WEEKLY HIGHLIGHTS FOR WEEK ENDING 27 FEBRUARY 2004:
GRAVITY PROBE B LAUNCH DATE
The date for the Gravity Probe B space vehicle to launch from Vandenberg Air Force Base in Southern California has now been officially set for Saturday, April 17, 2004. The exact time of launch will be 10:09 AM Pacific Daylight Time.
We update these highlights every Friday, and we will post any new information about the launch on this Web site and on the GPB Update email list as soon as it becomes available.
VANDENBERG AIR FORCE BASE OPERATIONS THIS WEEKThe following activities are currently underway at VAFB:
- Reconditioning of the dewar back to a pre-launch temperature of 1.65 K
was completed this Tuesday, February 24, 2004, and the dewar was sealed.
Conditioning is a long, iterative "topping off" process of evaporating helium gas from the dewar and adding more liquid helium until the dewar is 95% full. The helium gas “boiled off” during the evaporation phase removes heat from the dewar, converting some of the remaining liquid helium to a superfluid state—a fluid state with special properties that only helium exhibits when cooled to almost absolute zero. The liquid helium that is lost during the evaporative cooling process must then be replaced. After several of these conditioning cycles, 95% of the helium in the dewar ends up in the superfluid state, which will enable the helium to last throughout the duration of the mission.
- The temperature of the dewar's main tank is 1.6558K, and the main tank is 95.5% full. The Guard Tank level is 77.8%.
- Regression testing on the reworked Experiment Control Unit (ECU) has been completed, and analysis of the data is underway. Thus far, the ECU has been performing nominally.
- Small pyrotechnic charges (ordinance) are being installed in the Forward Equipment Enclosure (FEE), and the FEE will then be closed.
- General functional testing of the spacecraft is proceeding on schedule, and the spacecraft has been performing nominally.
- The launch vehicle is surrounded by the Mobile Service Tower (MST) on the launch pad. Boeing technicians are preparing to power up the launch vehicle on March 8, 2004.
Photo: The GP-B Cryo group performing a sub-atmospheric transfer of liquid helium into the dewar's main tank. Click on the thumbnail to view an enlargement of the photo.
GRAVITY PROBE B QUARTERLY REVIEW AT MARSHALL SPACE FLIGHT CENTER
A quarterly review of the Gravity Probe B mission was held today at the Marshall Space Flight Center (MSFC) in Huntsville, AL. Presentations were made by GP-B managers from Stanford, Lockheed Martin, and NASA. The review went quite well. A member of the independent review team (IRT) monitoring the presentations noted that the GP-B team appeared to be more ready than ever before, and Rex Geveden, Gravity Probe B Program Manager and Deputy Director of MSFC said that he was looking forward to a successful launch in April.
GRAVITY PROBE B IN THE NEWS
On Tuesday, February 24, 2004, the Los Angeles Times newspaper ran a front page, column one story on Gravity Probe B. The story is posted in the Print Edition section of the L. A. Times Web site, but you must be registered on the L. A. Times Web site in order to view it. (Registration is free.)
On Sunday evening, December 28, 2003, the Cover story on the CBS Evening News was on the subject of time—examined from both human and cosmic perspectives. The story featured interviews with a manager from Torneau Time Machines (the largest watch store in New York City), physicist Brian Greene (a proponent of String Theory), and our own Gravity Probe B Principal Investigator, Francis Everitt. Typical of television news, the entire story lasted a little over three minutes, but it was heart warming to see Francis and our spacecraft on the national news. Perhaps the best sound byte from Francis was a quote from St. Augustine that CBS chose not to use: "What was God doing before he made heaven and earth? ... He was preparing hell for those that would pry into such profound mysteries."
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