NIRISS External Calibration Template Parameters
JWST's NIRISS External Calibration template, available in the Astronomer’s Proposal Tool (APT), is used for calibration observations for the NIRISS instrument.
Introduction
Purple text indicates the parameter is Limited Access.
Boldface italics type indicates the name of an APT parameter or a value for a parameter.
Red text indicates restrictions on a parameter.
Black text indicates an important note.
Brown text indicates notes for the developers.
Green text indicates the name of the parameter used by Commanding.
Items in brackets - <value> - are required values.
Items in square brackets - [<value>] - are optional.
The following parameters are used to define NIRISS external calibration observations. If this template will be used for Multi-Instrument Multi-Field (MIMF) observations, you must add the Special Requirement WAVEFRONT SENSING = SENSING_ONLY .
The NIRISS External Calibration template consists of the following parameters:
| Field | Details | Values | Notes |
|---|---|---|---|
| General Information | |||
| Observation Number | assign observation number | number | |
| Observation Label | provide observation label | text | optional |
| Observations Comments | provide observation comments | text | optional |
| Mosaic Properties | specify mosaic parameters | number | if needed |
| Special Requirements | specify special requirements | choose from list | if needed |
| Template Specific Information | |||
| Pointing Type | select pointing type | PARALLEL, PRIME | |
| Target Acquisition Exposures | |||
| select target name | choose from list | ||
| Acquisition Target | select acquisition target | choose from list | |
| Acquisition Filter | default value | F480M | |
| Acquisition Mode | select target acquisition mode | choose from list | |
| Acquisition Readout Pattern | select readout pattern | NIS, NISRAPID | |
| Acquisition Number of Groups/Integration | select number of groups per integration | choose from list | |
| Dither Patterns | |||
| Dithers | select dither pattern type | choose from list | |
| Primary Dithers | select number of steps | choose from list | Required if AMI dither pattern type is selected |
| Subpixel Positions | select number of positions | choose from list | Required if AMI dither pattern type is selected |
| Image Dithers | select number of steps | choose from list | Required if Imaging dither pattern type is selected |
| Image Dithers | select number of steps | 2 | Automatically supplied if MIMF dither pattern type is selected |
| Image Dithers | select number of steps | choose from list | Required if WFSS dither pattern type is selected |
| Pattern Size | select pattern size | SMALL, MEDIUM, LARGE | Required if WFSS dither pattern type is selected |
| Science Exposures | |||
| Subarray | select subarray | choose from list | |
| Aperture | select aperture | choose from list | |
| Pupil Wheel | select pupil wheel element | choose from list | |
| Filter Wheel | select filter wheel element | choose from list | |
| Readout Pattern | select readout pattern | NIS, NISRAPID | |
| Number of Groups/Integration | specify number of groups per integration | number | |
| Number of Integrations/Exposure | specify number of integrations per exposure | number | |
General Information
The following parameters are generic to all templates, and are not discussed in this article: Observation Number, Observation Label, Observations Comments, Target Name, Mosaic Properties, and Special Requirements.
Target Name
Select the TARGET NAME [TBD] from the list of targets previously entered; see list of targets. If POINTING TYPE = PARALLEL, TARGET NAME = NONE. If POINTING TYPE = PRIME, NONE is not available.
Target Acquisition Parameters
Acquisition Target
When POINTING TYPE=PARALLEL, the Target Acquisition options are not available.
If no target acquisition is needed or if an offset star is to be used for the target acquisition observation, select the ACQUISITION TARGET [TACQ TARGET] to be NONE, or from the list of targets previously entered, respectively.
Select the ACQUISITION TARGET [TACQ TARGET] from the list of targets previously entered. When the science target is a Solar System target, the acquisition target MUST be the science target. Or, if no target acquisition is needed, select ACQUISITION TARGET to be NONE.
Notes for developers:
- If the acquisition target is different from the science target, APT should provide a warning if the distance between the ACQ and Science targets is greater than the Visit splitting distance found in the PRD . Also, if there are multiple pointings within a visit, then the rules have to apply to the greatest separation between acq target and pointing within the visit.
- If the observation target is a fixed target, remove solar system targets from the acquisition target options. If the observation target is a Solar system target, remove all options from the acquisition target list except for the observation target and NONE.
Acquisition Filter
The Target Acquisition FILTER is F480M.
Acquisition Mode
ACQUISITION MODE [TACQ MODE] = SOSSBRIGHT, SOSSFAINT, AMIBRIGHT, AMIFAINT
This field specifies the target acquisition mode to be used to obtain the acquisition data for bright or faint targets for SOSS or AMI observations. The SOSSBRIGHT or AMIBRIGHT modes are to be selected for targets with M-band magnitudes in the range 3.0 ≤ M ≤ 8.5, while the SOSSFAINT or AMIFAINT modes should be selected for targets with 8.5 ≤ M ≤ 14.5.
The SOSSFAINT and SOSSBRIGHT ACQUISITION MODEs are only meant to be used if the SUBARRAY for the subsequent exposures is SUBSTRIP96, SUBSTRIP256, or SUBTASOSS. The AMIFAINT and AMIBRIGHT ACQUISITION MODEs are only meant to be used if the SUBARRAY for the subsequent exposures is SUBTAAMI or SUB80. Other uses are not allowed because the science aperture is too far from the ACQUISITION TARGET the required slew would be greater than the visit splitting distance (see Guide star breaking distance table).
Note for developers: If SOSSBRIGHT or SOSSFAINT is selected, the TA subarray will be SUBTASOSS. If AMIBRIGHT or AMIFAINT is selected, the TA subarray will be SUBTAAMI.
Acquisition Readout Pattern
READOUT PATTERN [TACQ PATTERN] = NIS, NISRAPID
This field specifies the readout pattern to be used to obtain the acquisition data.
Note for developers: The NIS option is only available when TACQ MODE = AMIFAINT or SOSSFAINT.
Acquisition Number of Groups/Integration
NUMBER OF GROUPS/INTEGRATION [TACQ NGROUPS] = 3, 5, 7, 9, 11, 13, 15, 17, 19
This parameter specifies the number of groups in an integration.
Note that the NUMBER OF INTEGRATIONS/EXPOSURE is set to 1 for target acquisition observations.
Science Parameters
Pointing Type
POINTING TYPE = PARALLEL, PRIME (default)
This parameter enables the user to control whether the data will be obtained in parallel like other calibrations, or as a primary observation like regular science.
Note for developers:
- This field is not saved directly into the database.
- If PRIME, make TARGET NAME required, remove the NONE option, and make the default "None Selected." If a PARALLEL special requirement is present, remove it.
- If PARALLEL, set TARGET NAME = NONE (not changeable), set TACQ TARGET=NONE (not changeable), hide the target acquisition options, and set DITHER PATTERN TYPE = NONE. If a PARALLEL special requirement is not present, add it.
DITHER PATTERN TYPE [PATTERN TYPE] = NONE, AMI, IMAGING, MIMF, WFSS
This field specifies the science observation mode of the dither pattern. If POINTING TYPE = PARALLEL, the DITHER PATTERN TYPE options are not available.
None
This value indicates that no dithering will be performed.
AMI
This parameter is needed to specify an AMI dither. If this dither pattern type is selected, the following two parameters must be set:
Primary Dithers
PRIMARY DITHERS [PRIMARY DITHERS] = NONE, 2, 3, 4
This parameter indicates the number of steps in the primary dither.
Subpixel Positions
SUBPIXEL POSITIONS [SUBPIXEL POSITIONS] = NONE, 5, 9, 25
This parameter indicates the number of sub-pixel positions. These will be executed at each primary dither position.
Imaging
The following parameter is needed to specify the Imaging dither. If this dither pattern type is selected, the following parameter must be set.
Image Dithers
IMAGE DITHERS [IMAGE DITHERS] = 2, 3, 4
This parameter indicates the number of steps in the primary dither.
MIMF
The following parameter is needed to specify the MIMF dither. If this dither pattern type is selected, the following parameter will be set.
Image Dithers
IMAGE DITHERS [IMAGE DITHERS] = 2
This parameter indicates the number of steps in the primary dither. Note that the value of 2 is fixed for MIMF dithers; no other value is available.
WFSS
The following parameter is needed to specify the WFSS dither. If this dither pattern type is selected, the following two parameters must be set:
Image Dithers
IMAGE DITHERS [IMAGE DITHERS] = 2, 3, 4, 6, 8, 12, 16
This parameter indicates the number of steps in the primary dither.
Pattern Size
PATTERN SIZE [PATTERN SIZE] = SMALL, MEDIUM, LARGE
This parameter indicates the size of the dither.
The following parameters are used to define each external calibration exposure specification in an observation.
Subarray
SUBARRAY [SUBARRAY] = SUBTASOSS, SUBTAAMI, SUB64, SUB80, SUB128, SUB256, WFSS64R, WFSS64C, WFSS128R, WFSS128C, SUBSTRIP96, SUBSTRIP256, SUBAMPCAL, FULL
This parameter specifies the region of the SCA that is to be read out. See Table 1 for details.
Table 1. Subarrays for NIRISS External Calibration
Subarray | Size( cols x row) | Col corner | Row corner | Frame read time (s) |
|---|---|---|---|---|
SUBTASOSS | 64 x 64 | 891 | 63 | 0.04550 |
SUBTAAMI | 64 x 64 | 1905 | 932 | 0.04550 |
SUB64 | 64 x 64 | 1 | 1 | 0.04550 |
SUB80 | 80 x 80 | 1969 | 925 | 0.07452 |
SUB128 | 128 x 128 | 1 | 1 | 0.18060 |
SUB256 | 256 x 256 | 1 | 1 | 0.68876 |
WFSS64R | 2048 x 64 | 1 | 1 | 0.34060 |
WFSS64C | 64 x 2048 | 1 | 1 | 1.55724 |
WFSS128R | 2048 x 128 | 1 | 1 | 0.67596 |
WFSS128C | 128 x 2048 | 1 | 1 | 2.86860 |
SUBSTRIP96 | 96 x 2048 | 151 | 1 | 2.21292 |
SUBSTRIP256 | 256 x 2048 | 1 | 1 | 5.49132 |
SUBAMPCAL | 1792 x 512 | 257 | 1537 | 9.25452 |
FULL | 2048 x 2048 | 1 | 1 | 10.7368 |
Aperture
APERTURE = DEFAULT APERTURE, (see Table 2 for parameter values)
This parameter specifies the aperture used for the observation. DEFAULT APERTURE specifies the aperture currently mapped to the selected SUBARRAY (mapping in Appendix H5).
Table 2. Apertures for NIRISS External Calibration
| Apertures | ||
|---|---|---|
| NIS_CEN_OSS | NIS_WFSS64R3 | NIS_SUBAMPCAL |
| NIS_CEN | NIS_WFSS64C | NIS_SUBSTRIP96 |
| NIS_AMI1 | NIS_WFSS64C3 | NIS_SUBSTRIP256 |
| NIS_AMI2 | NIS_WFSS128 | NIS_FP1MIMF |
| NIS_AMI3 | NIS_WFSS128R | NIS_FP2MIMF |
| NIS_AMI4 | NIS_WFSS128R3 | NIS_FP3MIMF |
| NIS_AMITA | NIS_WFSS128C | NIS_FP4MIMF |
| NIS_SOSSTA | NIS_WFSS128C3 | NIS_FP5MIMF |
| NIS_WFSS_OFFSET | NIS_SUB64 | NIS_AMIFULL |
| NIS_WFSS64 | NIS_SUB128 | NIS_SOSSFULL |
| NIS_WFSS64R | NIS_SUB256 | NIS_WFSS |
Pupil Wheel Elements
PUPIL WHEEL [PUPIL] = CLEARP, F090W, F115W, F140M, F150W, F158M, F200W, NRM, GR700XD
This parameter specifies the pupil wheel element to be used for the exposure specification.
Note for developers: Several of these optical elements in the pupil wheel are used as options for the FILTER field in other NIRISS templates.
Filter Wheel
FILTER WHEEL [FILTER] = CLEAR, GR150R, GR150C, F277W, F356W, F380M, F430M, F444W, F480M
This parameter specifies the filter wheel element to be used for the exposure specification. For each exposure specification, specify the name of the element in the filter wheel.
Note for developers: The GR150R and GR150C optical elements are (also) used as options for the GRISM field in the NIRISS WFSS template.
Readout Pattern
READOUT PATTERN [READOUT PATTERN] = NIS, NISRAPID
This field specifies the readout pattern to be used to obtain the science data. NIS is used for longer exposure durations and NISRAPID is used for shorter exposure durations.
Number of Groups/Integration
NUMBER OF GROUPS/INTEGRATION [NGROUPS] specifies the number of groups in an integration. For readout pattern NIS, the range is 1-200, while for NISRAPID the range is 1-800.
Number of Integrations/Exposure
NUMBER OF INTEGRATIONS/EXPOSURE [NINTS] field specifies the number of times the integration is repeated. The allowed range is 1-10,000.