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This mission, SOLRAD 2 or GREB 2, was to have been the second of a series intended to monitor solar radiation, primarily in the soft x-ray range of the spectrum. This mission failed because of a launch malfunction.

The GREB program was classified at the time, the primary purpose was to receive signals from Soviet radar installations to learn about their air defense posture. The data were used by the U.S. Strategic Air Command. As a cover story, the satellites were equipped with instruments to measure solar radiation. Sometimes referred to as Galactic Radiation and Background (GRAB) satellites, or as part of the SOLar RADiation (SOLRAD) program, they were publicized as scientific missions, and did in fact return scientific data.

The SOLRAD 2 satellite was mounted on top of the Transit 3A satellite, as pictured, to be separated at deployment. Image credit: National Museum of the U.S. Navy

Alternate Names

  • GRAB 2
  • GREB 2

Facts in Brief

Launch Date: 1960-11-30
Launch Vehicle: Thor-Able
Launch Site: Cape Canaveral, United States
Mass: 91 kg

Funding Agency

  • Department of Defense-Department of the Navy (United States)


  • Solar Physics

Additional Information

Questions and comments about this spacecraft can be directed to: Dr. H. Kent Hills



NameRoleOriginal AffiliationE-mail
Mr. Robert W. KreplinGeneral ContactUS Naval Research
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