Hi,
Here is this weeks Gravity Probe B Mission Update:
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GRAVITY PROBE B MISSION UPDATE FOR 13 MAY 2005
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GP-B STATUS AT A GLANCE
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Mission Elapsed Time: 388 days (55 weeks/12.72 months)
Science Data Collection: 259 days (37 weeks/8.49 months)
Current Orbit #: 5,726 as of 4:00PM PST
Spacecraft General Health: Good
Roll Rate: Normal at 0.7742 rpm (77.5 seconds per revolution)
Gyro Suspension System (GSS): All 4 gyros digitally suspended in science mode
Dewar Temperature: 1.82 kelvin, holding steady
Global Positioning System (GPS) lock: Greater than 96.6%
Attitude & Translation Control (ATC): X-axis attitude error: 202.6 marcs rms
Y-axis attitude error: 90.7 marcs rms
Command & Data Handling (CDH): B-side (backup) computer in control
Multi-bit errors (MBE): 0
Single-bit errors (SBE): 9 (daily avg.)
Telescope Readout (TRE): Nominal
SQUID Readouts (SRE): Nominal
Gyro #1 rotor potential: -2.3 mV
Gyro #2 rotor potential: -3.1 mV
Gyro #4 rotor potential: -2.7 mV
Gyro #3 Drag-free Status: Backup Drag-free mode (normal)
MISSION DIRECTOR'S SUMMARY
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As of Mission Day 388, the Gravity Probe B vehicle and payload are in good health. All four gyros are digitally suspended in science mode. The spacecraft is flying drag-free around Gyro #3.
Our telescope pointing and guide star capture times continue to be excellent. The Experiment Control Unit continues to remain off during most orbits, resulting in reduced noise in the SQUID Readout Electronics system (SRE). Once a week, we power the ECU back on for a few hours in order to obtain and check certain readouts, such as the Dewar temperature, that are provided by the ECU.
Because the spacecraft has been in orbit for over a year now, we are able to conduct an analysis of the external temperature and solar array efficiencies by comparing current data from these systems with data collected a year ago.
In preparation for the end of the GP-B mission, which is fast approaching, we have begun delegating tasks to complete our final mission report, which we will deliver to NASA in July.
MISSION NEWS--GP-B PRINCIPAL INVESTIGATOR FRANCIS EVERITT HONORED BY NASA
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Following is a copy of the press release we sent out earlier this week, announcing this award. Photos are included in this week's highlights on our Web site,
http://einstein.stanford.edu.
Stanford experimental physicist Francis Everitt has been awarded a NASA Distinguished Public Service Medal. NASA Deputy Director Fred Gregory presented the medal to Everitt on April 27 at an awards ceremony at NASA Headquarters in Washington, D.C. Everitt is principal investigator of the Gravity Probe B (GP-B) experiment, a collaboration between Stanford University, NASA and Lockheed Martin Corp. that is testing predictions of Albert Einstein's 1916 general theory of relativity (his theory of gravitation) by means of four ultra-precise gyroscopes that have been orbiting the Earth in a satellite for just over a year.
The NASA Distinguished Public Service Medal is awarded to an individual whose distinguished accomplishments contributed substantially to NASA's mission. Contributions must be so extraordinary that other forms of recognition by NASA would be inadequate. This is the highest honor that NASA confers to an individual who is not a government employee.
Everitt obtained his doctorate at the University of London (Imperial College) in 1959 for research under Nobel laureate P. M. S. Blackett. He then spent two years at the University of Pennsylvania working on liquid helium. In 1962, Everitt joined William Fairbank and Leonard Schiff in the Stanford Physics Department as the first full-time research worker on the GP-B experiment. His efforts advanced the state of the art in the areas of cryogenics, magnetics, quantum devices, telescope design, control systems, quartz fabrication techniques, metrology and, most of all, gyroscope technology. His leadership as the principal investigator for GP-B advanced the GP-B program from the concept and technology development stages to the experiment's launch on April 20, 2004, and its ensuing orbital operations.
"None of us at the beginning had any idea how long it would take for the GP-B spacecraft to fly and take the science data," Everitt said when asked about the long life of the project. "But speaking for myself, I have never been bored."
Gravity Probe B was developed on the Stanford campus in the W. W. Hansen Experimental Physics Laboratory (HEPL). The current on-orbit GP-B mission operations center (MOC) is located in HEPL, where the science data is currently processed as well. From the MOC, the GP-B spacecraft is commanded with ground antennas in Alaska or Norway or through the NASA space net. HEPL supports a number of collaborative scientific research programs that cross traditional university departmental boundaries. The GP-B space mission itself was a successful interdepartmental collaboration of the Stanford Physics and Engineering departments.
"HEPL is one of the few places in the United States where an interdisciplinary experiment such as Gravity Probe B could be successfully carried out," said HEPL Director Robert Byer, a professor of applied physics.
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UPDATED NASA/GP-B FACTSHEET
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A recently updated NASA Factsheet on the GP-B mission and experiment is now available on our Web site in Adobe Acrobat PDF format. You can download this 6-page fact sheet at: http://einstein.stanford.edu/content/fact_sheet/GPB_FactSheet-0405.pdf
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PREVIOUS GP-B UPDATES
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If you wish to read any of our previous updates, our GP-B Web site includes a chronological archive of all the updates/highlights (with photos and drawings) that we have posted over the past 8 years: http://einstein.stanford.edu/highlights/hlindexmain.html
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OTHER LINKS THAT MAY INTEREST YOU
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Our GP-B Web site, http://einstein.stanford.edu contains lots of information about the Gravity Probe B experiment, general relativity, and the amazing technologies that were developed to carry out this experiment.
Visual tour of the GP-B spacecraft and payload from our GP-B Web site: http://einstein.stanford.edu/content/vehicle_tour/index.html
PDF file containing a 1/20 scale, paper model of the GP-B spacecraft that you can download print out, and assemble: http://einstein.stanford.edu/content/paper_model.
NASA's Marshall Space Flight Center also has a series of Web pages devoted to GP-B: (http://www.gravityprobeb.com)
Photo, taken through a telescope by Swiss physics teacher and amateur astronomer Stefano Sposetti, of GP-B spacecraft in orbit, passing near IM Pegasi: http://aida.astronomie.info/sposetti.
The Harvard-Smithsonian Center for Astrophysics (Cambridge) and York University (Toronto), with contributions from the Observatoire de Paris, have been studying the motions of the guide star, IM Pegasi for over a decade. To find out more, visit: http://www.yorku.ca/bartel/guidestar/
In addition, you'll find information in the Guide Star FAQ on our Web site: http://einstein.stanford.edu/content/faqs/faqs.html#guidestar and on pages 18-20 of the Gravity Probe B Launch Companion: http://einstein.stanford.edu/highlights/GP-B_Launch_Companion.pdf.
Track the GP-B satellite on the Web using NASA's Java-based J-Pass satellite tracking application at: http://science.nasa.gov/realtime/JPass/ Also, you can track the GP-B satellite on Personal Digital Assistants (PDAs) using either the Palm OS or Pocket PC operating systems with software from Big Fat Tail Productions: http://www.bigfattail.com.
The Einstein Exhibition at the Skirball Cultural Center in Los Angeles through May 2005: Information about the Einstein exhibition is available on the Skirball Center Web site: http://www.skirball.org/index.asp?s=exhibit&p=einstein.asp. If you can't make it to Los Angeles, you can visit the AMNH's virtual Einstein exhibit on the Web at: http://www.skirball.org/exhibit/amnh_frame.html.
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ABOUT THE GPB-UPDATE EMAIL LIST
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To subscribe to this list, send an email message to "majordomo@lists.Stanford.edu" with the command "subscribe gpb-update" in the body of the message (not in the Subject line).
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NASA - Stanford - Lockheed Martin
Gravity Probe B Program
"Testing Einstein's Universe"
http://einstein.stanford.edu
Bob Kahn
Public Affairs Coordinator
Phone: 650-723-2540
Fax: 650-723-3494
Email: kahn@relgyro.stanford.edu
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Regards,
LelandJ
