First of four Assigned ID: 381 ----- Attempting Submission 1 (Fri Feb 25 15:35:35 GMT 2011) ----- We propose to analyze 9 new orbits of FGS astrometry, secured under calibration proposals GO-12832 and GO-12383. These will be merged with over 180 previous Optical Field Angle Distortion (OFAD) and Long-term Stability orbits to produce a definitive OFAD calibration. On 22 January 2009 the articulating mirror assembly (AMA) of FGS-1r was adjusted to improve the fringe morphology for TRANS mode (fringe scanning) observations. Unfortunately, this improvement to TRANS introduced a significant discontinuity in the POS-mode OFAD calibration. Previously we routinely obtained millisecond of arc (mas) per-observation residuals, yielding typical parallax errors of 0.2 mas and similar precision for exoplanet perturbation orbital parameters. Attempting to bridge the AMA gap with our existing OFAD calibration, we find residuals in excess of 10 mas. If we do not recalibrate FGS-1r, scientific results from over 300 orbits of FGS-1r POS mode astrometry are at risk. This analysis will also result in useful scientific results for our OFAD field, the open Galactic cluster M35. Comparing our newly derived internal motions (from an eighteen year baseline for OFAD proper motions) to radial velocities should result in an accurate distance to M35. Our catalog of >100 stars in the optical wavelength covers a 26’x11’ field. Its average relative positional error should be better than 0.1 mas and therefore useful to calibrate the distortions of any astrometric device. We request $120,246 to support a rescue of over 300 orbits of FGS astrometry, the generation of a velocity dispersion and distance to M35, and the preparation of a catalog to calibrate future and present astrometric instruments.

RESOLVED STELLAR POPULATIONS 0 Legacy true 0.0 0.0 false false false false SUPPORTED This object was generated by the targetselector and retrieved from the SIMBAD database. 06 09 6.0000 +24 21 0.00 J2000 FGS POS No F583W