44.3 Header Keywords
Table 44.3 lists the header keywords found in a WF/PC-1.c0h image header that many observers are likely to find useful; the STSDAS tasks hedit or imhead can be used to view any or all of the header and group keywords. WF/PC-1 keywords include items such as observing mode, integration time, and filters used, calibration steps performed and reference files used, and the properties of the data itself (e.g., number of groups, coordinates, scale, flux units, image statistics, and more). In Table 44.3, the group keywords are GROUPS through PHOTBW; keywords INSTRUME through SEQNAME are the general keywords.
| Keyword | Description |
|---|---|
| Information about the groups | |
| GROUPS | Multi-group image? |
| GCOUNT | Number of groups (number of detectors read out) |
| Coordinate-related keywords | |
| CRVAL1 | RA of reference pixel (deg) |
| CRVAL2 | Declination of reference pixel (deg) |
| CRPIX1 | X coordinate of reference pixel |
| CRPIX2 | Y coordinate of reference pixel |
| CD1_1 | Partial of RA with respect to x |
| CD1_2 | Partial of RA with respect to y |
| CD2_1 | Partial of declination with respect to x |
| CD2_2 | Partial of declination with respect to y |
| Image Contents | |
| ORIENTAT | Orientation of image (deg) |
| DETECTOR | CCD detector: WF 1-4, PC 5-8 |
| Bias level information (columns 3-14 of the .x0h/.x0d file) | |
| DEZERO | Bias level from EED extended register |
| BIASEVEN | Bias level based on average of odd columns in x0h/x0d file |
| BIASODD | Average bias level based on average of even columns |
| Pixel statistics | |
| GOODMIN | Minimum value of "good" pixels (not flagged in DQF) |
| GOODMAX | Maximum value of "good" pixels |
| DATAMEAN | Mean value of "good" pixels |
| GPIXELS | Number of good pixels |
| Photometry keywords | |
| PHOTMODE | Photometry mode |
| PHOTFLAM | Inverse sensitivity (units of erg/sec/cm2/е for 1 DN/sec) |
| PHOTZPT | Zero point (currently -21.10, if DOPHOTOM = yes) |
| PHOTPLAM | Pivot wavelength (in angstroms) |
| PHOTBW | rms bandwidth of filter (in angstroms) |
| Image keywords | |
| INSTRUME | Instrument used; always WFPC for either WF or PC |
| ROOTNAME | Rootname of the observation set |
| FILETYPE | SHP - standard header packet EXT - extracted engineering file EDQ - EED data quality file SDQ - science data quality file SCI - science data file |
| CAMERA | Camera in use: WF (wide-field), PC (planetary) |
| MODE | Mode: FULL (full resol.) or AREA (2x2 pixel summation) |
| SERIALS | Serial clocks: ON, OFF |
| Data type keywords | |
| IMAGETYP | DARK/BIAS/INTFLAT/KSPOTS /EXTERNAL/EARTH-CAL |
| CDBSFILE | GENERIC/BIAS/DARK/PREF/FLAT/MASK/ATOD/NO Is the image a reference file and if yes, type is specified |
| Reference file selection keywords | |
| DATE | Date file written (dd/mm/yy) |
| FILTNAM1 | First filter name |
| FILTNAM2 | Second filter name; blank if none |
| FILTER1 | First filter number (0-48) (Historical, but used in SOGS) |
| FILTER2 | Second filter number (0-48) |
| PFILTER1 | Preflash Filter 1 number (0-48); always 1=F122M |
| PFILTER2 | Preflash Filter 2 number (0-48); always 47=F1083N (WF) 35=F1042M (PC) |
| SHUTTER | Shutter in place during preflash or INTFLAT (A, B, or Unknown) |
| Calibration switches | |
| MASKCORR | Do mask correction: YES, NO, DONE |
| ATODCORR | Do A-to-D correction: YES, NO, DONE |
| BLEVCORR | Do bias level correction: YES, NO, DONE |
| BIASCORR | Do bias correction: YES, NO, DONE |
| PREFCORR | Do preflash correction: YES, NO, DONE |
| PURGCORR | Do purge correction-always NO |
| DARKCORR | Do dark correction: YES, NO, DONE |
| FLATCORR | Do flatfield correction: YES, NO, DONE |
| DOSATMAP | Output Saturated Pixel Map-always NO |
| DOPHOTOM | Fill photometry keywords: YES, NO, DONE |
| DOHISTOS | Make histograms: YES, NO, DONE |
| Calibration reference files used1 | |
| MASKFILE | Name of the input DQF of known bad pixels |
| ATODFILE | Name of the A-to-D conversion file |
| BLEVFILE | Engineering file with extended register data |
| BLEVDFIL | Engineering file data quality file (DQF) name |
| BIASFILE | Name of the bias frame reference file |
| BIASDFIL | Name of the bias frame reference DQF |
| PREFFILE | Name of the preflash reference file |
| PREFDFIL | Name of the preflash reference DQF |
| PURGFILE | Name of the purge reference file (dummy name) |
| PURGDFIL | Name of the purge reference DQF (dummy name) |
| DARKFILE | Name of the dark reference file |
| DARKDFIL | Name of the dark reference DQF |
| FLATFILE | Name of the flatfield reference file |
| FLATDFIL | Name of the flatfield reference DQF |
| PHOTTAB | Name of the photometry calibration table |
| SATURATE | Data value at which saturation occurs (always 4095 for WF/PC-1, which includes the bias) |
| Ephemeris data | |
| PA_V3 | Position angle of V3 axis of HST |
| RA_SUN | Right ascension of the sun (deg) |
| DEC_SUN | Declination of the sun (deg) |
| EQNX_SUN | Equinox of the sun |
| Exposure Information | |
| WEXPODUR | Commanded duration of exposure (seconds). For exposures less than 1/2 sec, WEXPODUR is set to 0. |
| PREFTIME | Predicted preflash time (sec); 30 for WFC and 8 for PC |
| DARKTIME | Estimate of darktime (in sec) |
| FGSLOCK | Commanded FGS lock (FINE, COARSE, GYROS, UNKNOWN) |
| Timing information | |
| DATE-OBS | UT date of start of observation (dd/mm/yy) |
| TIME-OBS | UT time of start of observation (hh:mm:ss) |
| EXPSTART | Exposure start time (Modified Julian Date) |
| EXPEND | Exposure end time (Modified Julian Date) |
| EXPTIME | Exposure duration (seconds) |
| EXPFLAG | How exposure time was calculated. (NORMAL, INTERRUPTED, INCOMPLETE, EXTENDED, UNCERTAIN, INDETERMINATE, or P REDICTED) |
| Proposal information | |
| TARGNAME | Proposer's target name |
| RA_TARG | Right ascension of the target (deg) (J2000) |
| DEC_TARG | Declination of the target (deg) (J2000) |
1Calibration reference file keywords are populated even when not used