Gravity Probe B
Orbiter
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Gravity Probe B was a satellite-based experiment to test two unverified predictions of general relativity: the geodetic effect and frame-dragging. Wikipedia
Launch date: April 20, 2004
Cost: 750 million USD
Manufacturer: Lockheed Martin
Orbit height: 404 mi
Launch mass: 3,100 kg (6,800 lb)
Mission duration: 6 years, 7 months and 17 days
Reference system: Geocentric