HST Observation Coordinated with NASA/Stanford Gravity Probe_B {GP-B} Experiment
Abstract
We propose to use six orbits to obtain WFPC2 images through several filters at two roll orientations for each of the three bright RS CVn stars {V<5.8} that are the candidates for use as the guide star of the NASA/Stanford Gravity Probe-B {GP-B} mission. GP-B is designed primarily to measure the "frame-dragging" effect predicted by general relativity, in this case the slow eastward rotation of locally inertial frames with respect to the "fixed stars" due to the diurnal rotation of the earth's mass. The uncertainty of the proper motion of the guide star in an extragalactic frame places one limit on the accuracy of the measurement of frame dragging. The standard error of the rate of motion during the mission should be less than 0.3 milliarcseconds per year. This level can be achieved for our RS CVn radio binaries by means of astrometric VLBI observations spanning about a decade. However, the presence of any third component orbiting the selected guide star with a period in the range of about 100 days to 100 years could cause the mean transverse motion of the image seen by GP-B to differ significantly from that measured by VLBI. Our proposed WFPC2 images will allow a search for plausible main-sequence companions not detectable by other means.
- Publication:
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HST Proposal
- Pub Date:
- July 1996
- Bibcode:
- 1996hst..prop.7209S