Reference File Conventions

Supported CRDS file formats

  • FITS

  • ASDF

  • JSON

  • YAML

Required Keywords and Properties

Reference files specify metadata as keyword values that CRDS often checks. In general, instrument configuration parameters can be used to automatically add reference files to CRDS rmaps which describe how to assign them. In essence, each reference file is required to specify the instrument configurations for which it is the best reference file. CRDS supports the use of patterns and/or substitutions for keyword values which enable as single reference file to support more than one instrument configuration.

Keywords For New File Formats

Newer file formats used for JWST such as ASDF and JSON have equivalent “keywords” that are generally organized hierarchically in a reference’s metadata tree.

For JWST, the calibration code defines file format schema which show the correspondence between “data model path” and more primitive representations like FITS keywords: Data Models Schema

The schema also describe related facts such as parameter type and valid values. For instance, the model path:

META.INSTRUMENT.DETECTOR

is equivalent to the FITS keyword:

DETECTOR

while:

META.INSTRUMENT.NAME

corresponds to:

INSTRUME

To isolate CRDS from physical file formats for JWST, CRDS generally uses data model paths to refer to metadata, by convention CRDS converts them to all upper case.

For ASDF, the equivalent metadata might be hierarchically encoded as:

meta:
   instrument:
       detector: NRS1
       name: NIRSPEC

In this case, the keyword DETECTOR does not exist at all in ASDF, but the model path still does.

Boilerplate Keywords

Both the HST and JWST projects define a small set of required keywords that define reference file provenance information, shown here in FITS format for simplicity:

Boiler Plate Keywords

FITS

DATAMODELS

VALUES

TELESCOP

META.TELESCOPE

HST, JWST

INSTRUME

META.INSTRUMENT.NAME

MIRI

REFTYPE (JWST)

META.REFERENCE.TYPE

DARK

FILETYPE (HST)

BIAS

USEAFTER

META.USEAFTER

2017-10-01T00:00:00

AUTHOR (JWST)

META.AUTHOR

Homer Simpson

PEDIGREE

META.PEDIGREE

DUMMY, GROUND, FLIGHT

HISTORY

META.HISTORY

File creation notes

COMMENT (HST)

Additional notes

DESCRIP

META.DESCRIPTION

Brief description

Matching Keyword Patterns

To support automatic rmap updates, any keyword used to assign best references must be added to the reference metadata. For example, if a FITS reference type uses DETECTOR to help assign a reference in the rmap, the reference file is required to define DETECTOR or P_DETECT.

Discrete/Real Values

Very often the applicability of a reference file can be defined by a single discrete real world value, or by a simple one word wild card such as ANY or N/A:

META.INSTRUMENT.DETECTOR = NRS1

Where applicable, a discrete valued keyword will describe the instrument configuration used to create the reference file.

HST Conditional Pattern Substitutions

Sometimes it is useful to apply one reference file to a number of specific real world keyword values, i.e. some limited set of readout patterns, not merely the single valued instrument configuration used to obtain the reference data.

HST used hidden substituion rules built into CDBS and CRDS to describe patterns of values not suitable for FITS keywords:

{'acs': {
       'APERTURE': {
           "DETECTOR=='WFC' and APERTURE=='ANY_FULL' and DATE_OBS < '2016-09-25'": 'NONE|WFC|WFC-FIX|WFC1|WFC1-CTE|WFC1-FIX|WFC1-IRAMP|WFC1-MRAMP|WFC2|WFC2-FIX|WFC2-MRAMP|WFC2-ORAMP|WFCENTER|WFC1A-512|WFC1B-512|WFC2C-512|WFC2D-512|WFC1A-1K|WFC1B-1K|WFC2C-1K|WFC2D-1K|WFC1A-2K|WFC1B-2K|WFC2C-2K|WFC2D-2K',
           "DETECTOR=='WFC' and APERTURE=='ANY_FULL' and DATE_OBS >= '2016-09-25'": 'NONE|WFC|WFC-FIX|WFC1|WFC1-CTE|WFC1-FIX|WFC1-IRAMP|WFC1-MRAMP|WFC2|WFC2-FIX|WFC2-MRAMP|WFC2-ORAMP|WFCENTER|WFC1A-512|WFC1B-512|WFC2C-512|WFC2D-512|WFC1A-1K|WFC1B-1K|WFC2C-1K|WFC2D-1K|WFC1A-2K|WFC1B-2K|WFC2C-2K|WFC2D-2K|WFC1-POL0V|WFC1-POL60V|WFC1-POL120V|WFC1-POL0UV|WFC1-POL60UV|WFC1-POL120UV|WFC1-IRAMPQ|WFC1-MRAMPQ|WFC2-MRAMPQ|WFC2-ORAMPQ|WFC1-SMFL|WFC2-SMFL',
           "DETECTOR=='WFC' and APERTURE=='ANY_WFC1_2K' and DATE_OBS < '2016-09-25'": 'WFC1-2K|WFC1-POL0UV|WFC1-POL0V|WFC1-POL120UV|WFC1-POL120V|WFC1-POL60UV|WFC1-POL60V|WFC1-IRAMPQ|WFC1-MRAMPQ|WFC1-SMFL',
           "DETECTOR=='WFC' and APERTURE=='ANY_WFC1_2K' and DATE_OBS >= '2016-09-25'": 'WFC1-2K',
           "DETECTOR=='WFC' and APERTURE=='ANY_WFC2_2K' and DATE_OBS < '2016-09-25'": 'WFC2-2K|WFC2-POL0UV|WFC2-POL0V|WFC2-POL120UV|WFC2-POL120V|WFC2-POL60UV|WFC2-POL60V|WFC2-MRAMPQ|WFC2-ORAMPQ|WFC2-SMFL',
           "DETECTOR=='WFC' and APERTURE=='ANY_WFC2_2K' and DATE_OBS >= '2016-09-25'": 'WFC2-2K',
       },
       'CCDAMP': {
           "DETECTOR=='HRC' and CCDAMP=='ANY'": 'A|ABCD|AD|B|BC|C|D',
           "DETECTOR=='WFC' and CCDAMP=='ABCDALL'": 'A|ABCD|B|C|D',
           "DETECTOR=='WFC' and CCDAMP=='ANY'": 'A|ABCD|AD|B|BC|C|D',
           },
       'CCDGAIN': {
           "DETECTOR=='HRC' and CCDGAIN=='-1'": '1.0|2.0|4.0|8.0',
           "DETECTOR=='WFC' and CCDGAIN=='-1'": '0.5|1.0|1.4|2.0',
           "DETECTOR in ['WFC', 'HRC'] and CCDGAIN=='-999'": '1.0|2.0|4.0|8.0',
           "DETECTOR in ['WFC', 'HRC'] and CCDGAIN=='-999.0'": '1.0|2.0|4.0|8.0',
           },
        'FILTER1': {
           "DETECTOR=='HRC' and FILTER1=='ANY'": 'CLEAR1S|F475W|F502N|F550M|F555W|F606W|F625W|F658N|F658N|F775W|F850LP|F892N|G800L|POL0UV|POL120UV|POL60UV',
           "DETECTOR=='SBC' and FILTER1=='ANY' and OBSTYPE=='IMAGING'": 'BLOCK1|BLOCK2|BLOCK3|BLOCK4|F115LP|F122M|F125LP|F140LP|F150LP|F165LP',
           "DETECTOR=='SBC' and FILTER1=='ANY' and OBSTYPE=='SPECTROSCOPIC'": 'PR110L|PR130L',
           "DETECTOR=='WFC' and FILTER1=='ANY'": 'CLEAR1L|F475W|F502N|F550M|F555W|F606W|F625W|F658N|F775W|F850LP|F892N|G800L|POL0UV|POL120UV|POL60UV'},
       'FILTER2': {
           "DETECTOR=='HRC' and FILTER2=='ANY'": 'CLEAR2L|CLEAR2S|F220W|F250W|F330W|F344N|F435W|F660N|F814W|FR388N|FR459M|FR505N|FR656N|FR914M|POL0V|POL120V|POL60V|PR200L',
           "DETECTOR=='WFC' and FILTER2=='ANY'": 'CLEAR2L|F330W|F435W|F660N|F814W|FR1016N|FR388N|FR423N|FR459M|FR462N|FR505N|FR551N|FR601N|FR647M|FR656N|FR716N|FR782N|FR853N|FR914M|FR931N|POL0V|POL120V|POL60V'},
       'FLASHCUR': {"FLASHCUR=='ANY'": 'HIGH|LOW|MED'},
       'LRFWAVE' : {
           "LRFWAVE == '3774.0'" : 'between 3710 3826',
           "LRFWAVE == '3880.0'" : 'between 3826 3936',
           "LRFWAVE == '3992.0'" : 'between 3936 4051',
           "LRFWAVE == '4105.0'" : 'between 4051 4167',
           "LRFWAVE == '4230.0'" : 'between 4167 4296',
           "LRFWAVE == '4362.0'" : 'between 4296 4421',
           "LRFWAVE == '4488.0'" : 'between 4421 4554',
           "LRFWAVE == '4620.0'" : 'between 4554 4686',
           "LRFWAVE == '4752.0'" : 'between 4686 4821',
           "LRFWAVE == '5038.0'" : 'between 4821 5271',
           "LRFWAVE == '5491.0'" : 'between 5271 5751',
           "LRFWAVE == '5998.0'" : 'between 5751 6271',
           "LRFWAVE == '6505.0'" : 'between 6271 6851',
           "LRFWAVE == '7205.0'" : 'between 6851 7471',
           "LRFWAVE == '7836.0'" : 'between 7471 8161',
           },
       'OBSTYPE': {"DETECTOR=='HRC' and FILTER1=='G800L' and OBSTYPE=='ANY'": 'CORONAGRAPHIC|IMAGING'},
       'NAXIS1': {
           "DETECTOR=='WFC' and APERTURE=='ANY_FULL'": 'ANY',
           },
       'NAXIS2': {
           "DETECTOR=='WFC' and APERTURE=='ANY_FULL'": 'ANY',
           },
       'LTV1': {
           "DETECTOR=='WFC' and APERTURE=='ANY_FULL'": 'ANY',
           },
       'LTV2': {
           "DETECTOR=='WFC' and APERTURE=='ANY_FULL'": 'ANY',
           },
       'SHUTRPOS': {"SHUTRPOS=='ANY'": 'A|B'},
       },
'cos': {'LIFE_ADJ': {"LIFE_ADJ=='-11'": '-1.0|1.0',
                     "LIFE_ADJ=='-11.0'": '-1.0|1.0'},
        'OPT_ELEM': {"DETECTOR=='FUV' and OPT_ELEM=='ANY'": 'G130M|G140L|G160M',
                     "DETECTOR=='NUV' and OPT_ELEM=='ANY'": 'G185M|G225M|G230L|G285M|MIRRORA|MIRRORB'}},
'stis': {'APERTURE': {"OBSTYPE=='IMAGING' and OPT_ELEM=='MIRCUV' and APERTURE=='ANY'": '25MAMA|2X2|6X6|F25NDQ1|F25NDQ2|F25NDQ3|F25NDQ4',
                      "OBSTYPE=='IMAGING' and OPT_ELEM=='MIRFUV' and APERTURE=='ANY'": 'F25LYA|F25ND3|F25ND5|F25NDQ|F25NDQ1|F25NDQ2|F25NDQ3|F25NDQ4|F25QTZ|F25SRF2',
                      "OBSTYPE=='IMAGING' and OPT_ELEM=='MIRNUV' and APERTURE=='ANY'": '25MAMA|2X2|6X6|F25CIII|F25CN182|F25CN270|F25MGII|F25ND3|F25ND5|F25NDQ|F25NDQ1|F25NDQ2|F25NDQ3|F25NDQ4|F25QTZ|F25SRF2',
                      "OBSTYPE=='IMAGING' and OPT_ELEM=='MIRVIS' and APERTURE=='ANY'": '0.05X29|0.05X31NDA|0.05X31NDB|0.09X29|0.1X0.03|0.1X0.06|0.1X0.09|0.1X0.2|0.2X0.05ND|0.2X0.06|0.2X0.06FPA|0.2X0.06FPB|0.2X0.06FPC|0.2X0.06FPD|0.2X0.06FPE|0.2X0.09|0.2X0.2|0.2X0.2FPA|0.2X0.2FPB|0.2X0.2FPC|0.2X0.2FPD|0.2X0.2FPE|0.2X0.5|0.2X29|0.3X0.05ND|0.3X0.06|0.3X0.09|0.3X0.2|0.5X0.5|1X0.06|1X0.2|25MAMA|2X2|31X0.05NDA|31X0.05NDB|31X0.05NDC|36X0.05N45|36X0.05P45|36X0.6N45|36X0.6P45|50CCD|50CORON|52X0.05|52X0.05F1|52X0.05F2|52X0.1|52X0.1B0.5|52X0.1B1.0|52X0.1B3.0|52X0.1F1|52X0.1F2|52X0.2|52X0.2F1|52X0.2F2|52X0.5|52X0.5F1|52X0.5F2|52X2|52X2F1|52X2F2|6X0.06|6X0.2|6X0.5|6X6|F25CIII|F25CN182|F25CN270|F25LYA|F25MGII|F25ND3|F25ND5|F25NDQ|F25NDQ1|F25NDQ2|F25NDQ3|F25NDQ4|F25QTZ|F25SRF2|F28X50LP|F28X50OII|F28X50OIII'},
         'CCDAMP': {"CCDAMP=='ANY'": 'A|B|C|D'},
         'CCDGAIN': {"CCDGAIN=='-1'": '1.0|2.0|4.0|8.0'},
         'CENWAVE': {"OBSTYPE=='SPECTROSCOPIC' and OPT_ELEM=='E140H' and CENWAVE=='-1'": '1234.0|1271.0|1307.0|1343.0|1380.0|1416.0|1453.0|1489.0|1526.0|1562.0|1598.0',
                     "OBSTYPE=='SPECTROSCOPIC' and OPT_ELEM=='E140M' and CENWAVE=='-1'": '1425.0',
                     "OBSTYPE=='SPECTROSCOPIC' and OPT_ELEM=='E230H' and CENWAVE=='-1'": '1763.0|1813.0|1863.0|1913.0|1963.0|2013.0|2063.0|2113.0|2163.0|2213.0|2263.0|2313.0|2363.0|2413.0|2463.0|2513.0|2563.0|2613.0|2663.0|2713.0|2762.0|2812.0|2862.0|2912.0|2962.0|3012.0',
                     "OBSTYPE=='SPECTROSCOPIC' and OPT_ELEM=='E230M' and CENWAVE=='-1'": '1978.0|2124.0|2269.0|2415.0|2561.0|2707.0',
                     "OBSTYPE=='SPECTROSCOPIC' and OPT_ELEM=='G140L' and CENWAVE=='-1'": '1425.0|1575.0',
                     "OBSTYPE=='SPECTROSCOPIC' and OPT_ELEM=='G140M' and CENWAVE=='-1'": '1173.0|1218.0|1222.0|1272.0|1321.0|1371.0|1387.0|1400.0|1420.0|1470.0|1518.0|1540.0|1550.0|1567.0|1616.0|1640.0|1665.0|1714.0',
                     "OBSTYPE=='SPECTROSCOPIC' and OPT_ELEM=='G230L' and CENWAVE=='-1'": '2376.0',
                     "OBSTYPE=='SPECTROSCOPIC' and OPT_ELEM=='G230LB' and CENWAVE=='-1'": '2375.0',
                     "OBSTYPE=='SPECTROSCOPIC' and OPT_ELEM=='G230M' and CENWAVE=='-1'": '1687.0|1769.0|1851.0|1884.0|1933.0|2014.0|2095.0|2176.0|2257.0|2338.0|2419.0|2499.0|2579.0|2600.0|2659.0|2739.0|2800.0|2818.0|2828.0|2898.0|2977.0|3055.0',
                     "OBSTYPE=='SPECTROSCOPIC' and OPT_ELEM=='G230MB' and CENWAVE=='-1'": '1713.0|1854.0|1995.0|2135.0|2276.0|2416.0|2557.0|2697.0|2794.0|2836.0|2976.0|3115.0',
                     "OBSTYPE=='SPECTROSCOPIC' and OPT_ELEM=='G430L' and CENWAVE=='-1'": '4300.0',
                     "OBSTYPE=='SPECTROSCOPIC' and OPT_ELEM=='G430M' and CENWAVE=='-1'": '3165.0|3305.0|3423.0|3680.0|3843.0|3936.0|4194.0|4451.0|4706.0|4781.0|4961.0|5093.0|5216.0|5471.0',
                     "OBSTYPE=='SPECTROSCOPIC' and OPT_ELEM=='G750L' and CENWAVE=='-1'": '7751.0|8975.0',
                     "OBSTYPE=='SPECTROSCOPIC' and OPT_ELEM=='G750M' and CENWAVE=='-1'": '10363.0|5734.0|6094.0|6252.0|6581.0|6768.0|7283.0|7795.0|8311.0|8561.0|8825.0|9286.0|9336.0|9806.0|9851.0',
                     "OBSTYPE=='SPECTROSCOPIC' and OPT_ELEM=='PRISM' and CENWAVE=='-1'": '1200.0|2125.0',
                     "OBSTYPE=='SPECTROSCOPIC' and OPT_ELEM=='X140H' and CENWAVE=='-1'": '1232.0|1269.0|1305.0|1341.0|1378.0|1414.0|1451.0|1487.0|1523.0|1560.0|1587.0',
                     "OBSTYPE=='SPECTROSCOPIC' and OPT_ELEM=='X140M' and CENWAVE=='-1'": '1425.0',
                     "OBSTYPE=='SPECTROSCOPIC' and OPT_ELEM=='X230H' and CENWAVE=='-1'": '1760.0|1810.0|1860.0|1910.0|1960.0|2010.0|2060.0|2110.0|2160.0|2210.0|2261.0|2310.0|2360.0|2410.0|2460.0|2511.0|2560.0|2610.0|2660.0|2710.0|2760.0|2810.0|2860.0|2910.0|2960.0|3010.0',
                     "OBSTYPE=='SPECTROSCOPIC' and OPT_ELEM=='X230M' and CENWAVE=='-1'": '1975.0|2122.0|2268.0|2414.0|2560.0|2703.0'},
         'DETECTOR': {"DETECTOR=='ANY'": 'CCD|FUV-MAMA|NUV-MAMA'},
         'OBSTYPE': {"OBSTYPE=='ANY'": 'IMAGING|SPECTROSCOPIC'},
         'OPT_ELEM': {"OBSTYPE=='IMAGING' and OPT_ELEM=='ANY'": 'MIRCUV|MIRFUV|MIRNUV|MIRVIS',
                      "OBSTYPE=='SPECTROSCOPIC' and OPT_ELEM=='ANY'": 'E140H|E140M|E230H|E230M|G140L|G140M|G230L|G230LB|G230M|G230MB|G430L|G430M|G750L|G750M|PRISM|X140H|X140M|X230H|X230M'}},
'wfc3': {'APERTURE': {"DETECTOR=='UVIS' and BINAXIS1=='1' and BINAXIS2=='1' and APERTURE=='CHIP1_SUB_NOCORNERS'": 'UVIS1-2K4-SUB|UVIS1-M512-SUB',
                      "DETECTOR=='UVIS' and BINAXIS1=='1' and BINAXIS2=='1' and APERTURE=='CHIP2_SUB_NOCORNERS'": 'UVIS2-2K4-SUB|UVIS2-M512-SUB',
                      "DETECTOR=='UVIS' and BINAXIS1=='1' and BINAXIS2=='1' and APERTURE=='CUSTOM_SUBARRAYS'": 'G280-REF|UVIS|UVIS-CENTER|UVIS-FIX|UVIS-QUAD|UVIS-QUAD-FIX|UVIS1|UVIS1-FIX|UVIS2|UVIS2-FIX',
                      "DETECTOR=='UVIS' and BINAXIS1=='1' and BINAXIS2=='1' and APERTURE=='FULLFRAME_2AMP'": 'UVIS|UVIS-CENTER|UVIS-FIX|UVIS1|UVIS1-FIX|UVIS2|UVIS2-FIX',
                      "DETECTOR=='UVIS' and BINAXIS1=='1' and BINAXIS2=='1' and APERTURE=='FULLFRAME_4AMP'": 'G280-REF|UVIS|UVIS-CENTER|UVIS-FIX|UVIS-IR-FIX|UVIS-QUAD|UVIS-QUAD-FIX|UVIS1|UVIS1-FIX|UVIS2|UVIS2-FIX|UVIS2-C512C-CTE|UVIS2-C1K1C-CTE',
                      "DETECTOR=='UVIS' and BINAXIS1=='1' and BINAXIS2=='1' and APERTURE=='QUAD_CORNER_SUBARRAYS'": 'UVIS-QUAD-SUB|UVIS1-2K2A-SUB|UVIS1-2K2B-SUB|UVIS1-C512A-SUB|UVIS1-C512B-SUB|UVIS2-2K2C-SUB|UVIS2-2K2D-SUB|UVIS2-C1K1C-SUB|UVIS2-C512C-SUB|UVIS2-C512D-SUB|UVIS2-M1K1C-SUB|UVIS2-M512C-SUB',
                      "DETECTOR=='UVIS' and BINAXIS1=='2' and BINAXIS2=='2' and APERTURE=='ANY'": 'G280-REF|UVIS|UVIS-CENTER|UVIS-FIX|UVIS-IR-FIX|UVIS-QUAD|UVIS-QUAD-FIX|UVIS1|UVIS1-FIX|UVIS2|UVIS2-FIX',
                      "DETECTOR=='UVIS' and BINAXIS1=='3' and BINAXIS2=='3' and APERTURE=='ANY'": 'G280-REF|UVIS|UVIS-CENTER|UVIS-FIX|UVIS-IR-FIX|UVIS-QUAD|UVIS-QUAD-FIX|UVIS1|UVIS1-FIX|UVIS2|UVIS2-FIX'},
         'CCDAMP': {"CCDAMP=='ANY'": 'A|ABCD|AC|AD|B|BC|BD|C|D',
                    "CCDAMP=='SINGLE_AMP'": 'A|B|C|D'},
         'CCDGAIN': {"DETECTOR=='IR' and CCDGAIN=='-1'": '2.0|2.5|3.0|4.0',
                     "DETECTOR=='IR' and CCDGAIN=='-1.'": '2.0|2.5|3.0|4.0',
                     "DETECTOR=='UVIS' and CCDGAIN=='-1'": '1.0|1.5|2.0|4.0',
                     "DETECTOR=='UVIS' and CCDGAIN=='-1.'": '1.0|1.5|2.0|4.0'},
         'CHINJECT': {"CHINJECT=='ANY'": 'CONT|LINE10|LINE17|LINE25|NONE'},
         'FILTER': {"DETECTOR=='IR' and FILTER=='ANY'": 'BLANK|F093W|F098M|F105W|F110W|F125W|F126N|F127M|F128N|F130N|F132N|F139M|F140W|F153M|F160W|F164N|F167N',
                    "DETECTOR=='UVIS' and FILTER=='ANY'": 'CLEAR|F200LP|F218W|F225W|F275W|F280N|F300X|F336W|F343N|F350LP|F373N|F390M|F390W|F395N|F410M|F438W|F467M|F469N|F475W|F475X|F487N|F502N|F547M|F555W|F588N|F600LP|F606W|F621M|F625W|F631N|F645N|F656N|F657N|F658N|F665N|F673N|F680N|F689M|F763M|F775W|F814W|F845M|F850LP|F953N|FQ232N|FQ243N|FQ378N|FQ387N|FQ422M|FQ436N|FQ437N|FQ492N|FQ508N|FQ575N|FQ619N|FQ634N|FQ672N|FQ674N|FQ727N|FQ750N|FQ889N|FQ906N|FQ924N|FQ937N'},
         'SAMP_SEQ': {"SAMP_SEQ=='ANY'": 'MIF1200|MIF1500|MIF600|MIF900|NONE|RAPID|SPARS10|SPARS100|SPARS200|SPARS25|SPARS350|SPARS50|STEP100|STEP200|STEP25|STEP400|STEP50|UNKNOWN'}}}

The HST substition patterns above are of the form:

<instrument>
    <keyword>
        <condition1> : <substitution1>
        <condition2> : <substitution2>
        ...

For each rmap update for instrument, for each matching keyword, each condition is evaluated with respect to the reference file header. If the condition is True then the corresponding substitution is used to replace the value of keyword for the purposes of updating the rmap.

JWST Pattern Keywords

JWST uses a more explicit approach where patterns are specified directly via reference metadata. The CAL code data models define optional keywords beginning with P_ that can have or-ed values.

For instance, in FITS parlance:

P_DETECT = NRCA1 | NRCA4 |

means that the reference file should be used for both DETECTOR=NRCA1 and DETECTOR=NRCA4.

Typically the P_ keyword name is truncated to the FITS 8 character limit as needed.

The trailing |-bar is required to satisfy the calibration code data model schema checks of allowed patterns.

If no pattern keyword is defined, CRDS will use the equivalent normal keyword specified to update the matching rules.

In terms of datamodels paths, the above value would be specified similarly:

META.INSTRUMENT.P_DETECTOR = NRCA1 | NRCA4 |

The following table defines the pattern keywords currently supported for JWST:

JWST Pattern Keyword Names

FITS

P_ FITS

P_ DATAMODELS

EXP_TYPE

P_EXP_TY

META.EXPOSURE.P_EXPTYPE

BAND

P_BAND

META.INSTRUMENT.P_BAND

DETECTOR

P_DETECT

META.INSTRUMENT.P_DETECTOR

CHANNEL

P_CHANNE

META.INSTRUMENT.P_CHANNEL

FILTER

P_FILTER

META.INSTRUMENT.P_FILTER

GRATING

P_GRATIN

META.INSTRUMENT.P_GRATING

PUPIL

P_PUPIL

META.INSTRUMENT.P_PUPIL

MODULE

P_MODULE

META.INSTRUMENT.MODULE

SUBARRAY

P_SUBARR

META.SUBARRAY.P_SUBARRAY

READPATT

P_READPA

META.EXPOSURE.P_READPATT

Each P_ keyword is explicitly defined in CRDS code as well as the CAL code data models. Relative to HST substitutions, the advantage of the JWST P_ keywords is that the pattern values can be defined in arbitrary combinations in the reference files instead of CRDS code.