Hi,
Here is the Gravity Probe B update for August 12, 2005.
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GRAVITY PROBE B MISSION UPDATE FOR 12 AUGUST 2005
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GP-B STATUS AT A GLANCE
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Mission Elapsed Time: 479 days (68 weeks/ 1.31 years)
Science Data Collection: 350 days (51 weeks/11.51 months)
Current Orbit #: 7,066 as of 1:00PM 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 96.7%
Attitude & Translation Control (ATC): X-axis attitude error: 144.1 marcs rms
Y-axis attitude error: 207.9 marcs rms
Command & Data Handling (CDH): B-side (backup) computer in control
Multi-bit errors (MBE): 0
Single-bit errors (SBE): 7 (daily avg.)
Telescope Readout (TRE): Nominal
SQUID Readouts (SRE): Nominal
Gyro #1 rotor potential: -0.7 mV
Gyro #2 rotor potential: -1.6 mV
Gyro #3 rotor potential: -2.6 mV
Gyro #4 rotor potential: -0.5 mV
Gyro #1 Drag-free Status: Backup Drag-free mode (normal)
MISSION DIRECTOR'S SUMMARY
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As of Mission Day 479, 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 #1.
With nearly a full year of science data captured, the mission is proceeding well. This past week, we made some routine adjustments during our final week of nominal science data collection. These adjustments included updating the star tracker star magnitudes, running an SRE calibration (SQUID Readout Electronics), updating the control gyro z-bias, and power cycling the ECU (Electronics Control Unit).
On Monday, August 15th, we will begin the final calibration phase of the mission. In this phase, we will be maneuvering the spacecraft to nearby stars and then back to the guide star to calibrate the Gyroscope Suspension System (GSS). This phase will last two weeks, ending around August 29th. If any helium remains, further calibrations will be performed at a different vehicle roll rate. Because of the nature of these calibrations, the science (data gathering) phase of the mission will end as soon as we begin these calibrations. By that point, we will have collected 352 days (or 11.5 months) of science data--a great success!
Note: During this final calibration phase, our weekly updates will be limited to the Mission Director's Summary, as our communications and public affairs team members will be concentrating their efforts on our End-of-Mission activities and our final report to NASA.
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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 has closed.However, you can visit the American Museum of Natural History'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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The email distribution list for this GP-B Weekly Highlights update is maintained on the Stanford University email lists server.
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).
You can unsubscribe at any time by sending an email message to "majordomo@lists.Stanford.edu" with the command, "unsubscribe gpb-update" in the body of the message (not in the Subject line.)
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Regards,
LelandJ
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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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