Hi,

I received this information the other day.

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GRAVITY PROBE B MISSION UPDATE CORRECTIONS -- June 21, 2004
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Following are two corrections to the June 18, 2004 GP-B update that I sent out this past Saturday.

1. The spacecraft's orbit is no longer continually in full sun
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The spacecraft's orbit only remains in full sun continually for approximately 3 weeks, and this happens twice during each year: From May 23 - June 13 and from November 21 - December 12. At all other times of the year, the spacecraft is eclipsed by the Earth's shadow for a percentage of each orbit. This eclipse period reaches a maximum value of approximately 40% of the orbit on September 12 and again on March 21.


2. Declination really is measured in degrees, not hours
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In the Errata section of last week's update, I inadvertently perpetuated one of the errors I was attempting to correct. The following information was kindly provided by Norbert Bartel, Professor of Astrophysics and Space Science at York University, Toronto, Canada.

Below is the position of the guide star, IM Pegasi, on December 5/6, 2003:

Right Ascension: (J2000) = 22h 53m 02.26s
Declination: (J2000) = +16d 50m 28.2s

In addition to his work in conjunction with the Harvard-Smisonian Center for Astrophysics in mapping the motion of IM Pegasi using VLBI (Very Long Baseline Interferometry), Professor Bartel wrote, directed, and produced a 26-minute video about GP-B called Testing Einstein's Universe. You can learn more about this video and purchase a copy on DVD from the Web site: http://www.astronomyfilms.com/

Regards,

LelandJ