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Solrad 11A, 11B (P74-1 (c,d))

Solrad 11A & 11B stacked [NRL]

Solrad 11 (also known as Solrad-Hi) was a series of three identical satellites (only 2 were launched) that were placed in a circular equatorial orbit of 20 earth radii. The satellites, which were oriented towards the sun, provided 100 percent real-time, continuous monitoring of solar X-ray, UV, and energetic particle emissions.

Both satellites contained a solid kick motor to raise apogee and perigee from the geostationary orbit, where they were dropped off to the operational high circular orbit. After these orbit raising maneuvers, the Solrad satellites separated from each other.

Experiments included:

  • broadband ion chambers observing solar X-rays between 0.1 and 60 Å,
  • proportional counters and scintillators observing solar X-rays between 2 and 150 keV. and
  • EUV detector covering three bands between 170 and 1000 Å,
  • a variable resolution Ebert-Fastie spectrometer covering the wavelength range of 1100 to 1600 Å (resolution: 1 to 25 Å),
  • a solar wind monitor,
  • solar proton, electron, and Alpha particle monitors,
  • two X-ray polarimeters (one utilizing Bragg scattering and the other utilizing Thompson scattering),
  • a Bragg spectrometer observing magnesium-11 and -12 lines,
  • a large-area auroral X-ray detector, and
  • a passively cooled solid-state X-ray detector to measure background X-ray emissions.

Originally it was planned, that these satellites would be replaced by similar three-satellite constellations launched at 2 year intervals thereafter. No follow-up missions happened.

Nation: USA
Type / Application: Research
Operator: Naval Research Laboratory (NRL), USAF STP (Space Test Program)
Contractors: Naval Research Laboratory (NRL)
Equipment: see above
Propulsion: Star-17A
Power: 4 deployable fixed solar arrays, batteries
Lifetime: 2 years (design)
Mass: 181 kg
Orbit: 118383 km × 119180 km, 25.7 (#11A); 115720 km × 116645 km, 25.6 (#11B)
Satellite COSPAR Date LS Launch Vehicle Remarks
Solrad 11A (P74-1, NRL-PL 175) 1976-023C 15.03.1976 CC LC-40 Titan-3(23)C with LES 8, LES 9, Solrad 11B
Solrad 11B (P74-1, NRL-PL 177) 1976-023D 15.03.1976 CC LC-40 Titan-3(23)C with LES 8, LES 9, Solrad 11A
Solrad 11C - not launched


Further STP missions: