Guide star catalog for the Spitzer Space Telescope pointing calibration and reference sensor

摘要

The pointing calibration and reference sensor (PCRS) of the Spitzer Space Telescope (SST) consists of two 4 by 4 pixel visible band detectors plus associated electronics per redundant side. Located in the cryogenic multi instrument chamber of the science telescope system, these detectors, which have a field of view of 40 by 40 arcsec each, define the telescope coordinate frame. Employing guide stars in the range from 7 to 10 magnitude, the PCRS is used, among other things, for measuring the alignment of the active external autonomous star tracker twice per day. To ensure adequate accuracy, the standard radial position error of the guide stars needs to be less than 120 milliarcsec (mas) out to J2009.5. Initial selection of guide star candidates is performed using the Tycho, Tycho-2, Hipparcos, and Tycho Double Star catalogs. To obtain sufficient depth, the 2MASS PSC, USNO A2.0, 2MASS XSC, and PGC catalogs are used for computing the disturbing effect of neighboring objects. In addition, the DSS is employed for determining the perturbing effect of the sky background for each of the guide star candidates. The paper describes the guide star requirements, the methodology used for computing star position error due to neighboring objects and sky background, and the staged development approach that resulted in a ground-based catalog with 196,087 high-quality guide stars for the PCRS.