scholarly journals Progress in VLBI Stellar Astrometry for the NASA/Stanford Relativity Mission (Gravity Probe B)

1998 ◽  
Vol 164 ◽  
pp. 385-386
Author(s):  
M. I. Ratner ◽  
D. E. Lebach ◽  
I. I. Shapiro ◽  
N. Bartel ◽  
M. F. Bietenholz ◽  
...  
Keyword(s):  
General Relativity ◽  
Standard Error ◽  
Proper Motion ◽  
Gravity Probe B ◽  
Frame Dragging ◽  
Vlbi Observations ◽  
Gravity Probe ◽  
Guide Star ◽  
Radio Stars ◽  
Relativity Mission

AbstractThe NASA/Stanford Relativity Mission (Gravity Probe B) is to test the unverified “frame-dragging” prediction of general relativity through measurements of the precessions of orbiting gyroscopes. For mission accuracy goals to be met, the proper motion of a “guide star,” whose position will be used as an inertial reference, must be determined in an extragalactic reference frame with a standard error less than 0.5 mas/yr. We discuss our VLBI observations of the current guide-star candidates (radio stars HR 1099, HR 5110, and HR 8703) and our techniques for obtaining differential astrometric positions with the needed accuracy.

scholarly journals VLBI astrometry for the NASA/Stanford gyroscope relativity mission Gravity Probe B

2007 ◽  
Vol 3 (S248) ◽  
pp. 190-191
Author(s):  
N. Bartel ◽  
R. R. Ransom ◽  
M. F. Bietenholz ◽  
D. E. Lebach ◽  
M. I. Ratner ◽  
...  
Keyword(s):  
Standard Error ◽  
Proper Motion ◽  
Parameter Estimate ◽  
Small Contribution ◽  
Gravity Probe B ◽  
Tests Of General Relativity ◽  
The Core ◽  
Upper Limit ◽  
Gravity Probe ◽  
Relativity Mission

AbstractWe used VLBI observations at 8.4 GHz between 1991 and 2005 to determine the motion of the RS CVn binary IM Pegasi (HR 8703), the guide star for the NASA/Stanford gyroscope relativity mission, Gravity Probe B (GP-B). The motion was determined relative to our primary reference, the core of the quasar 3C 454.3. The stability of this core was checked relative to two other extragalactic sources, B2250+194 and B2252+172, the former of which was tied to the ICRF. The core of 3C 454.3 is stationary relative to these two sources to within 30 μas yr−1 in each coordinate. IM Pegasi's radio morphology varies, but appears to be on average centered on the primary. We estimate the proper motion of IM Pegasi with a statistical standard error (sse) of 30 μas yr−1 in each coordinate. We also estimate the parallax with a statistical standard error of 75 μas and parameters of the orbit with sse's corresponding to 110 μas on the sky. Coupled with our upper limit of three times the sse on any systematic errors in each parameter %threefold higher upper limit on the systematic error contributions to each parameter estimate, these results ensure that the uncertainty of IM Pegasi's proper motion makes only a small contribution to the uncertainty of GP-B's tests of general relativity.

scholarly journals VLBI FOR GRAVITY PROBE B . V. PROPER MOTION AND PARALLAX OF THE GUIDE STAR, IM PEGASI

2012 ◽  
Vol 201 (1) ◽  
pp. 5 ◽  
Author(s):  
M. I. Ratner ◽  
N. Bartel ◽  
M. F. Bietenholz ◽  
D. E. Lebach ◽  
J.-F. Lestrade ◽  
...  
Keyword(s):  
Proper Motion ◽  
Gravity Probe B ◽  
Gravity Probe ◽  
Guide Star

Gyroscopes and charge control for the Relativity Mission Gravity Probe B

2000 ◽  
Vol 25 (6) ◽  
pp. 1181-1184 ◽  
Author(s):  
Saps Buchman ◽  
C.W.F. Everitt ◽  
Brad Parkinson ◽  
J.P. Turneaure ◽  
R. Brumley ◽  
...  
Keyword(s):  
Gravity Probe B ◽  
Charge Control ◽  
Gravity Probe ◽  
Relativity Mission

scholarly journals VLBI FOR GRAVITY PROBE B . III. A LIMIT ON THE PROPER MOTION OF THE “CORE” OF THE QUASAR 3C 454.3

2012 ◽  
Vol 201 (1) ◽  
pp. 3 ◽  
Author(s):  
N. Bartel ◽  
M. F. Bietenholz ◽  
D. E. Lebach ◽  
J. I. Lederman ◽  
L. Petrov ◽  
...  
Keyword(s):  
Proper Motion ◽  
Gravity Probe B ◽  
The Core ◽  
Gravity Probe

Status of the cryogenic telescope and guide star for Gravity Probe B

2000 ◽  
Vol 25 (6) ◽  
pp. 1189-1192 ◽  
Author(s):  
Suwen Wang ◽  
D.-H. Gwo ◽  
K.A. Bower ◽  
L.W. Huff ◽  
J.A. Lipa
Keyword(s):  
Gravity Probe B ◽  
Gravity Probe ◽  
Guide Star

Multiband Photometry of the Chromospherically Active & Spotted Binary System IM Peg—the Guide Star for the Gravity Probe B Mission

2010 ◽  
Vol 122 (892) ◽  
pp. 670-682 ◽  
Author(s):  
Robert Zellem ◽  
Edward F. Guinan ◽  
Sergio Messina ◽  
Antonino F. Lanza ◽  
Richard Wasatonic ◽  
...  
Keyword(s):  
Binary System ◽  
Gravity Probe B ◽  
Gravity Probe ◽  
Guide Star

Stress and its Effect on Surface Morphology in Multi-Layer Ti-Cu Films

1996 ◽  
Vol 441 ◽  
Author(s):  
Ping Zhou ◽  
Saps Buchman ◽  
Chris Gray ◽  
John Turneaure ◽  
James E. Turlo
Keyword(s):  
Surface Morphology ◽  
Smooth Surface ◽  
Total Thickness ◽  
Full Understanding ◽  
Gravity Probe B ◽  
Cu Films ◽  
Number Of Layers ◽  
Gravity Probe ◽  
Relativity Mission ◽  
Scanning Electron

AbstractWe have characterized the stress and its effects on surface morphology for multi-layer thin films of about 3μm total thickness, consisting of three or seven layers of Ti and Cu. These films constitute the electrostatic suspension electrodes for the gyroscope housings of the Relativity Mission Gravity Probe B. Full understanding of surface morphology is critical for meeting the complex requirements of this application.The residual stresses have been measured using a laser curvature technique, while the surface morphology was studied by scanning electron microscopy (SEM). We find that the surface morphology depends strongly on the stress, which evolves with the Ti-Cu multi-layer period. Average stress and the resulting surface roughness decrease for thinner Cu layers (increased total number of layers). Seven layer Ti-Cu films with low stress and very smooth surface have been successfully used for the electrodes of the gyroscope housings.

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