The extraction flow requires several calibration files. Default files are provided with the SPICE distribution under the irs/cal/ directory. In general, users will not need to change these files. Alternate files may be selected within the SPICE GUI using the Calibration Files Edit dialog. The calibration files are described below.
1.5.1 Wavsamp Files
Three files describe the “pseudo-rectangles” used to extract from the non-rectilinear spectrum on the array:
b[0,1,2,3]_wavsamp.tbl: Describes the location of the “pseudo-rectangles” in pixel coordinates.
b[0,1,2,3]_wavsamp_wave.fits: Maps the approximate wavelength for each pixel.
b[0,1,2,3]_wavsamp_offset.fits: Maps the approximate spatial offset for each pixel.
The prefix in the filenames, b[0,1,2,3] refers to the short-low (SL), short-high (SH), long-low (LL), and long-high (LH) IRS module, respectively (see the IRS Instrument Handbook).
1.5.2 Default Extraction Widths
The file containing the default width for point-source extraction from each slit can be found under the irs/cal directory:
b[0,2]_psf_fov.tbl: Lists the default width for extraction from each slit. Recall that for the high resolution slits (1,3), the extraction is done from the full slit.
The file containing the rectified stellar template used as the spatial profile for point-source optimal extraction from each slit, order, and nod position can be found under the irs/cal directory. See §2.5.3 for more information on optimal extraction.
b[0,1,2,3]_rectempl_[1,2][0,1,2].tbl: Rectified stellar templates for point-source optimal extraction. The suffix [1,2][0,1,2].tbl specifies the order and nod position (0 = slit center).
1.5.4 Flux Calibration Tables
The flux calibration from electrons per second to Janskys is performed based on the parameters given in calibration tables. Separate tables are used for point-source (default) or extended-source extraction.
b[0,1,2,3]_aploss_fluxcon.tbl: The correction used in extended-source extraction for light losses due to the extraction aperture.
b[0,1,2,3]_slitloss_fluxcon.tbl: The correction used in extended-source extraction for light losses from the slit due to the changing point spread function as a function of the wavelength.
b[0,1,2,3]_fluxcon.tbl: Contains the “tuning” parameters used by the Point Source Tune module, incorporating both slit and (in low-res) aperture losses.
These files are located in the cdf/ subdirectory under the spice/ directory. The extracted spectrum (Fe) in electrons/sec is converted to Jy (Fν) using the formula Fν = Fe/C where the flux conversion, C, is given by:
