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The SR4/GREB4 mission, also designated Sunray 4 or Solar Radiation 4 (SOLRAD 4) was a U.S. Navy solar radiation monitoring satellite. It was designed to measure X-ray radiation from the Sun and night-sky ultraviolet (Lyman-alpha) radiation.

It was launched as part of a 5-satellite payload on the Composite 1 launch on a Thor-Able Star rocket on 24 January 1962. The satellites failed to reach orbit due to a failure of the second stage.

Image credit: National Museum of the U.S. Navy

Alternate Names

  • SOLRAD 4
  • SR4/GREB4
  • Sunray 4

Facts in Brief

Launch Date: 1962-01-24
Launch Vehicle: Thor-Able-Star
Launch Site: Cape Canaveral, United States
Mass: 98.5 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: Coordinated Request and User Support Office

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