- Press Release
- Dec 2, 2022
NASA Gravity Probe B Status Report 31 Mar 2004
MISSION: Gravity Probe B (GP-B)
LAUNCH VEHICLE: Delta II
LAUNCH PAD: SLC-2, Vandenberg Air Force Base
LAUNCH DATE: April 17, 2004
LAUNCH TIME: 1:09:12 p.m. EDT (10:09:12 a.m. PDT)
The Gravity Probe B spacecraft is in NASA’s Payload Processing Facility
1610 on North Vandenberg Air Force Base in California, and preparations
are on schedule for a launch on April 17.
The spacecraft was mated to the payload attach fitting (PAF) on March
25. Closeouts to Gravity Probe B in preparation for going to the launch
pad have been completed. Today the spacecraft is being installed into
the transportation canister in preparation for being moved to Space
Launch Complex 2 on Thursday, April 1 and mated to the Boeing Delta II
At the pad, the rocket is enclosed within the gantry-like mobile
service tower and is powered up. A Simulated Flight test, which is a
plus count, has been completed successfully. This test activated the
electrical and mechanical flight systems on the vehicle as they will
occur from liftoff through spacecraft separation. A countdown test
with the first stage loaded with liquid oxygen was successfully
completed on March 18.
The next major test is the Flight Program Verification to be conducted
on April 5. This is an integrated test of the Delta II vehicle and the
Gravity Probe B spacecraft. Installation of the fairing around the
spacecraft is scheduled for April 8.
The Gravity Probe B mission is a relativity experiment developed by
NASA’s Marshall Space Flight Center, Stanford University and Lockheed
Martin. The spacecraft will test two extraordinary predictions of
Albert Einstein’s general theory of relativity that he advanced in 1916:
the geodetic effect (how space and time are warped by the presence of
the Earth) and frame dragging (how Earth’s rotation drags space and time
around with it).
Gravity Probe B consists of four sophisticated gyroscopes that will
provide an almost perfect space-time reference system. The mission will
look in a precise manner for tiny changes in the direction of spin.
Gravity Probe B will be launched into a 400-nautical-mile-high polar
orbit for a 16-month mission.
Government oversight of launch preparations and the countdown management
on launch day is the responsibility of NASA’s John F. Kennedy Space
Center. The launch service is provided to NASA by Boeing Launch