Gravity Probe B is in NASA spacecraft processing hangar 1610 on North Vandenberg Air Force Base. The spacecraft and mission team have successfully completed a four-day mission simulation.

Conditioning of the dewar to a superfluid state has been completed. Conditioning is the process of taking liquid helium at a temperature of about 4 Kelvin (-452 degrees F) to a colder state, known as superfluid, which will allow the helium to last throughout the duration of the mission. Filling the dewar with superfluid helium is a slow and repetitive process. The dewar is now 95% full of superfluid helium at a temperature of 1.65 Kelvin (-456 degrees F), and it will be maintained in this state from now until launch.

In upcoming spacecraft activities, electrical testing is scheduled for Oct. 8, ordnance installation is scheduled for Oct. 20-24, and solar array installation is scheduled to begin Oct. 27.

The first stage of the Boeing Delta II was erected on Space Launch Complex 2 on Monday, Sept. 15, as scheduled. Mating of the second stage atop the first stage also occurred as planned on Sept. 18.

The attachment of the nine strap-on solid rocket boosters in sets of three is scheduled for Oct. 6-8. Integrated testing of the vehicle will begin on Oct. 14. This will be followed on Oct. 29 by guidance and control system checks. An exercise that involves loading of liquid oxygen aboard the first stage and a limited “minus count” will be conducted on Nov. 4. A Simulated Flight test, a “plus count” that tests the launch vehicle systems as if it were in powered flight, will be performed on the following day, Nov. 5.

Gravity Probe B will be transported from the spacecraft hangar to Space Launch Complex 2 on Nov. 18 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 spacecraft arrived at Vandenberg Air Force Base on July 11 from the Lockheed Martin plant in Sunnyvale, Calif.

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-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-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 Expendable Launch Systems.