THE NRO STAPF 

Approved for Release: 2017/08/17 COS099722 

¢ NATIONAL RECON1\lAiSSANCE OFFICE 

WASHiNGTON, D.C. 

18 Septembe:r 1968 

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MEMORANDUM FOR CHAIRMAN, SIGINT OVERHEAD RECONNAISSANCE 

SUBCOMMITTEE ( .. 

SUBJECT: CONVOY I Mission Description 

The CONVOY I Mission Description is forwarded as an attachment 

to this correspondence. This Elint reconnaissance system is specifically 

designed to collect data on the DOG HOUSE emitter and is an add-on 

module to the STRAWMAN I (THRESHER/REAPER) SIGINT mission 

scheduled for launch on 1 October 1968. 

This mission description supplements the briefing provided the 

SIGINT Overhead Reconnaissance Subcommittee by theNRO member on 

24 July 1968. 

Attachment 

As Stated 

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/ 5i~ t:{:::; V':?f~ .-~~ ;::;;;-. EDWLNF. SWEENEY 

Colonel, USAF 

Deputy Director for 

Satellite Operations 

Tep S~CRET 

Approved for Release: 2017/08/17 COS099722 

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Approved for Release: 2017/08/17 COS099722 

MISSION DESCRIPTION 

CONVOY I 

The CONVOY I payload is an add-on module to Missions 

7164/7233 (THRESHER/REAPER) and is Gpecifically designed to 

collect data on a priority basis from the DOG HOUSE emitter. 

The basic system block diagram is depicted in Figure 1. 

A preamplifier is used to set the system noise level. The output 

is down-converted and applied to two separate signal channels. 

Each of these channels has a 20 MHz bandpass filter which is 

designed to pass only one of the DOG HOUSE beams, thereby 

minimizing interference between beams. The output of each filter 

is applied to a limiter to permit the system to handle large signal 

excursions while accurately reproducing the RF signal characteristics and remain within the dynamic range of the divider circuit. 

After limiting, the signals in each channel are frequency divided 

by 8 so that the 20 MHz frequency excursion in each band is 

reduced to 2.5 MHz after division. Following division, the two 

bands are filtered, down-converted and recombined with the total 

two beam frequency bands extending from 500 KHz to 5.5 MHz. 

Amplitude data is preserved, however, by detecting the output of 

each bandpass filter, low pass filtering and modulating a VCO. 

EARPOP 

CONVOY I contains its own recognizer circuitry independent of the primary payload. It consists of an amplitude threshold 

circuit which produces a standard amplitude, variable pulse width 

output when a signal of greater than -82 dbm. (referenced to receiver 

input) is received. This pulse is then integrated and passed through 

a pulse width threshold circuit. When the pulse width exceeds 2.5 

milliseconds, an output voltage is generated that switches the 

CONVOY I output to the DSU (recorder). The recognizer will retain 

the DSU for CONVOY I for 32 seconds after the last intercept has 

heen l'eceiv ed, at which time the DSU will revert back to THRESHER/ 

REAPER use, 

Recognition of the DOG HOUSE signal by CONVOY I will 

override THRESHER/REAPER use of the DSU. If it is desired to 

ensure other target signals are afforded higher priority when within 

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Approved for Release: 2017/08/17 COS099722 
HANDLE VIA 

Approved for Release: 2017/08/17 COS099722 

th.e intercept envelope (theoretically horizon to horizon) of DOG 

HOUSE, CONVOY I nlUst be disabled. However, considerable 

flexibility is afforded in that the payload may be enabled for any 

specific time period desired. DSU may be in the OFF, STANDBY 

or STEADY-STATE-ACTUATE mode. 

A summary of payload specifications iF. as follows: 

Frequency: 

RF Threshold: 

Recognition Threshold 

Dynamic Range: 

Predection Outputs: 

Reference Tones: 

Channell 386-406 MHz 

Channel 2 406-426 MHz 

-82 dbm 

-82 dbm to -25 dbm 

Channell.5 to 3.0 MHz 

Channel 2 3.0 to 5.5 MHz 

6 MHz 

25 KHz (modulated by 

ANGSQ53A Code) 

EARPOP 

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Approved for Release: 2017/08/17 COS099722 

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