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For release: 11-08-04
Release #: 04-276  

Testing Einstein's Theory: Hartselle native plays role in NASA Gravity Probe B mission

Photo description: Sanford

As a major NASA mission begins science operations, Hartselle, Ala., native Joe A. Sanford can make a rare claim — that he helped test Albert Einstein's General Theory of Relativity.

Photo: Sanford (NASA/MSFC)

Sanford, who resides in Hartselle, is a member of NASA's Gravity Probe B team. Also known as GP-B, the experiment will test Einstein's theory that space and time are slightly distorted by the presence of massive objects such as planets and stars.

As a flight systems design engineer, Sanford is part of the Gravity Probe B design team at NASA's Marshall Space Flight Center in Huntsville, Ala., providing technical oversight of the space vehicle's mission-critical gas management assembly, which delivers ultra-high purity helium fuel to spin-up the gyroscopes.

Gravity Probe B launched April 20 from Vandenberg Air Force Base, Calif., aboard a Boeing Delta II launch vehicle. Orbiting 400 miles above Earth, the Gravity Probe B space vehicle circles the globe every 90 minutes, crossing over both poles.

The experiment will measure, very precisely, tiny changes in the direction of spin of four gyroscopes contained in the spacecraft satellite. So free are the gyroscopes from disturbance that they will provide an almost perfect space-time reference system.

These measurements will enable scientists to track two effects -- how space and time are very slightly warped by the presence of the Earth, and how the Earth's rotation very slightly drags space-time around with it.

Einstein proposed the General Theory of Relativity in 1916, approximately 80 years before the advent of technology capable of testing this aspect of his theory.

Gravity Probe B's 12-month science-data acquisition period will be followed by a month post-science period for calibrations. By 2005 the Gravity Probe B mission will be complete, and a one-year period is planned for scientific analysis of the data.

Sanford has a bachelor's degree in mechanical engineering from the University of Alabama in Huntsville.

NASA's Gravity Probe B program is managed at the Marshall Space Flight Center. NASA's prime contractor for the mission, Stanford University in Stanford, Calif., conceived the experiment and is responsible for the design of the science instrument, as well as for mission operations and data analysis. A major subcontractor, Lockheed Martin of Sunnyvale, Calif., designed and built the spacecraft as well as portions of the science instrument.

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


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