MIRI Low Resolution Spectroscopy Template Parameters
JWST's MIRI Low Resolution Spectroscopy template, available in the Astronomer’s Proposal Tool (APT), has parameters for specifying and scheduling observations.
Purple text indicates the parameter is Limited Access.
Boldface italics type indicates the name of an APT parameter or a value for a parameter.
text indicates restrictions on a parameter. Red
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 MIRI Low Resolution Spectroscopy (LRS) template is to be used for all observations using the low resolution spectroscopy mode of MIRI, and this article describes allowed values for all parameters. Advice on how to choose values which optimize your science can be found in the MIRI LRS APT Template.
The MIRI Low Resolution Spectroscopy template consists of the following parameters:
|assign observation number|
|Observation Label||provide observation label||text||optional|
|Observation Comments||provide observation comments||text||optional|
|select Target Name||choose from list||from Target List|
|specify ETC Workbook Calculation ID||number||for science exposures (optional) and target acquisition exposures|
|specify mosaic parameters||number||if needed|
|specify special requirements||choose from list||if needed|
|Template Specific Information|
|Target Acquisition Exposure|
|select acquisition target||choose from list|
|select filter name||choose from list|
|select acquisition readout pattern||choose from list|
|select number of groups per integration||choose from list|
|select number of integrations per exposure||1||only allowed value|
|select subarray||choose FULL or SLITLESSPRISM|
|Dither Type||select dither type||choose from list|
|Number of Spectral Steps||enter number of spectral steps||1, 2, 3, ...||for DITHER TYPE=MAPPING only|
|Spectral Step Offset||enter offset per spectral step||any positive number||for DITHER TYPE=MAPPING only|
|Number of Spatial Steps||enter number of spatial steps||1, 2, 3, ...||for DITHER TYPE=MAPPING only|
|Spatial Step Offset||enter offset per spatial step||any positive number||for DITHER TYPE=MAPPING only|
|select readout pattern||choose from list|
specify number of groups per integration
specify number of integrations per exposure
|Number of Exposures/Dither||specify number of times to repeat the exposure for each dither position||number|
The following parameters are used to define MIRI Target Acquisition observations. Note that for Low Resolution Spectroscopy, the science target is generally used for the acquisition, although when necessary, an offset star may be used. For more information on defining a target acquisition specification, see MIRI Target Acquisition Overview..
If an offset star is to be used for the target acquisition observation, select the ACQUISITION TARGET NAME [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”.
Note for developers: For APT, the ACQUISITION TARGET field should always be present, but should be defaulted to the prime target for the Observation.
Note for developers: If the acquisition target is different from the science target, APT should provide an error 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.
Note for developers: LRS target acquisition will use the FULL array.
Note for developers: 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 Target Filter
TARGET ACQUISITION FILTER [TACQ FILTER] = F560W, F1000W, F1500W, FND
This parameter specifies the TARGET ACQUISITION FILTER to be used for the target acquisition.
Acquisition Readout Pattern
READOUT PATTERN [TACQ PATTERN] = FAST (default), FASTGRPAVG
This field specifies the readout pattern to be used to obtain the acquisition data.
Acquisition Number of Groups/Integration
4, 6, 8, 10, 12, 22, 36, 44, 66, 86, 98
This field specifies the number of groups in an integration. When SUBARRAY=FULL, the only values available are 4, 6, 8, 10.
Acquisition Number of Integrations/Exposure
The NUMBER OF INTEGRATIONS/EXPOSURE [TACQ NINTS] is set to 1 for target acquisition observations.
SUBARRAY [SUBARRAY] = FULL, SLITLESSPRISM
This parameter specifies the region of the detector to be read out. For more details about these subarrays, see Subarray.
The TIME SERIES OBSERVATION special requirement is only allowed when SUBARRAY = SLITLESSPRISM. Note that time series observations cannot have parallels attached to them so you must add the NO PARALLEL special requirement.
Note that the dither pattern does NOT apply to the target acquisition image. To preserve very precise wavelength calibration of the slitless spectrum, dithering is not enabled for the SUBPRISM subarray.
DITHER TYPE [PATTERN_TYPE] = NONE, ALONG SLIT NOD, MAPPING
This parameter specifies the primary pattern to be used for dithering. There are two primary patterns available for use with the LRS, one for point sources and one for extended targets.
Along Slit Nod
This option selects a pattern for point sources. Two exposures are taken, one at each of two points along the slit. No further parameters are required.
This option selects a grid pattern of dither points. The following additional parameters are required.
Number of Spectral Steps
NUMBER OF SPECTRAL STEPS [NUMBER_OF_SPECTRAL_STEPS] = 1, 2, 3, …
This parameter specifies the number of steps in the spectral direction.
Spectral Step Offset
This parameter specifies the offset per step in the spectral direction. The offsets are given in arcseconds, and can be any positive floating point value.
Number of Spatial Steps
NUMBER OF SPATIAL STEPS [NUMBER_OF_SPATIAL_STEPS] = 1, 2, 3, …
This parameter specifies the number of steps in the spatial direction.
Spatial Step Offset
This parameter specifies the offset per step in the spatial direction. The offsets are given in arcseconds, and can be any positive floating point value.
Note for developers: see MIRI Dithering Details for dithering details.
For each exposure to be executed at each position in a dither pattern, specify the READOUT PATTERN, NUMBER OF GROUPS/INTEGRATION, NUMBER OF INTEGRATIONS/EXPOSURE, and the NUMBER OF EXPOSURES/DITHER. For more information on defining an exposure specification, see Exposure time.
READOUT PATTERN [READOUT PATTERN] = FAST (default), SLOW, FASTGRPAVG
This field specifies the readout pattern to be used to obtain the data.
Note for developer: SLOW is only available when SUBARRAY = FULL.
Number of Groups/Integration
NUMBER OF GROUPS/INTEGRATION [NGROUPS] specifies the number of groups in an integration.
NUMBER OF GROUPS/INTEGRATION must be 2 or greater.
If READOUT PATTERN = FASTGRPAVG, it is recommended that NUMBER OF GROUPS/INTEGRATION be at least 4. For all other READOUT PATTERNs, a number of 2-4 is allowed but not recommended.
Number of Integrations/Exposure
NUMBER OF INTEGRATIONS/EXPOSURE [NINTS] field specifies the number of times the integration is repeated/ The default value is 1.
Number of Exposures/Dither
NUMBER OF EXPOSURES/DITHER [NEXP] specifies the number of times the exposure is to be repeated at each dither position. The default value is 1.
If NUMBER OF EXPOSURES/DITHER > 1, the NO PARALLEL special requirement is required.
Note for developer: If NUMBER OF EXPOSURES/DITHER > 1. provide the following error: " The Special Requirement NO PARALLEL must be used with this Observation." and the following diagnostic explanation: "The NO PARALLEL requirement is required for Coordinated Parallels; Time Series observations; external observations with NUMBER OF EXPOSURES/DITHER > 1 and dithering; NIRSpec observations with Auto Calibrations; NIRCam Grism Time Series; and engineering templates (FGS Internal Flat, MIRI Anneal, MIRI External Flat, NIRSpec Internal Lamp, NIRSpec MSA Masking, NIRSpec MSA Anneal, NIRISS Internal Flat, all WFSC)."
Version 10 (June 17, 2019)
- PROPINSTJWST-91381 - updated Acquisition Number of Groups/Integration section.
Version 9 (April 18, 2019)
- Editorial change (moved change log to main article).
Version 8 (December 21, 2018)
- PROPINSTJWST-91122 - added developer note in Acquisition Target section restricting acquisition target options for fixed vs. solar system observations.
- PROPINSTJWST-87189 - removed SLOW option from acq readout.
Version 7 (August 10. 2018)
- PR 89798 - Updated Acquisition Number of Groups/Integration section.
Version 6 (May 14, 2018)
PR 89879 - NO PARALLEL special requirement required for external observations with NEXP>1, added red note and developer note.
PR 89323 - Updated red notes in Number of Groups/Integration for FASTGRAVP
Version 5 (December 27, 2017)
- PR 89483 - added restriction on Acq Target for SS observations
- PR 88411 - added note about TSO requirement and NO PARALLEL
- PR 86278 - added option for no target acquisition
Version 4 (November 20, 2017)
- PR 87189 - updated readout pattern SLOW to be non-LAP
- PR 87895 - updated Exposure field labels to Groups/Integration and Integrations/Exposure
- PR 88896 - made TA Number of Groups/Integration be a picklist
Version 3 (May 11, 2017)
- PR 85610 - renamed Dither Types
Version 2 (January 16, 2017)
- PR 85608 - updated TA parameters
- PR 85922 - renamed SUBPRISM to SLITLESSPRISM
- PR 80734 - added Number of Exposures parameter
- PR 85925 - set default Readout Pattern
- PR 85925 - added restriction on Number of Groups
- PR 85863 - updated developer note for Acquisition Target
- PR 85608 - removed statement about Acq Flux
- PR 81292 - removed inconsistency in name of dither parameters
Version 1 (May 6, 2016)
This is the converted Word File from Chapter 11.