Gravity Probe B
Gravity Probe B was a NASA–Stanford University experiment testing the geodetic and frame-dragging predictions of general relativity in polar Earth orbit. Four cryogenic gyroscopes tracked tiny changes in their spin directions relative to a distant guide star. The mission separated the precession caused by Earth’s mass from the smaller effect caused by its rotation. Launched on 20 April 2004, it collected its principal science measurements from August 2004 to August 2005; the final analysis was published in 2011.
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Identity
- Aliases
- GP-BGravity Probe-BGPB
- Name
- Gravity Probe B
- Status
- completed
Details
- Astronauts
- -
- Description
- Gravity Probe B was a NASA–Stanford University experiment testing the geodetic and frame-dragging predictions of general relativity in polar Earth orbit. Four cryogenic gyroscopes tracked tiny changes in their spin directions relative to a distant guide star. The mission separated the precession caused by Earth’s mass from the smaller effect caused by its rotation. Launched on 20 April 2004, it collected its principal science measurements from August 2004 to August 2005; the final analysis was published in 2011.
- Destination
- Polar Earth orbit, approximately 640 km altitude
- Outcome
- The final four-gyroscope analysis measured geodetic precession of −6601.8 ± 18.3 milliarcseconds per year and frame dragging of −37.2 ± 7.2 milliarcseconds per year, consistent with general relativity’s predictions of −6606.1 and −39.2 respectively. The two measurements have different uncertainties; the smaller frame-dragging effect was measured much less precisely.
- Programs
- -
- Start Date
- 2004-04-20
- Vehicle Families
Links
Assets & Meta
- Creation Time
- October 29, 2026 at 15:16:21 UTC
- Updated Time
- October 29, 2026 at 15:25:58 UTC
Other
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