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.