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TOP SECREt 

NATIONAL RECONNAISSANCE OFFICE 

SATELLITE OPERATIONS C.ENTER 

DESCRIPTI N 

51 I T 1551 

7166-7235 

WARNING 

F 

NS 

This document con tams mformation affecting the national security of the United 

States wlthm the meaning of the espionage laws U S. Code Tille 18, Sections 793 

and 794 The law prohibits its transmission or the revelation of Its conlents in any 

manner to an unauthoflzed person, as well as lIs use in any matter prejudicial 10 the 

safety or Interest of the United States or for the benefit of any foreign government 

to the detriment of the UOited States. It IS to be seen only by pe.fsonnel especially 

mdoctrlnated and autholl1ed 10 receive mformation in the designated control channels. 

Its security must be mamtalned 10 accordance With r~ulations pertaining to the desig· 

nated controls. 

prepared for sigint overhead reconnaissance subcommittee 

.. handle via "ImAI..EN ... -KlEYHDI..E contral oOIJ . 

CONTROL NO. TCS-37S73-70 

TO~ SECRET 

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TOP SEGRET TALENT ·KEYHOLE CONTROL SYSTEM 

Mission Description 7166/7235 

1. INTRODUCTION 

Miss:,ons 7166 and 7235 are SIOINT payloads carried aboard a 3-axisstabilized satellite system which is designed to collect SIGINT data in the 

125 to 3300 MHz frequency spectrum. Both payloads collect electronic signals, 

store intercepted data in digital and analog form, and later transmit this data 

to various satellite tracking stations throughout the world. This mission 

description will discuss the technical and operational considerations applicable 

to each payload. 

2. MISSION 7166 

2.1 GeneraL 

Mission 7166 is a frequency scanning, electronic reconnaissance 

system which intercepts pulsed and continuous wave (CW) radiation from 125 

to 2100 MHz. The payload can coHcct Electronic Order of Battle (BOB) or 

Techn:~cal Intelligence (1'1) data. In the BOB m ode I the payload digitizes the 

frequency, pulse repetition interval (pRI). pulse width (PW), pulse amplitude 

(p A), time of intercept. and relative position of the intercepted signal. When 

in the TI mode, the payload records 5 MHz predetected analog data in addition 

. to the digital information just discussed. The major components of the payload are the antennas, the receivers, the recognizers, the frequency matchers, 

and the Pre-D/CWI unit; each will be discussed. Figure 2.1 is a block diagram 

of the payload. Table 2.1 shows the payload characteristics. 

2. 2 Antennas. 

Two six-arm, cavity-backed, dual-mode, flat-spiral antennas are 

used for bands 2 and 3. The band 2 antenna is an erectable structure with a 

diameter of approximately 80 inches. It is deployed from the vehicle by means 

of a boom to reduce interference effects. The band 3 antenna is als 0 erectable 

and has a diameter of approximately 40 inches. Band 4 and 5 antennas are 

fixed structures mounted on the deck of the vehicle. They are 18 and 11 inches 

in diameter, respectively. Aside from the diameter, the only difference between 

antennas is that a metal horn is used to reduce vehicle effects in band 4. 

Amplitude-differencing circuits process the outputs of the sum and 

difference modes of the antennas to produce the emitter apex angle (rho). The 

apex angle is the coverage angle which generates the circumference of the 

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Table 2.1 

MISSION 7166 PAYLOAD CHARACTERISTICS 

Receiver Bands 

Item 

Frequency Range (I'v1Hz) 125 to 260 260 to 530 530 to 1060 1060 to 2100 

Scan Times (sec) 

(No Intercepts) 

Nominal 

Alternate 

Normal Bandwidth (MHz) 

Narrowband Bandwidth 

Normal Step Size (I'v1Hz) 

Narrowband Step Size 

Number of Steps 

Normal 

Narrowband 

Dwell Time (msec) 

I-Sec Scan 

4-Sec Scan 

16-See Scan 

PRI (msec) 

4 

1 or 16 

2. a 

0.5 

1. 75 

0.4375 

78 

312 

12. 'if 1 

Sl t..l 

204 *4 

Minimum 0.1 

Maximum 100 

Minimum PW (usee) 2.0 

Maximum PW (msec) 3,8 

Sensitivity (dbm) -47 

(Selectable -59 

Thresholds) -65 

-71 

4 

lor 16 

4.0 

NA 

1. 84 

NA 

156 

NA 

6.4 -t1 

25.5 ±1 

102 !4 

0.1 

100 

0.5 

3.8 

-72 

-83 

4 4 

I or 16 1 or 16 

4.0 .'5.0 

1.0 NA 

3,5 3.72 or 3.60 

0.875 NA 

156 312 

624 NA 

6.41:1 3.2 ±1 

25.5 !1 12.7 t1 

1021'4 51 t4 

0.1 0.1 

100 100 

1.0 0,3 

3.8 3,8 

-63 -76 

-68 -82 

-73 

-83 

Dynamic Range (dbm) 

Field-of-view (nm) 

(radius of circle) 

From Selected Threshold to ··45 dbm. 

ilLENtKEYHOLE ~.:..A CONTROL SY5Tt~ 

Selectable from 103 to 207 Q1orizon to horizon 

available for TI only). 

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TOP SECRET HANDI E. VIA. 

TALENT ·KEYHOlE CONTROL SYSTEM 

ground circle of coverage. The dual-mode design of the antennas also 

provides a mode phase difference which is processed to produce an indication 

of emitter azimuth (theta) with respect to the vehicle ground track. 

2.3 Receivers. 

Mission 7166 processes signals in four frequency bands: band 2, 

125 to 260 MHz; band 3, 260 to 530 MHz, band 4, 530 to 1060 MHz, and band 

5, 1060 to 2100 MHz. Each band utilizes a dual-channel serially scanned 

superheterodyne receiver. Bands 2 and 4 are double-conversion superheterodyne receivers and bands 3 and 5 are single-conversion superheterodyne 

receivers. 

There are two basic scan modes, full-band scan and selectablefrequency-range scan. In full-band scan, each receiver remains tuned to a 

fixed frequency for a dwell time determined by the scan rate selected. If an 

emitter is not detected, the receiver steps to the next higher frequency and 

repeats the process until the complete band is scanned. If an emitter is detected, 

the scan stops for a period of time required to process the emitter or the PRI 

verification time. whichever is shorter. Scan is resumed upon completion of 

emitter processing. 

In selectable-frequency-range scan, the receivers scan between the 

frequency limits specified by the frequency matchers. Any or aU of the eight 

frequency matchers may be programmed, and any of the scan modes or rates 

. may be selected when using the frequency matchers. 

Bands 2 and 4 have selectable bandwidths, normal and narrowband. 

When in the narrowband mode, the receiver is step tuned to each narrow frequency range within the normal frequency step. Scan times in the narrowband 

m ode are four times the normal scan rates. The narrowband m ode provides 

increased sensitivity and geopositioning accuracies. 

2.4 Rec ognizer • 

The recognizer recognizes desired emitters by comparing stored 

parameters with the digitized parameters of the intercept. When a recognition 

occurs. the payload records the intercept on the 5 MHz recorder (see section 

4. 2). There are eight recognizer words, and each of these words may be 

enabled or disabled by stored program commands. 

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Tap SECRET TALENT ·KEYHOLE 

2. 5 Frequency Match e r • 

The frequency matcher allows narrower frequency limits to be scanned. 

The magnetic core memory of the frequency matcher has a capability of storing 

eight words, each with high and low frequency limits and band number. Each 

of the eight words may be enabled Or disabled by command. When a band is 

activated. ~he memory to", scallned fo)' a word which is associated with that band. 

The word is clocked from the memo'c'Y into the shift register and, if that word 

is enabled, it is compared with the frequency word. A frequency match allows 

normal scan through the limits stored until the high frequency limit of the memory 

word is reached. At this point, another word is clocked out of the mem ory; and 

the frequency matcher generates a slew scan signal to the scan control until a 

match occurs between the frequency word and the word in memory. A frequency 

match resumes normal scan through the limits of the memory word. If no other. 

words are enabled, or if the enabled words do not match the specific frequencies 

being scanned, the slew signal to the scan control will continue to the end of seem. 

The frequency matcher may be enabled or disabled. If disabled, the receiver 

bands will scan normally. 

2.6 PredetectionjCWI Units. 

The predetection (pre-D) unit detects the presence of inband signals and 

converts them to a specified bandwidth and amplitude range. The analog signal 

output is composed of Pre-D video, reference tones, and a tag burst. The 

Pre-D video signal is a sinuSOidal waveform preserving the pulse width at the 

Pre-D IF inputs. The reference !:ones are provided whenever the payload ON 

command is received. The tag b'urst occurs whenever the intercept has been 

within the cone of coverage and has a pulse width greater than the specified 

minimum. 

The CW indicator detects the presence of CW signals and outputs an 

alarm to the data handler. The CW signal power is indicated. 

3. MISSION 7235 

3.1 General. 

Mission 7235 is an S-band frequency-scanning, electronic reconnaissance 

system that precisely measures the location, frequency, PW, PRI, and PAof 

electromagnetic emitters in the 1800to 3300 MHz frequency range. CWemitters 

are a1Go processed. The payload digitizes each parameter measurement and 

outputs a digital word for each confirmed intercept. This output is stored in one 

of three core storage units (CSU's) in the satellite. Simultaneously with the 

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TOP SE6RET HANOI E \lIA 

TALENT -KEYHOLE CONTROL 5YSTf:M 

processing of digital data, the payload matches measured emitter parameters 

against stored rec ognizer settings. A match will stop the payload on the 

emitter frequency and cause the payload to output a predetected IF signal and 

a supplemental digital word for recording on the 5 :MHz wideband tape recorder 

(Data Storage Unit or "DSU"). The major components of the payload are the 

antennas, the RF and IF assemblies, the data handler, the recognizer, and 

the frequency matcher; each will be discussed. Table 3.1 lists the Mission 

7235 payload characteristicf'. Figure 3.1 is a block diagram of the Mission 

7235 payload. 

3.2 Antenl1as. 

Twelve fixed antennas are used, six in the low band (1800 to 2437.5 

:tvlHz) and six in the high band (2400 to 3300 MHz). Five antennas in each nest 

comprise the phase array. The sixth antelma is a spiral-fed horn which 

provides a difference pattern for amplitude-ratio determination. The phase 

antennas are Circularly polarized and have a nominal gain of 9 db. 

Emitter location is determined by measuring the relative phase of the 

received signal in an interferometer array of five antennas. Simultaneous 

phase measurements are made in orthogonal directions on each received pulse. 

Both coarse and fine phase measurements are made; the combination permits 

phase ambiguities to be resolved. On the ground, the transmitted phase 

readings are used to com pute the direction cosines of the line- of-sight to each 

emitter. From the direction cosines and ephemeris data, the precise 

. geographical location of each emitter can be computed. 

Mission 7235 is capable of locating emitters. with respect to the boresight of the antenna nest, to 7.5 nm with a probability of 95 percent. This 

accuracy is obtained for target locations out to an elevation .angle of 23 deg. 

from antenna boresight. For received signals with a signal-to-noise ratio 

less than 20 db (PA <l -82 dbm), the quoted accuracy is obtained by averaging 

a minimum of two intercept words (eight pulses). For signal strengths greater 

than - 82 dbm. this accuracy can be obtained with a single pulse measurement. 

Vehicle alignment, attitude errors, and knowledge of the ephemeris will add to 

the payload error and increase the overall system error to about 10 urn. 

3.3 RF Assembly. 

3.3.1 RF Bandpass Filter. Two RF bandpass filters attenuate signals outside 

the passband from 500 to 10,000 MHz by 50 db minimum. The low-band filter 

has a bandpass of 1800 to 2450 MHz; the high-band filter, 2400 to 3300 MHz. 

TOP SEeRET EXCLUPf.O FROM AUTOMATIC PEG~A"DING 

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Table 3.1 

MISSION 7235 PAYLOAD CHARACTERISTICS 

Item 

Frequency C overage (MHz) 

Scan Rate (sec) 

Search Step Size 

Dwell Time (msec) 

Nominal 

Alternate 

PRI (usec) 

Minimum 

Maximum 

Resolution 

PW (usec) 

. Minimum 

.Mucimum 

Sensitivity (dbm) 

(Selectable) 

Dynamic Range (dbm) 

Field--of-Vlew (nm) 

Maximum 

Minimum 

I 

'. 

Value 

1800 to 3300 

5.6 sec nominal (no intercepts), 

15 sec in alternate mode 

2.5 

6, 14 (with 2 msec settling time for 

no intercept) 

22.5 (with signal) 

22. '; (with 2 msec settling time for 

no intercept) 

45 (with signal) 

100 

8192 

l.0 

0.4 

Signals;> 24 encoded as CW 

-93, -88, or -83 

40db above selected threshold 

Gross Track: 

246 

173 

In Track: 

90.6 

66,5 

(Horlzon'-to-horizon available for TI 

only) 

TCS,,<:57573;..70 

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3.3.2 Stripline Mixer. The mainstripline accepts the seven separate 

inputs from the system antenna/?' plilS the input from the local oscillator. 

These inputs are mixed in the main stripline and produce eight IF outputs. 

Five of the IF outputs are amplitude and phase matched to provide directionfinding signals. Two outpUts are amplitude matched with a 90-deg phase 

offset to provide a means for real"'image detection. The eighth output is 

amplitude matched with the phase outputs and is used for amplitude-ratio 

inhibit detection. A detection circuit is also provided to monitor the local 

oscillator signal level. The noise figure of theRF front end is established 

by the mixer •. The mixer .singlesideband noise figure is 8 db maximum. 

3.3.3 Local Oscillators. The local oscillators are electronically tuned 

solid-state microwave YIG oscillators. One oscillator is required for the 

low band (1780 to 2417.5 MHz) and one for the high band (2420 to 3320 MHz). 

The digital control count changes 1 count for·each 2.S-MHz frequency step. 

There are 256 steps in the low band 361 frequencies in the high band. Only 

one band may be operated at one time. Control is provided by a DIA converter. 

3.4 fF Assembly. 

The IF assembly of the payload contains the following: 

Sixteen IF preamplifiers, eight for eachRF band 

Five phase channels 

Signal indicate (SI) generator 

Signal combiner 

R ealli mage .confirmcircuit 

AIR inhibit circuit 

Two log IF (amplitude) channels 

Threshold circuit 

Analog-to-digital converter 

Frequency confirm circuit 

Pulse width confirm circuit 

Tag and tone generator 

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CONTROCNO TCS-37573-70 

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TALENT·KEYHOLE CON1ROi. svStrM 

The IF assembly provides the circuitry to accept signals from the balanced 

mixers in the RF assembly and provide the basic input fUnctions to the data 

handler. The center frequency of the IF channels is 20 MHz. The frequency 

confirrn bandwidth is 3 MHz. The bandwidt.h of the phase chanJle!s is nominally 

4. 5 ~"iHz. The signal for the predetected output is taken from the IF 

preamplifiers where the bandwidth is nominally 10 MHz. 

3,5 Data HancUer. 

The data hancller processes and encodes received signal parameters, 

status, time, and attitude information. The data handler also provides buffer 

storage for the output words and controls the frequency scan circuits. 

3,6 .Recognizer. 

The recognizer is a subassembly which stores frequency, PW, and 

PRI for matching against the parameters of incoming signals. The parameters 

are loaded into eight recognizer sets which may be inuividually enabled/disabled 

by the programmer. If the parameters of an incoming signal match the parameters of any enabled recognizer set the frequency scan is stopped and a 5 MHz 

analog recording is made. At the end of the record period, frequency scan 

resumes. 

3.7 Frequency Matcher.! 

The frequency range of each payload band may be reduced. A partial 

frequency scan is obtained by loading the desired frequency limits into 

appropriate payload digital registers. Only one frequency matcher may be 

used in each of the two payload bands. 

4. OPERATIONS 

4.1 EOB. 

Both Missions 7166 and 7235 collect Eon data in a similar manner. 

Each payload scans through its frequency range until an intercept is made, 

at which time the payload scanning stops. Signals which are above a 

selected sensitivity threshold, within the payload field of view, and within 

the processing bandwidth qualify as a valid intercept. The payloads digitize 

the pararl1eters of the intercepted signal, as well as the signal's location 

relative to the satellite, and then they store this information in two of the 

three digital storage devices (CSU's) in the eatellite. Data can be stored from 

rev to rev, so that payload EO]3 operation is not: generally readout limited. 

The frequency scanning range of each payload may be limited by use offrequency 

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matchers as previously discussed. Mission 7166 has eight frequency 

matchers I and 7235 has two. 

4.2 TI. 

In addition to storing digital data. both missions can record analog 

data on a 5 MHz recorder (Data Storage Unit or "DSU"). There are two 

recorders (one for redundancy) and each can be operated in several different 

modes. Either the selected recorder can be operated continuously aild 

assigned to one payload, or the recorder can be shared by both payloads and 

used only when :.l valid sig:aal is recognized" In the latter mode, two types 

of operation are available: 

Type 1. If the DSU is not available for recording, receiver 

scan is resumed after a 125-msec delay for DSU request. If the 

DSU is available, scan is stopped for recording for a preselected 

period of 8, 32. or 300 sec. 

Type 2. If the DSU is not available for recording, receiver 

scan is resUl11ed after a 60-sec delay unless a PDSU Available" 

signal is obtained. If the DSU signal is received, scan is stopped 

for recording for a preselected time of 4, 16, or 64 sec. 

The DSU is defined to be not available for recording one mission if the other 

missi(>n had previously selected it.for use. Data may be stored on the DSU' s 

from rev to rev until a ma.x.imum ofBO minutes is recorded. Each payload 

can store as many aseightdifferertt sets of recognizel.- parameters. 

4.3 Command and Control. 

The comman(j and controlsystem which supports missions 7166 and 

7235 allowsextremelyflexib!eoperation. Bott'1 the CSU's and the DSU's can 

store data from rev tp revaUowingmultiple readins. The satellite command 

programmer generally requires loading only once per day, and it allows the 

payload configuration to be alterE;!dmany times on a:ny pass •. Multiple payload 

recognizers and frequencyma,tchen3canbeused(eight in all cases except the 

7235 frequency matcti~rs iwhereq:nly<twoate available), and any or all of the 

recognizers and .matcherscan be.chilllgedduring contact by a tracking station. 

TCS- 375 73-70 

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