Computer Science – Performance
Scientific paper
Nov 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009wfc..rept...30k&link_type=abstract
Instrument Science Report WFC3 2009-30, 20 pages
Computer Science
Performance
Hubble Space Telescope, Hst, Space Telescope Science Institute, Wide Field Camera 3, Wfc3
Scientific paper
We present the first on-orbit observations to characterize the photometric performance of the in- frared (IR) camera on WFC3, based on data collected during the Servicing Mission Orbital Ver- ification 4 Phase (SMOV4) shortly after the installation of the WFC3 instrument on HST. The photometric zero points and stability of the detector are measured in all 15 IR filters, using two different HST spectrophotometric standards; the hot white dwarf star GD 153 and the cooler solar analog P330E. The measured counts of these stars are calculated from dithered, high signal-to-noise imaging observations. We find that the total system throughput of WFC3/IR is better than expected from the Thermal Vacuum (TV3) testing campaign, exhibiting efficiency gains of ~10 - 15% at all wavelengths. Repeat observations in all 15 filters are obtained at time intervals of 1 day, 1 week, and 1 month, and demonstrate that the throughput is stable to <1% in the medium and wide band filters. We update the Exposure Time Calculator (ETC) with these preliminary results by fitting a smooth curve (3rd order polynomial) to the ratios of the efficiency gains over previous predictions, in the medium and wide band filters. This polynomial is multiplied into the SYNPHOT throughput routines. We calculate photometric zero points for the IR camera, factoring in the new on-orbit sensitivity measurements, in three photometric systems, STMAG, ABMAG, and VEGAMAG. A much more detailed Cycle 17 calibration plan, including observations targeting additional primary standards, begins in October 2009.
Bohlin Ralph
Brown Tim
Deustua Susana
Kalirai Jason S.
Kimble Randy A.
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