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Gravity Probe B

Testing Einstein's Universe



Gravity Probe B is "Go" for launch on Monday, April 19, 2004 at 10:01 AM Pacific Daylight Time, from Vandenberg Air Force Base in Southern California.

Please Note: Satellite launches are sometimes subject to postponement for a variety of reasons, ranging from technical issues to weather conditions. The GP-B satellite has only a one-second launch window. If all launch conditions are not "Go" at the scheduled launch time on Monday, April 19th, the launch countdown will be stopped, and another attempt will be made approximately four minutes earlier (9:57 AM) on Tuesday, April 20. If conditions are not "Go" on Tuesday, it will be necessary to stand down on Wednesday, while the Dewar's guard tank is refilled, and then another launch attempt will occur on Thursday, April 22 at approximately 9:49 AM. And, if conditions are not "Go" on Thursday, another attempt will occur on Friday, April 23 at 9:45 AM. Should further launch attempts be necessary, we will post updated launch information on this Web site.


  • Public Viewing at Vandenberg: Several areas in the vicinity of Vandenberg provide good vantage points for the general public to view rocket launches. Click here for a map showing the locations of some of these viewing sites. The Weather Station on Firefighter Road provides the best vantage point, but it has very limited parking. You'll need to hike a quarter mile to the cement viewing stands, which will accommodate approximately 250 people. The viewing area near the Vandenberg AFB Golf Course is the closest to the launch tower. It has good parking and the easiest access for people who have trouble walking.The launch countdown will be broadcast on a public address system at the Weather Station. Little or no official launch commentary is expected to be available at the viewing area near the golf course.
  • Viewing the launch at Stanford University: We have reserved Cubberley Auditorium, here on the Stanford campus, for local GP-B staff, their families, and the general public (press, and media included), to view the launch, projected on a large screen, via NASA TV. Members of the GP-B team will be on hand to provide commentary and answer questions. Doors will open at 8:30 AM.

    Cubberley Auditorium is located just off the main Quad, in the School of Education, next to the clock tower at the intersection Escondido Mall and Lasuen Mall. (Click here to view an interactive map or download a PDF map.) The nearest public parking is in the metered lots next to Tresidder Union. Metered parking costs $0.25 per 10 minutes (bring lots of quarters). If you don't have a Stanford parking permit, the nearest public parking is in the metered lots next to Tresidder Union. Metered parking costs $0.25 per 10 minutes. At the Tresidder parking lots, you can pay for parking with bills and credit cards, as well as cash. Parking meters at smaller lots and on campus streets only accept change--bring lots of quarters if you plan to use these meters. You may wish to park off campus and then take the free Margurite shuttle to the Main Quad.

  • Viewing the launch on NASA TV: The GP-B launch will be covered live on NASA Television, beginning two hours before launch (11:00 AM EDT / 8:00 AM PDT) and running through separation of the GP-B space vehicle from the launch vehicle (2:30 PM EDT / 11:30 AM PDT). The coverage includes launch commentary and live video feeds from Vandenberg AFB. NASA TV is carried on some cable networks. Via satellite, NASA TV is broadcast on AMC-9 (or possibly AMC 2), Transponder 9C, located at 85 degrees West longitude. The frequency is 3880.0 MHz. Polarization is vertical and audio is monaural at 6.8 MHz.
  • Viewing the launch on the Internet: Two pre-launch events will be Webcast on NASA Direct. The GP-B launch coverage will also be Webcast on NASA direct, as well as on NASA TV on the Web. For more information about NASA's GP-B Webcasts on NASA Direct, see For information about viewing NASA TV on the Web, using either the Real Player or Windows Media Player, see You'll find a list of alternate sources of NASA TV on the Web at

We will update these announcements over this weekend if there is any change in launch status or other important information to report.


  • Installation of the payload fairing—the "nose cone" at the top of the launch vehicle that surrounds and protects the spacecraft during launch has been completed. Four minutes and 41 seconds after launch, the fairing will split apart and be jettisoned into space, in preparation for the second stage rocket to position the spacecraft in its circular polar orbit and proper orientation towards the guide star, IM Pegasi.
  • The launch vehicle, with its payload and fairing at the top, are still surrounded by the Mobile Service Tower (MST). Very early Monday morning, the MST will be rolled away, leaving the launch vehicle standing in readiness as the launch countdown begins.
  • Yesterday, the temperature of the Dewar's main tank was 1.797K, and the Dewar was 95.5% full. The Guard Tank level was 76.6%.
  • A Flight Readiness Review (FRR) was successfully conducted yesterday, and Gravity Probe B is "Go" for launch.

Photos: Both photos, taken by Russ Underwood of Lockheed Martin Corporation, show the GP-B space vehicle being encapsulated in the fairing, inside the lMobile Service Tower, atop the rocket. Click on the thumbnails to view enlarged copies of these photos.


Today, Gravity Probe B Co-Principal Investigator, John Turneaure, was interviewed by Ira Flatow on NPR Talk of the Nation—Science Friday. This Sunday evening, April 18th, a feature story about Gravity Probe B and principal investigator, Francis Everitt, is scheduled to air on ABC World News Tonight (San Francisco Bay Area KGO Channel 7 at 5:30 PM PDT).

Tuesday, Gravity Probe B was the lead story in the Science section of the New York Times, (you'll need to register on the NY Times site to view the story on their Web site), and it was one of the front page stories in the San Jose Mercury News. In addition, a story about GP-B appeared on the New Scientis Web site yesterday.

The official pre-launch Gravity Probe B mission and science briefing was held on Friday, April 2, 2004 at 1:00 PM Eastern Daylight Time at NASA Headquarters in Washington, D.C. The participants in the briefing (pictured from left to right in the photo) were:

  • Anne Kinney, Director of Astronomy/Physics Division, NASA Headquarters
  • Rex Geveden, Program Manager, GP-B and Deputy Director, NASA's Marshall Space Flight Center in Huntsville, Alabama.
  • Francis Everitt, GP-B Principal Investigator at Stanford University, Stanford, California
  • Bradford Parkinson, GP-B Co-Principal Investigator at Stanford University, Stanford California
  • Kip Thorne, Feynman Professor of Theoretical Physics, California Institute of Technology, Pasadena, California

Following this press briefing, stories about Gravity Probe B appeared in a number of newspapers around the country. For example:

On November 10, 2003, about a dozen members of the local press and media put on clean room suits and took their video recorders and cameras into the space vehicle preparation room, where they photographed the space vehicle and interviewed GP-B Principal Investigator Francis Everitt, Co-PI Brad Parkinson, NASA GP-B Program Manager Rex Geveden, Lockheed Martin Manager Jeff Vanden Beukel, as well as other GP-B, NASA, and Lockheed Martin staff.

Click here to view a QuickTime video clip of Rex Geveden, Brad Parkinson, and Francis Everitt talking about Gravity Probe B.


If you are interested in automatically receiving these weekly highlights and other important GP-B mission information by email, you can subscribe to our Gravity Probe B Update email list by sending an email message to "" with the command "subscribe gpb-update" in the body of the message (not in the Subject line). You can unsubscribe from this mailing list at any time by sending an email message to the same address with the command, "unsubscribe gpb-update" in the body of the message.

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