Solrad 11 Credit - US Navy

SOLRAD was Satellite Techniques' first major project and NRL's first post-Vanguard satellite. Conceived by the Space Science Division as a means of measuring and analyzing Solar Radiation, twelve SOLRAD satellites were successfully launched between June 1960 and March 1976. The first SOLRAD had an immediate scientific impact. Equipped with both X-ray and Lyman-alpha sensors, SOLRAD I quickly determined that radio fade-outs were caused by solar X-ray emissions. Subsequent SOLRADs also had important, although not quite so dramatic, scientific payoffs.

By 1972 the SolRad series satellite had grown from a 19 kg polished aluminum ball measuring 51 cm in diameter and with a useful lifetime of 10 months, to a 118 kg 12-sided cylinder measuring 76 cm x 58 cm and with a seven year life.

The SolRad satellite carried a classified ELINT payload, called Grab. It was kept secret for nearly 40 years, until its existence was revealed by the Director of the National Reconnaissance Organization (NRO) during NRL's 75th anniversary jubilee events.

Typical orbit: 58972 km circular orbit, 40.4 deg inclination. Mass: 170 kg (370 lb).

• 1968 March 5 - Explorer 37 - Program: Explorer. Launch Site: Wallops Island. Launch Complex: LA3A. Launch Vehicle: Scout. FAILURE: Partial Failure. Mass: 198 kg (436 lb). Perigee: 353 km (219 mi). Apogee: 433 km (269 mi). Inclination: 59.30 deg. Period: 92.40 min.
  Solar Explorer B; radiation data; off-nominal orbit.

• 1971 July 8 - Explorer 44 - Program: Explorer. Launch Site: Wallops Island. Launch Complex: LA3A. Launch Vehicle: Scout. Mass: 118 kg (260 lb). Perigee: 433 km (269 mi). Apogee: 632 km (392 mi). Inclination: 51.10 deg. Period: 95.20 min.
  Solar radition data. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B).

• 1976 March 15 - Solrad 11A - Launch Site: Cape Canaveral. Launch Complex: LC40. Launch Vehicle: Titan. Mass: 181 kg (399 lb). Perigee: 118,383 km (73,559 mi). Apogee: 119,180 km (74,050 mi). Inclination: 25.70 deg. Period: 7,344.30 min.
  Solar radiation data. Spacecraft engaged in practical applications and uses of space technology such as weather or communication (US Cat C).

• 1976 March 15 - Solrad 11B - Launch Site: Cape Canaveral. Launch Complex: LC40. Launch Vehicle: Titan. Mass: 181 kg (399 lb). Perigee: 115,720 km (71,900 mi). Apogee: 116,645 km (72,479 mi). Inclination: 25.60 deg. Period: 7,116.70 min.
  Solar radiation data. Spacecraft engaged in practical applications and uses of space technology such as weather or communication (US Cat C).