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NASA Gravity Probe B Mission, Testing Einstein's Theory of Gravity Completes First Year in Space



 
 
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Old May 4th 05, 10:07 PM
Jacques van Oene
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Default NASA Gravity Probe B Mission, Testing Einstein's Theory of Gravity Completes First Year in Space

NASA Gravity Probe B Mission, Testing Einstein's Theory of Gravity Completes
First Year in Space

05.03.05


Steve Roy
Marshall Space Flight Center, Huntsville, Ala.
(Phone: 256.544.0034)
Status Report: 05-066


Is Einstein's general theory of relativity correct? Testing two
extraordinary predictions of that theory is the goal of Gravity Probe B, or
GP-B, a satellite that just marked its first anniversary in space. Published
in 1916 and hailed as one of the most brilliant creations of the human mind,
Albert Einstein's general theory of relativity weaves together space and
time into a four-dimensional "fabric," called spacetime, and defines gravity
as the warping and twisting of spacetime by massive objects.

With this theory, Einstein forever changed our notions of space, time, and
gravity. And although it has become one of the cornerstones of modern
physics, general relativity is the least tested of Einstein's theories.
While the warping and twisting of spacetime is calculated to be enormous in
the neighborhood of ultra-massive black holes, these effects are minuscule
and difficult to measure in the vicinity of a tiny celestial object such as
our Earth.

The GP-B spacecraft uses four ultra-precise, spherical gyroscopes to
experimentally test, with unprecedented precision, two specific effects
predicted by Einstein's theory: 1) the geodetic effect--the amount by which
the Earth warps local spacetime in which it resides, and 2) the
frame-dragging effect--the amount by which the rotating Earth drags local
spacetime around with it. At the one-year mark the spacecraft continues to
perform very well. The four on board gyroscopes have experienced and
measured relativistic effects for almost eight months. After completing the
mission and thoroughly analyzing the data the team plans to release the
final results in the summer of 2006.

One year ago, on April 20, 2004, GP-B was launched into a nearly perfect
polar orbit from Vandenberg Air Force Base, Calif. atop a Boeing Delta II
launch vehicle. During a four-month initialization phase, the spacecraft
underwent a complete checkout and optimization of all systems. Over 10,000
commands were successfully executed by on-board computers. The four
gyroscopes were spun up to their final speeds, averaging 72 Hz, or 4,300
rpm, and their spin axes were aligned with the GP-B guide star -- IM
Pegasi/HR 8703. The GP-B team began the science phase of the mission,
collecting data on the changing spin axis orientation of the four gyros that
will ultimately confirm or disprove the geodetic and frame-dragging
predictions of general relativity.

"Developing GP-B was a supreme challenge, requiring the skillful integration
of an extraordinary range of new technologies. It could never have been done
without the kind of unique long-term collaboration we have had between
Stanford, NASA, and Lockheed Martin," said GP-B Principal Investigator,
Francis Everitt, of Stanford University. "It is wonderful to be at the stage
we are, with the experiment working so well and proceeding steadily with the
analysis of the science data."

It is fitting that the completion of the Gravity Probe B experiment, the
most rigorous test to date of general relativity, will come to fruition this
year--the 100th anniversary of Einstein's "miracle" year, in which he
published four seminal papers, including the special theory of relativity
and his paper on the production and transformation of light, for which he
was awarded the Nobel Prize in 1921. "The GP-B team has shown that through
hard work and sustained effort, great things can be accomplished", said Tony
Lyons, NASA's GP-B program manager at the Marshall Space Flight Center in
Huntsville, Ala. "The spacecraft keeps getting better as we get farther into
the mission, and that's a tribute to the hard work of our excellent team."

The GP-B team is in the process of measuring the amount of liquid helium
remaining in the spacecraft's dewar. Shortly before the helium runs out, the
team plans to perform a series of instrument calibrations. "The purpose of
the calibration phase is to ensure data accuracy and analysis integrity
prior to releasing results," says Mac Keiser, project chief scientist.

Was Einstein Correct? Mac Keiser is not saying. Project policy maintains
that the program will not release scientific results obtained during the
mission until after the data analysis is completed next year.

NASA's Marshall Space Flight Center manages the GP-B program. NASA's prime
contractor for the mission, Stanford University, conceived the experiment
and is responsible for the design and integration of the science instrument,
as well as for mission operations and data analysis. Lockheed Martin, a
major subcontractor, designed, integrated and tested the space vehicle and
built some of its major payload components. NASA's Kennedy Space Center,
Fla., and Boeing Expendable Launch Systems, Huntington Beach, Calif., was
responsible for the launch of the Delta II.

More information about the Gravity Probe B mission is available at:


http://www.gravityprobeb.com

and

http://einstein.stanford.edu/


--
--------------

Jacques :-)

www.spacepatches.info


 




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