Reference File Types

The pathloss correction step uses a pathloss reference file.

CRDS Selection Criteria

Pathloss reference files are selected on the basis of EXP_TYPE values for the input science data set. Only NIRSPEC IFU, FIXEDSLIT and MSA data perform a pathloss correction in build 7.

Pathloss Reference File Formats

The PATHLOSS reference files are FITS files with extensions for each of the aperture types. The FITS primary data array is assumed to be empty.

The NIRSPEC IFU reference file has four extensions, one pair for point sources, and one pair for uniform sources. In each pair, there are either 3-d arrays for point sources, because the pathloss correction depends on the position of the source in the aperture, or 1-d arrays for uniform sources. The pair of arrays are the pathloss correction itself as a function of decenter in the aperture (pointsource only) and wavelength, and the variance on this measurement (currently estimated).

The NIRSPEC FIXEDSLIT reference file has this FITS structure:

HDU No. Name Type Cards Dimensions Format
0 PRIMARY PrimaryHDU 15 ()  
1 PS ImageHDU 29 (21, 21, 21) float64
2 PSVAR ImageHDU 29 (21, 21, 21) float64
3 UNI ImageHDU 19 (21,) float64
4 UNIVAR ImageHDU 19 (21,) float64
5 PS ImageHDU 29 (21, 21, 21) float64
6 PSVAR ImageHDU 29 (21, 21, 21) float64
7 UNI ImageHDU 19 (21,) float64
8 UNIVAR ImageHDU 19 (21,) float64
9 PS ImageHDU 29 (21, 21, 21) float64
10 PSVAR ImageHDU 29 (21, 21, 21) float64
11 UNI ImageHDU 19 (21,) float64
12 UNIVAR ImageHDU 19 (21,) float64
13 PS ImageHDU 29 (21, 21, 21) float64
14 PSVAR ImageHDU 29 (21, 21, 21) float64
15 UNI ImageHDU 19 (21,) float64
16 UNIVAR ImageHDU 19 (21,) float64

HDU #1-4 are for the S200A1 aperture, while #5-8 are for S200A2, #9-12 are for S200B1 and #13-16 are for S1600A1. Currently there is no information for the S400A1 aperture.

The NIRSPEC IFU reference file just has 4 extensions after the primary HDU, as the behavior of each slice is considered identical.

The NIRSPEC MSASPEC reference file has 2 sets of 4 extensions, one for the 1x1 aperture size, and one for the 1x3 aperture size. Currently there are no other aperture sizes.