Vanadium 50, I searched the net I cannot see if NASA's final report is published in any peer-reviewed article, so I am not sure if this is a worthwhile test for telling frame-dragging due to Earth's rotation.
What I did manage to lay my hands on is a document at stanford university website:http://einstein.stanford.edu/content...020509-web.pdf
I quote the below from the pdf doc page 6. "The gyroscope is a spinning spherical body. Conceptually, therefore, Gravity Probe B is simple. All it needs is a star, a telescope, and a spinning sphere. The difficulty lies in the numbers. To reach the 0.5 marc-s/yr experiment goal calls for:
1) One or more exceedingly accurate gyroscopes with drift rates < 10-11 deg/hr, i.e. 6 to 7 orders of magnitude better than the best modeled inertial navigation gyroscopes
2) A reference telescope ~3 orders of magnitude better than the best previous star trackers
3) A sufficiently bright suitably located guide star (IM Pegasi was chosen) whose proper motion with respect to remote inertial space is known to <0.5 marc-s/yr
4) Sufficiently accurate orbit information to calibrate the science signal and calculate the two predicted effects"
Going by its method I am not sure what is it really trying to prove and accomplish?