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This spacecraft carried one experiment on a flight of 1 h 51 min to an altitude of 10,224 km. The spacecraft weighed about 60 kg (132 lb). Upon completion of the flight, the spacecraft impacted in the Atlantic ocean near Bermuda. The spacecraft was provided with continuous tracking and telemetry from Wallops Island and Bermuda. It studied the gravitational effect on time measurements (relativistic or Einstein redshift) by use of a hydrogen maser oscillator system (clock). This was to verify one of the results expected from Einstein's general theory of relativity. The spacecraft support experiment consisted of an s-band telemetry transponder, a battery, and a cooling system.

Alternate Names

  • Gravitational Redshift P
  • Gravity Probe A
  • R7606-1701
  • Relativity

Facts in Brief

Launch Date: 1976-06-17
Launch Vehicle: Scout
Launch Site: Wallops Island, United States
Mass: 60 kg

Funding Agency

  • NASA-Office of Space Science (United States)


  • Astronomy

Additional Information

Questions and comments about this spacecraft can be directed to: Coordinated Request and User Support Office



NameRoleOriginal AffiliationE-mail
Mr. Hubert D. CalahanProgram ManagerNASA Headquarters
Mr. Frederick E. VreulsProject ManagerNASA Marshall Space Flight Center
Dr. Rudolf DecherProject ScientistNASA Marshall Space Flight
Dr. Nancy G. RomanProgram ScientistNASA Headquarters
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