Re: NASA Gravity Probe B mission enters science phase, ready to test Einstein's theory (Forwarded)

From: Jim Greenfield (greenfield_7_at_hotmail.com)
Date: 09/09/04 

Date: 8 Sep 2004 22:43:04 -0700

Andrew Yee <ayee@nova.astro.utoronto.ca> wrote in message news:<vRL%c.24286$lP4.1396941@news20.bellglobal.com>...
> Don Savage
> NASA Headquarters
> (202) 358-1547
>
> Steve Roy
> Media Relations Dept.
> (256) 544-0034
>
> Robert Kahn
> Stanford University, Stanford, Calif.
> (650) 723-2540
>
> Buddy Nelson
> Lockheed Martin, Sunnyvale, Calif.
> (510) 797-0349
>
> Status report no.: 04-228
>
> For release: 09/07/04
>
> NASA Gravity Probe B mission enters science phase, ready to test Einstein's theory
>
> Gravity Probe B (GP-B), a NASA spacecraft to test two predictions of Albert
> Einstein's general theory of relativity, achieved a major milestone this past
> week with the completion of the Initialization and Orbit Calibration (IOC) phase
> of its mission and the transition into the science phase. The GP-B mission is
> now one step closer to shedding new light on the fundamental properties of our
> universe.
>
> "This is the moment we have been waiting for," said Francis Everitt, GP-B
> science Principal Investigator at Stanford University. "It represents a
> magnificent effort by the entire Stanford-NASA-Lockheed Martin team."
>
> The GP-B spacecraft was launched on April 20, 2004 from Vandenberg Air Force
> Base, Calif., aboard a Boeing Delta II expendable launch vehicle. For the past
> four months, GP-B has been orbiting 400 miles above Earth, completing system
> checkouts and fine-tuning one of the most sophisticated science instruments ever
> put in orbit. On August 27 the spacecraft began science data collection.
>
> "It's been a long, amazing road to get to this point," said Rex Geveden, deputy
> director of NASA's Marshall Space Flight Center in Huntsville, AL. "When Gravity
> Probe B was first proposed more than 40 years ago, the technology required for
> this experiment did not yet exist. At least nine new technologies had to be
> invented and perfected, with the program's advances only possible through
> breakthroughs in cryogenics, drag-free satellite technology, and new
> manufacturing and measuring technologies."
>
> The spacecraft uses four ultra-precise gyroscopes to test two extraordinary
> predictions of Einstein's 1916 theory that space and time are distorted by the
> presence of massive objects. Specifically, it is testing two effects:
>
> 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.
>
> "It's great to be in our science mode," said Gaylord Green, GP-B Program Manager
> at Stanford University. "The team is ecstatic that the demanding IOC phase is
> over and the science phase has begun. Most importantly, all systems are meeting
> or exceeding the requirements of the mission."
>
> At launch, the spacecraft's Dewar (the largest ever put in orbit) contained
> approximately 650 gallons of superfluid helium-enough to maintain the gyroscopes
> in a cryogenic state for an estimated 16 months. The GP-B mission time line
> originally specified two months for initialization, checkout, and instrument
> tuning, 13 months of relativity data collection, and one final month of
> instrument re-calibration. The IOC phase actually required a little over four
> months to complete. Although this results in a slightly shorter data collection
> period than originally planned, GP-B will significantly surpass its mission
> performance requirements.
>
> Tuning up the Attitude and Translation Control system to achieve the
> extraordinarily precise pointing and drag-free positioning requirements of the
> spacecraft, as well as refining the set-up up the science gyros, accounted for
> the IOC extension. "These are items that cannot be tested on the ground," said
> Gaylord Green. "Using the extra time required for the checkout phase, the team
> obtained invaluable information about the GP-B science instrument."
>
> The science phase is the heart of the GP-B mission. During this phase, at least
> twice a day, data is relayed from Earth-based ground stations or NASA's data
> relay satellites to the GP-B Mission Operations Center at Stanford University in
> Stanford, Calif. This data includes space vehicle and instrument performance
> information, as well as the very precise measurements of the gyroscopes'
> spin-axis alignment relative to its guide star, IM Pegasi. Over the course of a
> year, the anticipated spin axis drift for the geodetic effect is a minuscule
> angle of 6,614.4 milliarcseconds, and the anticipated spin axis drift for the
> frame-dragging effect is even smaller, only 40.9 milliarcseconds. This angle is
> so small that if someone were to climb a slope of 40.9 milliarcseconds for 100
> miles, he would rise only one inch in altitude, measured to an accuracy of
> better than 1/100th of an inch.
>
> The GP-B mission has already achieved many extraordinary accomplishments:
>
> * GP-B is the first satellite ever to achieve both 3-axis attitude control
> (pitch, yaw, and roll), and 3-axis drag-free control (while orbiting the Earth,
> the whole spacecraft flies around one of the science gyros).
>
> * The GP-B gyros, which are performing perfectly in orbit, will be listed in the
> forthcoming edition of the Guinness Book of World Records as being the roundest
> objects ever manufactured.
>
> * The spin-down rates of all four gyros are considerably better than expected.
> GP-B's conservative requirement was a characteristic spin-down period (time
> required to slow down to ~37% of its initial speed) of 2,300 years. Recent
> measurements show that the actual characteristic spin-down period of the GP-B
> gyros exceeds 10,000 years-well beyond the requirement.
>
> * The magnetic field surrounding the gyros and SQUIDs (Super-conducting QUantum
> Interference Device) has been reduced to 10-7 gauss, less than one millionth of
> the Earth's magnetic field-the lowest ever achieved in space.
>
> * The gyro readout measurements from the SQUID magnetometers have unprecedented
> precision, detecting fields to 10-13 gauss, less than one trillionth of the
> strength of Earth's magnetic field.
>
> * The science telescope on board the spacecraft is tracking the guide star, IM
> Pegasi (HR 8703), to superb accuracy, and it is also collecting long-term
> brightness data on that star.
>
> The GP-B program will not release the scientific results obtained during the
> mission until after the science phase has concluded. It is critically important
> to thoroughly analyze the data to ensure its accuracy and integrity prior to
> releasing the results.
>
> 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.

If time passes differently under changed gravity, then time passes
differently at the earth's center, than at the surface, (or a point
above the surface).
Hands up all those who think the earth's center takes a different
amount of time to complete an orbit of the sun, than the
surface???????????????

Jim G
c'=c+v

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