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31.3 CDBS Reference Relations

The CDBS relations for the FOS reference files and reference tables are described below. Note that these are relations that point to the reference files and tables: they do not contain the data used. Multiple entries are allowed for each reference file or table type which are distinguished by effective (or USEAFTER) date.

cyccs0r: This table is used to determine the aperture area for paired -apertures. If STEP-PATT=OBJ-SKY (or STAR-SKY) is used, it is only for sky subtraction.
cyccs1r: This table is used to determine which aperture (UPPER or LOWER) of a paired aperture was used for observing an object or sky -spectrum.
cyccs2r: Regions of the sky spectrum known to have emission lines. These regions are not smoothed before the sky is subtracted from the object -spectrum.

The cyccs2r table values were never formally confirmed after science verification (SV). This had little or no practical impact as, only a few sky observations were taken, none of which were intended to aid the proposed science.

cyccs3r: Filter widths used for smoothing the sky or background spectra.
cyccs4r: Polarimetry information regarding waveplate pass direction angles, initial waveplate position angles, the pixel number at which the wavelength shift between the two pass directions is to be determined for computing the merged spectrum, and the phase and amplitude coefficients for correction of polarization angle ripple.
cyccs5r: The shift in pixels to be applied to the sky spectrum before subtraction.
cyccs6r: Dispersion coefficients to generate wavelength scales. There is one entry for each detector, disperser, aperture, and polarizer combination.
cyccs7r: GIM correction scale factors used to scale the modeled shift of the spectrum due to the earth's magnetic field.
cyccs8r: Predicted background count rates as a function of geomagnetic position used to scale the background reference file.
cyccs9r: Un-illuminated diode ranges for each detector and grating combination. Used to determine the background scattered light.
cyccsar: List of OTA focus positions versus time. Used to correct for aperture sensitivity dependent on focus position.
cyccsbr: As a function of detector and disperser combination, coefficients to normalize aperture throughputs to the -reference aperture used to determine the average inverse sensitivity -calibration.
cyccscr: Throughput corrections versus focus as a function of the combination of detector, disperser, and aperture.
cyccsdr: As a function of detector and disperser combination, throughput correction factors to account for changes in -instrument sensitivity over time.
coccg2r: Paired pulse correction table used to correct for non-linear response of the diode electronics. Both detectors have the same correction constants, which are time independent. This table is shared with GHRS.
cybacr: This relation is for the background reference files. For each detector there is one file that is used as a default background count rate in the event no background spectra were observed.
cyfltr: This relation is for the flatfield reference files. These files are used to remove the small scale diode and photocathode non-uniformities. There are separate files for each detector, disperser, aperture, and polarizer combination.
cyivsr: (polarimetry only) This relation is for inverse sensitivity reference files. These files are used to convert corrected count rates to absolute flux units. There are separate files for each detector, disperser, aperture and polarizer combination.

Figure 31.3: Pre-COSTAR Inverse Sensitivity -Curves for Red High -Dispersion -Gratings

Figure 31.4: Post-COSTAR Sensitivity Curves for High Dispersion -Gratings

Figure 31.5: Post-COSTAR Sensitivity Curves for Low Dispersion -Gratings

cyretr: This relation is for retardation reference files used for spectropolarimetric data. The files are used to create the observation matrix f(w). There are separate files for each detector, disperser, and polarizer combination. The three available retardation files for the blue detector and waveplate B are plotted in Figure 31.6 with the appropriate disperser shown.

Figure 31.6: Retardation Reference Files

cyddtr: This is the relation for the disabled diode files. The table is used only if the keyword DEFDDTBL = F in the .d0h file. The disabled diode information is also contained in the .ulh file. DEFDDTBL must be set to F for proper re-calibration of any FOS data! Over the operational lifetime of the FOS, 26 FOS/BL and 17 FOS/RD diodes were disabled. Note that the diodes listed in Tables 31.4 and 31.5 are numbered such that the first diode in the diode array is 0 and the last diode is 511. For use in IRAF and STSDAS, the diode number would be the diode number in the table + 1. .

**Blue Detector Disabled Diodes**
DISABLED Dead Channels	DISABLED Noisy Channels		DISABLED Cross-Wired Channels	ENABLED But Occasionally Reported Noisy
49	31	268	47	8
101	73	398	55	138
223	144	415		139
284	201	427		209/210
292	218	451		381
409	225	465		421
441	235	472		426
471	241	497
8	16		2	7

**Red Detector -Disabled Diodes**
DISABLED Dead Channels	DISABLED Noisy Channels	ENABLED But Occasionally Reported Noisy
2	110	97	258/259
6	189	114/115	261
29	285	116	268
197	380	142	285
153	381	163	410
212	405	174
289	409	181
308	412	225
486		243
9	8	14

cyaisr: This is the relation for the average inverse sensitivity reference files. These files are used to convert corrected count rates to absolute flux units. There is one file for each detector and disperser combination. Figures 31.2 and 31.3 show the pre-COSTAR inverse sensitivity for the most commonly used gratings for both detectors. The post-COSTAR sensitivity curves are plotted in Figures 31.4 and 31.5
cypsf: This is the relation for the monochromatic pre-COSTAR point spread functions for the FOS, covering the wavelength range 1200-5400 Å for the blue side and 1600-8400 Å for the red side. These PSFs were modeled using the TIM software. In Figure 31.7, a sample blue side FOS PSF at 1400 Å is shown.

Figure 31.7: Example of a Pre-COSTAR Point Spread Function for the FOS

cylsf: This is the relation for the monochromatic -pre-COSTAR line spread functions for all of the non-occulting FOS apertures computed using the PSFs in cypsf. Figure 31.8 shows a sample monochromatic pre-COSTAR FOS LSF for the blue side 4.3 aperture. Pre-COSTAR LSFs are available at each PSF wavelength. Observation-derived LSFs are not stored in CDBS.

Figure 31.8: Example of a Pre-COSTAR Line Spread Function for the FOS

cyqinr: This is the relation for the data quality initialization files. These files were intended to flag intermittent or noisy diodes, but were never kept up to date since dead diode quality flagging is handled in the calfos pipeline through the use of the DDTHFILE dead diode reference file.

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