Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aas...21548107c&link_type=abstract
American Astronomical Society, AAS Meeting #215, #481.07; Bulletin of the American Astronomical Society, Vol. 42, p.571
Astronomy and Astrophysics
Astronomy
Scientific paper
We present an overview of the calibration and properties of data from the IRAC instrument aboard the Spitzer Space Telescope taken after the depletion of cryogen. The cryogen depleted on 15 May 2009, and shortly afterward a two-month-long calibration and characterization campaign was conducted. IRAC started nominal science observations for the warm mission on 28 July 2009. The array temperature and bias setpoints were revised on 19 September 2009 to take advantage of the lower power dissipation by the instrument and improve sensitivity. The final sensitivities are comparable to the cryogenic mission with the 3.6 micron array being slightly less sensitive (10-15%) and the 4.5 micron array within 5% of the cryogenic sensitivity. The photometric, gain, and bias stability are excellent with photometry repeatable to the percent level for standard observations. While the array bias pattern and linearity solutions have changed from the cryogenic values, the data are stable, and better than milli-mag photometry is achievable for long-stare photometric observations. The current absolute photometric uncertainties are 5-7% and 4% at 3.6 and 4.5 microns, respectively. These values are slightly higher than the 3% absolute uncertainty for the cryogenic data; however, the warm calibration will improve with continued collection of calibration data and analysis. The expectation is that the warm calibration will match the cryogenic calibration after one year of science observations. As predicted, the optical properties are very similar to cryogenic. Warm IRAC operations fully support all science that was conducted in the cryogenic mission and all currently planned warm science projects (including Exploration Science programs). We expect that IRAC will continue to make ground-breaking discoveries in star formation, the nature of the early universe, and in our understanding of the properties of exoplanets. Support for this work was provided by NASA.
Ashby Matthew L. N.
Carey Sean Joseph
Fazio Giacomo
Glaccum William J.
Hoffmann William F.
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