Update on NICMOS Reference Flies

The response of the three NICMOS detectors when observing a standard star showed variations of 2-4% during both the era before the installation of the NICMOS Cooling System, NCS (1997-98) and during the era of NCS operation 2002-08. If uncorrected, these variations could affect the quality of reduced NICMOS images, introducing errors in the photometry. Here we discuss steps taken to mitigate these effects, including the creation of dynamic reference files that takes into account the variations in detector response. This includes the photometric calibration tables and the flat-field and dark reference files. Furthermore, updates have been made to the calnica calibration software to accommodate these new reference files. Using these new reference files will in some cases improve the photometric accuracy of NICMOS images by ∼2-3%.