| Gravity
Probe B is at NASA spacecraft processing hangar 1610 on
North Vandenberg Air Force Base. 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.
Upcoming is
the attachment of the nine strap-on solid rocket boosters
in sets of three 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.
Gravity Probe
B arrived at Vandenberg Air Force Base on July 11 from
the Lockheed Martin plant in Sunnyvale, Calif. The 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. Gravity Probe B consists of
four sophisticated gyroscopes to be launched into a 400-mile-high
orbit for a mission lasting 18 months.
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. |
