In this section we describe the data files that have to do with spectroscopic calibration, including dark subtraction, wavelength calibration, non-linearity corrections, flat-fielding, wavelength calibration, and flux conversion. Table 6.4 lists all of the calibration files delivered by the Spitzer Heritage Archive for a spectroscopic AOR.
Table 6.4: Calibration Files Delivered.
Name
Description
Format (d)
Channels
Size (kb)
b*flatfield.fits
The first data plane contains a 2D flat-field image. NaNs are fatally flagged or unreliable pixels. The second plane stores the uncertainty image (nominally set to 0.001). See Sections 4.1.2 and 5.1.17. See tablenote (a).
128 × 128 × 2
32-bit real
0,1,2,3
150
b*flatfield_cmask.fits
Mask of regions to flat-field. The region of the image which will have the flat-field applied contains the value zero. Regions in the flat-field which are deemed "uncertain” have values 256 (bit 8). Regions which are not to be flat-fielded (as determined by wavsamp_omask) are set to 128 (bit 7). See tablenote (a).
128 × 128
16-bit int
0,1,2,3
37
b*fluxcon.tbl
Conversion from electrons/sec to Jy. Of the 20 columns, the most useful are: Col 1 = spectral order; Col 2 = reference wavelength in microns; Col 8 = flux conversion factor in (electron/sec)/Jy; Col 9 = uncertainty in the flux conversion factor; Col 10 = ao, Col 12 = a1, Col 14 = a2, Col 16 = a3, Col 18 = a4, Col 20 = a5, where a0, a1, … a5are the coefficients in the polynomial fit described in Section 5.7.4. Also see Section 4.1.4 and Table 6.5 and tablenote (a).
ASCII
0,1,2,3
5
b*fovmask.fits
Maps FOV values to the image. See tablenote (c).
128 × 128
16-bit int
0,1,2,3
37
b*lincal.fits
Non-linearity model cube. The first plane gives the α coefficients of each pixel. The second plane gives the signal threshold in electrons for applicability of the non-linearity model. Samples exceeding this threshold are not corrected. The third plane contains the uncertainties of each α coefficient. See also Section 5.1.11 and tablenote (a).
128 × 128 × 3
32-bit real
0,1,2,3
200
b*lincal_cmask.fits
Masks pixels not to be corrected for non-linearity. Pixels whose linearity is not corrected are set to have values of 4096. See tablenote (a).
128 × 128
16-bit int
0,1,2,3
37
b*lincal_satcor.fits
Linearity model used during "satcor" (saturation correction) process.
128 x 128 x 3
32-bit int
0,1,2,3
200
b*lincal_satcor_cmask.fits
Pixel mask bits for b*lincal_satcor.fits file. It uses the same bits as the b*lincal_cmask.fits file.
128 x 128
16-bit int
0,1,2,3
37
b*linecorr.tbl
Reference file.
ASCII
0,1,2,3
1
b*omask.fits
Gives locations of the orders for use in stray light removal.
128 x 128
16-bit int
0,1,2,3
37
b*pmask.fits
Mask of semi-permanent bad pixels in the array.
128 × 128 × N
16-bit int
0,1,2,3
37
b*r#dark.fits
Dark subtraction cube, in electrons. See tablenote (b).
128 × 128 × N
32-bit real
0,1,2,3
281
b*r#dark_cmask.fits
Masks unilluminated pixels to prevent division by flat. See tablenote (b).
128 × 128 × N
16-bit int
0,1,2,3
132
b*r#dark_unc.fits
Dark uncertainties. See tablenote (b).
128 × 128 × N
32-bit real
0,1,2,3
281
b*umask.fits
Unilluminated region mask.
128 × 128
16-bit int
0,1,2,3
37
b*wavsamp.tbl
This file is the fundamental element of the wavelength calibration. It defines the parameters of the pseudo-rectangles in array pixel coordinates. The columns of the table are: Column 1 = spectral order, Columns 2 and 3 = x and y coordinates of the center of a given pseudo-rectangle, Column 4 = wavelength (microns) associated with that rectangle. Subsequent columns define the corners of the rectangles. See Sections 4.1.3 and 5.7.3
ASCII
0,1,2,3
32
b*wavsamp_offset.fits
This FITS file gives the distance on the sky in arcseconds from a given pixel to the field-of-view center.
128 × 128
32-bit real
0,1,2,3
67
b*wavsamp_omask.fits
This FITS file shows the order number associated with a given region in an image. For the low-resolution modules (LL and SL), the first and second order spectral regions are denoted by 1 and 2 respectively. The bonus order is denoted by the number 3 (although it is really a first order spectrum). For the high-resolution modules (SH and LH), the echelle orders range from m=11 (reddest) to m=20 (bluest).
128 × 128
16-bit int
0,1,2,3
37
b*wavsamp_wave.fits
This FITS file shows the wavelength associated with a given pixel. The extraction procedure involves interpolation, so this association is for informational purposes only, and is not appropriate for science quality extractions. The exact wavelength and cross-dispersion solution is provided in the wavesamp.tbl file.
128 × 128
32-bit real
0,1,2,3
67
b0_lmask.fits
Short Low Stray Light Correction Mask.
128 × 128
16-bit int
0
37
b0_pkumask.fits
Mask unilluminated areas of the Peak-Up arrays.
128 × 128
16-bit int
0
37
b0_psf_fov.tbl
Slit FOV and PSF information. See tablenote (c).
ASCII
0
2
b0_slt_coeffs.tbl
Stray light coefficients.
ASCII
0
2
b2_psf_fov.tbl
Slit FOV and PSF information. See tablenote (c).
ASCII
2
2
cal_set*txt
Identifies what set of CAL files was used in the processing.
ASCII
0,1,2,3
1
cdelt12_distort_blue.tbl
Astrometric distortion coefficients.
ASCII
0
2
cdelt12_distort_blue.tbl
Astrometric distortion coefficients.
ASCII
0
2
cdelt12_distort_full*.tbl
Astrometric distortion coefficients.
ASCII
0
2
cdelt12_distort_red.tbl
Astrometric distortion coefficients.
ASCII
0
2
instrument_FOV.tbl
Gives locations of the FOVs on the focal plane. See tablenote (c).
ASCII
0,1,2,3
5
slit_pa_offsets.tbl
Gives twist angle offsets (north through east) of the FOVs on the focal plane. See tablenote (c).
ASCII
0,1,2,3
1
(a) For the LH module, the calibration files are different for campaigns pre25/post24. For the SL module, the calibration files are different for campaigns pre33/post32, and for the LL module, the calibration files are different for campaigns pre45/post44.
(b) The darks for LH and LL are campaign-dependent.
(c) See Section 6.6.4 for more information on FOV.
(d) N = number of samples per ramp.
Table 6.5: Wavelength ranges used to derive fluxcon.tbl.
Order
λ0 (μm)
λ1 (μm)
SL2
5.25
7.55
SL3
7.39
8.42
SL1
7.58
13.81**
LL2
14.24
20.84
LL3
19.91
21.10
LL1
20.42
37.86
SH20
9.89
10.6113
SH19
10.39
11.23
SH18
10.96
11.90
SH17
11.59
12.60
SH16
12.30
13.33
SH15
13.11
14.30
SH14
14.03
15.23
SH13
15.14
16.39
SH12
16.32
17.89
SH11
17.75
19.50
LH20
19.05
20.55
LH19
19.81
21.66
LH18
20.90
22.90
LH17
22.10
24.28
LH16
23.48
25.74
LH15
25.02
27.42
LH14
26.76
29.38
LH13
28.80
31.57
LH12
31.04
34.11
LH11
33.74
36.83
**excludes part of teardrop, which starts at 13.44 microns. See Section 7.3.8
are the coefficients in the polynomial fit described in Section 5.7.4. Also see Section 4.1.4 and Table 6.5 and tablenote (a).