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M. Lampton (Space Sciences Laboratory, University of California, Berkeley), SNAP Collaboration
The SNAP science program requires photometric discovery and detailed multiband photometric and spectroscopic follow-up observations of at least 2000 Type Ia supernovae with redshifts spanning the range Z=0.3 to 1.7. The telescope is a two-meter aperture three-mirror anastigmat yielding diffraction limited images over a one degree field. Data are sent to the ground station and analyzed within a few days of receipt to allow detection and targetted spectroscopy near peak luminosity. The SNAP imager has a 0.7 square degree instrumented field of view and comprises CCD and HgCdTe devices to span the wavelength range of 350 nm to 1700 nm. A 2D-symmetric array of fixed filters is deployed over the sensors and the focal plane is operated in a step-and-stare mode to perform broadband photometry over fixed regions of the sky. The spectrograph is equipped with an image slicer to accommodate a working field of 3 x 3 arcseconds. A prism disperser yields a resolution of the order of 100, sufficient for SN classification, while offering high throughput over the entire 350-1700nm waveband. A dichroic beamsplitter images the visible spectrum onto a silicon CCD and the NIR spectrum onto a HgCdTe imager. The science requirements and satellite operational constraints that lead to this particular focal plane configuration will be described. The R&D activities we are undertaking to insure timely availability of the CCD and MCT sensors will also be presented.
This work has been supported by the U.S. Dept. of Energy, Office of Science, under contract DE-AC03-76SF00098.
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.