The Step Thirteen / Plymouth Rock 3 satellite was part of a series of so called Program 11 or P-11 "Subsatellite Ferrets", low orbit ELINT/SIGINT satellites to pinpoint and characterize different Radar emitters in the Soviet Union and Warsaw pact states.
The satellites were based on Lockheed's P-11 bus, which was designed to fit on the aft rack of the Agena-D upper stage. The bus contained each one or two focused payload black boxes and different antenna configurations according to payload, as well as deployable solar arrays. The satellite featured two solid rocket motors, which allowed them to rise and circularize their orbit after deployment from the host satellite. Both spin or gravity gradient stabilization was possible.
Step Thirteen was a SIGINT mission targeted at general search payload for ABM radars. Plymouth Rock-3 was a general search SIGINT payload in the 1000-2650 MHz band, where earlier versions had been flown as Aftrack payloads.
This subsatellite was deployed from the propulsion rack of the Agena-D stage of a KH-7 Gambit-1 reconnaissance satellite. It used two solid-fuel kick-motors to maneuver itself into its operational orbit after deployment.
| Nation: | USA |
|---|---|
| Type / Application: | ELINT, SIGINT |
| Operator: | US Air Force (USAF) |
| Contractors: | Lockheed (bus); Haller/Raymond/Brown Division of Singer (Step 13 payload); Applied Technology Industries (Plymouth Rock payload) |
| Equipment: | ? |
| Configuration: | P-11 bus |
| Propulsion: | Kick motor |
| Power: | Solar cells, batteries |
| Lifetime: | |
| Mass: | |
| Orbit: | 295 km × 334 km, 95.50° |
| Satellite | COSPAR | Date | LS | Launch Vehicle | Remarks | |
|---|---|---|---|---|---|---|
| Step Thirteen / Plymouth Rock 3 (P-11 4302, Mission 7305/7306, OPS 5063) | 1964-068B | 23.10.1964 | Va PALC-2-3 | Atlas-LV3 Agena-D | with KH-7 13 |
