AKA: Greb;Solrad;Tattletale. Status: Operational 1960. First Launch: 1960-04-13. Last Launch: 1962-04-26. Number: 6 . Gross mass: 18 kg (39 lb). Height: 0.51 m (1.67 ft).
The project was originally called "Tattletale," then renamed GRAB. Since the true nature of the satellite was supposed to not be apparent to the Russians, this was revised to GREB (the acronym Galactic Radiation Experimental Background was retroactively dreamed up to explain the name). To further muddy the waters the satellites were launched under the title SOLRAD (the cover purpose being to study solar radiation).
Work on GRAB began around the time of the first successful Vanguard launch. Reid Meyo of the Naval Research Laboratory Countermeasures Branch had developed an electronic intelligence antenna for submarine periscopes. At the same time NRL was seeking quick military exploitation of the Vanguard satellite that it had developed. Reid was sitting in a hotel restaurant in Pennsylvania one night and got the idea that they could simply put his periscope antenna in orbit aboard a Vanguard. The original calculations, in the best tradition of aerospace engineering, were done on the restaurant placemat.
GRAB's receivers were used to catalogue the waveforms and pulse repetition frequencies of Soviet air defense radars. GRABs were launched not by Vanguard rockets but as piggy-back or cluster payloads with other satellites. One inert dummy was used to prove the multiple satellite launching technique. Of five operational GRAB satellites, only two reached orbit and operated successfully. GRAB data was given by NRL to the Strategic Air Command and the National Security Agency (which may indicate communications were also intercepted).
Operational ELINT satellites were taken over by the NRO, and remain classified.
Electric System: 0.006 average kW.
Credit: Manufacturer Image
ELINT satellite, retransmitting to US ground stations signals from Soviet radar stations. Classified at time; official purpose and secondary payload collected solar radiation data. Officially: Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B).
The first Scout vehicle (#111) was launched from Vandenberg AFB and carried the Navy's Solar Radiation (SOLRAD 4B) payload (which was actually the last classified Grab ELINT satellite). However, a third stage failure resulted in payload impact 225-NM downrange. Solar radiation monitor.