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S. M. Kent, S. S. Allam (Fermilab), R. C. Bohlin (STScI), S. E. Deustua (AAS), M. L. Lampton (UCBerkely SSL), N. Mostek, S. Mufson (Indiana U.), M. Richmond (Rochester Inst. Tech.), J. A. Smith (LANL), D. Tucker (Fermilab), B. E. Woodgate (NASA GSFC), SNAP Collaboration
The SNAP mission will obtain both images and spectra of faint supernovae using a mosaic of imaging detectors and an integral field unit spectrograph, which has an entrance aperture width of 3 arcseconds. The requirement on the absolute astrometric accuracy of the supernova positions is that the errors be small compared to the pointing accuracy of the SNAP spacecraft itself, which will be of order 1 arcsecond. Existing astrometric catalogs, such as the USNO CCD Astrometric Catalog (UCAC) provide the requisite accuracy, but the relatively bright magnitude limits and low density of stars in the SNAP supernova fields create some challenges for transferring calibrations to the faint objects. The SNAP focal plane is over half a meter wide and is subdivided into over 70 detector/filter combinations. We examine different strategies for transferring calibrations from existing catalogs to this complex focal plane, including obtaining new ground observations to set up a denser grid of faint, secondary astrometric standards and using techniques to combine data from large numbers of images within the SNAP supernova fields to determine the hundreds of parameters needed to describe the calibrations. We also examine techniques for doing relative astrometry, which can be done to much higher accuracy and is needed for aligning images to detect supernovae and to measure galaxy ellipticities in the SNAP weak lensing survey.
The author(s) of this abstract have provided an email address for comments about the abstract: skent@fnal.gov
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.