Gravity Probe A
Gravity Probe A was a NASA–Smithsonian Astrophysical Observatory experiment that compared a rocket-borne hydrogen maser with ground clocks to test gravitational redshift. Launched from Wallops Island on 18 June 1976, its Scout D rocket carried the clock on a ballistic flight reaching roughly 10,000 km altitude. A two-way transponder link allowed the analysis to remove first-order Doppler shifts and separate the gravitational frequency shift from effects of motion.
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Identity
- Aliases
- GP-AGravity Probe-AVessot–Levine rocket experimentGravitational Redshift Space-Probe Experiment
- Name
- Gravity Probe A
- Status
- completed
Details
- Astronauts
- -
- Description
- Gravity Probe A was a NASA–Smithsonian Astrophysical Observatory experiment that compared a rocket-borne hydrogen maser with ground clocks to test gravitational redshift. Launched from Wallops Island on 18 June 1976, its Scout D rocket carried the clock on a ballistic flight reaching roughly 10,000 km altitude. A two-way transponder link allowed the analysis to remove first-order Doppler shifts and separate the gravitational frequency shift from effects of motion.
- Destination
- Suborbital ballistic flight to approximately 10,000 km altitude
- End Date
- 1976-06-18
- Launch Site
- Outcome
- The experiment detected the gravitational frequency shift predicted by relativity. The 1979 final report gave a redshift-test precision of 0.014%, combining statistical and estimated bias uncertainties. That interpretation assumed isotropic light propagation and the applicability of the second-order Doppler correction; the precision describes this specific test rather than all predictions of general relativity.
- Programs
- -
- Start Date
- 1976-06-18
- Vehicle Families
- -
Links
- Official Url
- https://ntrs.nasa.gov/citations/19800011717
Assets & Meta
- Creation Time
- October 29, 2026 at 15:28:44 UTC
- Updated Time
- October 29, 2026 at 15:28:44 UTC
Other
- Affiliations
- Space Stations
- -
- Vehicles
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