Section 6. Wide Field/Planetary Camera
Observation datasets produced by the Wide Field/Planetary Camera (WF/PC) are calibrated by the calwfp task. This task requires a set of reference files to perform the calibration, as described in this section. One reference table is used by calwfp.
All reference files for the WF/PC calibration must be in GEIS format. All files must contain four groups of two-dimensional data. The groups correspond to the CCD detectors in the WF/PC camera in the nominal readout order. That is, group 1 contains the image from CCD WFC1 or PC5, group 2 contain the image from CCD WFC2 or PC6, etc. The keyword DETECTOR in the group parameter block should agree with this convention. The data is of either 2-byte integer (INTEGER*2) or single-precision real (REAL*4) data type.
Reference file headers must be copies of the headers created during generic conversion for the WF/PC science image (*. D0H) file. This is to ensure a common header format throughout the WF/PC calibration process. This header format will be known as the WF/PC generic header. Additional keywords (especially comment and history keywords) may be appended to the headers. However, the size of the group parameter block should not be changed.
6.1 Data Quality Files
Most WF/PC reference files are accompanied by a data quality file (DQF) that flags unsatisfactory pixel values. This information is propagated in the output DQF produced by calwfp. The DQFs are all of short integer (INTEGER*2) data type, have the same number of dimensions as the files associated with them, and have headers in the same format as the WF/PC generic header.
By convention, DQF pixel values of 0 designate good pixels. The values of the DQFs of all images used in the processing are bitwise ORed together. Generic calibration defects are flagged with the value 2.
Table 6-1 shows the DQF condition codes used in routine WF/PC pipeline processing.
Table 6-1. WF/PC Data Quality Flag Values
Condition |
Value |
Comment |
|---|---|---|
GOODPIXEL |
0 |
Unflagged pixel |
SOFTERROR |
1 |
R-S error in data transmission |
CALIBDEFECT |
2 |
Generic problem with reference file |
STATICDEFECT |
4 |
Static defect in WF/PC |
ATODSAT |
8 |
A-to-D converter was saturated - value unknown |
DATALOST |
16 |
Missing data |
BADPIXEL |
32 |
Generic bad pixel - reason not specified |
6.2 WF/PC Reference Files
WF/PC reference files are stored in the archive as a FITS header file and a binary data file. They must be converted to GEIS format for use with calwfp . Although the header files do follow the FITS conventions, the header listings in this section do not adhere precisely to these conventions.
In the header listings contained in this section, beware of the following:
The single quotes required around character strings have been omitted.
Numerical values have not been right justified.
The third column in the listing denoting the variable type is additional information, not part of the FITS header itself.
All WF/PC reference files have image headers that contain the same keywords as shown in the following header listing. For the descriptions of the individual reference files, only a partial header listing is given to show which keywords are essential and are likely to change from one reference file to another.
The following reference files are used for calibrating WF/PC observations:
Static Mask: Formerly known as the data quality mask, this file flags those pixels that always contain degraded values (e.g., blocked columns, hot pixels). This mask is routinely incorporated into the DQF generated in the RSDP pipeline by calwfp (the .C1H file).
A-to-D Lookup Tables: These files are used to correct the image data for a pattern introduced by the analog-to-digital converter electronics. This correction replaces the short integer pixel values obtained from the WF/PC with floating-point values that remove the systematic degradation introduced by this hardware problem. The mka2d task in the STSDAS wfpc package can create and modify A-to-D reference files. It requires the voltage errors associated with each bit in the 12-bit A-to-D converter to create new A-to-D lookup tables.
Bias Reference File and DQF: These files are subtracted from the image to remove the structure in the electronic bias.
Preflash Reference File and DQF: These files are used to perform the preflash correction. The signal introduced by the use of the preflash lamp is removed by subtracting this reference file. The reference file is scaled by the preflash exposure time to allow for variations in the requested preflash exposure. The subtraction of the reference file corrects for the uneven illumination pattern of the preflash image. Because the preflash is obtained by illuminating the backside of the shutter with an internal lamp, the difference in reflectivity of the two shutter blades requires reference files specific to each shutter blade.
Superpurge Reference File and DQF: These files are used to remove residual images of highly overexposed sources. However, it creates a nonuniform residual image over the entire detector that decays with time. The level of this global residual image in a readout depends on both the time since the purge was performed and the time since the last erase prior to the readout. The superpurge reference file must be scaled and subtracted from all images obtained after a superpurge in which the residual is still significant. Note, however, that the superpurge correction was never implemented in the calwfp pipeline.
Dark Reference File and DQF: The WF/PC CCDs generate a spurious signal during exposures known as dark current. This signal is a function of the time since the last erase command and the operating temperature of the CCD detectors and varies from pixel to pixel. The dark reference file is scaled by the time since the last erase command and subtracted from the image.
Flat Field Reference File and DQF: Variations in sensitivity between pixels in the CCD detectors are corrected by applying a flat field reference file. This file contains the normalized inverse sensitivity (gain) for each pixel in the detector. It is made from internal exposures in conjunction with streaked earth flats. The image is multiplied by the flat field file after correction for additive effects (i.e., bias, preflash, superpurge, and dark).
6.2.1 Generic Image Header: All WF/PC Reference Files
The following listing shows a standard header used by all WF/PC reference files.
SIMPLE = F data conforms to the fits standard L1
BITPIX = 16 bits per data value I2
DATATYPE= INTEGER*2 datatype of the group array C10
NAXIS = 2 number of data axes I2
NAXIS1 = length of 1st data axis I2
NAXIS2 = length of 2nd data axis I2
GROUPS = T data has groups L1
GCOUNT = 1 number of groups per observation (1-4) I2
PCOUNT = 37 number of parameters I2
PSIZE = 1536 bits in each parameter block I2
/ GROUP PARAMETERS: OSS
PTYPE1 = CRVAL1 right ascension of reference pixel (deg) C08
PDTYPE1 = REAL*8 C18
PSIZE1 = 64 I2
PTYPE2 = CRVAL2 declination of reference pixel (deg) C08
PDTYPE2 = REAL*8 C18
PSIZE2 = 64 I2
PTYPE3 = CRPIX1 x-coordinate of reference pixel C08
PDTYPE3 = REAL*4 C18
PSIZE3 = 32 I2
PTYPE4 = CRPIX2 y-coordinate of reference pixel C08
PDTYPE4 = REAL*4 C18
PSIZE4 = 32 I2
PTYPE5 = CD1_1 partial of the right ascension w.r.t. x C08
PDTYPE5 = REAL*4 C18
PSIZE5 = 32 I2
PTYPE6 = CD1_2 partial of the right ascension w.r.t. y C08
PDTYPE6 = REAL*4 C18
PSIZE6 = 32 I2
PTYPE7 = CD2_1 partial of the declination w.r.t. x C08
PDTYPE7 = REAL*4 C18
PSIZE7 = 32 I2
PTYPE8 = CD2_2 partial of the declination w.r.t. y C08
PDTYPE8 = REAL*4 C18
PSIZE8 = 32 I2
PTYPE9 = DATAMIN minimum value of the data C08
PDTYPE9 = REAL*4 C18
PSIZE9 = 32 I2
PTYPE10 = DATAMAX maximum value of the data C08
PDTYPE10= REAL*4 C18
PSIZE10 = 32 I2
PTYPE11 = MIR_REVR is the image mirror reversed? C08
PDTYPE11= LOGICAL*4 C18
PSIZE11 = 32 I2
PTYPE12 = ORIENTAT orientation of the image (deg) C08
PDTYPE12= REAL*4 C18
PSIZE12 = 32 I2
PTYPE13 = FILLCNT number of segments containing fill C08
PDTYPE13= INTEGER*4 C18
PSIZE13 = 32 I2
PTYPE14 = ERRCNT number of segments containing errors C08
PDTYPE14= INTEGER*4 C18
PSIZE14 = 32 I2
PTYPE15 = FPKTTIME time of the first packet C08
PDTYPE15= REAL*8 (Modified Julian Date) C18
PSIZE15 = 64 I2
PTYPE16 = LPKTTIME time of the last packet C08
PDTYPE16= REAL*8 (Modified Julian Date) C18
PSIZE16 = 64 I2
PTYPE17 = CTYPE1 first coordinate type C08
PDTYPE17= CHARACTER*8 C18
PSIZE17 = 64 I2
PTYPE18 = CTYPE2 second coordinate type C08
PDTYPE18= CHARACTER*8 C18
PSIZE18 = 64 I2
PTYPE19 = DETECTOR CCD detector: WFC 1-4, PC 5-8 C08
PDTYPE19= INTEGER*4 C18
PSIZE19 = 32 I2
/ GROUP PARAMETERS: PODPS
PTYPE20 = DEZERO bias level from EED extended register C08
PDTYPE20= REAL*4 C18
PSIZE20 = 32 I2
PTYPE21 = BIASEVEN bias level from EED extended register C08
PDTYPE21= REAL*4 C18
PSIZE21 = 32 I2
PTYPE22 = BIASODD bias level from EED extended register C08
PDTYPE22= REAL*4 C18
PSIZE22 = 32 I2
PTYPE23 = GOODMIN minimum value of the "good" pixels C08
PDTYPE23= REAL*4 C18
PSIZE23 = 32 I2
PTYPE24 = GOODMAX maximum value of the "good" pixels C08
PDTYPE24= REAL*4 C18
PSIZE24 = 32 I2
PTYPE25 = DATAMEAN mean value of the "good" pixels C08
PDTYPE25= REAL*4 C18
PSIZE25 = 32 I2
/ GROUP PARAMETERS: DATA QUALITY FILE SUMMARY
PTYPE26 = GPIXELS number of "good" pixels (DQF=0) C08
PDTYPE26= INTEGER*4 C18
PSIZE26 = 32 I2
PDTYPE27= INTEGER*4 C18
PSIZE27 = 32 I2
PTYPE28 = CALIBDEF number of "calibration defect" pixels (DQF=2) C08
PDTYPE28= INTEGER*4 C18
PSIZE28 = 32 I2
PTYPE29 = STATICD number of "static defect" pixels (DQF=4) C08
PDTYPE29= INTEGER*4 C18
PSIZE29 = 32 I2
PTYPE30 = ATODSAT number of "AtoD saturated" pixels (DQF=8) C08
PDTYPE30= INTEGER*4 C18
PSIZE30 = 32 I2
PTYPE31 = DATALOST number of "data lost" pixels (DQF=16) C08
PDTYPE31= INTEGER*4 C18
PSIZE31 = 32 I2
PTYPE32 = BADPIXEL number of "generic bad" pixels DQF=32) C08
PDTYPE32= INTEGER*4 C18
PSIZE32 = 32 I2
/ GROUP PARAMETERS: PHOTOMETRY
PTYPE33 = PHOTMODE photometry mode C08
PDTYPE33= CHARACTER*24 C18
PSIZE33 = 192 I2
PTYPE34 = PHOTFLAM inverse sensitivity C08
PDTYPE34= REAL*4 C18
PSIZE34 = 32 I2
PTYPE35 = PHOTZPT zero point C08
PDTYPE35= REAL*4 C18
PSIZE35 = 32 I2
PTYPE36 = PHOTPLAM pivot wavelength C08
PDTYPE36= REAL*4 C18
PSIZE36 = 32 I2
PTYPE37 = PHOTBW RMS bandwidth of the filter C08
PDTYPE37= REAL*4 C18
PSIZE37 = 32 I2
/ WFPC DATA DESCRIPTOR KEYWORDS
INSTRUME= WFPC instrument in use C04 exp
ROOTNAME= rootname of the observation set C12
FILETYPE= SCI shp, ext, edq, sdq, sci C03
/ SCIENCE INSTRUMENT CONFIGURATION
CAMERA = camera in use: WF (wide-field), PC (planetary) C02
MODE = instr. mode: FULL (full res.), AREA (area int.) C04
SERIALS = serial clocks: ON, OFF C03
/ IMAGE TYPE CHARACTERISTICS
IMAGETYP= EXTERNAL DARK/BIAS/INTFLAT/KSPOTS/EXTERNAL/EARTH-CALIB C18
CDBSFILE= NO GENERIC/BIAS/DARK/PREF/FLAT/MASK/ATOD/NO C18
PKTFMT = packet format code I4
DATE = date file written (dd/mm/yy) C08
/ FILTER CONFIGURATION
FILTNAM1= first filter name C08
FILTNAM2= second filter name C08
FILTER1 = first filter number (0-48) I2
FILTER2 = second filter number (0-48) I2
PFILTER1= preflash filter 1 number (0-48) I2
PFILTER2= preflash filter 2 number (0-48) I2
/ INSTRUMENT STATUS USED IN DATA PROCESSING
TECTEMP1= -1.00 TEC cold junction #1 temperature (Celsius) R4
TECTEMP2= -1.00 TEC cold junction #2 temperature (Celsius) R4
TECTEMP3= -1.00 TEC cold junction #3 temperature (Celsius) R4
TECTEMP4= -1.00 TEC cold junction #4 temperature (Celsius) R4
TECTEMP5= -1.00 TEC cold junction #5 temperature (Celsius) R4
TECTEMP6= -1.00 TEC cold junction #6 temperature (Celsius) R4
TECTEMP7= -1.00 TEC cold junction #7 temperature (Celsius) R4
TECTEMP8= -1.00 TEC cold junction #8 temperature (Celsius) R4
WBA3PCTM= Bay 3 temperature (Celsius) R4
KSPOTS = status of Kelsall spot lamps: ON, OFF C03
SHUTTER = UNKNOWN shutter in place during preflash or INTFLAT C07
/ RSDP CONTROL KEYWORDS
MASKCORR= YES do mask correction: YES, NO, DONE C08
ATODCORR= do A-to-D correction: YES, NO, DONE C08
BLEVCORR= do bias level correction: YES, NO, DONE C08
BIASCORR= do bias correction: YES, NO, DONE C08
PREFCORR= do preflash correction: YES, NO, DONE C08
PURGCORR= do purge correction: YES, NO, DONE C08
DARKCORR= do dark correction: YES, NO, DONE C08
FLATCORR= do flat field correction: YES, NO, DONE C08
DOSATMAP= output Saturated Pixel Map: YES, NO, DONE C08
DOPHOTOM= fill photometry keywords: YES, NO, DONE C08
DOHISTOS= make histograms: YES, NO, DONE C08
OUTDTYPE= REAL output image datatype: REAL, LONG, SHORT C06
/ CALIBRATION REFERENCE FILES
MASKFILE= name of the input DQF of known bad pixels C18
ATODFILE= name of the A-to-D conversion file C18
BLEVFILE= engineering file with extended register data C18
BLEVDFIL= engineering file DQF C18
BIASFILE= name of the bias frame reference file C18
BIASDFIL= name of the bias frame reference DQF C18
PREFFILE= name of the preflash reference file C18
PREFDFIL= name of the preflash reference DQF C18
PURGFILE= name of the purge reference file C18
PURGDFIL= name of the purge reference DQF C18
DARKFILE= name of the dark reference file C18
DARKDFIL= name of the dark reference DQF C18
FLATFILE= name of the flat field reference file C18
FLATDFIL= name of the flat field reference DQF C18
PHOTTAB = name of the photometry calibration table C18
/ DEFAULT KEYWORDS SET BY STSCI
SATURATE= 4095 data value at which saturation occurs I2
WSCALE = 1.0 scale factor for output image R4
WZERO = 0.0 zero point for output image R4
/ PLANETARY SCIENCE KEYWORDS
PA_V3 = 0.0 position angle of v3 axis of HST R4
RA_SUN = 0.0 right ascension of the sun (deg) R8
DEC_SUN = 0.0 declination of the sun (deg) R8
EQNX_SUN= 2000.0 equinox of the sun R4
MTFLAG = F moving target flag L1
EQRADTRG= 0.0 equatorial radius of target R4
FLATNTRG= 0.0 flattening of target R4
NPDECTRG= 0.0 north pole declination of target R4
NPRATRG = 0.0 north pole right ascension of target R4
ROTRTTRG= 0.0 rotation rate of target R4
LONGPMER= 0.0 longitude of prime meridian R4
EPLONGPM= 0.0 epoch of longitude of prime meridian R4
SURFLATD= 0.0 surface feature latitude R4
SURFLONG= 0.0 surface feature longitude R4
SURFALTD= 0.0 surface feature altitude R4
/ PODPS FILL VALUES
PODPSFF = 0=(no PODPS fill), 1=(PODPS fill present) I2
STDCFFF = 0=(no ST DCF fill), 1=(ST DCF fill present) I2
STDCFFP = ST DCF fill pattern (hex) C04
RSDPFILL= -100 bad data fill value for calibrated images I2
/ EXPOSURE TIME AND RELATED INFORMATION
WEXPODUR= commanded duration of exposure (seconds) I4
NSHUTA17= number of AP17 shutter B closes I4
PREFTIME= predicted preflash time (seconds) R4
DARKTIME= dark time (seconds) R4
PURGTIME= -1 time since last SuperPurge (seconds) R4
WEXPOTIM= major frame pulse time preceding exposure start I4
PSTRTIME= predicted obs. start time (yyyy:ddd:hh:mm:ss) C18
PSTPTIME= predicted obs. stop time (yyyy:ddd:hh:mm:ss) C18
/ EXPOSURE INFORMATION
EQUINOX = J2000 equinox of the celestial coordinate system C08 exp
SUNANGLE= angle between sun and V1 axis (deg) R4 exp
MOONANGL= angle between moon and V1 axis (deg) R4 exp
SUN_ALT = altitude of the sun above Earth's limb (deg) R4 exp
FGSLOCK = commanded FGS lock (FINE,COARSE,GYROS,UNKNOWN) C07 exp
DATE-OBS= UT date of start of observation (dd/mm/yy) C08 exp
TIME-OBS= UT time of start of observation (hh:mm:ss) C08 exp
EXPSTART= exposure start time (Modified Julian Date) R8
EXPEND = exposure end time (Modified Julian Date) R8 exp
EXPTIME = exposure duration (seconds)--calculated R4
EXPFLAG = exposure interruption indicator C13 exp
/ TARGET & PROPOSAL ID
TARGNAME= proposer's target name C30 exp
RA_TARG = right ascension of the target (deg) R8 exp
DEC_TARG= declination of the target (deg) R8 exp
PEQUINOX= proposed equinox of celestial coordinate system C18 exp
PROPOSID= PEP proposal identifier I4 all
PEP_EXPO= PEP exposure identifier including sequence C15 all
LINENUM = PEP proposal line number C15 exp
SEQLINE = PEP line number of defined sequence C15 exp
SEQNAME = PEP define/use sequence name C15 exp
END
[Listing Version 02 18-MAY-1992]
6.2.2 Static Bad Pixel Mask Files (MSK): <unique name>.R0H
The static mask files (formerly known as the data quality masks) contain flags for those pixels that always contain degraded values. This mask is routinely incorporated into the data quality file generated in the RSDP pipeline by calwfp.
Format: The static mask file is a short integer (INTEGER*2) image file of four groups with the same dimensions as the WF/PC science image. The image contains values of 0 in all pixels, except for those with known static defects. Defective pixels are flagged with the value 4.
Flags and Indicators: The flags and indicators used to select the static mask reference files are CAMERA (the camera value can be either WF or PC) and MODE (which can be either AREA or FULL).
Restrictions: The static mask reference file is not accompanied by a data quality file. The header of the static mask image is a copy of the WF/PC science data header.
The following listing shows a sample WF/PC static mask reference file.
BITPIX = 16 / bits per data value I2
DATATYPE= INTEGER*2 / data type of the array CHR
PTYPE10 = DATAMIN / minimum value of the data CHR
PDTYPE10= REAL*4 CHR
PSIZE10 = 32 I2
PTYPE11 = DATAMAX / maximum value of the data CHR
PDTYPE11= REAL*4 CHR
PSIZE11 = 32 I2
PTYPE21 = DETECTOR / CCD detector: WFC 1-4, PC 5-8 CHR
PDTYPE21= INTEGER*4 CHR
PSIZE21 = 32 I2
PTYPE23 = GOODMIN / minimum value of the "good" pixels CHR
PDTYPE23= REAL*4 CHR
PSIZE23 = 32 I2
PTYPE24 = GOODMAX / maximum value of the "good" pixels CHR
PDTYPE24= REAL*4 CHR
PSIZE24 = 32 I2
PTYPE25 = DATAMEAN / mean value of the "good" pixels CHR
PDTYPE25= REAL*4 CHR
PSIZE25 = 32 I2
PTYPE26 = GPIXELS / number of "good" pixels (DQF=0) CHR
PDTYPE26= INTEGER*4 CHR
PSIZE26 = 32 I2
PTYPE28 = CALIBDEF / number of "calibration defect" pixels (DQF=2) CHR
PDTYPE28= INTEGER*4 CHR
PSIZE28 = 32 I2
PTYPE29 = STATICD / number of "static defect" pixels (DQF=4) CHR
PDTYPE29= INTEGER*4 CHR
PSIZE29 = 32 I2
INSTRUME= WFPC / instrument in use CHR
ROOTNAME= / rootname of the observation set CHR
FILETYPE= MSK / file type: msk, a2d, bas, prf, spg, drk, flt CHR
CAMERA = / camera in use: WF (wide-field), PC (planetary) CHR
MODE = / instr. mode: FULL (full res.), AREA (area int.) CHR
SERIALS = / serial clocks: ON, OFF CHR
FILTNAM1= / first filter name CHR
FILTNAM2= / second filter name CHR
FILTER1 = / first filter number (0-48) I2
FILTER2 = / second filter number (0-48) I2
PFILTER1= / preflash filter 1 number (0-48) I2
PFILTER2= / preflash filter 2 number (0-48) I2
EXPTIME = / exposure time (seconds) R4
TRGTNAME= / target name CHR
SHUTTER = UNKNOWN / shutter in place during preflash: A, B, UNKNOWN CHR
IMAGETYP= SPECIAL / image type: SCIENCE/BIAS/DARK/PREF/FLAT/SPECIAL CHR
CDBSFILE= MASK / CDBS: YES/NO/BIAS/DARK/PREF/FLAT/MASK/ATOD/SPG CHR
DATE = / date file written (dd/mm/yy) CHR
END
[Listing Version 01 24-MAY-1990]
6.2.3 A-to-D Lookup Table Files (A2D): < unique name>.R1H
The A-to-D lookup table files are used to correct the image data for a pattern introduced by the analog-to-digital converter electronics. This is done by replacing the short integer pixel values obtained from the WF/PC with floating-point values that remove the systematic degradation introduced by this hardware problem.
Format: The A-to-D lookup table file is a single-precision (REAL*4) image file with a line length (NAXIS1) of 4096 and multiple lines. The first line contains a value of -1 in pixel 1 and the Bay 3 temperature (in degrees Kelvin) for each A-to-D lookup table in subsequent pixels. The index of these pixels must correspond to the line containing that lookup table. The remainder of the first line is filled with -1 values.
Flags and Indicators: The flag and indicator used to select the A-to-D reference files is CAMERA (the camera value can be either WF or PC).
Restrictions: The A-to-D lookup table is not accompanied by a data quality file. The header of the A-to-D lookup table image is a copy of the WF/PC science data header. The file must have four groups (one for each detector).
The following listing shows a partial image header for an A-to-D lookup table.
BITPIX = 16 / bits per data value I2
DATATYPE= INTEGER*2 / data type of the array CHR
PTYPE10 = DATAMIN / minimum value of the data CHR
PDTYPE10= REAL*4 CHR
PSIZE10 = 32 I2
PTYPE11 = DATAMAX / maximum value of the data CHR
PDTYPE11= REAL*4 CHR
PSIZE11 = 32 I2
PTYPE21 = DETECTOR / CCD detector: WFC 1-4, PC 5-8 CHR
PDTYPE21= INTEGER*4 CHR
PSIZE21 = 32 I2
PTYPE23 = GOODMIN / minimum value of the "good" pixels CHR
PDTYPE23= REAL*4 CHR
PSIZE23 = 32 I2
PTYPE24 = GOODMAX / maximum value of the "good" pixels CHR
PDTYPE24= REAL*4 CHR
PSIZE24 = 32 I2
PTYPE25 = DATAMEAN / mean value of the "good" pixels CHR
PDTYPE25= REAL*4 CHR
PSIZE25 = 32 I2
PTYPE26 = GPIXELS / number of "good" pixels (DQF=0) CHR
PDTYPE26= INTEGER*4 CHR
PSIZE26 = 32 I2
PTYPE28 = CALIBDEF / number of "calibration defect" pixels (DQF=2) CHR
PDTYPE28= INTEGER*4 CHR
PSIZE28 = 32 I2
PTYPE29 = STATICD / number of "static defect" pixels (DQF=4) CHR
PDTYPE29= INTEGER*4 CHR
PSIZE29 = 32 I2
INSTRUME= WFPC / instrument in use CHR
ROOTNAME= / rootname of the observation set CHR
FILETYPE= A2D / file type: msk, a2d, bas, prf, spg, drk, flt CHR
CAMERA = / camera in use: WF (wide-field), PC (planetary) CHR
MODE = / instr. mode: FULL (full res.), AREA (area int.) CHR
SERIALS = / serial clocks: ON, OFF CHR
FILTNAM1= / first filter name CHR
FILTNAM2= / second filter name CHR
FILTER1 = / first filter number (0-48) I2
FILTER2 = / second filter number (0-48) I2
PFILTER1= / preflash filter 1 number (0-48) I2
PFILTER2= / preflash filter 2 number (0-48) I2
EXPTIME = / exposure time (seconds) R4
TRGTNAME= / target name CHR
SHUTTER = UNKNOWN / shutter in place during preflash: A, B, UNKNOWN CHR
IMAGETYP= SPECIAL / image type: SCIENCE/BIAS/DARK/PREF/FLAT/SPECIAL CHR
CDBSFILE= ATOD / CDBS: YES/NO/BIAS/DARK/PREF/FLAT/MASK/ATOD/SPG CHR
DATE = / date file written (dd/mm/yy) CHR
END
[Listing Version 01 24-MAY-1990]
6.2.4 Bias Files (BAS): <unique name>.R2H
The structure in the electronic bias is removed by subtracting the bias reference file (with its accompanying data quality file).
Format: The bias reference file and its associated data quality file are REAL*4 image files with the same number of dimensions as the WF/PC science image. It is made from the average of a large number of bias readouts. The A-to-D and bias level removal corrections must be done before averaging these files. This file therefore contains only the pattern superimposed upon the DC bias level.
Flags and Indicators: The flags and indicators used to select the bias reference files are CAMERA (the camera value can be either WF or PC) and MODE (which can take a value of either AREA or FULL).
Restrictions: The bias reference file must be accompanied by a data quality file. The header of the bias image is a copy of the WF/PC science data header.
The following partial image header shows keywords used in the bias reference file.
BITPIX = 16 / bits per data value I2
DATATYPE= INTEGER*2 / data type of the array CHR
PTYPE10 = DATAMIN / minimum value of the data CHR
PDTYPE10= REAL*4 CHR
PSIZE10 = 32 I2
PTYPE11 = DATAMAX / maximum value of the data CHR
PDTYPE11= REAL*4 CHR
PSIZE11 = 32 I2
PTYPE21 = DETECTOR / CCD detector: WFC 1-4, PC 5-8 CHR
PDTYPE21= INTEGER*4 CHR
PSIZE21 = 32 I2
PTYPE23 = GOODMIN / minimum value of the "good" pixels CHR
PDTYPE23= REAL*4 CHR
PSIZE23 = 32 I2
PTYPE24 = GOODMAX / maximum value of the "good" pixels CHR
PDTYPE24= REAL*4 CHR
PSIZE24 = 32 I2
PTYPE25 = DATAMEAN / mean value of the "good" pixels CHR
PDTYPE25= REAL*4 CHR
PSIZE25 = 32 I2
PTYPE26 = GPIXELS / number of "good" pixels (DQF=0) CHR
PDTYPE26= INTEGER*4 CHR
PSIZE26 = 32 I2
PTYPE28 = CALIBDEF / number of "calibration defect" pixels (DQF=2) CHR
PDTYPE28= INTEGER*4 CHR
PSIZE28 = 32 I2
PTYPE29 = STATICD / number of "static defect" pixels (DQF=4) CHR
PDTYPE29= INTEGER*4 CHR
PSIZE29 = 32 I2
INSTRUME= WFPC / instrument in use CHR
ROOTNAME= / rootname of the observation set CHR
FILETYPE= BAS / file type: msk, a2d, bas, prf, spg, drk, flt CHR
CAMERA = / camera in use: WF (wide-field), PC (planetary) CHR
MODE = / instr. mode: FULL (full res.), AREA (area int.) CHR
SERIALS = / serial clocks: ON, OFF CHR
FILTNAM1= / first filter name CHR
FILTNAM2= / second filter name CHR
FILTER1 = / first filter number (0-48) I2
FILTER2 = / second filter number (0-48) I2
PFILTER1= / preflash filter 1 number (0-48) I2
PFILTER2= / preflash filter 2 number (0-48) I2
EXPTIME = / exposure time (seconds) R4
TRGTNAME= / target name CHR
SHUTTER = UNKNOWN / shutter in place during preflash: A, B, UNKNOWN CHR
IMAGETYP= SPECIAL / image type: SCIENCE/BIAS/DARK/PREF/FLAT/SPECIAL CHR
CDBSFILE= BIAS / CDBS: YES/NO/BIAS/DARK/PREF/FLAT/MASK/ATOD/SPG CHR
DATE = / date file written (dd/mm/yy) CHR
END
[Listing Version 01 24-MAY-1990]
6.2.5 Preflash Files (PRF): <unique name>.R3H
The WF/PC preflash reference file and its associated data quality file are used to remove the signal introduced by the preflash lamp. This signal is removed by subtracting this reference file. The reference file is scaled by the preflash exposure time to allow for variations in the requested preflash exposure. The subtraction of the reference file corrects for the uneven illumination pattern of the preflash image. Since the preflash is obtained by illuminating the backside of the shutter with an internal lamp, the difference in reflectivity of the two shutter blades requires reference files specific to each shutter blade.
Format: The preflash reference file is a single-precision real (REAL*4) image file with the same number of dimensions as the WF/PC science image. It is made from the average of a large number of preflash exposures. The A-to-D, bias level removal, and bias image subtraction corrections must be done to these files before averaging. The file must be scaled to the equivalent of a 1-second preflash exposure.
Flags and Indicators: The flags and indicators used to select the preflash reference files are CAMERA (the camera value can be either WF or PC), MODE (which can be either AREA or FULL), SHUTTER (which can take one of three values: A, B, or UNKNOWN), and the values of PREFTIME, PFILTER1, and PFILTER2. Only one set of filters is used for each camera (WF and PC) in normal operation. Each shutter blade requires a separate preflash reference file. The preflash exposure time provided the basis for the selection of the preflash reference file (PREFTIME > 0).
Restrictions: The preflash reference file must be accompanied by a data quality file. The header of the preflash reference file is a copy of the WF/PC science data header.
The following listing shows a partial header for the preflash reference file.
BITPIX = 16 / bits per data value I2
DATATYPE= INTEGER*2 / data type of the array CHR
PTYPE10 = DATAMIN / minimum value of the data CHR
PDTYPE10= REAL*4 CHR
PSIZE10 = 32 I2
PTYPE11 = DATAMAX / maximum value of the data CHR
PDTYPE11= REAL*4 CHR
PSIZE11 = 32 I2
PTYPE21 = DETECTOR / CCD detector: WFC 1-4, PC 5-8 CHR
PDTYPE21= INTEGER*4 CHR
PSIZE21 = 32 I2
PTYPE23 = GOODMIN / minimum value of the "good" pixels CHR
PDTYPE23= REAL*4 CHR
PSIZE23 = 32 I2
PTYPE24 = GOODMAX / maximum value of the "good" pixels CHR
PDTYPE24= REAL*4 CHR
PSIZE24 = 32 I2
PTYPE25 = DATAMEAN / mean value of the "good" pixels CHR
PDTYPE25= REAL*4 CHR
PSIZE25 = 32 I2
PTYPE26 = GPIXELS / number of "good" pixels (DQF=0) CHR
PDTYPE26= INTEGER*4 CHR
PSIZE26 = 32 I2
PTYPE28 = CALIBDEF / number of "calibration defect" pixels (DQF=2) CHR
PDTYPE28= INTEGER*4 CHR
PSIZE28 = 32 I2
PTYPE29 = STATICD / number of "static defect" pixels (DQF=4) CHR
PDTYPE29= INTEGER*4 CHR
PSIZE29 = 32 I2
INSTRUME= WFPC / instrument in use CHR
ROOTNAME= / rootname of the observation set CHR
FILETYPE= PRF / file type: msk, a2d, bas, prf, spg, drk, flt CHR
CAMERA = / camera in use: WF (wide-field), PC (planetary) CHR
MODE = / instr. mode: FULL (full res.), AREA (area int.) CHR
SERIALS = / serial clocks: ON, OFF CHR
FILTNAM1= / first filter name CHR
FILTNAM2= / second filter name CHR
FILTER1 = / first filter number (0-48) I2
FILTER2 = / second filter number (0-48) I2
PFILTER1= / preflash filter 1 number (0-48) I2
PFILTER2= / preflash filter 2 number (0-48) I2
EXPTIME = / exposure time (seconds) R4
TRGTNAME= / target name CHR
SHUTTER = UNKNOWN / shutter in place during preflash: A, B, UNKNOWN CHR
IMAGETYP= SPECIAL / image type: SCIENCE/BIAS/DARK/PREF/FLAT/SPECIAL CHR
CDBSFILE= PREF / CDBS: YES/NO/BIAS/DARK/PREF/FLAT/MASK/ATOD/SPG CHR
DATE = / date file written (dd/mm/yy) CHR
END
[Listing Version 01 24-MAY-1990]
6.2.6 Superpurge Files (SPG): <unique name>.R4H
Note: Superpurge files were never implemented in the calwfp pipeline.
The WF/PC superpurge reference file and its associated data quality file are used in the superpurge calibration procedure. The superpurge procedure removes residual images of highly overexposed sources. However, it creates a nonuniform residual image over the entire detector that decays with time. The level of this global residual image in a readout depends upon both the time since the purge was performed and the time since the last erase prior to the readout. The superpurge reference file must be scaled and subtracted from all images obtained after a superpurge in which the residual is still significant.
Format: The superpurge reference file is a single-precision real (REAL*4) image file with the same number of dimensions as the WF/PC science image. It is made from the average of a large number of dark readouts obtained soon after a superpurge. The A-to-D, bias level removal, bias image subtraction, and preflash image subtraction corrections must be done to these files prior to averaging. The details of the scaling required are described in Lauer ( PASP, 1989), taking all times in seconds. That is, the reference file is multiplied by the scale factor PS prior to subtraction from the image, where
PS = 30\left(\frac{600}{RT-DT}\right)^{1/3} \left[1.0-\left(\frac{RT-DT}{RT}\right)^{1/3}\right]
RT is the time in seconds since last purge DT is the dark time in seconds for this exposure
Flags and Indicators: The flags and indicators used to select the superpurge reference files are CAMERA (the camera can be either WF or PC) and MODE (which can be either AREA or FULL).
Restrictions: The superpurge reference file must be accompanied by a data quality file. The header of the superpurge image is a copy of the WF/PC science data header.
The following listing shows part of a sample image header for a superpurge reference file.
BITPIX = 16 / bits per data value I2
DATATYPE= INTEGER*2 / data type of the array CHR
PTYPE10 = DATAMIN / minimum value of the data CHR
PDTYPE10= REAL*4 CHR
PSIZE10 = 32 I2
PTYPE11 = DATAMAX / maximum value of the data CHR
PDTYPE11= REAL*4 CHR
PSIZE11 = 32 I2
PTYPE21 = DETECTOR / CCD detector: WFC 1-4, PC 5-8 CHR
PDTYPE21= INTEGER*4 CHR
PSIZE21 = 32 I2
PTYPE23 = GOODMIN / minimum value of the "good" pixels CHR
PDTYPE23= REAL*4 CHR
PSIZE23 = 32 I2
PTYPE24 = GOODMAX / maximum value of the "good" pixels CHR
PDTYPE24= REAL*4 CHR
PSIZE24 = 32 I2
PTYPE25 = DATAMEAN / mean value of the "good" pixels CHR P
DTYPE25= REAL*4 CHR
PSIZE25 = 32 I2
PTYPE26 = GPIXELS / number of "good" pixels (DQF=0) CHR
PDTYPE26= INTEGER*4 CHR
PSIZE26 = 32 I2
PTYPE28 = CALIBDEF / number of "calibration defect" pixels (DQF=2) CHR
PDTYPE28= INTEGER*4 CHR
PSIZE28 = 32 I2
PTYPE29 = STATICD / number of "static defect" pixels (DQF=4) CHR
PDTYPE29= INTEGER*4 CHR
PSIZE29 = 32 I2
INSTRUME= WFPC / instrument in use CHR
ROOTNAME= / rootname of the observation set CHR
FILETYPE= SPG / file type: msk, a2d, bas, prf, spg, drk, flt CHR
CAMERA = / camera in use: WF (wide-field), PC (planetary) CHR
MODE = / instr. mode: FULL (full res.), AREA (area int.) CHR
SERIALS = / serial clocks: ON, OFF CHR
FILTNAM1= / first filter name CHR
FILTNAM2= / second filter name CHR
FILTER1 = / first filter number (0-48) I2
FILTER2 = / second filter number (0-48) I2
PFILTER1= / preflash filter 1 number (0-48) I2
PFILTER2= / preflash filter 2 number (0-48) I2
EXPTIME = / exposure time (seconds) R4
TRGTNAME= / target name CHR
SHUTTER = UNKNOWN / shutter in place during preflash: A, B, UNKNOWN CHR
IMAGETYP= SPECIAL / image type: SCIENCE/BIAS/DARK/PREF/FLAT/SPECIAL CHR
CDBSFILE= SPG / CDBS: YES/NO/BIAS/DARK/PREF/FLAT/MASK/ATOD/SPG CHR
DATE = / date file written (dd/mm/yy) CHR
END
[Listing Version 01 24-MAY-1990]
6.2.7 Dark Files (DRK): <unique name>.R5H
The WF/PC dark reference file and its associated data quality file are used to correct the dark current. The WF/PC CCDs generate a spurious signal during exposures known as dark current. This signal is a function of the time since the last erase command and the operating temperature of the CCD detectors and varies from pixel to pixel. The dark reference file is scaled by the time since the last erase command and subtracted from the image.
Format: The dark reference file is a single-precision (REAL*4) image file with the same number of dimensions as the WF/PC science image. It is made from the average of a large number of dark images. The A-to-D, bias level removal, bias image subtraction, and preflash image subtraction corrections must be done to these files prior to averaging. Ideally, the CCD detectors should not have been saturated by either sources or the superpurge operation for several hours prior to the acquisition of the dark images used to make this reference file. The dark reference file must be scaled to the equivalent of a 1-second exposure.
Flags and Indicators: The flags and indicators used to select the dark reference files are CAMERA (the camera value can be either WF or PC), MODE (which can be either AREA or FULL), and SERIALS (which can be either ON or OFF).
Restrictions: The dark reference file must be accompanied by a data quality file. The header of the dark reference file is a copy of the WF/PC science data header.
The following listing shows a partial image header for a sample dark reference file.
BITPIX = 16 / bits per data value I2
DATATYPE= INTEGER*2 / data type of the array CHR
PTYPE10 = DATAMIN / minimum value of the data CHR
PDTYPE10= REAL*4 CHR
PSIZE10 = 32 I2
PTYPE11 = DATAMAX / maximum value of the data CHR
PDTYPE11= REAL*4 CHR
PSIZE11 = 32 I2
PTYPE21 = DETECTOR / CCD detector: WFC 1-4, PC 5-8 CHR
PDTYPE21= INTEGER*4 CHR
PSIZE21 = 32 I2
PTYPE23 = GOODMIN / minimum value of the "good" pixels CHR
PDTYPE23= REAL*4 CHR
PSIZE23 = 32 I2
PTYPE24 = GOODMAX / maximum value of the "good" pixels CHR
PDTYPE24= REAL*4 CHR
PSIZE24 = 32 I2
PTYPE25 = DATAMEAN / mean value of the "good" pixels CHR
PDTYPE25= REAL*4 CHR
SIZE25 = 32 I2
PTYPE26 = GPIXELS / number of "good" pixels (DQF=0) CHR
PDTYPE26= INTEGER*4 CHR
PSIZE26 = 32 I2
PTYPE28 = CALIBDEF / number of "calibration defect" pixels (DQF=2) CHR
PDTYPE28= INTEGER*4 CHR
PSIZE28 = 32 I2
PTYPE29 = STATICD / number of "static defect" pixels (DQF=4) CHR
PDTYPE29= INTEGER*4 CHR
PSIZE29 = 32 I2
INSTRUME= WFPC / instrument in use CHR
ROOTNAME= / rootname of the observation set CHR
FILETYPE= DRK / file type: msk, a2d, bas, prf, spg, drk, flt CHR
CAMERA = / camera in use: WF (wide-field), PC (planetary) CHR
MODE = / instr. mode: FULL (full res.), AREA (area int.) CHR
SERIALS = / serial clocks: ON, OFF CHR
FILTNAM1= / first filter name CHR
FILTNAM2= / second filter name CHR
FILTER1 = / first filter number (0-48) I2
FILTER2 = / second filter number (0-48) I2
PFILTER1= / preflash filter 1 number (0-48) I2
PFILTER2= / preflash filter 2 number (0-48) I2
EXPTIME = / exposure time (seconds) R4
TRGTNAME= / target name CHR
SHUTTER = UNKNOWN / shutter in place during preflash: A, B, UNKNOWN CHR
IMAGETYP= SPECIAL / image type: SCIENCE/BIAS/DARK/PREF/FLAT/SPECIAL CHR
CDBSFILE= DARK / CDBS: YES/NO/BIAS/DARK/PREF/FLAT/MASK/ATOD/SPG CHR
DATE = / date file written (dd/mm/yy) CHR
END
[Listing Version 01 13-JUN-1990]
6.2.8 Flat Field Reference Files (FLT): < unique name>.R6H
The variations in sensitivity between pixels in the CCD detectors are corrected by applying a flat field reference file. This file contains the normalized inverse sensitivity (gain) for each pixel in the detector. It is made from internal exposures in conjunction with streaked earth flats. The image is multiplied by the flat field file after correcting for bias, preflash, superpurge, and dark.
Format: The flat field reference file is a single-precision (REAL*4) image file with the same number of dimensions as the WF/PC science image. The A-to-D, bias level removal, and bias image subtraction corrections must be done to these files. The preflash and dark corrections are not usually relevant to the short, bright, flat field exposures (but may be in some cases). The flat fields must be normalized to 1.0 and inverted (1/x) to allow the correction process to use multiplication. Normalization should be based on all pixels not flagged in the flat field file’s data quality file in all four detectors (groups). It is important that the range of values in the flat field files have reasonable limits. Pixels that fall outside the acceptable range of sensitivity, or which are located in dead regions, should be set to 1 in the flat field file and flagged in the data quality file.
Flags and Indicators: The flags and indicators used to select the flat field reference files are CAMERA (the camera value can be either WF or PC), MODE (which can be either AREA or FULL), FILTNAM1, and FILTNAM2. There are 48 filter elements and two cameras and two modes possible for each element. In addition, some filter elements can be used in combination with others, and all the flat fields are time-dependent, thereby requiring more than 300 flat field reference files in CDBS.
Restrictions: The flat field reference file must be accompanied by a data quality file. The header of the flat field reference file is a copy of the WF/PC science data header.
The following listing shows a partial image header from a sample flat field reference file.
BITPIX = 16 / bits per data value I2
DATATYPE= INTEGER*2 / data type of the array CHR
PTYPE10 = DATAMIN / minimum value of the data CHR
PDTYPE10= REAL*4 CHR
PSIZE10 = 32 I2
PTYPE11 = DATAMAX / maximum value of the data CHR
PDTYPE11= REAL*4 CHR
PSIZE11 = 32 I2
PTYPE21 = DETECTOR / CCD detector: WFC 1-4, PC 5-8 CHR
PDTYPE21= INTEGER*4 CHR
PSIZE21 = 32 I2
PTYPE23 = GOODMIN / minimum value of the "good" pixels CHR
PDTYPE23= REAL*4 CHR
PSIZE23 = 32 I2
PTYPE24 = GOODMAX / maximum value of the "good" pixels CHR
PDTYPE24= REAL*4 CHR
PSIZE24 = 32 I2
PTYPE25 = DATAMEAN / mean value of the "good" pixels CHR
PDTYPE25= REAL*4 CHR
PSIZE25 = 32 I2
PTYPE26 = GPIXELS / number of "good" pixels (DQF=0) CHR
PDTYPE26= INTEGER*4 CHR
PSIZE26 = 32 I2
PTYPE28 = CALIBDEF / number of "calibration defect" pixels (DQF=2) CHR
PDTYPE28= INTEGER*4 CHR
PSIZE28 = 32 I2
PTYPE29 = STATICD / number of "static defect" pixels (DQF=4) CHR
PDTYPE29= INTEGER*4 CHR
PSIZE29 = 32 I2
INSTRUME= WFPC / instrument in use CHR
ROOTNAME= / rootname of the observation set CHR
FILETYPE= FLT / file type: msk, a2d, bas, prf, spg, drk, flt CHR
CAMERA = / camera in use: WF (wide-field), PC (planetary) CHR
MODE = / instr. mode: FULL (full res.), AREA (area int.) CHR
SERIALS = / serial clocks: ON, OFF CHR
FILTNAM1= / first filter name CHR
FILTNAM2= / second filter name CHR
FILTER1 = / first filter number (0-48) I2
FILTER2 = / second filter number (0-48) I2
PFILTER1= / preflash filter 1 number (0-48) I2
PFILTER2= / preflash filter 2 number (0-48) I2
EXPTIME = / exposure time (seconds) R4
TRGTNAME= / target name CHR
SHUTTER = UNKNOWN / shutter in place during preflash: A, B, UNKNOWN CHR
IMAGETYP= SPECIAL / image type: SCIENCE/BIAS/DARK/PREF/FLAT/SPECIAL CHR
CDBSFILE= FLAT / CDBS: YES/NO/BIAS/DARK/PREF/FLAT/MASK/ATOD/SPG CHR
DATE = / date file written (dd/mm/yy) CHR
END
[Listing Version 01 24-MAY-1990]
6.3 WF/PC Tables
6.3.1 Photometry Group Parameters Table: <unique name>.CW0
The photometry group parameters table contains those computed photometry group parameters that correspond to each calibrated photometry mode for both the Wide-Field and Planetary Cameras.
Format: Records of photometry parameters are organized by the PHOTMODE string, camera, detector, and first and second filter names.
Selection Scheme: Records are selected on the basis of an exact match to the PHOTMODE string.
Restrictions: The table must include all entries listed in the “Column Name” column of Table 6-2, which shows a sample table of computed photometry parameters (<unique name>.CW0).
Table 6-2. WF/PC Computed Photometry Parameters Table, <unique name>.
Column Name |
Data Type |
Units |
Description |
|---|---|---|---|
Description |
PHOTBW |
R |
– |
CAMERA |
CH*2 |
– |
Camera in use (WF or PC) |
DETECTOR |
I |
– |
Chip number (WF: 1-4; PC: 5-8) |
FILTNAM1 |
CH*6 |
– |
Name of first filter |
FILTNAM2 |
CH*6 |
– |
Name of second filter |
PHOTMODE |
CH*30 |
– |
Photometry mode |
PHOTFLAM |
R |
DN/sec/cm2/Å |
Inverse sensitivity |
PHOTZPT |
R |
– |
Zero point |
PHOTPLAM |
R |
– |
Pivot wavelength |