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Old 02-18-2009, 08:03 AM   #1
dayzero
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Join Date: Oct 2008
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Exclamation 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.
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Old 02-18-2009, 11:07 AM   #2
Czymra
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Default Re: Gravity Probe B Update / Frame Dragging Expmnt.

Can someone translate that?
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Old 02-20-2009, 11:02 AM   #3
dayzero
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Join Date: Oct 2008
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Thumbs up 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.
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Old 02-21-2009, 07:56 AM   #4
dayzero
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Default Re: Gravity Probe B Update / Frame Dragging Expmnt.

Awesome vid Kathleen!
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