2.4 Headers and Keywords
Both the primary and extension headers in a WFC3 science data file contain keywords. These keywords store a wide range of information about the observations themselves (e.g., observing mode, exposure time, detector, etc.), as well as any processing done or to be done on the data.
The primary header keywords apply to all extensions in the FITS file. The extension headers carry extension-specific keywords, i.e., information relevant only to the image in a particular extension. For example, observation parameters, calibration switches, and reference file names are stored in the primary header. The World Coordinate System and related parameters, on the other hand, are stored in the extension headers because this information can vary from one set of extensions to another.
In Table 2.8 and Table 2.9, we list the WFC3 keywords that appear in the primary header and SCI extension header, respectively. Columns 1 and 2 give the name of the keyword and a short description. The third column gives the format used for the value of the keyword: "L" for boolean values, "C" for characters, "R" for real values, and "I" for integer values, followed by the precision of the value. Columns 4 and 5 show to which detector the keyword applies.
Table 2.10 lists the keywords that appear in the headers of the ERR, DQ, SAMP, and TIME extensions belonging to an imset in a WFC3 data file. Note that the SAMP and TIME extensions apply only to IR data.
AstroDrizzle adds additional keywords which are not listed in this handbook, and when it adds extensions does not update the NEXTEND
keyword value. Consult the DrizzlePac Handbook for further information. Users can use the Python task fits.info to view all extensions in a file. The pattern keywords refer to the WFC3 dithering patterns which are discussed in greater detail in Section 4.2.
Table 2.8: WFC3 Primary Header Keywords
Keyword | Description | Format | UVIS | IR |
---|---|---|---|---|
SIMPLE | data conform to FITS standard | L1 | Y | Y |
BITPIX | bits per data value | I2 | Y | Y |
NAXIS | number of data axes | I2 | Y | Y |
EXTEND | file may contain standard extensions | L1 | Y | Y |
NEXTEND | number of standard extensions | I2 | Y | Y |
GROUPS | image is in group format | L1 | Y | Y |
DATE | date this file was written (yyyy-mm-dd) | C10 | Y | Y |
FILENAME | name of file | C39 | Y | Y |
FILETYPE | type of data found in data file | C09 | Y | Y |
TELESCOP | telescope used to acquire data | C03 | Y | Y |
INSTRUME | identifier for instrument used to acquire data | C06 | Y | Y |
EQUINOX | equinox of celestial coordinate system | R4 | Y | Y |
DATA DESCRIPTION KEYWORDS | ||||
ROOTNAME | rootname of the observation set | C34 | Y | Y |
IMAGETYP | type of exposure identifier | C18 | Y | Y |
PRIMESI | instrument designated as prime | C06 | Y | Y |
TARGET INFORMATION | ||||
TARGNAME | proposer's target name | C30 | Y | Y |
RA_TARG | right ascension of the target (deg) (J2000) | R8 | Y | Y |
DEC_TARG | declination of the target (deg) (J2000) | R8 | Y | Y |
PROPOSAL INFORMATION | ||||
PROPOSID | PEP proposal identifier | I4 | Y | Y |
LINENUM | proposal logsheet line number | C15 | Y | Y |
PR_INV_L | last name of principal investigator | C30 | Y | Y |
PR_INV_F | first name of principal investigator | C20 | Y | Y |
PR_INV_M | middle name initial of principal investigator | C20 | Y | Y |
EXPOSURE INFORMATION | ||||
SUNANGLE | angle between sun and V1 axis | R4 | Y | Y |
MOONANGL | angle between moon and V1 axis | R4 | Y | Y |
SUN_ALT | altitude of the sun above Earth's limb | R4 | Y | Y |
FGSLOCK | commanded FGS lock (FINE, COARSE, GYROS, UNKNOWN) | C18 | Y | Y |
GYROMODE | number of gyros scheduled for observation | C1 | Y | Y |
REFFRAME | guide star catalog version | C8 | Y | Y |
MTFLAG | moving target flag; T if it is a moving target | L1 | Y | Y |
DATE-OBS | UT date of start of observation (yyyy-mm-dd) | C10 | Y | Y |
TIME-OBS | UT time of start of observation (hh\:mm\:ss) | C08 | Y | Y |
EXPSTART | exposure start time (Modified Julian Date) | R8 | Y | Y |
EXPEND | exposure end time (Modified Julian Date) | R8 | Y | Y |
EXPTIME | exposure duration (seconds)--calculated | R4 | Y | Y |
EXPFLAG | exposure interruption indicator | C13 | Y | Y |
QUALCOM1 | data quality comment 1 | C68 | Y | Y |
QUALCOM2 | data quality comment 2 | C68 | Y | Y |
QUALCOM3 | data quality comment 3 | C68 | Y | Y |
QUALITY | data quality summary | C68 | Y | Y |
DARKTIME | fiducial pixel dark time (secs) | R4 | Y | N |
POINTING INFORMATION | ||||
PA_V3 | position angle of V3-axis of HST (deg) | R4 | Y | Y |
TARGET OFFSETS (POSTARGS) | ||||
POSTARG1 | POSTARG in axis 1 direction | R4 | Y | Y |
POSTARG2 | POSTARG in axis 2 direction | R4 | Y | Y |
DIAGNOSTIC KEYWORDS | ||||
OPUS_VER | OPUS software system version number | C18 | Y | Y |
AWSYSVER | cloud infrastructure package version | C18 | Y | Y |
AWSDPVER | cloud docker image version | C18 | Y | Y |
CSYS_VER | calibration software system version id | C18 | Y | Y |
CAL_VER | CALWF3 code version | C24 | Y | Y |
PROCTIME | pipeline processing time (MJD) | R8 | Y | Y |
SCIENCE INSTRUMENT CONFIGURATION | ||||
OBSTYPE | observation type - imaging or spectroscopic | C14 | Y | Y |
OBSMODE | operating mode | C10 | Y | Y |
SCLAMP | lamp status, NONE or name of lamp which is on | C14 | Y | Y |
NRPTEXP | number of repeat exposures in set: default 1 | I2 | Y | Y |
SUBARRAY | data from a subarray (T) or full frame (F) | L1 | Y | Y |
DETECTOR | detector in use: UVIS or IR | C04 | Y | Y |
FILTER | element selected from filter wheel | C07 | Y | Y |
APERTURE | aperture name | C16 | Y | Y |
PROPAPER | proposed aperture name | C16 | Y | Y |
DIRIMAGE | direct image for grism or prism exposure | C09 | Y | Y |
NSAMP | number of MULTIACCUM samples | I2 | N | Y |
SAMP_SEQ | MULTIACCUM exposure time sequence name | C08 | N | Y |
SAMPZERO | sample time of the zeroth read (sec) | R4 | N | Y |
SUBTYPE | size/type of IR subarray | C08 | N | Y |
CTEIMAGE | type of Charge Transfer Image, if applicable | C04 | Y | N |
CTEDIR | serial or parallel | C08 | Y | N |
CRSPLIT | number of cosmic ray split exposures | I2 | Y | N |
CTE CORRECTION PARAMETERS | ||||
CTE_NAME | name of the CTE algorithm | C23 | Y | N |
CTE_VER | Version number of the CTE algorithm | C23 | Y | N |
CTEDATE0 | Date of WFC3/UVIS installation in HST (MJD) | R8 | Y | N |
CTEDATE1 | Reference date of CTE model pinning (MJD) | R8 | Y | N |
PCTETLEN | Maximum length of CTE trail | R8 | Y | N |
PCTERNOI | Read noise amplitude | R8 | Y | N |
PCTENFOR | Number iterations used in CTE forward modeling | I4 | Y | N |
PCTENPAR | Number of iterations used in parallel transfer | I4 | Y | N |
PCTENSMD | read-noise mitigation algorithm | I4 | Y | N |
PCTETRSH | over-subtraction threshold | R8 | Y | N |
PCTEFRAC | Scaling of CTE model (relative to CTEDATE1) | R8 | Y | N |
FIXROCR | Fix readout cosmic rays | I4 | Y | N |
SCAN KEYWORDS | ||||
SCAN_TYP | Type of scanning path | C18 | Y | Y |
SCAN_WID | scan width (arcsec) | R8 | Y | Y |
ANG_SIDE | angle between sides of parallelogram (deg) | R8 | Y | Y |
DWELL_LN | dwell pts/line for scan pointing | I4 | Y | Y |
DWELL_TM | wait time at each dwell point (sec) | R8 | Y | Y |
SCAN_ANG | position angle of scan line (deg) | R8 | Y | Y |
SCAN_RAT | commanded rate of the line scan (arcsec/sec) | R8 | Y | Y |
NO_LINES | number of lines per scan | I4 | Y | Y |
SCAN_LEN | scan length (arcsec) | R8 | Y | Y |
SCAN_COR | scan coordinate frame of ref: (celestial,vehicle) | C18 | Y | Y |
CSMID | Channel Select Mechanism ID (UVIS/IR) | C7 | Y | Y |
CALIBRATION SWITCHES: PERFORM, OMIT, COMPLETE, SKIPPED | ||||
DQICORR | data quality initialization | C08 | Y | Y |
BLEVCORR | subtract bias level measured from overscan, (UVIS) or reference pixels (IR) | C08 | Y | Y |
CRCORR | combine observations to reject cosmic rays/, identify cosmic ray hits | C08 | Y | Y |
DARKCORR | subtract dark image | C08 | Y | Y |
FLATCORR | flat-field data | C08 | Y | Y |
FLUXCORR | Scale the UVIS chips to get uniform flux correction | C08 | Y | N |
PCTECORR | Perform the pixel based CTE correction | C08 | Y | N |
PHOTCORR | populate photometric header keywords | C08 | Y | Y |
DRIZCORR | drizzle processing | C08 | Y | Y |
NLINCORR | correct for detector nonlinearities | C08 | N | Y |
RPTCORR | combine individual repeat observations | C08 | N | Y |
UNITCORR | convert to count rates (see also BUNIT) | C08 | N | Y |
ZSIGCORR | zero read signal correction | C08 | N | Y |
ZOFFCORR | subtract MULTIACCUM zero read | C08 | N | Y |
ATODCORR | correct for A to D conversion errors | C08 | Y | N |
BIASCORR | subtract bias image | C08 | Y | N |
EXPSCORR | process individual observations after cr-reject | C08 | Y | N |
FLSHCORR | post flash correction | C08 | Y | N |
SHADCORR | apply shutter shading correction | C08 | Y | N |
CALIBRATION REFERENCE FILES | ||||
BPIXTAB | bad pixel table | C23 | Y | Y |
CCDTAB | detector calibration parameters | C23 | Y | Y |
OSCNTAB | table containing overscan (UVIS) or reference pixel (IR) locations | C23 | Y | Y |
CRREJTAB | cosmic ray rejection parameters | C23 | Y | Y |
DARKFILE | superdark image file name | C23 | Y | Y |
PFLTFILE | pixel to pixel flat-field file name | C23 | Y | Y |
DFLTFILE | delta flat-field file name | C23 | Y | Y |
LFLTFILE | low order flat | C23 | Y | Y |
GRAPHTAB | the HST graph table | Y | Y | |
COMPTAB | the HST components table | Y | Y | |
IDCTAB | distortion coefficients table | C23 | Y | Y |
DGEOFILE | distortion correction image (no longer used, kept in the header for compatibility) | C23 | Y | Y |
MDRIZTAB | AstroDrizzle parameter table | C18 | Y | Y |
NLINFILE | detector nonlinearities file | C23 | N | Y |
ATODTAB | analog to digital correction file | C23 | Y | N |
BIASFILE | superbias image file name | C23 | Y | N |
FLSHFILE | post flash correction file name | C23 | Y | N |
SHADFILE | shutter shading correction file | C23 | Y | N |
PCTETAB | The default parameters and reference data for the CTE correction | C18 | Y | N |
IMPHTTAB | The default values for the photometric keywords | C18 | Y | Y |
DRKCFILE | Superdark reference for CTE corrected files | C23 | Y | N |
BIACFILE | Superbias reference for CTE corrected files | C23 | Y | N |
SNKCFILE | map of sink-pixel locations | C23 | Y | N |
D2IMFILE | 2-D non-polynomial distortion correction table | C23 | Y | N |
NOPOLFILE | 2-D non-polynomial filter dependent distortion | C23 | Y | N |
COSMIC RAY REJECTION ALGORITHM PARAMETERS | ||||
MEANEXP | reference exposure time for parameters | R4 | Y | Y |
SCALENSE | multiplicative scale factor applied to noise | R4 | Y | Y |
INITGUES | initial guess method (MIN or MED) | C03 | Y | Y |
SKYSUB | sky value subtracted (MODE or NONE) | C04 | Y | Y |
SKYSUM | sky level from the sum of all constituent images | R4 | Y | Y |
CRSIGMAS | statistical rejection criteria | C15 | Y | Y |
CRRADIUS | rejection propagation radius (pixels) | R4 | Y | Y |
CRTHRESH | rejection propagation threshold | R4 | Y | Y |
BADINPDQ | data quality flag bits to reject | I2 | Y | Y |
REJ_RATE | rate at which pixels are affected by cosmic rays | R4 | Y | Y |
CRMASK | flag CR-rejected pixels in input files (T/F) | L1 | Y | Y |
MDRIZSKY | sky value computed by AstroDrizzle | R4 | Y | Y |
PHOTOMETRY KEYWORDS | ||||
PHOTMODE | observation configuration for photometric calibration | C50 | Y | Y |
PHOTFLAM | inverse sensitivity, ergs/cm2/Ang/electron | R8 | Y | Y |
PHTFLAM1 | Ch1 Inv Sens, use PHOTFLAM for UV filters | R8 | Y | N |
PHTFLAM2 | Ch2 Inv Sens, use PHOTFLAM if FLUXCORR=COMPLETE | R8 | Y | N |
PHTRATIO | PHTFLAM2/PHTFLAM1 ratio | R8 | Y | N |
PHOTFNU | inverse sensitivity, Jy* sec/electron | R8 | Y | Y |
PHOTZPT | ST magnitude zero point | R4 | Y | Y |
PHOTPLAM | pivot wavelength (Angstroms) | R4 | Y | Y |
PHOTBW | RMS bandwidth of filter plus detector | R4 | Y | Y |
POST FLASH PARAMETERS | ||||
FLASHDUR | exposure time in seconds: 0.1 to 409.5 | R4 | Y | N |
FLASHCUR | post flash current (zero, low, medium, high) | C07 | Y | N |
FLASHSTA | status: SUCCESSFUL, ABORTED, NOT PERFORMED | C16 | Y | N |
FLASHLVL | requested APT post flash, electrons/pixel | R4 | Y | N |
SHUTRPOS | shutter position: A or B | C05 | Y | N |
CHARGE INJECTION PARAMETERS | ||||
CHINJECT | charge injection mode | C08 | Y | N |
OTFR KEYWORDS | ||||
T_SGSTAR | OMS calculated guide star control | C18 | Y | Y |
PATTERN KEYWORDS | ||||
PATTERN1 | primary pattern type | C24 | Y | Y |
P1_SHAPE | primary pattern shape | C18 | Y | Y |
P1_PURPS | primary pattern purpose | C10 | Y | Y |
P1_NPTS | number of points in primary pattern | I2 | Y | Y |
P1_PSPAC | point spacing for primary pattern (arc-sec) | R4 | Y | Y |
P1_LSPAC | line spacing for primary pattern (arc-sec) | R4 | Y | Y |
P1_ANGLE | angle between sides of parallelogram patt (deg) | R4 | Y | Y |
P1_FRAME | coordinate frame of primary pattern | C09 | Y | Y |
P1_ORINT | orientation of pattern to coordinate frame (deg) | R4 | Y | Y |
P1_CENTR | center pattern relative to pointing (yes/no) | C03 | Y | Y |
PATTERN2 | secondary pattern type | C24 | Y | Y |
P2_SHAPE | secondary pattern shape | C18 | Y | Y |
P2_PURPS | secondary pattern purpose | C10 | Y | Y |
P2_NPTS | number of points in secondary pattern | I2 | Y | Y |
P2_PSPAC | point spacing for secondary pattern (arc-sec) | R4 | Y | Y |
P2_LSPAC | line spacing for secondary pattern (arc-sec) | R4 | Y | Y |
P2_ANGLE | angle between sides of parallelogram patt (deg) | R4 | Y | Y |
P2_FRAME | coordinate frame of secondary pattern | C09 | Y | Y |
P2_ORINT | orientation of pattern to coordinate frame (deg) | R4 | Y | Y |
P2_CENTR | center pattern relative to pointing (yes/no) | C03 | Y | Y |
PATTSTEP | position number of this point in the pattern | I2 | Y | Y |
ENGINEERING PARAMETERS | ||||
CCDAMP | CCD amplifier readout configuration | C04 | Y | Y |
CCDGAIN | commanded gain of CCD | R4 | Y | Y |
CCDOFSAB | commanded CCD bias offset for amps A\&B | I4 | N | Y |
CCDOFSCD | commanded CCD bias offset for amps C\&D | I4 | N | Y |
CCDOFSTA | commanded CCD bias offset for amplifier A | I4 | Y | N |
CCDOFSTB | commanded CCD bias offset for amplifier B | I4 | Y | N |
CCDOFSTC | commanded CCD bias offset for amplifier C | I4 | Y | N |
CCDOFSTD | commanded CCD bias offset for amplifier D | I4 | Y | N |
CALIBRATED ENGINEERING PARAMETERS | ||||
ATODGNA | measured gain for amplifier A | R4 | Y | Y |
ATODGNB | measured gain for amplifier B | R4 | Y | Y |
ATODGNC | measured gain for amplifier C | R4 | Y | Y |
ATODGND | measured gain for amplifier D | R4 | Y | Y |
READNSEA | measured read noise for amplifier A | R4 | Y | Y |
READNSEB | measured read noise for amplifier B | R4 | Y | Y |
READNSEC | measured read noise for amplifier C | R4 | Y | Y |
READNSED | measured read noise for amplifier D | R4 | Y | Y |
BIASLEVA | bias level for amplifier A | R4 | Y | Y |
BIASLEVB | bias level for amplifier B | R4 | Y | Y |
BIASLEVC | bias level for amplifier C | R4 | Y | Y |
BIASLEVD | bias level for amplifier D | R4 | Y | Y |
ASSOCIATION KEYWORDS | ||||
ASN_ID | unique identifier assigned to association | C10 | Y | Y |
ASN_TAB | name of the association table | C23 | Y | Y |
ASN_MTYP | role of the member in the association | C12 | Y | Y |
Table 2.9: WFC3 SCI extension header keywords
Keyword | Description | Format | UVIS | IR |
---|---|---|---|---|
XTENSION | extension type | C08 | Y | Y |
BITPIX | bits per data value | I2 | Y | Y |
NAXIS | number of data axes | I2 | Y | Y |
NAXIS1 | length of first data axis | I4 | Y | Y |
NAXIS2 | length of second data axis | I4 | Y | Y |
PCOUNT | number of group parameters | I2 | Y | Y |
GCOUNT | number of groups | I2 | Y | Y |
ORIGIN | FITS file originator | C30 | Y | Y |
DATE | date this file was written (yyyy-mm-dd) | C10 | Y | Y |
INHERIT | inherit the primary header | L1 | Y | Y |
EXTNAME | extension name | C08 | Y | Y |
EXTVER | extension version number | I2 | Y | Y |
ROOTNAME | rootname of the observation set | C34 | Y | Y |
EXPNAME | exposure identifier | C25 | Y | Y |
DATAMIN | the minimum value of the data | R8 | Y | Y |
DATAMAX | the maximum value of the data | R8 | Y | Y |
BUNIT | brightness units | C18 | Y | Y |
BSCALE | scale factor for array value to physical value | R8 | Y | Y |
BZERO | physical value for an array value of zero | R8 | Y | Y |
CCD CHIP IDENTIFICATION | ||||
CCDCHIP | CCD chip (1 or 2) | I2 | Y | N |
WORLD COORDINATE SYSTEM AND RELATED PARAMETERS | ||||
WCSAXES | number of World Coordinate System axes | I2 | Y | Y |
CRPIX1 | xcoordinate of reference pixel | R8 | Y | Y |
CRPIX2 | ycoordinate of reference pixel | R8 | Y | Y |
CRVAL1 | first axis value at reference pixel | R8 | Y | Y |
CRVAL2 | second axis value at reference pixel | R8 | Y | Y |
CTYPE1 | the coordinate type for the first axis | C08 | Y | Y |
CTYPE2 | the coordinate type for the second axis | C08 | Y | Y |
CD1_1 | partial of first axis coordinate w.r.t. x | R8 | Y | Y |
CD1_2 | partial of first axis coordinate w.r.t. y | R8 | Y | Y |
CD2_1 | partial of second axis coordinate w.r.t. x | R8 | Y | Y |
CD2_2 | partial of second axis coordinate w.r.t. y | R8 | Y | Y |
LTV1 | offset in X to subsection start | R4 | Y | Y |
LTV2 | offset in Y to subsection start | R4 | Y | Y |
LTM1_1 | reciprocal of sampling rate in X | R4 | Y | Y |
LTM2_2 | reciprocal of sampling rate in Y | R4 | Y | Y |
PA_APER | position Angle of reference aperture center (deg) | R8 | Y | Y |
VAFACTOR | velocity aberration plate scale factor | R8 | Y | Y |
ORIENTAT | position angle of image y axis (degrees East of North) | R4 | Y | Y |
RA_APER | right ascension of aperture reference position | R8 | Y | Y |
DEC_APER | declination of aperture reference position | R8 | Y | Y |
REPEATED EXPOSURES INFORMATION | ||||
NCOMBINE | number of image sets combined during CR rejection | I2 | Y | Y |
PHOTOMETRY KEYWORDS | ||||
PHOTMODE | observation configuration for photometric calibration | C50 | Y | N |
PHOTFLAM | inverse sensitivity, ergs/cm2/Ang/electron | R8 | Y | N |
PHTFLAM1 | PHOTFLAM on chip 1 when scales are not uniform | R8 | Y | N |
PHTFLAM2 | PHOTFLAM on chip 2 when scales are not uniform | R8 | Y | N |
PHTRATIO | Ratio of PHTFLAM1/PHTFLAM2 | R8 | Y | N |
PHOTFNU | inverse sensitivity, Jy*sec/electron | R8 | Y | N |
PHOTZPT | ST magnitude zero point | R4 | Y | N |
PHOTPLAM | pivot wavelength (Angstroms) | R4 | Y | N |
PHOTBW | RMS bandwidth of filter plus detector | R4 | Y | N |
READOUT DEFINITION PARAMETERS | ||||
CENTERA1 | subarray axis1 center point in unbinned detector pix | I4 | Y | Y |
CENTERA2 | subarray axis2 center point in unbinned detector pix | I4 | Y | Y |
SIZAXIS1 | subarray axis1 size in unbinned detector pixels | I4 | Y | Y |
SIZAXIS2 | subarray axis2 size in unbinned detector pixels | I4 | Y | Y |
BINAXIS1 | axis1 data bin size in unbinned detector pixels | I2 | Y | Y |
BINAXIS2 | axis2 data bin size in unbinned detector pixels | I2 | Y | Y |
READOUT PARAMETERS | ||||
SAMPNUM | MULTIACCUM sample number | I2 | N | Y |
SAMPTIME | total integration time (sec) | R4 | N | Y |
DELTATIM | integration time of this sample (sec) | R4 | N | Y |
ROUTTIME | UT time of array readout (MJD) | R8 | N | Y |
TDFTRANS | number of TDF transitions during current sample | I4 | N | Y |
DATA PACKET INFORMATION | ||||
FILLCNT | number of segments containing fill | I4 | Y | Y |
ERRCNT | number of segments containing errors | I4 | Y | Y |
PODPSFF | PODPS fill present (T/F) | L1 | Y | Y |
STDCFFF | science telemetry fill data present (T/F) | L1 | Y | Y |
STDCFFP | science telemetry fill pattern (hex) | C06 | Y | Y |
IMAGE STATISTICS AND DATA QUALITY FLAGS | ||||
NGOODPIX | number of good pixels | I4 | Y | Y |
SDQFLAGS | serious data quality flags | I4 | Y | Y |
GOODMIN | minimum value of good pixels | R4 | Y | Y |
GOODMAX | maximum value of good pixels | R4 | Y | Y |
GOODMEAN | mean value of good pixels | R4 | Y | Y |
SNRMIN | minimum signal to noise of good pixels | R4 | Y | Y |
SNRMAX | maximum signal to noise of good pixels | R4 | Y | Y |
SNRMEAN | mean value of signal to noise of good pixels | R4 | Y | Y |
SOFTERRS | number of soft error pixels (DQF1) | I4 | Y | Y |
MEANDARK | average dark level subtracted | R4 | Y | Y |
MEANBLEV | average bias level subtracted | R4 | Y | Y |
MEANFLSH | mean number of counts in post flash exposure, DN/pixel | R4 | Y | N |
RADESYS | Equatorial coordinate system | C4 | Y | Y |
OCX10 | original linear term from IDCTAB | R8 | Y | Y |
OCX11 | original linear term from IDCTAB | R8 | Y | Y |
OCY10 | original linear term from IDCTAB | R8 | Y | Y |
OCY11 | original linear term from IDCTAB | R8 | Y | Y |
IDCSCALE | pixel scale from the IDCTAB reference file | R4 | Y | Y |
IDCTHETA | orientation of detector's Y-axis w.r.t. V3 axis | R4 | Y | Y |
IDCXREF | reference pixel location in X | R4 | Y | Y |
IDCYREF | reference pixel location in Y | R4 | Y | Y |
IDCV2REF | reference pixel's V2 position | R8 | Y | Y |
IDCV3REF | reference pixel's V3 position | R8 | Y | Y |
D2IMERR1 | Maximum error of D2IM correction for axis 1 | R8 | Y | N |
D2IMDIS1 | Detector to image correction type | C6 | Y | N |
D2IM1 | Version number of WCSDVARR extension | C10 | Y | N |
D2IM1 | Number of independent variables in D2IM function | C9 | Y | N |
D2IM1 | Axis number of the 1st variable in a D2IM function | C10 | Y | N |
D2IM1 | Axis number of the 2nd variable in a D2IM function | C10 | Y | N |
D2IMERR2 | Maximum error of D2IM correction for axis 2 | R8 | Y | N |
D2IMDIS2 | Detector to image correction type | C6 | Y | N |
D2IM2 | Version number of WCSDVARR extension | C10 | Y | N |
D2IM2 | Number of independent variables in D2IM function | C9 | Y | N |
D2IM2 | Axis number of the 1st variable in a D2IM function | C10 | Y | N |
D2IM2 | Axis number of the 2nd variable in a D2IM function | C10 | Y | N |
D2IMEXT | Y | N | ||
WCSNAMEO | Coordinate system title | C4 | Y | Y |
WCSAXESO | Number of coordinate axes | I1 | Y | Y |
CRPIX1O | Pixel coordinate of reference point | R4 | Y | Y |
CRPIX2O | Pixel coordinate of reference point | R4 | Y | Y |
CUNIT1O | Units of coordinate increment and value | C3 | Y | Y |
CUNIT2O | Units of coordinate increment and value | C3 | Y | Y |
CTYPE1O | Right ascension, gnomonic projection | C8 | Y | Y |
CTYPE2O | Declination, gnomonic projection | C8 | Y | Y |
CRVAL1O | [deg] Coordinate value at reference point | R8 | Y | Y |
CRVAL2O | [deg] Coordinate value at reference point | R8 | Y | Y |
MJDREF | [d] MJD of fiducial time | R8 | Y | Y |
RADESYSO | Equatorial coordinate system | C4 | Y | Y |
CD1_1O | partial of first axis coordinate w.r.t. x | R8 | Y | Y |
CD1_2O | partial of first axis coordinate w.r.t. y | R8 | Y | Y |
CD2_1O | partial of second axis coordinate w.r.t. x | R8 | Y | Y |
CD2_2O | partial of second axis coordinate w.r.t. y | R8 | Y | Y |
A_ORDER | SIP polynomial order, axis 1, detector to sky | I1 | Y | Y |
A_0_2 | SIP distortion coefficient | R8 | Y | Y |
A_0_3 | SIP distortion coefficient | R8 | Y | Y |
A_0_4 | SIP distortion coefficient | R8 | Y | Y |
A_1_1 | SIP distortion coefficient | R8 | Y | Y |
A_1_2 | SIP distortion coefficient | R8 | Y | Y |
A_1_3 | SIP distortion coefficient | R8 | Y | Y |
A_2_0 | SIP distortion coefficient | R8 | Y | Y |
A_2_1 | SIP distortion coefficient | R8 | Y | Y |
A_2_2 | SIP distortion coefficient | R8 | Y | Y |
A_3_0 | SIP distortion coefficient | R8 | Y | Y |
A_3_1 | SIP distortion coefficient | R8 | Y | Y |
A_4_0 | SIP distortion coefficient | R8 | Y | Y |
B_ORDER | SIP polynomial order, axis 2, detector to sky | I1 | Y | Y |
B_0_2 | SIP distortion coefficient | R8 | Y | Y |
B_0_3 | SIP distortion coefficient | R8 | Y | Y |
B_0_4 | SIP distortion coefficient | R8 | Y | Y |
B_1_1 | SIP distortion coefficient | R8 | Y | Y |
B_1_2 | SIP distortion coefficient | R8 | Y | Y |
B_1_3 | SIP distortion coefficient | R8 | Y | Y |
B_2_0 | SIP distortion coefficient | R8 | Y | Y |
B_2_1 | SIP distortion coefficient | R8 | Y | Y |
B_2_2 | SIP distortion coefficient | R8 | Y | Y |
B_3_0 | SIP distortion coefficient | R8 | Y | Y |
B_3_1 | SIP distortion coefficient | R8 | Y | Y |
B_4_0 | SIP distortion coefficient | R8 | Y | Y |
WCSNAME | Coordinate system title | C30 | Y | Y |
MDRIZSKY | Sky value computed by AstroDrizzle | R4 | Y | Y |
CPERR1 | Maximum error of NPOL correction for axis 1 | R4 | Y | N |
CPDIS1 | Prior distortion function type | C6 | Y | N |
DP1 | Version number of WCSDVARR extension | C10 | Y | N |
DP1 | Number of independent variables in CPDIS function | C9 | Y | N |
DP1 | Axis number of the 1st variable in a CPDIS function | C10 | Y | N |
DP1 | Axis number of the 2nd variable in a CPDIS function | C10 | Y | N |
CPERR2 | Maximum error of NPOL correction for axis 2 | R8 | Y | N |
CPDIS2 | Prior distortion function type | C6 | Y | N |
DP2 | Version number of WCSDVARR extension | C10 | Y | N |
DP2 | Number of independent variables in CPDIS function | C9 | Y | N |
DP2 | Axis number of the 1st variable in a CPDIS function | C10 | Y | N |
DP2 | Axis number of the 2nd variable in a CPDIS function | C10 | Y | N |
CUNIT1 | Units of coordinate increment and value | C3 | Y | Y |
CUNIT2 | Units of coordinate increment and value | C3 | Y | Y |
WCSNAMEA | Coordinate system title | C20 | N | Y |
WCSAXESA | Number of coordinate axes | I1 | N | Y |
CRPIX1A | Pixel coordinate of reference point | R4 | N | Y |
CRPIX2A | Pixel coordinate of reference point | R4 | N | Y |
CUNIT1A | Units of coordinate increment and value | C3 | N | Y |
CUNIT2A | Units of coordinate increment and value | C3 | N | Y |
CTYPE1A | TAN (gnomonic) projection + SIP distortions | C12 | N | Y |
CTYPE2A | TAN (gnomonic) projection + SIP distortions | C12 | N | Y |
CRVAL1A | [deg] Coordinate value at reference point | R8 | N | Y |
CRVAL2A | [deg] Coordinate value at reference point | R8 | N | Y |
RADESYSA | Equatorial coordinate system | C4 | N | Y |
CD1_1A | partial of first axis coordinate w.r.t. x | R8 | N | Y |
CD1_2A | partial of first axis coordinate w.r.t. y | R8 | N | Y |
CD2_1A | partial of second axis coordinate w.r.t. x | R8 | N | Y |
CD2_2A | partial of second axis coordinate w.r.t. y | R8 | N | Y |
Table 2.10 : WFC3 extension header keywords (imset extensions 2-5)
Extension Type | ||||||
Keyword | Description | Format | ERR | DQ | SAMP | TIME |
(UVIS and IR) | (IR Only) | |||||
XTENSION | extension type | C08 | Y | Y | Y | Y |
BITPIX | number of bits per data pixel | I4 | Y | Y | Y | Y |
NAXIS | number of data axes | I1 | Y | Y | Y | Y |
NAXIS1 | length of first data axis | I4 | Y | Y | Y | Y |
NAXIS2 | length of second data axis | I4 | Y | Y | Y | Y |
PCOUNT | number of group parameters | I2 | Y | Y | Y | Y |
GCOUNT | number of groups | I2 | Y | Y | Y | Y |
ORIGIN | FITS file originator | C30 | Y | Y | Y | Y |
DATE | date this file was written (yyyy-mm-dd) | C10 | Y | Y | Y | Y |
INHERIT | inherit the primary header | L1 | Y | Y | Y | Y |
EXTNAME | extension name | C08 | Y | Y | Y | Y |
EXTVER | extension version number | I2 | Y | Y | Y | Y |
ROOTNAME | rootname of the observation set | C34 | Y | Y | Y | Y |
EXPNAME | exposure identifier | C25 | Y | Y | Y | Y |
BUNIT | brightness units | C18 | Y | Y | Y | Y |
WORLD COORDINATE SYSTEM AND RELATED PARAMETERS | ||||||
WCSAXES | number of World Coordinate System axes | I2 | Y | Y | Y | Y |
CRPIX1 | x-coordinate of reference pixel | R8 | Y | Y | Y | Y |
CRPIX2 | y-coordinate of reference pixel | R8 | Y | Y | Y | Y |
CRVAL1 | first axis value at reference pixel | R8 | Y | Y | Y | Y |
CRVAL2 | second axis value at reference pixel | R8 | Y | Y | Y | Y |
CTYPE1 | the coordinate type for the first axis | C08 | Y | Y | Y | Y |
CTYPE2 | the coordinate type for the second axis | C08 | Y | Y | Y | Y |
CD1_1 | partial of first axis coordinate w.r.t. x | R8 | Y | Y | Y | Y |
CD1_2 | partial of first axis coordinate w.r.t. y | R8 | Y | Y | Y | Y |
CD2_1 | partial of second axis coordinate w.r.t. x | R8 | Y | Y | Y | Y |
CD2_2 | partial of second axis coordinate w.r.t. y | R8 | Y | Y | Y | Y |
LTV1 | offset in X to subsection start | R4 | Y | Y | - | - |
LTV2 | offset in Y to subsection start | R4 | Y | Y | - | - |
LTM1_1 | reciprocal of sampling rate in X | R4 | Y | Y | - | - |
LTM2_2 | reciprocal of sampling rate in Y | R4 | Y | Y | - | - |
PA_APER | position angle of reference aperture center (deg) | R8 | Y | Y | - | - |
VAFACTOR | velocity aberration plate scale factor | R8 | Y | Y | - | - |
IMAGE STATISTICS AND DATA QUALITY FLAGS | ||||||
NGOODPIX | number of good pixels | I4 | Y | - | - | - |
SDQFLAGS | serious data quality flags | I4 | Y | - | - | - |
GOODMIN | minimum value of good pixels | R4 | Y | - | - | - |
GOODMAX | maximum value of good pixels | R4 | Y | - | - | - |
GOODMEAN | mean value of good pixels | R4 | Y | - | - | - |
-
WFC3 Data Handbook
- • Acknowledgments
- • What's New in This Revision
- Preface
- Chapter 1: WFC3 Instruments
- Chapter 2: WFC3 Data Structure
- Chapter 3: WFC3 Data Calibration
- Chapter 4: WFC3 Images: Distortion Correction and AstroDrizzle
- Chapter 5: WFC3 UVIS Sources of Error
- Chapter 6: WFC3 UVIS Charge Transfer Efficiency - CTE
-
Chapter 7: WFC3 IR Sources of Error
- • 7.1 WFC3 IR Error Source Overview
- • 7.2 Gain
- • 7.3 WFC3 IR Bias Correction
- • 7.4 WFC3 Dark Current and Banding
- • 7.5 Blobs
- • 7.6 Detector Nonlinearity Issues
- • 7.7 Count Rate Non-Linearity
- • 7.8 IR Flat Fields
- • 7.9 Pixel Defects and Bad Imaging Regions
- • 7.10 Time-Variable Background
- • 7.11 IR Photometry Errors
- • 7.12 References
- Chapter 8: Persistence in WFC3 IR
- Chapter 9: WFC3 Data Analysis
- Chapter 10: WFC3 Spatial Scan Data