Gravity Probe B is in NASA spacecraft processing facility 1610 on North Vandenberg Air Force Base. Solar array installation began on Tuesday. There are four arrays to be installed and tested. Two of the four arrays are now installed, and installation of the third solar array is in progress. Installing each array is a 3-day process and includes a functional deployment test. Solar array installation activities are targeted for completion by Friday, Nov. 7. The Delta II payload adapter will be delivered to the spacecraft processing facility on Nov. 10.

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 1.695 K, which is well within the expected rate of rise. The dewar will be topped off at the pad prior to launch.

At the launch pad, integrated testing of the vehicle continues on schedule. Qualification testing has been completed on the Redundant Inertial Flight Control Assembly (RIFCA). This is the navigation and guidance control unit for the Delta II. The tests simulated launch conditions in the unique helium environment that will be created within the payload fairing by the Gravity Probe B spacecraft. Routine integrated guidance and control system checkout of the vehicle was successfully completed as scheduled last week.

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

Marshall Space Flight Center’s equivalent of a Mission Readiness Review is scheduled to be held in Huntsville on Nov. 12.

In final launch preparation activities, Gravity Probe B will be transported from the spacecraft processing facility to Space Launch Complex 2 on Nov. 19 and hoisted atop the second stage. Then the final major test before launch, the Flight Program Verification, will be conducted on Nov. 20. 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.