Section 7. Wide Field/Planetary Camera 2 ---------------------------------------- Observation datasets produced by the Wide Field/Planetary Camera 2 u (WFPC 2) are calibrated by the **calwp2** task. This task requires a set of reference files to perform the calibration, as described in this section. All reference files for the WFPC 2 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 WFPC 2 camera in the nominal readout order. That is, group 1 contains the image from CCD PC1, group 2 contains the image from CCD WFC2, group 3 contains the image from CCD WFC3, and group 4 contains the image from CCD WFC4. The keyword DETECTOR in the group parameter block should agree with this convention. The data is of either 2-byte integer (INTEGER\*2) or singleprecision real (REAL\*4) data type. Reference file headers must be copies of the headers created during generic conversion for the WFPC 2 science image (\*. D0H) file. This is to ensure a common header format throughout the WFPC 2 calibration process. This header format will be known as the WFPC 2 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. 7.1 Data Quality Files ~~~~~~~~~~~~~~~~~~~~~~ Most WFPC 2 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 **calwp2**. 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 WFPC 2 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 7-1 shows the DQF condition codes used in routine WFPC 2 pipeline processing. **Table 7-1. WFPC 2 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 WFPC 2 camera | +---------------+------+------------------------------------------------------------------+ | ATODSAT |8 |A-to-D converter was saturated - value unknown | +---------------+------+------------------------------------------------------------------+ | DATALOST |16 |Missing data BADPIXEL 32 Generic bad pixel - reason not specified | +---------------+------+------------------------------------------------------------------+ | OVERLAP |64 |Portion of image not corrected for aberration | +---------------+------+------------------------------------------------------------------+ | NOTUSED |128 |Flag value not used | +---------------+------+------------------------------------------------------------------+ | CTTRAPCOL |256 |Column above charge transfer trap | +---------------+------+------------------------------------------------------------------+ | UNFIXHOTPIX |512 |Highly variable hot pixel, cannot be fixed | +---------------+------+------------------------------------------------------------------+ | FIXABLEHOTPIX |1024 |Moderate hot pixel (fix via warmpix task) | +---------------+------+------------------------------------------------------------------+ 7.2 WFPC 2 Reference Files ~~~~~~~~~~~~~~~~~~~~~~~~~~ WFPC 2 reference files are composed of a FITS header file and a binary data file. 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 WFPC 2 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 WFPC 2 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 calwp2 (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 WFPC 2 with floating-point values that remove the systematic degradation introduced by this hardware problem. **Bias Reference File and DQF:** These files are subtracted from the image to remove the structure in the electronic bias. **Dark Reference File and DQF:** The WFPC 2 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 and dark). **Shutter Shading Reference File:** When a WFPC 2 exposure is relatively short, shutter shading (resulting from the finite time of flight of the shutter blade) gives rise to uneven illumination across the field of view. This is corrected by means of an additive correction that varies spatially according to the shutter shading reference file, which is scaled for the appropriate exposure time. 7.2.1 Generic Image Header: All WFPC 2 Reference Files ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ The following listing shows a standard header used by all WFPC 2 reference files. :: Instrument: WIDEFIELD PLANETARY CAMERA II Revised: 20-AUG-93 File Type: SCIENCE DATA HEADER 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 = 38 number of parameters I2 PSIZE = 1760 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: PC 1, WFC 2-4 C08 PDTYPE19= INTEGER*4 C18 PSIZE19 = 32 I2 / GROUP PARAMETERS: PODPS PTYPE20 = DEZERO mean bias level from EED extended register C08 PDTYPE20= REAL*4 C18 PSIZE20 = 32 I2 PTYPE21 = BIASEVEN bias level for even-numbered columns C08 PDTYPE21= REAL*4 C18 PSIZE21 = 32 I2 PTYPE22 = BIASODD bias level for odd-numbered columns 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 PTYPE27 = SOFTERRS number of "soft error" pixels (DQF=1) C08 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 "A to D 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 PTYPE33 = OVERLAP number of "image overlap" pixels (DQF=64) C08 PDTYPE33= INTEGER*4 C18 PSIZE33 = 32 I2 / GROUP PARAMETERS: PHOTOMETRY PTYPE34 = PHOTMODE photometry mode C08 PDTYPE34= CHARACTER*48 C18 PSIZE34 = 384 I2 PTYPE35 = PHOTFLAM inverse sensitivity C08 PDTYPE35= REAL*4 C18 PSIZE35 = 32 I2 PTYPE36 = PHOTZPT zero point C08 PDTYPE36= REAL*4 C18 PSIZE36 = 32 I2 PTYPE37 = PHOTPLAM pivot wavelength C08 PDTYPE37= REAL*4 C18 PSIZE37 = 32 I2 PTYPE38 = PHOTBW RMS bandwidth of the filter C08 PDTYPE38= REAL*4 C18 PSIZE38 = 32 I2 / WFPC-II DATA DESCRIPTOR KEYWORDS INSTRUME= WFPC2 instrument in use C06 ROOTNAME= rootname of the observation set C12 FILETYPE= SCI shp, ext, edq, sdq, sci C03 / SCIENCE INSTRUMENT CONFIGURATION MODE = instr. mode: FULL (full res.), AREA (area int.) C04 SERIALS = serial clocks: ON, OFF C03 / IMAGE TYPE CHARACTERISTICS IMAGETYP= EXT DARK/BIAS/IFLAT/UFLAT/VFLAT/KSPOT/EXT/ECAL C18 CDBSFILE= NO GENERIC/BIAS/DARK/FLAT/MASK/ATOD/SHAD/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 FILTROT = partial filter rotation angle (degrees) R4 LRFWAVE = linear ramp filter wavelength R4 / INSTRUMENT STATUS USED IN DATA PROCESSING UCH1CJTM= TEC cold junction #1 temperature (Celsius) R4 UCH2CJTM= TEC cold junction #2 temperature (Celsius) R4 UCH3CJTM= TEC cold junction #3 temperature (Celsius) R4 UCH4CJTM= TEC cold junction #4 temperature (Celsius) R4 UBAY3TMP= Bay 3 A1 temperature (deg C) R4 KSPOTS = status of Kelsall spot lamps: ON, OFF C03 SHUTTER = shutter in place during IFLAT (A or B) C01 ATODGAIN= analog to digital gain (Electrons/DN) R4 / RSDP CONTROL KEYWORDS MASKCORR= PERFORM do mask correction: PERFORM, OMIT, COMPLETE C08 ATODCORR= do A-to-D correction: PERFORM, OMIT, COMPLETE C08 BLEVCORR= do bias level correction: PERFORM, OMIT, COMPLET C08 BIASCORR= do bias correction: PERFORM, OMIT, COMPLETE C08 DARKCORR= do dark correction: PERFORM, OMIT, COMPLETE C08 FLATCORR= do flat field correction: PERFORM, OMIT, COMPLETE C08 SHADCORR= do shaded shutter correction: PERFORM, OMIT, COMPLETE C08 DOSATMAP= OMIT output saturated pixel map: PERFORM, OMIT, COMPLETE C08 DOPHOTOM= fill photometry keywords: PERFORM, OMIT, COMPLETE C08 DOHISTOS= OMIT make histograms: PERFORM, OMIT, COMPLETE 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 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 SHADFILE= name of the reference file for shutter shading C18 PHOTTAB = name of the photometry calibration table C18 GRAPHTAB= the HST graph table C18 COMPTAB = the HST components table C18 / DEFAULT KEYWORDS SET BY STSCI SATURATE= 4095 data value at which saturation occurs I2 USCALE = 1.0 scale factor for output image R4 UZERO = 0.0 zero point for output image R4 / READOUT DURATION INFORMATION READTIME= Length of time for CCD readout in clock ticks I4 / 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 UEXPODUR= commanded duration of exposure (seconds) I4 NSHUTA17= number of AP17 shutter B closes I4 DARKTIME= dark time (seconds) R4 UEXPOTIM= 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 SUNANGLE= angle between sun and V1 axis (deg) R4 MOONANGL= angle between moon and V1 axis (deg) R4 SUN_ALT = altitude of the sun above Earth's limb (deg) R4 FGSLOCK = commanded FGS lock (FINE,COARSE,GYROS,UNKNOWN) C07 DATE-OBS= UT date of start of observation (dd/mm/yy) C08 TIME-OBS= UT time of start of observation (hh:mm:ss) C08 EXPSTART= exposure start time (Modified Julian Date) R8 EXPEND = exposure end time (Modified Julian Date) R8 EXPTIME = exposure duration (seconds)--calculated R4 EXPFLAG = exposure interruption indicator C13 / TARGET & PROPOSAL ID TARGNAME= proposer's target name C30 RA_TARG = right ascension of the target (deg) (J2000) R8 DEC_TARG= declination of the target (deg) (J2000) R8 PROPOSID= PEP proposal identifier I4 PEP_EXPO= PEP exposure identifier including sequence C15 LINENUM = PEP proposal line number C15 SEQLINE = PEP line number of defined sequence C15 SEQNAME = PEP define/use sequence name C15 END 7.2.2 Static Bad Pixel Mask Files (MSK): .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 calwp2. **Format:** The static mask file is a short integer (INTEGER\*2) image file of four groups with the same dimensions as the WFPC 2 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 flag and indicator used to select the static mask reference files is 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 WFPC 2 science data header. The following listing shows a sample WFPC 2 static mask reference file. :: BITPIX = 16 / bits per data value I2 DATATYPE= INTEGER*2 / data type of the array C10 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 PTYPE19 = DETECTOR / CCD detector: PC 1, WFC 2-4 C08 PDTYPE19= INTEGER*4 C18 PSIZE19 = 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 PTYPE26 = GPIXELS / number of "good" pixels (DQF=0) C08 PDTYPE26= INTEGER*4 C18 PSIZE26 = 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 INSTRUME= WFII / instrument in use C04 ROOTNAME= / rootname of the observation set C12 FILETYPE= MSK / file type: msk, bas, drk, flt C03 MODE = / instr. mode: FULL (full res.), AREA (area int.) C04 SERIALS = / serial clocks: ON, OFF C03 IMAGETYP= SPECIAL / image type: EXT/BIAS/DARK/IFLAT/UFLAT/VFLAT/ECAL C18 CDBSFILE= MASK / CDBS: YES/NO/BIAS/DARK/FLAT/MASK/ATOD/SHAD C18 DATE = / date file written (dd/mm/yy) C08 FILTNAM1= / first filter name C08 FILTNAM2= / second filter name C08 FILTER1 = / first filter number (0-48) I2 FILTER2 = / second filter number (0-48) I2 SHUTTER = / shutter in place during IFLAT (A or B) C01 ATODGAIN= / analog to digital gain (Electrons/DN) R4 EXPTIME = / exposure duration (seconds) -- calculate R4 TARGNAME= / target name C30 END [Listing Version 01 09-JUL-1992] 7.2.3 A-to-D Lookup Table Files (A2D): .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 WFPC 2 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 ATODGAIN. **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 WFPC 2 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 C10 PTYPE10 = DATAMIN / minimum value of the data C08 PDTYPE10= REAL*4 C18 PSIZE10 = 32 I2 PTYPE11 = DATAMAX / maximum value of the data C08 PDTYPE11= REAL*4 C18 PSIZE11 = 32 I2 PTYPE21 = DETECTOR / CCD detector: PC 1, WFC 2-4 C08 PDTYPE21= INTEGER*4 C18 PSIZE21 = 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 PTYPE26 = GPIXELS / number of "good" pixels (DQF=0) C08 PDTYPE26= INTEGER*4 C18 PSIZE26 = 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 INSTRUME= WFPC2 / instrument in use C06 ROOTNAME= / rootname of the observation set C12 FILETYPE= A2D / file type: msk, a2d, bas, drk, flt, shd C03 MODE = / instr. mode: FULL (full res.), AREA (area int.) C04 SERIALS = / serial clocks: ON, OFF C03 IMAGETYP= SPECIAL / image type: EXT/BIAS/DARK.IFLAT/UFLAT/VFLAT/ECAL C18 CDBSFILE= ATOD / CDBS: YES/NO/BIAS/DARK/FLAT/MASK/ATOD/SHAD C18 DATE = / date file written (dd/mm/yy) C08 FILTNAM1= / first filter name C08 FILTNAM2= / second filter name C08 FILTER1 = / first filter number (0-48) I2 FILTER2 = / second filter number (0-48) I2 SHUTTER = / shutter in place during IFLAT: ( A or B) C01 ATODGAIN= / analog to digital gain (Electrons/DN) R4 EXPTIME = / exposure time (seconds) R4 TARGNAME= / target name C30 END [Listing Version 01 24-MAY-1990] 7.2.4 Bias Files (BAS): .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 WFPC 2 science image. It is made from the average of a large number of bias readouts. The bias level removal correction 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 MODE (which can take a value of either AREA or FULL) and ATODGAIN (which can take a value of either 7.0 or 15.0). **Restrictions:** The bias reference file must be accompanied by a data quality file. The header of the bias image is a copy of the WFPC 2 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 C10 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 PTYPE19 = DETECTOR / CCD detector: PC 1, WFC 2-4 C08 PDTYPE19= INTEGER*4 C18 PSIZE19 = 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 PTYPE26 = GPIXELS / number of "good" pixels (DQF=0) C08 PDTYPE26= INTEGER*4 C18 PSIZE26 = 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 INSTRUME= WFPC2 / instrument in use C06 ROOTNAME= / rootname of the observation set C12 FILETYPE= BAS / file type: msk, a2d, bas, drk, flt, shd C03 MODE = / instr. mode: FULL (full res.), AREA (area int.) C04 SERIALS = / serial clocks: ON, OFF C03 IMAGETYP= SPECIAL / image type: EXT/BIAS/DARK/IFLAT/UFLAT/VFLAT/ECAL C18 CDBSFILE= BIAS / CDBS: YES/NO/BIAS/DARK/FLAT/MASK C18 DATE = / date file written (dd/mm/yy) C08 FILTNAM1= / first filter name C08 FILTNAM2= / second filter name C08 FILTER1 = / first filter number (0-48) I2 FILTER2 = / second filter number (0-48) I2 SHUTTER = / shutter in place during IFLAT (A or B) C01 ATODGAIN= / analog to digital gain (Electrons/DN) R4 EXPTIME = / exposure duration (seconds) -- calculated R4 TARGNAME= / target name C30 END [Listing Version 01 09-JUL-1992] 7.2.5 Dark Files (DRK): .R3H ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ The WFPC 2 dark reference file and its associated data quality file are used to correct the dark current. The WFPC 2 CCDs generate a spurious signal during exposures know n 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 WFPC 2 science image. It is made from the average of a large number of dark images. The bias level removal and bias image subtraction corrections must be done to these files prior to averaging. Ideally, the CCD detectors should not have been saturated by sources 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 MODE (which can be either AREA or FULL), SERIALS (which can be either ON or OFF), and ATODGAIN (which can be either 7.0 or 15.0). **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 WFPC 2 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 C10 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 PTYPE19 = DETECTOR / CCD detector: PC 1, WFC 2-4 C08 PDTYPE19= INTEGER*4 C18 PSIZE19 = 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 PTYPE26 = GPIXELS / number of "good" pixels (DQF=0) C08 PDTYPE26= INTEGER*4 C18 PSIZE26 = 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 INSTRUME= WFPC2 / instrument in use C06 ROOTNAME= / rootname of the observation set C12 FILETYPE= DRK / file type: msk, a2d, bas, drk, flt, shd C03 MODE = / instr. mode: FULL (full res.), AREA (area int.) C04 SERIALS = / serial clocks: ON, OFF C03 IMAGETYP= SPECIAL / image type: EXT/BIAS/DARK/IFLAT/UFLAT/VFLAT/ECAL C18 CDBSFILE= DARK / CDBS: YES/NO/BIAS/DARK/FLAT/MASK/ATOD/SHAD C18 DATE = / date file written (dd/mm/yy) C08 FILTNAM1= / first filter name C08 FILTNAM2= / second filter name C08 FILTER1 = / first filter number (0-48) I2 FILTER2 = / second filter number (0-48) I2 SHUTTER = / shutter in place during IFLAT (A or B) C01 ATODGAIN= / analog to digital gain (Electrons/DN) R4 EXPTIME = / exposure duration (seconds) -- calculated R4 TARGNAME= / target name C30 END Listing Version 01 09-JUL-1992] 7.2.6 Flat Field Reference Files (FLT): < uniquename>.R4H ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 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 flat lamp exposures, the combination of streaked earth flats or processed observations of astronomical sources. The image is multiplied by the flat field file after correcting for bias and dark. The flat field reference file is a single-precision (REAL\*4) image file with the same number of dimensions as the WFPC 2 science image. The bias level removal and bias image subtraction corrections must be done to these files. The dark correction is 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 MODE (the mode can be either AREA or FULL), FILTNAM1, and FILTNAM2. There are 71 filter elements; in addition, some filter elements can be used in combination with others. The variety of modes plus the time-dependencies of some of the flat fields requires that several hundred WFPC 2 flat fields reside 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 WFPC 2 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 C10 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 PTYPE19 = DETECTOR / CCD detector: PC 1, WFC 2-4 C08 PDTYPE19= INTEGER*4 C18 PSIZE19 = 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 PTYPE26 = GPIXELS / number of "good" pixels (DQF=0) C08 PDTYPE26= INTEGER*4 C18 PSIZE26 = 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 INSTRUME= WFPC2 / instrument in use C06 ROOTNAME= / rootname of the observation set C12 FILETYPE= FLT / file type: msk, a2d, bas, drk, flt, shd C03 MODE = / instr. mode: FULL (full res.), AREA (area int.) C04 SERIALS = / serial clocks: ON, OFF C03 IMAGETYP= SPECIAL / image type: EXT/BIAS/DARK/IFLAT/UFLAT/VFLAT/ECAL C18 CDBSFILE= FLAT / CDBS: YES/NO/BIAS/DARK/FLAT/MASK/ATOD/SHAD C18 DATE = / date file written (dd/mm/yy) C08 FILTNAM1= / first filter name C08 FILTNAM2= / second filter name C08 FILTER1 = / first filter number (0-48) I2 FILTER2 = / second filter number (0-48) I2 SHUTTER = / shutter in place during IFLAT (A or B) C01 ATODGAIN= / analog to digital gain (Electrons/DN) R4 EXPTIME = / exposure duration (seconds) -- calculated R4 TARGNAME= / target name C30 END [Listing Version 01 09-JUL-1992] 7.2.7 Shutter Shading Reference Files (SHD): .R5H ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ When a WFPC 2 exposure is relatively short, shutte r shading (resulting from the finite time of flight of the shutter blade) gives rise to uneven illumination across the field of view. It is corrected by applying the shutter shading reference file in the following way: output = input \* (1 + reference time x shutter shading/exposure time) where *reference time* is 1 second. **Format:** The shutter shading reference file is a single-precision (REAL\*4) image file with the same number of dimensions as the WFPC 2 science image. **Flags and Indicators:** The flags and indicators used to select the shutter shading reference files are SHUTTER (which can have the value A or B) and MODE (which can be AREA or FULL). **Restrictions:** The shutter shading reference file is not accompanied by a data quality file. The header of the shutter shading reference file is a copy of the WFPC 2 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 C10 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 PTYPE19 = DETECTOR / CCD detector: PC 1, WFC 2-4 C08 PDTYPE19= INTEGER*4 C18 PSIZE19 = 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 PTYPE26 = GPIXELS / number of "good" pixels (DQF=0) C08 PDTYPE26= INTEGER*4 C18 PSIZE26 = 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 INSTRUME= WFPC2 / instrument in use C06 ROOTNAME= / rootname of the observation set C12 FILETYPE= SHD / file type: msk, a2d, bas, drk, flt, shd C03 MODE = / instr. mode: FULL (full res.), AREA (area int.) C04 SERIALS = / serial clocks: ON, OFF C03 IMAGETYP= SPECIAL / image type: EXT/BIAS/DARK/IFLAT/UFLAT/VFLAT/ECAL C18 CDBSFILE= SHAD / CDBS: YES/NO/BIAS/DARK/FLAT/MASK/ATOD/SHAD C18 DATE = / date file written (dd/mm/yy) C08 FILTNAM1= / first filter name C08 ILTNAM2= / second filter name C08 FILTER1 = / first filter number (0-48) I2 FILTER2 = / second filter number (0-48) I2 SHUTTER = / shutter in place during IFLAT (A or B) C01 ATODGAIN= / analog to digital gain (Electrons/DN) R4 EXPTIME = / exposure duration (seconds) -- calculated R4 TARGNAME= / target name C30 END [Listing Version 01 09-JUL-1992]