

38 kyd 48 kyd0.25 ls 0.25 ps

1280,640,320 Hz 111. Current Radars

Such a system has an important advantage over single-frequency C- or X-band systems other than the reductionin jamming potential, e.g., the capability of providing track-ing at the higher frequency band at much lower elevationangles without clutter or multipath interference. Kittredgeetal. [231 have reported on Naval Research Laboratorytests of a test X/Ka system. At ranges of 8000-10 000 yd,with a target aircraft at 200 ft altitude, the X-band multi-path produced large error signals approaching ±1.8 mil. Inanother exercise, with the Ka-band system operating andwith the aircraft at 100 ft altitude and 13 800 yd range, theoverall elevation tracking error was 0.21 mil rms. In theirsummary, they pointed out that accurate tracking of theaircraft at 100 ft altitude had been accomplished out to 18mi range using the Ka-band system.

The range accuracy of the laser has led to its use as arange standard. The addition of angle tracking to a lasersystem provides an even better capability (where there is noatmospheric limitation) for angular precision at very lowelevation angles beyond that obtainable with the highestmicrowave frequencies. Results with the laser shownmounted on an AN/MPS-36 in Fig. 4 show a precision of0.04 rms mil in angle and 0.3 rms foot in range. The limi-

Since the modified SCR-584, the AN/FPS-16, and theAN/FPQ-6 (plus their mobile versions, the AN/MPS-25and AN/TPQ-1 8), a number of different instrumentationradars have been built, including the following: PRELORT,VERLORT, HIPORT, AN/FPQ-10, EAIR, MAIR, MIDI,AN/MPS-36, CAPRI (i.e., AN/FPS-105), HAIR, Cotal,Aquitane, Bearne, Bretagne, RIR-778, and a number ofdifferent modifications to NIKE Ajax radars. A surveyreveals six companies that have recently delivered or arenow delivering their latest model. (The survey did notinclude radars which are modified versions of previouslybuilt systems.)

In this section, one of the recent radars produced byeach of the companies surveyed is described by a photo-graph (where available) and a table of characteristics, features,and options. (See Figs. 5 through 12 and Tables I throughVI.) Terminology and data are, insofar as possible, in theform used by the manufacturer in his descriptive material.(The units are given as they appeared in the original data.)The radars are grouped in alphabetical order by countryand then by manufacturer. The data are not all inclusive,and the reader who wishes further information is referredto the references at the end of this paper.


Fig. 6. RIS-4 C/A radar [25]. (Courtesy Selenia)

Fig. 7 Trail-X radar [261. (Courtesy AIL, Cutler Hammer)

Fig. 9. RIR 778 radar console [281. (Courtesy Lincoln Laboratory,M.I.T.)

Fig. 10. TRADEX radar. (Courtesy Lincoln Laboratory, M.I.T.)

_ww-' ' e

Fig. 8. AN/TPQ-39(V) [271. (Courtesy RCA) Fig. 11. ALTAIR radar. (Courtesy Lincoln Laboratory, M.I.T.)

762 IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS NOVEMBER 1976

:A

TABLE II

Italy: RIS-4 C/A Radar (Fig. 6)

System Performance

Fig. 12. ALCOR radar. (This photograph was taken while protec-tive radome was being erected.) (Courtesy Lincoln Laboratory,M.I.T.)

TABLE I

England: ST 858 Radar (Fig. 5)

System Performance

Angle Jitter 0.030 rms; Bias . 080 rBias can be reducedlRange Jitter 3m rms; Bias -20 m Lwith calibration.Ttacking S/N > 10 dB for 1 m2 target < 3s km.

Angle Systematic Error

Range Systematic Error

Tracking Range

System Characteristics

AntennaSizeGainFeedPolarization

TransmitterFrequencyPeak PowerPRFPulsewidth

ReceiverTypeNoise Figure

Angle Tracking

Tracking VelocityTracking Acceleration

Range Tracking (Digital)Tracking Velocity'Tracking Acceleration

Features

Skin/beacon tracking.Digital range tracking.

0.2 mil; noise error 0.3 mil rms(S/N = 10 dB)

8 m; noise error 1.5 m rms(S/N = 10 dB).

Up to 1280 km on beacon.

3.0 m diameter.40 dB.Conical scan - Cassegrain geometry.Ih. V, RHC, LHC (selectable).

5450-5825 MHz.250 kW.920. 820, 460. 230.1.0 pA sec (skin); beacon 2-pulse 0.5 It sec

with 2.0- 10 pt sec spacing.

Dual-channel skin/beacon.Skin: 4 dB. Beacon sensitivity: -94 dBm.

Az - continuous; El - from -50 to +850( plunge for tests).

35 0/*c.300/sec2.

10000 m/sec.50gOptions

Data processing computerrecorder, plotting board.

System Characteristics

AntennaSize

GainFeedPolarization

TransmitterFrequencyPeak PowerPulsewidth

ReceiverTypeNoise Figure

Angle TrackingTracking VelocityTracking Acceleration

Range Tracking(Analog/Digital)Tracking VelocityTracking AccelerationRange Quantum

Features

Skin/beacon-operation.Static or mobile installation.MTI (Moving Target Indication).Self Surveillance Mode.

1.4 m dia. (antenna shown is standardI-meter version for 800-series radar).39dB.Amplitude monopulse - twist Cassegrain.Vertical.

8.6 - 9.5 GHz.200 kW @ 1.5 kHz PRF.0.67 pt sec 1.5 kHz.0.33 p sec @4.4kHz.

Three-channel monopuse and logrithmic10 dB (referred to antenna feed).

Az - continuous; El from -50 to +850.300/sec.200/sec2.

80 km (clear)/24 km (MTI).800 m/sec.ISO m/sec25 m.

Options

Director mounted television.AD8 PPI Display.

TABLE III

France: Adour Radar

Adour Radar (Thompon Houston - Hotchkiss Brandt)

Though no information was received directly, the Adour Radar isthought to have the following characteristics:

System Performance

Angular Precision (S/N - 20 dB)Range Precision (S/N - 20 dB)Range (S/N * O dB)

System Parameters

AntennaDiameterGainPolarization

TransmitterFrequencyPeak PowerPulsewidth

ReceiverNoise FigureSensitivity

Features

0.2 mil (20 dB S/N).3 m.200 km(1 m2).

3 m.42 dB.Vertical.

5450--5825 MHz.I MW.1.7 A sec

8.5 dB.-134 dBW.

Options

Skin and/or BeaconOperation.

Digital Range System.

Multiple PolarizationLow Noise Amplifier.Fixed or Mobile.


TABLE IV

United States: Trail-X Radar (Fig. 7)

System Performance

Angle PrccisionRange PrecisionTracking Range

System ('hanr teristics

AntennaDiameter and GainCGain

eeecPoljrizat ion

1Fra nsm it ter

FIreq uenoyPeak PowerPRI-i Iossei\Idth

ReAwejver

Noise FigureDynamic Range

Angle Tracking

Tracking VelocityTracking Acceleration

Range Tracking (Digital)Tracking VelocityTracking AccelerationBandwidth

Features

Computer centered.Mobile or fixed installation.One-man operation.Torquer drives in pedestal,

0. I mil rms.5 meters rms.More than 200 km ( min)

7 feete4 dBC onical scan (66 Hz rate).V ti. LHC RHC (selectable)

35O kW,400, 800, or 600

1 (3 or 0.5 P se Beacon code400 pulse pairs - 0. aP secr

Dual channe.3.5 dB (skin), 13 dB (beacon).90 dB.

Az -- continuous, El - from -50 to +850operate (plunge for tests),

300/sec.200/sec2.

3000 m/sec.485 m/sec2.0.25, 5,or 0Hz

Options

Low-noise beacon receiver 3.5 dB.Central processor Nova 8202-2 orRolm 1o02 with 16-inch PPIdisplay.

TABLE V

AN/TPQ-39(V) Radar

TABLE VI

RIR 778 Radar

System Performance

Angle Accuracy 0.2

Range Accuracy 3 yTracking Range 97

System CharacteristicsAntennaDiameter 2Gain 42Feed CorPolarization Ve

TransmitterFrequency 5.4Peak Power MPRF 300Pulsewidth 0.'

ReceiverNoise Figure <8Dynamic Range 75AFC Range Be

PedestalTracking Velocity 0-Motion AzLeveling 3 1

Range Tracking (Digital) 50Tracking Velocity 0Tracking Acceleration 0Resolution I

Computer Nc

Features

Computer based operation.Mobile configuration available.Remote control operation.Provable static and dynamiccalibration.

25 mil rms S/N 6 dB excludingglint, scintillationmultipath, weak

yards rms. signal errorsnmi (I m2 with S/N 6 dB).

feei.dB (" S.44GHz.nical scan 80'7 crossover,rtical.

[ 5 9 (liz.AW.1-575 pps.5/0 5 (two pulse code for beacon),

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va 800 (Data General Corp.)

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Nike Hercules Pedestal.X/Ka dual frequency operation,Nth-time-around range tracking.Dual skin-beacon display capability

IV. High-Power Large-Aperture Range InstrumentationRadars

Long-range ballistic-missile measurements are made duringboth the launch and terminal phases, with different demandsfor each. During the launch phase the prime concern issafety, and the objective of the radar measurements is tocontinuously determine, during the powered flight, the im-pact point if thrust were to be terminated. Typical of theradars used for the launch phase are the AN/FPS-16 (and/orthe AN/FPQ-6) in one or more modified versions.

Radars for the terminal phase/metric measurements fallinto two classes: 1) those radars already designed, such as

the AN/FPS-16 and AN/FPQ-6, and used for the terminalphase in either ground or ship-based instrumentation sites,or 2) one-of-a-kind units specifically designed for makingsuch measurements. There have been a number of radarsspecifically designed for measurements on ballistic missiles,including the AMRAD, the RAMPART (originally thepincushion radar) and the HAPDAR radars at WSMR, andthe DIPR at Canton Island. In these radars the emphasishas been on phenomenology or testing of radar concepts.

This emphasis has been changing recently at the threeKREMS terminal-phase radars located on the KwajaleinMissile Range at Roi Namur, part of Kwajalein Atoll, inthe Marshall Islands. The three radars (TRADEX, ALTAIR,and ALCOR) are sensors for the Pacific Range Electromag-netic Signature Studies (PRESS) program under the direc-


tion of the M.I.T. Lincoln Laboratory. Each of these radarsfeatures very high power, a large antenna, and wide signalbandwidth. Their operational frequencies span from VHFto C-band, providing data on the characteristics of bothsatellites and reentering ballistic missiles. These radars havebeen used mainly for gathering phenomenological data andcorollary metric data for ABM studies and reentry-physicsresearch. The need for more accurate metric data, for bothsatellites and ballistic missiles, is leading to an upgrading ofthe metric capability of these radars.

The TRADEX radar was the original sensor for PRESS.Erected in 1963, it provided angle, Doppler, and nth-time-around range tracking at UHF. A VHF capability was sub-sequently added, using the common 84-ft reflector, forinterim data collection pending completion of ALTAIR.After ALTAIR became operational in 1970, TRADEX wasconverted to an L-band tracker (1.75 MW peak power, 300kW average) and S-band illuminator/receiver (2.6 MW peak,110 kW average).

The ALTAIR radar with its 150-ft-diameter reflector hasthe longest range and widest beam of the three radars. Thusit can view widely dispersed elements of a distant reentrycomplex. It is used to perform initial tracking prior tohandover of targets to the other two sensors. It can tracksimultaneously at VHF (10 MW peak power, 110 kW aver-age) and UHF (20 MW peak, 110 kW average).

ALCOR, the third KREMS sensor, affords the highestresolution and precision of the three. Its wide bandwidth(500 MHz at C-band), and narrow beamwidth (5 mrad,given by the 40-ft-diameter reflector), enable resolutionof individual targets in multitarget clusters. Transmitterpower is 2.5 MW peak and 10 kW average. ALCOR achievesa precision of 0.1 m in range and 0.05 mrad in angle withbiases of 5 m in range and 0.075 mrad in angle.

One can readily see that some of the developments thathave been discussed are applicable to the future, particularlyin upgrading single radars. But two requirements appear todominate the future: 1) to achieve multiple-object datacapability and 2) to keep overall range costs down. Themultiple-object tracking requirement leads in turn to theneed for integrating the resulting track and metric data.This is particularly important when one must ascertainspatial and temporal relationships among many eventsoccurring during one mission or exercise.

The phased-array radar, either with a limited scan or afull scan, is an approach that offers a potential for meetingsome of the expressed requirements. The phased arraypresents an opportunity for direct integration of multiple-target tracks and the metric data associated with eachtrack. There have been at least three developments thusfar that embody the limited-scan approach. Weaponsystems have already been developed using full-scan phasedarrays to generate multiple-target data of fire-controlquality.

One might then question: will history repeat itself? Willthe phased-array fire-control radar of today evolve to thephased-array range instrumentation radar of tomorrowjust as the SCR 584 radar evolved to current instrumenta-tion radars? Oddly enough, this repetition of history, yetto occur for the phased array, is already occurring forthe single-target tracker itself. The release in 1974 fromArmy inventory to the test ranges of a substantial quantityof Nike-Hercules systems has already initiated a number ofmodifications of these systems for range instrumentationradar use. Perhaps with this turn of events there will bethe opportunity to see another complete cycle in a uniquespecies.

V. The Future

Discussions with individuals in the forefront of rangeplanning reveal that potential mission requirements includethe following:

1) tracking of several targets simultaneously;2) closer integration of instrumentation systems;3) support for operational tests, evaluation, training,

and large-force exercises across a broad spectrum ofwarfare.

These needs are further confirmed by the Director ofDefense Research and Engineering report to the SenateArmed Services Committee which states that "... [Rangesmust] meet a continuing requirement for realistic, free-play,multiple-aircraft, air-to-air and air-to-ground testing andtraining . ..." Also expressed in the report is the fact that... [Range costs] continue an 8% per annum upwardtrend ... [29]."

Acknowledgment

The author wishes to express appreciation to his col-leagues for their review and comments on this paper. Alsoappreciated are the data and photographs furnished by AIL,Cutler Hammer; Lincoln Laboratory, M.I.T.; Marconi;RCA; Selenia; and Vitro.


References

[1] V.W. Hammond and J.W. Bomholdt, "The evolution of testranges and the changing requirements they serve-An over-view," NATO AGARDograph 219. Range Instrumentation,Weapon Systems Testing and Related Techniques, pp. 1-1 -1-10, Feb. 1976 [available through National Technical In-formation Service (NTIS), 5285 Port Royal Road, Springfield,Va. 22151].

[2] D.K. Barton, "The future of pulse radars for missile and spacerange instrumentation," IRE Trans. Mil. Electron., vol. MIL-5,pp. 330-351, Oct. 1961.

[3] , "Recent developments in radar instrumentation,"Astronaut. Aerosp. Eng., pp. 54-59, July 1963.

[4] J.H. Dunn, D.D. Howard, and K.B. Pendleton, "Trackingradar," in ch. 21,Radar Handbook, M.I. Skoinik, Ed. NewYork: McGraw-Hill, 1970.

[5] J.T. Nessmith, "New performance records for instrumenta-tion radar," Space/Aeronaut., pp. 86-93, Dec. 1962, (re-printed: D.K. Barton, Monopulse Radars, vol. 1, The ArtechRadar Library, 1974).

[6] Proc. Conf Coherent Radars for Range Instrumentation,Mar. 5-7, 1974, published by Secretariat, Range CommandersCouncil, White Sands Missile Range, N.Mex. 88002.

[7] R.D. Mitchell, M.R. Paglee, G.M. Sparks, and G.H. Stevens,"Radar detection and tracking in ground clutter," See [1,pp. 4-14-20].

[8] G.M. Sparks and G.H. Stevens, "Automatic detection, acqui-sition, and tracking in clutter using a coherent trackingradar," Rec. IEEE 1975 Int. Radar Conf, Arlington, Va.,Apr. 21-23, 1975, pp. 402-407.

[9] R.A. Craft, RCA Corp., New York, N.Y., United StatesPatent 3 840 174, Oct. 8, 1974.

[10] A.E. Hoffman-Heyden, "AFETR on-axis developments," Tech.Rep. ETR-TR-01, pp. 3-36, Sept. 1974. A compilation ofpapers presented at the On-Axis Software Conf., Patrick AFBase, Fla., June 25-27, 1974. (Available through DefenseDocumentation Center, Alexandria, Va. 22314.)

[11] "IRIG tracking radar compatibility and design standards forG-band (4 to 6 GHz) radars." Electronic Trajectory Measure-ments Group, Range Commanders Council, ASTIA Doc.AD A010280, Apr. 1974. (Available through Defense Docu-mentation Center, Alexandria, Va. 22314.)

[12] C.G. Hammer, V.B. Kovac, and A.E. Hoffman-Heyden, "Useof boresight tower lock-ons for MIPIR RF axis calibration,"RCA Int. Service Corp., MTP, Patrick Air Force Base, Fla.,Rep. 20-SR-72-08, May 19,1972.

I

[13] D.D. Howard, "Radar target angular scintillation in trackingand guidance systems based on echo signal phase front distor-tion," Proc. NEC 15, 1959, pp. 840-849.

[14] A.E. Hoffman-Heyden, "AFETR on-axis radar system evalu-uation," see [10, pp. 469-518].

[15] O.J.W. Christ, "Real-time Kalman analytic study," see [10,pp. 439-468].

[16] E.P. Schelonka, "Adaptive control techniques for on-axisradars," see [8, pp. 396401] .

[17] B.L. Clark, and J.A. Gaston, "On-axis pointing and the man-euvering target," NAECON '75 Rec., pp. 163-170.

[18] E.J. Poilock, "Minimal error trajectories on line," see [1,pp. 14-1-14-29].

[19] Executive Summary, GEOS 11 C-Band Radar System Project,vol. 1, Final Rep. for NASA-Wallops Station, Wolf Researchand Development Corp., and RCA Corp., Oct. 1970.

[201 C.D. Leitao, and R.L. Brooks, "C-band radar range measure-ments: An assessment of accuracy," presented at the Int.Assoc. Geodesy Int. Symp. Electromagnetic Distance Mea-surement and Atmospheric Refraction, Boulder, Colo., June1969.

[21] J.H. Berbert, "GEOS observation systems inter-comparisonresults," Technical Information Division, Code 250, GoddardSpace Flight Center, Greenbelt, Md., Rep. X-932-74-212.

[22] K. Guard, and W.T. Wells, "Milimeter range precision fromC-band radar CSP measurements," presented at the 1970 FallMeeting Amer. Geophysical Union, San Francisco, Calif.

[23] F. Kittredge, E. Ornstein, and M.C. Licitra, "Millimeter radarfor low angle tracking," EASCON '74 Rec., pp. 72-75.

[24] Marconi Radar Systems Ltd., New Parks, Leicester, England,LE3 1 UF.

[25] Selenia, 2 Via Tiburtina KM.12,4-00131 Roma, CasellaPostale 7083-00100 Roma, Italia.

[26] AIL, Cutler-Hammer, Deer Park, N.Y. 11729.[27] L.E. Kitchens, and D.N. Thomson, "The AN/TPS-39(V)

digital instrumentation radar," EASCON '74, Rec., pp. 76-80.[28] Automation Industries, Inc., Vitro Services, Industrial Park,

Ft. Walton Beach, Fla. 32548.[29] M.R. Currie, statement to the Research and Development

Subcommittee of the Senate Committee on Armed Services,March 7, 1975, Hearings before the Committee on ArmedServices, United States Senate, Ninety-Fourth Congress, firstsession, on 5.920, Part 6, Research and Development (GPO,1975), pp. 2758-2759.

Josh T. Nessmith (S'46-A'48-M'55-SM'58) received the B.E.E. degree from the GeorgiaInstitute of Technology, Atlanta, in 1947 and the M.S.E.E. and Ph.D. degrees from theUniversity of Pennsylvania, Philadelphia, in 1957 and 1965, respectively.

He joined RCA in 1952 following a two-year period of teaching radar theory at theCAA Aeronautical Center. His early assignments involved modification of search radarand fire-control equipment for tactical ground systems. He later became involved withsystem project engineering on the early versions of the AN/FPS-16 and AN/FPQ-6 instru-mentation radars. In 1959 he was assigned to the conceptual phase of the TRADEXprogram, later becoming system project manager for design and development and RCATRADEX Program Manager, responsible for all modifications and operation and main-tenance of the sensor system. In 1965 he was assigned to direct the systems engineeringeffort within the Missile and Surface Radar Division, a position he held for six years.From 1971 through 1974 he served as Deputy Program Manager and Manager, SystemsEngineering on the AEGIS Program. He is currently Manager, Systems, with responsibilityfor the systems engineering effort on radar and weapon systems.

Dr. Nessmith is an active member of the IEEE Radar Systems Panel. He was alsoone of the original organizers of the Oklahoma City IRE section.


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