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ELINT Sub-Satellites

Ferret Sub Satellite


By © Charles P. Vick 2007 All Rights Reserved


Sub satellite - SIGINT Spacecraft Series – ( NRO/USAF/USN/CIA/NSA Program AFP-989, 283)

Code name P-11 and commercial Small Research Satellite (SRS), Sub-Satellites was the first in a long series of earth orbit NRO/USAF/CIA/USN/NSA, SIGINT (signals intelligence) spacecraft used by the intelligence Community for a variety of mission. They were launched from the CORONA-4, 4A, 4B, ARGON KH-5, LANYARD KH-6, GAMBIT KH-7, HEXAGON KH-9 and JUMPSEAT Titan-23B Ascent Agena-D and later Titan-34B Ascent Agena-D boosters series with up to 44 identified as successfully orbited based on Dr. Jonathan McDowell published research. Their first successful launch was June 27, 1963 and their last successful launch was June 25 1984. The small SIGINT ferret spacecraft were actually nothing more than services specific sophisticated earth orbit space based earth receiving stations operating over the emitted electro magnetic radio spectrum frequency range. The design was based on the Lockheed P-11 – Small Research Satellite (SRS) bus design and SS A or SS B or SS C or SS D series spacecraft primarily launched on the aft rack of the Agena-B, Agena-D and Ascent Agena-D host last rocket stage of the launch vehicles and from the rack holders of the KH-9 HEXAGON reconnaissance spacecraft.

They were flown in at least two design variations one spin-stabilized at 60-80 revolution per minute and the other gravity gradient stabilized through the use of long deployed boom mass concentrations. The spacecraft design advertised by Lockheed as the LMSC (SRS) Small Research Satellite had a gross mass of 800 pounds with a bus weight of 250 or 300 pounds. Both configurations hold four cubic feet of space for internal payloads including large external surface area availability. They have an optimal built in solar panel power capacity up to and between 1,200 and 2,700 watt-hour/day capacity with one to three solid propellant motors were used to launch them into higher or lower orbits than the host rocket stage or spacecraft. As many as four of these of a similar design by Boeing inc. S 3’s with a mass of 590 – 650 pounds, that were larger when launched on a single KH-9, HEXAGON spacecraft in addition the standard two Lockheed P-11 derivation designs launched from the Agena-B and Agena-D host stages. They were designed to monitor and pick up from the ground electronic signals intelligence (ELINT), radio, communications intelligence (COMINT) and radar emitters emissions intelligence (RADINT) in addition to the missile test telemetry intelligence (TELINT) acquisitions capabilities all coming under the general SIGINT heading.

The technology for these SIGINT spacecraft were slow in coming on line development wise but later proved out highly successfully once the technology was perfected. Like any new technology program it had its issues that slowed its initial progress. During the era they were developed it literally became a serious chase to just keep up with the developing different kinds of monitor able electronic emissions that these systems were able to monitor crying for larger more sophisticated systems able to do multiple missions at the same time.

The constellation of spacecraft was able to receive and send the data to several global ground stations via radio signal operated by NSA personnel. The data was then processed and analyzed at NSA headquarters for further analysis distribution to the intelligence community.


 1. McDowell, Jonathan , U. S. Reconnaissance Satellites Programs, Part 2: Beyond Imaging, Quest, Vol. 4, No. 4, p.41.

2. Day, Dwayne A., Ferrets of the High Frontier, Spaceflight, Vol. 46, February 2004, pp. 75-81.

3. http://www.wpafb.af.mil/museum/space_flight/sf6b.htm, Lockheed Research Satellite Engineering Development Model,

4. MSD LMSC SRS Alternate Configurations, Lockheed Missile & Space Company, Inc, June 1, 1987

5. Small Satellite Program for SAMSO space test program, S3-1, S3-2, S3-3

6. A strange Spacecraft – the P-11 ELINT sub satellite, from the Sven Grahn web site,


7. Dr Day, Dwayne A., Robotic Ravens, Spaceflight, Vol. 47, No. 11, Nov. 2005, pp. 426-433.


ELINT Sub-Satellite Series

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Page last modified: 21-07-2011 13:04:26 ZULU