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TRS Mk. 2 (ERS)

TRS Mk2 [Smithsonian]

From 1962 the US Air Force launched a series very small technology satellites called ERS (Environmental Research Satellites). The satellites were built by TRW Systems Group for the United States Air Force Office of Aerospace Research (AFOAR). Depending on the shape, these satellites are also referred to as the Tetrahedral Research Satellite (TRS) or Octahedral Research Satellite (ORS).

The basic configuration of the TRS Mk.2 spacecrafts was a regular tetrahedron measuring 23 cm on a side. Solar cells mounted on each side of the faces provide sufficient electrical power to operate the experiments and the telemetry system when the satellite is illuminated by the sun. No internal battery or command system were provided. The satellite subsystems consisted of electrical power, antenna, telemetry, experiments, and mechanical structure.


  • ERS 11: unflown Prototype
  • ERS 12: measured the intensity of charged particles in the magnetosphere. The payload consisted of an omni-directional radiation detector to measure electron levels greater than 0.5 and 5 MeV and proton levels between 10 and 20 MeV and 50 to 100 MeV.
  • ERS 13: carried omni-directional radiation detectors to measure electron and proton levels in order to determine the intensity of charged particles in the magnetosphere.
  • ERS 14: ?
Nation: USA
Type / Application: Experimental
Operator: US Air Force (USAF)
Contractors: TRW Systems Group
Equipment: various: see above
Configuration: Tetrahedron 0.23 m (TRS Mk.2)
Propulsion: None
Power: Solar cells
Satellite COSPAR Date LS Launch Vehicle Remarks
ERS 11 - not launched
ERS 12 1963-039B 17.10.1963 CC LC-13 Atlas-LV3 Agena-D with Vela 1, Vela 2
ERS 13 1964-040C 17.07.1964 CC LC-13 Atlas-LV3 Agena-D with Vela 3, Vela 4
ERS 14 - not launched


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