Kenneth Mighell (National Optical Astronomy Observatory)
Keywords: Astronomy, Astronomical Catalogs
Abstract:
Planning is underway for the post-cryogenic (“warm”) operation of the Spitzer Space Telescope which will start around April 2009 after all of the liquid helium has been depleted. Only channels 1 and 2 (3.6 and 4.5 microns) of Spitzer’s Infrared Array Camera (IRAC) will be operational at full sensitivity at that time — providing an unmatched sensitivity from 3 to 5 microns until the James Webb Space telescope is launched. The other channels of all remaining instruments will not operate at the elevated temperatures (25-30K) of Spitzer will experience during its warm mission phase. Last year at AMOS 2006, I showed how the recorded flux of bright point sources observed with IRAC Ch1 is corrupted by lossy detectors which have large intrapixel quantum efficiency variations. During the past year, I have worked closely with members of Spitzer’s IRAC Instrument Team to demonstrate that my NASA-funded MATPHOT algorithm for precision stellar photometry and astrometry can yield an improvement in the precision of stellar photometry obtained from IRAC Ch1 observations of bright stars of more than 100% over the best results obtained with aperture photometry corrected with the radial correction recommended in the IRAC Data Handbook. I will describe results of an ongoing effort to develop new calibration procedures for IRAC Ch1 and Ch2 which have the potential of significantly improving the precision of IRAC bright point-source photometry. This timely research effort is intended to not only enhance the science return of existing IRAC Ch1 and Ch2 observations in the Spitzer data archive but also those that will be made during the Spitzer Warm Mission.
Date of Conference: September 12-15, 2007
Track: Astronomy and Astronomical Catalogs