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