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Project Camelot General Discussion Reactions, feedback and suggestions on interviews, current events and experiences. |
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02-18-2009, 08:03 AM | #1 |
Avalon Senior Member
Join Date: Oct 2008
Location: Southern England
Posts: 458
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Gravity Probe B Update / Frame Dragging Expmnt.
I've been following this experiment for a few years now - they're nearly there with the privately funded analysis, due to NASA's weird funding issues.
1. Gravity Probe B Status Update--February 16, 2009 (Bob Kahn) ---------------------------------------------------------------------- Message: 1 Date: Tue, 17 Feb 2009 02:34:00 -0800 From: Bob Kahn Subject: Gravity Probe B Status Update--February 16, 2009 To: gpb-update@lists.stanford.edu ================================ GP-B STATUS UPDATE -- February 16, 2009 ================================ OBSERVATION OF FRAME DRAGGING --------------------------------------------- The latest GP-B results, detailed in the papers and NASA report described below, show substantial improvement over the preliminary results announced at the April 2007 meeting of the American Physical Society (APS). At that time the geodetic effect was measured with a total uncertainty of 1%, but evidence of the frame-dragging effect was inconclusive. The latest data analysis that includes a model for the "roll-polhode resonance torque" yields a 15% statistical uncertainty for the Frame-Dragging effect. This 15% uncertainty does not include all systematic effects. You can view graphs of these extraordinary results on our website at: http://einstein.stanford.edu/highlights/hl_021609.html. The data analysis leading up to this important result proved more subtle than expected. 'Patch-effect' anomalies on the gyro rotor and housing have complicated the gyro behavior in two ways: 1. A changing polhode path affecting the determination of the gyro scale factor. 2. Two larger than expected Newtonian torques. Put simply, while mechanically both rotor and housing are exceedingly spherical, electrically they are not. Steadily advancing progress, reported to NASA directly and via successive meetings of the SAC, has brought a rather complete understanding of these effects. A turning point came last August with the incorporation of an elegant approach for computing the detailed history of the "roll-polhode resonance" torques discovered a year earlier by Jeff Kolodziejczak of NASA MSFC. The result was a large reduction in previously unexplained discrepancies between the four gyroscopes. Much further work remains to bring the analysis to completion. To date, limits in computational power have bounded the processing to essentially one point per 97-minute GP-B satellite orbit. The driving period of the roll-polhode resonance torques is at the difference between the 77.5 sec roll period of the spacecraft and a harmonic of the gyroscope polhode period. High-speed computing techniques now in development will lead to more detailed analyses, and allow GP-B to approach the intrinsic limit of the gyro readout. ISSI PRESENTATIONS/PUBLICATIONS & FINAL NASA SCIENCE REPORT -------------------------------------------------------------------------------------- Early last October, five members of our GP-B team presented papers on various aspects of the GP-B data analysis at the International Space Science Institute (ISSI) workshop in Bern, Switzerland on "The Nature of Gravity: Confronting Theory and Experiment in Space." The five papers summarize the interim results of the GP-B experiment, as also reported to our GP-B external Science Advisory Committee (SAC) at their 18th meeting on August 29, 2008. Following the ISSI meeting, the papers were submitted for publication in the international, refereed journal, Space Science Reviews. They will be reprinted in a hardcover book in the Space Sciences Series of the ISSI, both to be published by Springer later this year. The papers, along with an introductory preface, comprise the contents of a document entitled "Gravity Probe B Science Results-NASA Final Report," now posted on our website. You can view/download a PDF copy at: http://einstein.stanford.edu/content...020509-web.pdf. GP-B FUNDING ------------------------ We are profoundly honored that in January, 2008 Richard Fairbank (founder, Chairman and CEO of Capital One Financial Services Company and one of the three sons of GP-B co-founder, William Fairbank) made a private donation of $512K to Stanford, specifically to support GP-B's continuing data analysis work. Fairbank's generous offer was subsequently matched by both Stanford and NASA. This support carried the program until 30 September 2008. All of us here at GP-B are most grateful to Mr. Fairbank for his generous support. Discussions begun last summer with Dr. Turki al Saud, Vice President for Research Institutes at the King Abdulaziz City for Science and Technology (KACST) in Saudi Arabia, have led to the creation of an important Stanford-KACST collaboration, with Professor Charbel Farhat of the Stanford Aero-Astro Department as Co-PI for GP-B data analysis. As part of this agreement, KACST provided funding for GP-B from October 2008 through December 2009. To maximize the benefit to the scientific and engineering community, we plan to make the capstone of the GP-B program a conference on Fundamental Physics and Innovative Engineering in Space, in honor of William Fairbank. We thank NASA for forty-four years of continued support since issuing the first research Grant NSG-582 to the program in March 1964. The March 2007 "GP-B Post-Flight Analysis-Final Report" (http://einstein.stanford.edu/content...91907-scrn.pdf) contained an extensive history of GP-B and the NASA personnel who guided it. It is appropriate here to express further special thanks to three individuals, the MSFC Manager Mr. Anthony T. Lyons, the HQ Program Scientist for Physics of the Cosmos Dr. Michael H. Salamon, and the HQ Program Executive Dr. Alan P. Smale. Lastly, we are most grateful to the GP-B Science Advisory Committee (SAC) for their continuing advice and support. =================== PREVIOUS GP-B UPDATES =================== 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/highlig...indexmain.html ============================= OTHER LINKS THAT MAY INTEREST YOU ============================= Our NEW AND IMPROVED 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. Video and/or audio of May 18, 2006 public lecture by Principal Investigator, Professor Francis Everitt, on GP-B. You can view a Flash video of the lecture in your Web browser: http://einstein.stanford.edu/Media/E...orm-flash.html You can also download either a video or audio only copy of the lecture to an iPod from the Stanford University iTunes U Web site: http://itunes.stanford.edu, This Web page automatically launches the Apple iTunes program on both Macintosh and Windows computers, with a special Stanford on iTunes U "music store," containing free downloads of Stanford lectures, performances, and events. Francis Everitt's "Testing Einstein in Space" lecture is located in the Faculty Lectures section. People with audio-only iPods can download the version under the Audio tab; people with 5th generation (video) iPodfs can download the version under the Video tab. Visual tour of the GP-B spacecraft and payload from our GP-B Web site: http://einstein.stanford.edu/content...our/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 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 Extraordinary Technologies page-Telescope & Guide Star section on our Web site: http://einstein.stanford.edu/TECH/te...html#telescope ========================== ABOUT THE GPB-UPDATE EMAIL LIST ========================== The email distribution list for this GP-B Weekly Highlights update is maintained on the new Stanford University Mailman lists server. To subscribe to this list, send an email message to: gpb-update-join@lists.stanford.edu The subject and body of the message will be ignored, so it doesn't matter what you put there. |
02-18-2009, 11:07 AM | #2 |
Avalon Senior Member
Join Date: Nov 2008
Location: Germany
Posts: 1,151
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Re: Gravity Probe B Update / Frame Dragging Expmnt.
Can someone translate that?
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02-20-2009, 11:02 AM | #3 |
Avalon Senior Member
Join Date: Oct 2008
Location: Southern England
Posts: 458
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Re: Gravity Probe B Update / Frame Dragging Expmnt.
it was an unusual satellite probe featuring 4 perfect spheres in gyroscopes at perfect zero to test relativity of mass to space/time.
the theory is called 'frame dragging' where the mass of the earth theoretically 'drags' space/time. nasa nearly pulled the launch, which was strange as I believe it was one of the most expensive and longest-in-preparation missions ever. then, once it came back, nasa pulled the funding required to crunch through all the data. hmm. so they left nasa and finally got independent funding, and the crunching is now back on track. the links down the end have some good presentations, and there's a pretty lucid scientist down there too. |
02-21-2009, 07:56 AM | #4 |
Avalon Senior Member
Join Date: Oct 2008
Location: Southern England
Posts: 458
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Re: Gravity Probe B Update / Frame Dragging Expmnt.
Awesome vid Kathleen!
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