Gravity Probe B is in NASA spacecraft processing facility 1610 on North Vandenberg Air Force Base.  The installation of the four solar arrays, deployment testing and lighting tests have been successfully completed.  The Delta II payload adapter was mated to the GP-B spacecraft on Thursday, Nov. 13.

The spacecraft’s cryogenic dewar was sealed prior to beginning solar array installation at a temperature of 1.648 K.  The temperature is rising very slowly, but is expected to remain less that 1.88 K by the time launch occurs.  The current temperature is 1.7175 K, which is well within the expected rate of rise. The dewar will be topped off at the pad prior to launch.

A Simulated Flight test, a “plus count” that tests the launch vehicle systems as if the vehicle were in powered flight, was successfully completed on Nov. 6.  The exercise that involves loading of liquid oxygen aboard the first stage and a limited “minus count” was successfully conducted on Nov. 4. 

Marshall Space Flight Center’s equivalent of a Mission Readiness Review was held on Wednesday, Nov. 12.  This review, chaired my MSFC, is intended to certify readiness of Gravity Probe B for flight, the readiness of the spacecraft operations team and readiness of mission personnel and ground stations to achieve the science objectives.

The GP-B test results during the period that the spacecraft has been undergoing activities in processing facility 1610 are now having a final assessment prior to an engineering review to be held on Monday, Nov. 17.  This review will determine the readiness of GP-B to go to the pad.  It will also cover the readiness of the Delta II launch vehicle for spacecraft erection and for proceeding with final prelaunch activities.  Gravity Probe B will be placed into a transportation canister on Tuesday, Nov. 18 and transported to Space Launch Complex 2 the following day on Nov. 19.

The final major test before launch, the Flight Program Verification, will be conducted on Nov. 21.  This is an integrated test conducted after the Gravity Probe B spacecraft is mated atop the second stage of the launch vehicle.  The Delta II fairing will be installed around the spacecraft on Nov. 25 as part of final preparations for launch.

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 precision manner for tiny changes in the direction of spin.

Gravity Probe B will be launched into a 400 nautical-mile-high polar orbit for an 18-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.