MSA Reference File (NIRSpec only)

REFTYPE

MSA

Data model

MSAModel

Reference Selection Keywords for MSA

CRDS selects appropriate MSA references based on the following keywords. MSA is not applicable for instruments not in the table. All keywords used for file selection are required.

Instrument

Keywords

NIRSpec

INSTRUME, EXP_TYPE, DATE-OBS, TIME-OBS

Standard Keywords

The following table lists the keywords that are required to be present in all reference files. The first column gives the FITS keyword names. The second column gives the jwst data model name for each keyword, which is useful when using data models in creating and populating a new reference file. The third column gives the equivalent meta tag in ASDF reference file headers, which is the same as the name within the data model meta tree (second column).

FITS Keyword

Data Model Name

ASDF meta tag

AUTHOR

model.meta.author

author

DATAMODL

model.meta.model_type

model_type

DATE

model.meta.date

date

DESCRIP

model.meta.description

description

FILENAME

model.meta.filename

N/A

INSTRUME

model.meta.instrument.name

instrument: {name}

PEDIGREE

model.meta.pedigree

pedigree

REFTYPE

model.meta.reftype

reftype

TELESCOP

model.meta.telescope

telescope

USEAFTER

model.meta.useafter

useafter

NOTE: More information on standard required keywords can be found here: Standard Required Keywords

Reference File Format

The MSA reference file contains information on the metrology of the microshutter array and the associated fixed slits - relative positioning of each individual shutter (assumed to be rectangular) And the absolute position of each quadrant within the MSA.

The MSA reference file has 5 fields, named

1
data

Array with reference data for each shutter in Quadrant 1. It has 5 columns

NO

Shutter number (1- 62415)

x_center

X coordinate of the center (in meters)

y_center

Y coordinate of the center (in meters)

x_size

X size of teh aperture (in meters)

y_size

Y size of the aperture (in meters)

model

Transform from relative positions within Quadrant 1 to absolute positions within the MSA

2
data

Array with reference data for shutters in Quadrant 2, same as in 1 above

model

Transform from relative positions within Quadrant 2 to absolute positions within the MSA

3
data

Array with reference data for shutters in Quadrant 3, same as in 1 above

model

Transform from relative positions within Quadrant 3 to absolute positions within the MSA

4
data

Array with reference data for shutters in Quadrant 4, same as in 1 above

model

Transform from relative positions within Quadrant 4 to absolute positions within the MSA

5
data

Reference data for the fixed slits and the IFU, same as in 1, except NO is 6 rows (1-6) and the mapping is 1 - S200A1, 2 - S200A1, 3 - S400A1, 4 - S200B1, 5 - S1600A1, 6 - IFU

model

Transform from relative positions within eac aperture to absolute positions within the MSA