2.6 Headers, Keywords, and Relationship to Phase II

As with previous HST instruments, the FITS header keywords in COS data files store important information characterizing the observations and telemetry received during the observations, and describe the post-observation processing of your dataset. Each keyword follows FITS conventions and is no longer than eight characters. Values of keywords can be integer, real (floating-point), boolean, and character strings. Several keywords are HST and COS specific. Knowledge of the keywords and where to find them is an important first step in understanding your data. By examining your file headers using the astropy.io.fits and astropy.table modules in the stenv environment, you will find detailed information about your data including:

Target name, coordinates, proposal ID, and other proposal level information.
Observation and exposure time information such as observation start and duration.
Instrument configuration information such as detector, grating, central wavelength setting, and aperture.
Readout definition parameters such as subarray parameters.
Exposure-specific information such as more detailed timing, world coordinate system information, and Fine Guidance Sensor identification.
Calibration information such as the calibration switches and reference files used by the pipeline and parameters derived from the calibration, such as image statistics and wavelength shifts.

The keywords relevant for one COS data type will not necessarily be relevant to another. Accordingly, you will find that the header in a particular file type contains a unique combination of keywords appropriate for that type of observation. Long definitions for the keywords can also be accessed from the following Web page, which provides detailed explanations of the contents and algorithm for populating the keywords. This site also provides sample headers for different COS file types:
http://stdatu.stsci.edu/keyword/.

Keywords that deal with a particular topic, such as the instrument configuration, are grouped together logically throughout the headers. Table 2.15 lists a useful subset of these groups of keywords, indicates the name of the grouping, and where applicable, shows their relationship to the corresponding information from the Phase II proposal.

Table 2.16 (spectroscopy) and Table 2.17 (imaging) summarize the possible calibration switch keywords and indicate whether they are present for particular observations; Table 2.18 indicates reference file keywords corresponding to particular calibration steps. A calibration switch keyword is initially populated with values of OMIT, PERFORM or N/A in the raw uncalibrated science data (with the exception of XTRACTALG, which has values of 'BOXCAR' or 'TWOZONE' to select the extraction algorithm to be used, depending on lifetime position (LP)). After each calibration step is executed in the COS calibration pipeline, calcos will set the keyword switch to COMPLETE.

Table 2.15: Selected Header Keywords and Relationship to Phase II Parameters.

Header Keyword	Phase II Equivalent	Description
Gerneral File Information (Primary Header)
`FILENAME`		Name of file
`FILETYPE`		Type of data found in the file (SCI, ACQ, APT, ASN_TABLE)
`NEXTEND`		Number of extensions in the file
`DATE`		Date file was created
Program Information (Primary Header)
`PROPOSID`		4 or 5 digit program number
`PR_INV_L PR_INV_F` `PR_INV_M`	PI Last Name PI First Name PI Middle Initial	Last name of principal investigator First name of principal investigator Middle name initial of principal investigator
`LINENUM`	Visit_Number, Exposure_Number	Indicates the visit and exposure number from the Phase II proposal: Visit_Number, Exposure_Number
Target Information (Primary Header)
`TARGNAME`	TargetName	Name of target
`RA_TARG DEC_TARG`	RA DEC	Right ascension of the target (deg) (J2000) Declination of the target (deg) (J2000)
`POSTARG1 POSTARG2`	POSTARG POSTARG	Postarg in axis 1 direction Postarg in axis 2 direction
Science Instrument Configuration (Primary Header)
`OBSTYPE`		Observation type (`IMAGING` or `SPECTROSCOPIC`)
`OBSMODE`	Opmode	Operating mode (`ACCUM`, `TIME-TAG`)
`EXPTYPE`	Opmode	Exposure type (`EXTERNAL`/`SCI`, `WAVECAL`, `PHA`, `DARK`, `FLAT`, `ACQ`/`IMAGE`, `ACQ`/`SEARCH`, `ACQ`/`PEAKD`, `ACQ`/`PEAKXD`, `ENG` `DIAG`, or `MEM` `DUMP`)
`DETECTOR`	Config	Detector in use (`NUV` or `FUV`)
`SEGMENT`	SEGMENT	FUV detector segment in use (`FUVA`, `FUVB`, `BOTH`, or `N`/`A`)
`DETECTHV`		FUV detector high voltage state (`NomAB`, `NomA`, `NomB`, `Off`, `Low`)
`SUBARRAY`		Data from a subarray (`T`) or full frame (`F`)
`LAMPUSED`		Lamp status, `NONE` or name of lamp which is on (`P1`, `D1`, `P2`, or `D2`)
`LAMPSET`		Spectral calibration lamp current value (milliamps)
`LIFE_ADJ`	LIFETIME-POS	Detector life time adjustment position
`OPT_ELEM`	SpElement	Optical element in use (grating or mirror name)
`CENWAVE`	Wavelength	Central wavelength for grating settings
`APERTURE`	Aperture	Aperture name
`PROPAPER`	Aperture	Proposed aperture name
`APER_FOV`		Aperture field of view description in mm
`APMPOS`		Aperture Mechanism Position from telemetry
`APERXPOS`		Aperture Block Pos. cross dispersion (telemetry)
`FPPOS`	FPPOS	Grating offset index (1–4) for spectrum dithers (`FPPOS`)
`TAGFLASH`	FLASH	Type of flashed exposures in `TIME-TAG` (`NONE`, `AUTO`, or `UNIFORMLY-SPACED`)
`EXTENDED`	Extended	Is the target extended (`Yes` or `No`)
`NRPTEXP`	NumberOfIterations	Number of repeat exposures in dataset: `Default` = `1`
`EXP_NUM`		Exposure number for repeated observations
`SHUTTER`		External shutter position (`OPEN` or `CLOSED`)
Engineering Parameters (Primary Header)
`FPOFFSET`		FP offset from nominal, in motor steps
`DEVENTA`		Digital event counter, FUV segment A (counts s^–1)
`DEVENTB`		Digital event counter, FUV segment B (counts s^–1)
`FEVENTA`		Fast event counter, FUV segment A (counts s^–1)
`FEVENTB`		Fast event counter, FUV segment B (counts s^–1)
`MEVENTS`		NUV MAMA event counter (counts s^–1)
Target Acquisition Dataset Identifiers (Primary Header)
`ACQSNAME`		Rootname of first acquisition search exposure
`ACQINAME`		Rootname of first acquisition image exposure
`PEAKXNAM`		Rootname of first x-dispersion peakup exposure
`PEAKDNAM`		Rootname of first dispersion peakup exposure
`ACQ_NUM`		Total number of exposures in acquisition sequence
Archive Search Keywords (Primary Header)
`BANDWID`		Bandwidth of the data
`SPECRES`		Approximate resolving power at central wavelength
`CENTRWV`		Central wavelength of the data
`MINWAVE`		Minimum wavelength in spectrum
`MAXWAVE`		Maximum wavelength in spectrum
`PLATESC`		Plate scale (arcsec/pixel)
Association Keywords (Primary Header)
`ASN_ID`		Unique identifier assigned to association
`ASN_MTYP`		Role of the member in the association
`ASN_TAB`		Name of the association table
*Exposure Information (in Extension header 1 or greater)*
`DATE-OBS`		UT date of start of observation (yyyy-mm-dd)
`TIME-OBS`		UT time of start of observation (hh:mm:ss)
`EXPTIME`		Corrected exposure time (seconds). For FUV exposures, the largest of `EXPTIMEA` and `EXPTIMEB`
`EXPTIMEA`		Corrected FUV Segment A exposure time (seconds)
`EXPTIMEB`		Corrected FUV Segment B exposure time (seconds)
`RAWTIME`		Exposure time of an individual raw exposure (seconds)
`EXPSTART`		Exposure start time (Modified Julian Date)
`EXPEND`		Exposure end time (Modified Julian Date)
`EXPSTRTJ`		Exposure start time (Julian Date)
`EXPENDJ`		Exposure end time (Julian Date)
`PLANTIME`	TimePerExposure	Planned exposure time (seconds)
`NINTERPT`		Number of exposure interrupts
`ORIENTAT`		Position angle of image y-axis (degrees)
`SUNANGLE`		Angle between sun and V1 axis
`MOONANGL`		Angle between moon and V1 axis
`SUN_ALT`		Altitude of the sun above Earth’s limb
`FGSLOCK`		Commanded FGS lock (Fine, Coarse, Gyros, Unknown)
`GYROMODE`		Number of gyros scheduled for observation
`REFFRAME`		Guide star catalog version
*Aperture Information (in Extension header 1 or greater)*
`RA_APER DEC_APER`		RA of reference aperture center Declination of reference aperture center
`PA_APER`		Position angle of reference aperture center
`SHIFT1A`		Wavecal shift determined for FUV segment A or NUV stripe A in dispersion direction (pixels)
`SHIFT1B`		Wavecal shift determined for FUV segment B or NUV stripe B in dispersion direction (pixels)
`SHIFT1C`		Wavecal shift determined for NUV stripe C in dispersion direction (pixels)
`SHIFT2A`		Offset in cross-dispersion direction for FUV segment A or NUV stripe A (pixels)
`SHIFT2B`		Offset in cross-dispersion direction for FUV segment B or NUV stripe B (pixels)
`SHIFT2C`		Offset in cross-dispersion direction for NUV stripe C (pixels)
`SP_LOC_A`		Cross-dispersion location at which calcos extracted the FUV segment A or NUV stripe A spectrum
`SP_LOC_B`		Cross-dispersion location at which calcos extracted the FUV segment B or NUV stripe B spectrum
`SP_LOC_C`		Cross-dispersion location at which calcos extracted the NUV stripe C spectrum
`SP_NOM_A`		Nominal location of the spectral extraction region for FUV segment A or NUV stripe A based on the wavecal aperture location
`SP_NOM_B`		Nominal location of the spectral extraction region for FUV segment B or NUV stripe B based on the wavecal aperture location
`SP_NOM_C`		Nominal location of the spectral extraction region for NUV stripe C based on the wavecal aperture location
`SP_OFF_A`		Offset from SP_NOM_A at which the spectrum was found
`SP_OFF_B`		Offset from SP_NOM_B at which the spectrum was found
`SP_OFF_C`		Offset from SP_NOM_C at which the spectrum was found
`SP_SLP_A`		Slope of FUV segment A or NUV stripe A spectrum
`SP_SLP_B`		Slope of FUV segment B or NUV stripe B spectrum
`SP_SLP_C`		Slope of NUV stripe C spectrum
`SP_HGT_A`		Height in pixels of the FUV Segment A spectral extraction region
`SP_HGT_B`		Height in pixels of the FUV Segment B spectral extraction region
`DPIXEL1A`		Fractional part of pixel coordinate for FUV segment A or NUV stripe A (pixels). Average binning error
`DPIXEL1B`		Fractional part of pixel coordinate for FUV segment B or NUV stripe B (pixels). Average binning error
`DPIXEL1C`		Fractional part of pixel coordinate for NUV stripe C (pixels). Average binning error
TIME-TAG Parameters (in Extension header 1 or greater)
`BUFFTIME`	BUFFER-TIME	Onboard memory half-buffer-fill time
`OVERFLOW`		Number of science data overflows
`NBADEVNT`		Total number of events deleted in screening (NUV)
`NBADEVTA`		Total number of events deleted in screening (FUV, segment A)
`NBADEVTB`		Total number of events deleted in screening (FUV, segment B)
`NEVENTS`		Total number of events in raw data (NUV)
`NEVENTSA`		Total number of events in raw data (FUV, segment A)
`NEVENTSB`		Total number of events in raw data (FUV, segment B)
FUV TIME-TAG Parameters (in Extension header 1 or greater)
TBRST_A TBRST_B		Time lost to bursts on FUV segment A (seconds) Time lost to bursts on FUV segment B (seconds)
TBADT_A TBADT_B		Time lost to BADTCORR screening on FUV segment A (sec) Time lost to BADTCORR screening on FUV segment B (sec)
NPHA_A NPHA_B		Number of events lost due to pulse height screening on segment A Number of events lost due to pulse height screening on segment B
NBRST_A NBRST_B		Number of events lost due to burst screening on segment A Number of events lost due to burst screening on segment B
NBADT_A NBADT_B		Number of events flagged by BADTCORR for segment A Number of events flagged by BADTCORR for segment B
NOUT_A NOUT_B		Number of events outside the active area for segment A Number of events outside the active area for segment B
NUV TIME-TAG Parameters (in Extension header 1 or greater)
`NBADT`		Number of events flagged by BADTCORR
`TBADT`		Time lost to BADTCORR screening (sec)
*TAFGFLASH Parameters (in Extension header 1 or greater)*
`NUMFLASH`		Integer number of flashes
`LMPDURi`		Duration of flash i, seconds
`LMP_ONi`		Lamp turn-on time for flash i, seconds since EXPSTART
`LMPOFFi`		Lamp turn-off time for flash i, seconds since EXPSTART
`LMPMEDi`		Median time of flash i, seconds since EXPSTART
Velocity Reference Frame Conversion (in Extension header 1 or greater)
`V_HELIO`		Geometric to heliocentric velocity
`V_LSRSTD`		Heliocentric to standard solar LSR
Doppler Correction Parameters (in Extension header 1 or greater)
`ORBITPER`		Orbital period used onboard for Doppler correction
`DOPPER`		Doppler shift period (seconds)
`DOPPMAGV`		Doppler shift magnitude (Km/sec)
`DOPPON`		Doppler correction flag (T or F)
`DOPPZERO`		Commanded time of zero Doppler shift (MJD)
Instrument Doppler Correction Parameters (in Extension header 1 or greater)
`ORBTPERT`		Orbital period used onboard for Doppler correction
`DOPMAGT`		Doppler shift magnitude (low-res pixels)
`DOPPONT`		Doppler correction flag (T or F)
`DOPPZEROT`		Commanded time of zero Doppler shift (MJD)
Global Count Parameters (in Extension header 1 or greater)
`GLOBRATE`		Global count rate (NUV)
`GLOBRT_A`		Global count rate (FUV, segment A)
`GLOBRT_B`		Global count rate (FUV, segment B)
Subarray Readout Parameters¹ (in Extension header 1 or greater)
`NSUBARRY`		Number of subarrays (1–8)
`CORNER[N]X`		Subarray N axis1 corner pt in unbinned detector pixels. Valid values of N are 0 to 7
`CORNER[N]Y`		Subarray N axis2 size in unbinned detector pixels, with N=0 to 7
`SIZE[N]Y`		Subarray N axis1 corner pt in unbinned detector pixels, with N=0 to 7
`SIZE[N]X`		Subarray N axis2 size in unbinned detector pixels, with N=0 to 7
Stim Pulse Parameters (in Extension header 1 or greater; for FUV data only)
`STIMRATE`		Approximate STIM pulse injection rate
STIMA_LX STIMA_LY STIMA_RX STIMA_RY		Segment A Left STIM pulse X centroid in raw data Segment A Left STIM pulse Y centroid in raw data Segment A Right STIM pulse X centroid in raw data Segment A Right STIM pulse Y centroid in raw data
STIMB_LX STIMB_LY STIMB_RX STIMB_RY		Segment B Left STIM pulse X centroid in raw data Segment B Left STIM pulse Y centroid in raw data Segment B Right STIM pulse X centroid in raw data Segment B Right STIM pulse Y centroid in raw data
STIMA0LX STIMA0LY STIMA0RX STIMA0RY		Reference location of Segment A Left STIM pulse X coordinate Reference location of Segment A Left STIM pulse Y coordinate Reference location of Segment A Right STIM pulse X coordinate Reference location of Segment A Right STIM pulse Y coordinate
STIMB0LX STIMB0LY STIMB0RX STIMB0RY		Reference location of Segment B Left STIM pulse X coordinate Reference location of Segment B Left STIM pulse Y coordinate Reference location of Segment B Right STIM pulse X coordinate Reference location of Segment B Right STIM pulse Y coordinate
STIMASLX STIMASLY STIMASRX STIMASRY		RMS width of Segment A Left STIM pulse X coordinate RMS width of Segment A Left STIM pulse Y coordinate RMS width of Segment A Right STIM pulse X coordinate RMS width of Segment A Right STIM pulse Y coordinate
STIMBSLX STIMBSLY STIMBSRX STIMBSRY		RMS width of Segment B Left STIM pulse X coordinate RMS width of Segment B Left STIM pulse Y coordinate RMS width of Segment B Right STIM pulse X coordinate RMS width of Segment B Right STIM pulse Y coordinate
Pulse Height Parameters (in Extension header 1 or greater for FUV data only)
`PHALOWRA PHALOWRB`		Pulse height screening lower limit for segment A Pulse height screening lower limit for segment B
`PHAUPPRA PHAUPPRB`		Pulse height screening upper limit for segment A Pulse height screening upper limit for segment B
Image Statistics and Data Quality Flags (in Extension header 1 or greater)
`NGOODPIX`		Number of good pixels (NUV)
`NGOOD_A`		Number of good pixels (FUV, segment A)
`NGOOD_B`		Number of good pixels (FUV, segment B)
`SDQFLAGS`		Serious data quality flags. (Can be modified as a calcos parameter; see Section 3.4.22)
`GOODMAX`		Maximum value of good pixels (NUV)
`GOODMAXA`		Maximum value of good pixels (FUV, segment A)
`GOODMAXB`		Maximum value of good pixels (FUV, segment B)
`GOODMEAN`		Mean value of good pixels (NUV)
`GOODMN_A`		Mean value of good pixels (FUV, segment A)
`GOODMN_B`		Mean value of good pixels (FUV, segment B)
`SOFTERRS`		Number of soft error pixels (DQF=1)
Deadtime Correction Keywords (in Extension header 1 or greater)
DEADRT DEADRT_A DEADRT_B		Count rate used for the NUV dead time correction (cps) Count rate used in the FUV Segment A dead time correction (cps) Count rate used in the FUV Segment B dead time correction (cps)
DEADMT DEADMT_A DEADMT_B		NUV Deadtime correction method (`DATA`, `DEVENTS`, or `MEVENTS`) FUVA Deadtime correction method (`DATA`, DEVENTS, or `MEVENTS`) FUVB Deadtime correction method (`DATA`, `DEVENTS`, or `MEVENTS`)
TIME-TAG Events Orientation Keywords (in Extension header 1 or greater)²
TCTYP2 TCTYP3		Axis type for dimension 1 Axis type for dimension 2
TCRVL2 TCRVL3		Sky coordinates of 1st axis Sky coordinate of 2nd axis
TCDLT2 TCDLT3		Axis 1 degrees per pixels Axis 2 degrees per pixels
TCRPX2 TCRPX3		Axis 1 pixel of tangent plane direction Axis 2 pixel of tangent plane direction
TALEN2 TALEN3		Length of axis 1 Length of axis 2
TC2_2 TC2_3 TC3_2 TC3_3		Partial of first axis coordinate with respect to x Partial of first axis coordinate with respect to y Partial of second axis coordinate with respect to x Partial of second axis coordinate with respect to y
TCUNI2 TCUNI3		Units of first coordinate value Units of second coordinate value
World Coordinate System and Related Parameters (in Extension header 1 or greater)
`WCSAXES`		Number of World Coordinate System axes
CRPIX1 CRPIX2		x-coordinate of reference pixel y-coordinate of reference pixel
CRVAL1 CRVAL2		First axis value at reference pixel Second axis value at reference pixel
CTYPE1 CTYPE2		The coordinate type for the first axis The coordinate type for the second axis
CD1_1 CD1_2 CD2_1 CD2_2		Partial of first axis coordinate with respect to x Partial of first axis coordinate with respect to y Partial of second axis coordinate with respect to x Partial of second axis coordinate with respect to y
CUNIT1 CUNIT2		Units of first coordinate value Units of second coordinate value
LTV1 LTV2		Offset in X to subsection start Offset in Y to subsection start
LTM1_1 LTM2_2		Reciprocal of sampling rate in X Reciprocal of sampling rate in Y
Detector Voltages (in Extension header 1 or greater)
`HVLEVELA`		Actual segment A commanded HV level (counts)
`HVLEVELB`		Actual segment B commanded HV level (counts)

¹ For FUV data subarrays 0–3 refer to segment A, and subarrays 4–7 refer to segment B.
² The values for these keywords are currently deleted from the output files except for NUV Imaging.

Table 2.16: Spectroscopic Calibration Switch Keywords.

EXPTYPE	EXTERNAL/SCI EXTERNAL/CAL				WAVECAL		DARK		FLAT
DETECTOR	FUV		NUV		FUV	NUV	FUV	NUV	FUV	NUV
OBSMODE	TIME-TAG	ACCUM	TIME-TAG	ACCUM	TIME-TAG	TIME-TAG	TIME-TAG	TIME-TAG	TIME-TAG	TIME-TAG
Module
`BRSTCORR`	Omit	N/A	N/A	N/A	Omit¹	N/A	Omit¹	N/A	Omit²	N/A
`BADTCORR`	Perform	N/A	Perform	N/A	Perform	Perform	Perform	Perform	Perform	Perform
`PHACORR`	Perform	Perform	N/A	N/A	Perform	N/A	Perform	N/A	Perform	N/A
`RANDCORR`	Perform	Perform	N/A	N/A	Perform	N/A	Perform	N/A	Perform	N/A
`RANDSEED`	–1	–1	N/A	N/A	–1	N/A	–1	N/A	–1	N/A
`XWLKCORR²`	Omit	N/A	N/A	N/A	Perform	N/A	Perform	N/A	Perform	N/A
`YWLKCORR`	Perform	N/A	N/A	N/A	Perform	Perform	Perform	N/A	Perform	N/A
`TEMPCORR`	Perform	Perform	N/A	N/A	Perform	N/A	Perform	N/A	Perform	N/A
`GEOCORR`	Perform	Perform	N/A	N/A	Perform	N/A	Perform	N/A	Perform	N/A
`DGEOCORR`	Perform	Perform	N/A	N/A	Perform	N/A	Perform	N/A	Perform	N/A
`IGEOCORR`	Perform	Perform	N/A	N/A	Perform	N/A	Perform	N/A	Perform	N/A
`DOPPCORR`	Perform	Perform	Perform	Perform	N/A	N/A	N/A	N/A	N/A	N/A
`DEADCORR`	Perform	Perform	Perform	Perform	Perform	Perform	Perform	Perform	Perform	Perform
`FLATCORR`	Perform	Perform	Perform	Perform	Perform	Perform	Omit	Omit	Omit	Omit
`XTRACTALG¹`	TWOZONE	TWOZONE	BOXCAR	BOXCAR	BOXCAR	BOXCAR	BOXCAR	BOXCAR	BOXCAR	BOXCAR
`ALGNCORR¹`	Perform	Perform	Omit	Omit	Omit	Omit	Omit	Omit	Omit	Omit
`DQICORR`	Perform	Perform	Perform	Perform	Perform	Perform	Perform	Perform	Perform	Perform
`WAVECORR`	Perform	Perform	Perform	Perform	Perform	Perform	Omit	Omit	Omit	Omit
`X1DCORR`	Perform	Perform	Perform	Perform	Perform	Perform	Omit	Omit	Omit	Omit
`BACKCORR`	Perform	Perform	Perform	Perform	Perform	Perform	Omit	Omit	Omit	Omit
`FLUXCORR`	Perform	Perform	Perform	Perform	N/A	N/A	Omit	Omit	Omit	Omit
`TDSCORR`	Perform	Perform	Perform	Perform	N/A	N/A	Omit	Omit	Omit	Omit
`HELCORR`	Perform	Perform	Perform	Perform	N/A	N/A	Omit	Omit	Omit	Omit
`TRCECORR¹`	Perform	Perform	Omit	Omit	Omit	Omit	Omit	Omit	Omit	Omit
`STATFLAG`	T	T	T	T	T	T	T	T	T	T

¹ FUV data taken at LP1 and LP2 will still use BOXCAR extraction. ALGNCORR and TRCECORR will be set to OMIT.

² XWLKCORR is OMIT for LP=4 and PERFORM for all other LPs. DGEOCORR is PERFORM for LP=4 and OMIT for all other LPs.

Table 2.17: Imaging Calibration Switch Keywords.

EXPTYPE	EXTERNAL/SCI EXTERNAL/CAL		WAVECAL	DARK	FLAT	ACQ/IMAGE
DETECTOR	NUV		NUV	NUV	NUV	NUV
OBSMODE	TIME-TAG	ACCUM	TIME-TAG	TIME-TAG	TIME-TAG	ACCUM
Modules
`BADTCORR`	Perform	N/A	Perform	Perform	Perform	N/A
`FLATCORR`	Perform	Perform	Perform	Omit	Omit	Perform
`DEADCORR`	Perform	Perform	Perform	Perform	Perform	Perform
`DQICORR`	Perform	Perform	Perform	Perform	Perform	Perform
`PHOTCORR`	Perform	Perform	Perform	Omit	Omit	Perform
`TDSCORR`	Perform	Perform	Perform	Omit	Omit	Perform
`STATFLAG`	T	T	T	T	T	T

Table 2.18: Reference File Keywords.

Note that some reference files depend on LP (lifetime position), cenwave, etc. See https://hst-crds.stsci.edu/.

Note also that reference file names in italic bold (e.g., BRSTTAB) apply only to FUV data.

Reference File	Description
BRSTTAB	Burst parameter table
BRFTAB	Baseline reference frame reference table
BADTTAB	Bad time interval reference table
PHATAB	Pulse height discrimination reference table
GEOFILE	Geometric distortion table
DGEOFILE	Delta Geometric Correction Reference File
YWLKFILE	Y Walk Correction Lookup Reference Image
XWLKFILE	X Walk Correction Lookup Reference Image
DEADTAB	Deadtime reference file
FLATFILE	Pixel to pixel flat-field reference file
LAMPTAB	Template calibration lamp spectra table
WCPTAB	Wavecal parameters table
DISPTAB	Dispersion coefficient reference table
BPIXTAB	Bad pixel table
GSAGTAB	Gain sag table
XTRACTAB	1-D spectral extraction information table
FLUXTAB	Photometric throughput table
TDSTAB	Time-dependent sensitivity correction table
SPWCSTAB	Spectroscopic World Coordinate System table
TRACETAB	1-D spectral trace table
PROFTAB	2-D spectrum profile table
HVTAB	High voltage command level reference table
SPOTTAB	Hot spot reference table
TWOZXTAB	Two-zone spectral extraction information table

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COS Data Handbook

2.6 Headers, Keywords, and Relationship to Phase II

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