March 31, 2004

GP-B

Status   (processing notes)

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 rocket.

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 Services.

MESSENGER

Status   (processing notes)

MESSENGER is at the Astrotech Space Operations facilities near Kennedy Space Center where it is undergoing prelaunch testing.  Testing of the spacecraft’s radio system uplink and downlinks through the KSC/JPL interface with the Deep Space Network is underway.  This testing will last about ten days. Autonomy testing is also underway.  This verifies MESSENGER’s ability to operate on its own when not in direct contact with Earth.  Installation of thermal blankets continues.

On April 13, the spacecraft will be moved from its current location in the hazardous processing facility where it has been since arrival to an adjacent non-hazardous payload processing facility.  The remainder of its final assembly and testing will be completed there.  The spacecraft will return to the hazardous processing facility when ready for fueling, spin balance testing and mating to the upper stage.

MESSENGER has been built for NASA by the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland.

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