ERS Credit - NASA

The Environmental Research Satellites were especially designed for piggyback launching from large primary mission vehicles. Ranging in mass from 0.7 to 45 kg, and carrying from 1 to 14 experiments, these ERS "hitch-hiker" spacecraft provided an inexpensive, flexible vehicle capable of making scientific and engineering measurements in space. A major role of the ERS satellites was to act as a test bed to determine the reliability of improved components and subsystems destined for use in later generations of spacecraft.

A unique feature of the system was its capability to function without a battery. The key to this advantage was the design which permitted solar cells, fastened to all exterior surfaces of the vehicle, to maintain constant exposure of about 15 percent of the sun. The ERS was a small satellite, measuring in one version only 22 cm on a side and weighing 680 g; the larger version weighed 45 kg and was a 51 cm diameter cylinder. At least 12 satellites were launched from 1962 for a variety of missions and sponsors. The 8-sided version was designated the OV-5 and became a part of a program conducted by the Air Force Office of Aerospace Research. Prime Contractor was TRW Systems Group of TRW Inc.

Typical orbit: 3353 x 57494 km, 54.1 deg inclinaton. Mass: 45 kg (99 lb). Associated Launch Vehicle: Atlas LV-3A / Agena B, Atlas LV-3A / Agena D, SLV-3 Atlas / Agena D, Thor Agena B, Titan 3C.

• 1962 September 17 - TRS - Launch Site: Vandenberg. Launch Vehicle: Delta.

• 1962 November 11 - TRS 1 - Launch Site: Vandenberg. Launch Vehicle: Atlas.

• 1963 July 19 - TRS 10 - Launch Site: Vandenberg. Launch Vehicle: Atlas.

• 1965 July 20 - ORS 3 - Launch Site: Cape Canaveral. Launch Vehicle: Atlas. Mass: 5.00 kg (11.00 lb). Perigee: 566 km (351 mi). Apogee: 111,793 km (69,464 mi). Inclination: 36.90 deg. Period: 2,595.40 min.

  Radiation data. Space craft engaged in investigation of spaceflight techniques and technology (US Cat A).

• 1966 June 9 - ORS 2 - Launch Site: Vandenberg. Launch Vehicle: Atlas. Mass: 15 kg (33 lb). Perigee: 178 km (110 mi). Apogee: 3,641 km (2,262 mi). Inclination: 90.00 deg. Period: 125.10 min.

  Metal-to-metal bonding experiments. Space craft engaged in investigation of spaceflight techniques and technology (US Cat A).

• 1966 August 19 - ORS 1 - Launch Site: Vandenberg. Launch Vehicle: Atlas. Mass: 5.00 kg (11.00 lb). Perigee: 3,680 km (2,280 mi). Apogee: 3,700 km (2,200 mi). Inclination: 89.70 deg. Period: 167.60 min.

  Cold welding experiments. Space craft engaged in investigation of spaceflight techniques and technology (US Cat A).

• 1967 April 28 - ERS 18 - Launch Site: Cape Canaveral. Launch Vehicle: Titan. Mass: 9.00 kg (19.80 lb). Perigee: 8,991 km (5,586 mi). Apogee: 110,842 km (68,873 mi). Inclination: 0.00 deg. Period: 2,831.30 min.

  Radiation research. Space craft engaged in investigation of spaceflight techniques and technology (US Cat A).