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WFC3 G141 Calibrations

WFC3/IR G141 calibration and reference files

The configuration and calibration files presented at the bottom of this page are in the correct format to be used with the aXe extraction software and the aXeSIM simulation software. To use these calibration products with aXe and aXeSIM, copy them into a directory and set your AXE_CONFIG_PATH environment variable to point to that directory.

The files were created using both ground-test (flat-field cube) and in-flight data (sensitivity and master sky), wth details given in WFC3 ISRs 2008-16, 2009-18, 2011-01 and 2011-05.

Calibrations are derived based on object positions determined from F140W direct imaging. Offsets from WFC3 ISR 2010-12 may need to be applied if positions are determined from imaging in other filters.

The master sky image should only be applied to data reprocessed using calwf3 v2.0 or later. It is also necessary to use them together with the aXe configuration file WFC3.IR.G141.V1.0.conf or later. WFC3 ISR 2011-01 gives details of how the master sky images were created.

April 12, 2012: Analysis of standard star data obtained in Cycle 18 and re-analysis of SMOV data has revealed that the v2 sensitivity function for the -1st order derived in WFC3 ISR 2011-05 (WFC3.IR.G141.m1st.sens.2.fits) contains a ~100nm wide dip centered at ~1250nm which is spurious. Fluxes derived using this sensitivity function will be up to 50% too low in this spectral region. We recommend that the file WFC3.IR.G141.m1st.sens.2.5.fits be used instead. While based on the the -1st order sensitivity function presented in WFC3 ISR 2009-17, this calibration file has now been successfully vetted using both SMOV and Cycle 18 standard star data. The aXe configuration file WFC3.IR.G141.V2.5.conf has been updated to reflect this change. We anticipate releasing an improved sensitivity function for the -1st order once higher signal-to-noise calibration data are available.

Jan 24, 2011: Updated G141 sensitivity, flat-field, and configuration files are available, based on additional analysis of standard star data obtained in Cycle 17. The new files are designated as version 2. Note that the zeroth-order sensitivity file remains at version 1. Details of the data analysis are given in WFC3 ISR 2011-05.

Nov 23, 2010: An updated G141 configuration file (V1.5) is available, which contains changes to fix a problem encountered when using the 'fluxcube' method in aXe to produce a contamination image. It was noticed that the zeroth-order spectra were not showing up in the contamination image and therefore that order was being neglected when estimating the contamination in spectra. The V1.5 configuration files contain appropriate changes to the definitions for the zeroth-order spectra (BEAM B) to fix this problem.

Calibration Files