HST Keyword Dictionary

Space Telescope Science Institute

3700 San Martin Drive

Baltimore, MD 21212

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Keyword Definitions for the

Faint Object Camera
Science Data Header

dated 14-APR-94

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BACCORR: background subtraction correction; Datatype: CHARACTER*08 Units:; Subtract dark-count images. The dark-count reference file multiplied by the exposure time is subtracted from the input science file. The dark-count file is a full-frame image (512 x 1024 or 1024 x 1024), so if the science file is smaller than full frame, only the appropriate section of the dark-count file is used.
Source :(calguide)

BACHFILE: background reference header file; Datatype: CHARACTER*18 Units: FILENAME; The background files contain data used to subtract dark count from FOC science images. It is used for the background calibration. Background data files contain one group of data. Every background data file has the same format as an image. It is either a 1024 sample by 1024 line image for use with normal pixel format images, or a 512 sample by 1024 line image for use with zoom pixel format images. Each pixel in the background data file is a single-precision real (REAL*4) count rate value in counts per second.
Source :

BLMHFILE: blemish header file; Datatype: CHARACTER*18 Units: FILENAME; The FOC data quality initialization files contain a priori information about the effect of the FOC's photocathodes on the quality of output data values. The data quality initialization file is used in conjunction with relation CGQ1_FIL_MSK to construct the FOC data quality mask.
Source :

CAMMODE: coronographic apodizer mask: INBEAM, NOTUSED; Datatype: CHARACTER*07 Units:; In the FOC/288 configuration, the OCC Mode uses the f/96 camera with the compact Cassegrain assembly and an apodizing mask. The 0.4-arcsec occulting finger is used to produce a Lyot-type coronagraph. The 0.8-arcsec occulting finger is not available in this Operating Mode. (PROP_INST--SEC_8_2.TEX)
Source :

COMPTAB: the HST components table; Datatype: CHARACTER*18 Units: FILENAME; See PHOTMODE and related photometry keywords.
Source :

DNFORMT: bits in each data number (8/16); Datatype: INTEGER*2 Units:; Source :

FILTNAMi: filter element name for wheel 1; Datatype: CHARACTER*06 Units:; Source :

F_RATIO: focal ratio; Datatype: INTEGER*2 Units:; set to 288 if the coronographic apodizer mask (CAMMODE) is in the beam; otherwise the focal ratio is set to 96. (OPR.20224)
Source :

GEOCORR: geometric correction; Datatype: CHARACTER*08 Units:; Geometric correction. A raw FOC image is slightly distorted (about 2%)
Source :

GEODEFV: geo DN value for areas outside sci image; Datatype: REAL*4 Units: ????; Source :

GEOHFILE: geometric reference header file; Datatype: CHARACTER*18 Units: FILENAME; The geometric distortion correction data files contain data used to correct FOC science images for the geometric distortion caused by the FOC optics and the Photon Detector Assembly (PDA). It is used for the geometric calibration. The geometric distortion correction data files consist of the distorted and undistorted, sample and line coordinate values (REAL*4) of a grid of reference points on the FOC detector screen.
Source :

GRAPHTAB: the HST graph table; Datatype: CHARACTER*18 Units: FILENAME; See PHOTMODE and related photometry keywords.
Source :

ITFCORR: intensity transfer function correction; Datatype: CHARACTER*08 Units:; Apply format-dependent photometric correction. The reference files used in this step are called ITF files for historical reasons. They are not full-frame; there is one such file for each format. The format-dependent correction is applied by multiplying the image from the previous step (i.e., the dark-count subtracted image) by this file.
Source :(calguide)

ITFHFILE: itf reference header file; Datatype: CHARACTER*18 Units: FILENAME; The Intensity Transfer Function (ITF) files contain data used to correct FOC science images for spatial nonuniformities that depend on the image format. It is used for the format-dependent photometric correction. An ITF data file has the same form as an FOC image. The lengths of the axes are the same or larger than those of the image to be calibrated. Each entry is a REAL*4 scaling factor that is used to multiply the corresponding pixel DN count in the FOC science data file that is to be corrected.
Source :

KXDEPLOY: COSTAR deployed for FOC (T or F); Datatype: LOGICAL*1 Units: TRUE/FALSE; The logical DEPLOY keywords are to be set to True only if the COSTAR arm for that SI has been deployed. There are two conditions under which this keyword should be set to False. Before the servicing mission, a database flag will have to be set to instruct PODPS not to extract the COSTAR mirror positions from the SHP (the telemetry positions will still correspond to HSP data), set the DEPLOY keywords to False and set the mirror position keywords to a default value (99999). Once COSTAR is installed in HST, the database flag will be set to indicate that the COSTAR SHP entries are valid. PODPS should then populate the DEPLOY keywords based on the SHP position telemetry values. If any of the telemetered values for a given SI are the default value (99999), then the DEPLOY keyword for that SI should be set to false. This will allow for the possibility of deploying some COSTAR arms and not others.
Source :

LEDCOLOR: LED color (a color, blank , NONE or ERROR); Datatype: CHARACTER*10 Units:; If at least one telemetry item (XC1LEDSL, XC2LEDSL) is NOT fill, then the FOC LED selection table will be searched to determine the significance of the telemetered value or values. If the telemetry measurements are above a threshold count, then LEDMODE is ON , else it is OFF. If both telemetry measurements are valid, then both must agree on whether LEDMODE is ON or OFF. If they disagree, an error condition is generated. (cp2jld)
Source :

LEDMODE: led calibration status: ACTIVE, NOTUSED; Datatype: CHARACTER*07 Units:; calibration LED mode: ACTIVE,NOTUSED.
Source :[qexposure.ledmode]

LINEOFF: line offset (0.0-1023.75); Datatype: REAL*4 Units:; Line offset, mnemonic = XCCCUVRO.
Source :[qexposure.lineoff]

LINEPFM: lines per frame (64, 128, 256, 512, or 1024); Datatype: INTEGER*2 Units:; Number of lines per frame
Source :[qexposure.linepfm]

MIR_REVR: is the image mirror reversed; Datatype: CHARACTER* Units:; Source :

OPTCRLY: optical relay: F48, F96; Datatype: CHARACTER*03 Units:; magnifications in which the camera operates.
Source :[qexposure.optcrly]

OPTELTn: filter element, wheel 1 f48: (0-7), f96: (0-11); Datatype: INTEGER*2 Units:; (F48,F96) wheel n: 0,...,11. (wheel n=1..4)
Source :

ORIENTAT: the orientation of the image (deg); Datatype: CHARACTER* Units:; Source :

PXFORMT: format of the image: NORMAL, ZOOM; Datatype: CHARACTER*07 Units:; pixel format:
NORMAL: 512 samples, 512 lines 0.022x0.022 arcsec^2 ZOOM: 512 samples, 1024 lines 0.044x0.022 arcsec^2

Source :

PXLCORR: split zoom-format pixels; Datatype: CHARACTER*08 Units:; Correct for zoom mode. If the image was taken in zoom mode, the next step is to split the data values along the first image axis (the sample direction). For example, suppose the first three digital number values (DN) in the image are A, B, C. The first six DN values of the dezoomed image would be A/2, A/2, B/2, B/2, C/2, C/2. The length of the first axis (NAXIS1) is doubled, and the length of the second axis (NAXIS2) remains unchanged.
Source :(calguide)

SAMPOFF: sample offset (0.0-1023.75); Datatype: REAL*4 Units:; Sample offset, mnemonic = XCCCUHZO.
Source :[qexposure.sampoff]

SAMPPLN: samples per line (64, 128, 256, or 512); Datatype: INTEGER*2 Units:; Number of samples per line
Source :[qexposure.samppln]

SDECORR: spectrograph de correction; Datatype: CHARACTER*08 Units:; Apply spectrographic detector efficiency correction. This correction is only applied to spectrographic images. It includes both the flat-field correction and a conversion from counts to flux density. It is applied after geometric correction because the absolute sensitivity depends on wavelength, and a major function of the geometric correction for spectrographic images is to align the spectrum with the axes and set the dispersion. The correction is applied by multiplying by a spectrogaphic detector efficiency reference file. The use of an order-selecting filter can change the location of a given wavelength on the photocathode, so there are several reference files; the appropriate one is selected based on the filters used. These files are full-frame (1024 x 1024), so only a subset will be used if the science image is smaller than 1024 x 1024.
Source :(calguide)

SDEHFILE: sde reference header file; Datatype: CHARACTER*18 Units: FILENAME; The spectrographic detector efficiency data files are used for the spectrographic DE calibration step. A spectrographic DE data file has the same form as an FOC image. It always has dimensions 1024 samples by 1024 lines. Each entry is a REAL*4 scaling factor that is used to multiply the corresponding pixel DN count in the FOC science data file that is to be corrected. All images to be corrected will find their proper position inside the chosen spectrographic DE data file.
Source :

SHTMODE: shutter mode: INBEAM, NOTUSED; Datatype: CHARACTER*07 Units:; Source :

SMMMODE: spectro. mirror mechanism: INBEAM, NOTUSED; Datatype: CHARACTER*07 Units:; Source :

UNICORR: uniform de correction; Datatype: CHARACTER*08 Units:; Flat field correction flag.
Values are: 'PERFORM' (correction should be done), 'OMIT' (correction should not be done), 'COMPLETE' (correction has already been done).

Source : Phil Hodge

UNIHFILE: uniform de reference header file; Datatype: CHARACTER*18 Units:; Name of the UNI reference (calibration) image. This is the reciprocal of a flat field.
Source :

UNITAB: table of reciprocal flat field filenames; Datatype: CHARACTER*18 Units:; Name of the table that gives the names of the UNI reference images; see also UNIHFILE. This table is used to find the appropriate UNI file name based on the relay and wavelength of the observation.
Source :

WAVCORR: compute photometric parameters; Datatype: CHARACTER*08 Units:; Compute the absolute sensitivity. This does not affect the data values. The inverse sensitivity, pivot wavelength, and RMS bandwidth are computed and stored in the header of the output image. The zero-point magnitude and the observation mode are also saved in the output header. See keywords PHOTMODE, PHOTFLAM, PHOTZPT, PHOTPLAM, PHOTBW.
Source :(calguide)

HST Keyword Dictionary: 14-APR-94: (rose@stsci.edu)