MIRI Medium Resolution (Integral Field Unit) Spectroscopy Template Parameters
JWST's MIRI Medium Resolution (Integral Field Unit) 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 Medium Resolution (Integral Field Unit) Spectroscopy template is to be used for all observations using the medium 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 Medium Resolution Spectroscopy Template APT Guide.
The MIRI Medium Resolution (Integral Field Unit) 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|
|Acquisition Target||select acquisition target||choose from list|
|Acquisition Filter||select filter name||choose from list|
|Acquisition Readout Pattern||select acquisition readout pattern||choose from list|
|Acquisition Number of Groups/Integration||select number of groups per integration||choose from list|
|Acquisition Number of Integrations/Exposure||select number of integrations per exposure||1||only allowed value|
|Primary Channel||select primary channel||choose from list|
|Dither Type||select dither type||2-POINT, 4-POINT|
|Optimized For||select type of science dither optimized for||PRIMARY CHANNEL, EXTENDED SOURCE|
|Direction||select direction of dither pattern||POSITIVE, NEGATIVE|
|select if simultaneous imaging required||YES, NO|
|Imager Subarray||select subarray for Imager||choose from list||only if Simultaneous Imaging = YES|
|Detector||based on selection of Simultaneous Imaging parameter|
|Wavelength Range||select wavelength range||choose from list|
|Imager Filter||select filter||choose from list||only if Simultaneous Imaging = YES|
|Readout Pattern||select readout pattern||choose from list|
|Number of Groups/Integration|
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|
|Dither||select dither specification||choose from list|
The following parameters are used to define MIRI Target Acquisition observations. Note that for Medium Resolution Spectroscopy, the imager is used for the target acquisition and 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 MRS Target Acquisition.
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: MRS 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
This field specifies the number of groups in an integration.
Acquisition Number of Integrations
The NUMBER OF INTEGRATIONS/EXPOSURE [TACQ NINTS] is set to 1 for target acquisition observations.
PRIMARY CHANNEL [PRIMARY_CHANNEL] = ALL (default), CHANNEL1, CHANNEL2, CHANNEL3, CHANNEL4
The parameter specifies the channel of interest for this observation. This choice will drive the placement of the target, the size of offsets if a mosaic is request, what size field of view is displayed in Aladin, and the dither pattern. Note the ALL is functionally the same at CHANNEL1.
Most MIRI MRS observations will require dithering; see MIRI MRS Dithering
DITHER TYPE [PATTERN_TYPE] = 2-POINT, 4-POINT (default)
This parameter specifies the number of points to be used for dithering.
OPTIMIZED FOR [OPTIMIZED_FOR] = display the PRIMARY CHANNEL chosen above(default), EXTENDED SOURCE
Selecting the type of science (extended or not) the dither is optimized for controls the scale of the dither. If a target is chosen before a dither is created the default is PRIMARY CHANNEL unless the target was marked EXTENDED in which case the default is EXTENDED SOURCE.
|After OPTIMIZED FOR has a selected value, it will not change if a target is selected, a target's EXTENDED value is changed, or a new target is selected. The user must manually change the value.|
Note for developer: If the target is marked EXTENDED, change the default value to EXTENDED SOURCE.
Note for developer: Offer the actual value selected for PRIMARY CHANNEL above (e.g. CHANNEL1).
DIRECTION [DIRECTION]= POSITIVE, NEGATIVE (default)
Select the direction of the dither.
Note to developer: When DITHER TYPE is 2-POINT, use only the first two points of the dither pattern for the selected DIRECTION and OPTIMIZED FOR.
Simultaneous MIRI Imaging
SIMULTANEOUS IMAGING = YES (default), NO
This parameter specifies if simultaneous imaging is required. A value of YES will obtain imaging data at the same time as data is collected on both of the IFU detector arrays.
Note to developer: To store in the database, if SIMULTANEOUS IMAGING = YES then set DETECTOR = ALL, else set DETECTOR = MRS.
IMAGER SUBARRAY [SUBARRAY] = FULL (default), BRIGHTSKY, SUB256, SUB128, SUB64
This parameter is only relevant when SIMULTANEOUS IMAGING = YES. It specifies the region of the detector that is to be read out for the imager data. Note that if a value of IMAGER SUBARRAY other than FULL is used, there may be some data quality issues because of the switch from FULL which is used for the target acquisition. For more details about these subarrays, see
Note for developers: Inform the user with a warning if SUBARRAY other than FULL selected.
Note for developers: These tables show what should be displayed in the GUI, along with the appropriate commanding name for the database, for the two values of SIMULTANEOUS IMAGING.
SIMULTANEOUS IMAGING = NO
|#||Detector||No. of Exposures||Readout Pattern||No. of Groups||No. of Integrations||Dither|
|1||MRSShort||copied from above||copied from above||[NGROUPSSHORT]||[NINTSSHORT]||copied from above|
SIMULTANEOUS IMAGING = YES
No. of Exposures
No. of Groups
No. of Integrations
|MRSLong||copied from above||N/A|
[READOUT PATTERN LONG]
|copied from above|
copied from above
[READOUT PATTERN SHORT]
|copied from above|
For each exposure to be executed at each position in a dither pattern, specify the NUMBER OF EXPOSURES/DITHER, IMAGER FILTER, READOUT PATTERN, NUMBER OF GROUPS/INTEGRATION, NUMBER OF INTEGRATIONS/EXPOSURE, and DITHER. For more information on defining an exposure specification, see Exposure Parameters.
This field specifies the detector to be used, and is automatically populated based on the choice of SIMULTANEOUS IMAGING.
WAVELENGTH RANGE [WAVELENGTH_1_4, WAVELENGTH_2_3] = SHORT (A), MEDIUM (B), LONG (C)
Each of the four Integral Field Unit (IFU) image slicers covers a separate wavelength range. Each of these wavelength ranges can be covered by a set of three available gratings. You can request one grating by means of the WAVELENGTH RANGE parameter. Note the same wavelength region will be obtained with each IFU channel. So if you specify SHORT (A) then the short portion of the wavelength range will be obtained simultaneously with each IFU channel.
Note for developer: APT will populate the chosen WAVELENGTH RANGE value (with Short/Medium/Long only) into both WAVELENGTH_1_4 and WAVELENGTH_2_3.
Imager Filter Name
IMAGER FILTER [FILTER] = F560W, F770W, F1000W, F1130W, F1280W, F1500W, F1800W, F2100W, F2550W, OPAQUE, FLENS, F1065C, F1140C, F1550C,F2300C, F2550WR, P750L, FND
This field specifies the filters to be used to obtain the imaging data; this parameter is only relevant when SIMULTANEOUS IMAGING = YES.
Note to developer: If the PRIMARY CHANNEL = ALL, or CHANNEL1 -or- the dither is OPTIMIZED FOR = EXTENDED, and the IMAGER FILTER = F1280W, FND, F1500W, F1550C, F1800W, F2100W, F2300C, F2550W, or F2550WR, then warn that "for this filter the MRS dither pattern selected may cause the PSF in the simultaneous MIRI imaging to overlap. Maximum wavelengths for imager with no PSF overlap is lambda/D >= 6." Same warning if the PRIMARY CHANNEL = CHANNEL2 and the IMAGER FILTER = F2100W, or F2550W.
READOUT PATTERN = FAST, SLOW, FASTGRPAVG
This field specifies the readout pattern to be used to obtain the data.
Developer note: see tables above for commanding names.
Developer note: MRS has a default READOUT PATTERN of SLOW and Imager has a default READOUT PATTERN of FAST
If both SLOW and one of the FAST READOUT PATTERNs are used for the MRS in one observation, a TBD second settling time delay will be incurred each time there is a switch from one to the other.
If both SLOW and one of the FAST READOUT PATTERNs are used for the Imager in one observation, no settling time delay will be incurred, but there may be some data quality issues because of the switch.
Note to developer: inform the user with a warning in either of these cases.
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.
Developer note: see tables above for commanding names.
Number of Integrations/Exposure
NUMBER OF INTEGRATIONS/EXPOSURE [NINTS] specifies the number of times the integration is repeated; default = 1.
While the exposure time must be the same for the Short and Long detectors, the NUMBER OF GROUPS/INTEGRATION and NUMBER OF INTEGRATIONS/EXPOSURE can differ. Therefore the parameters for groups and integrations must conform to the following restriction:
NUMBER OF INTEGRATIONS/EXPOSURE (LONG) * NUMBER OF GROUPS/INTEGRATION (LONG) = NUMBER OF INTEGRATIONS/EXPOSURE(SHORT) * NUMBER OF GROUPS/INTEGRATION( SHORT)
Developer note: see tables above for commanding names.
Developer note: The MRS exposure determines the total exposure duration. If SIMULTANEOUS IMAGING = YES, for each triplet, compare the duration for the Imager exposure to the duration for the MRS exposures and give an error if the Imager exposure is longer.
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)."
Select the number corresponding to one of the dither specification previously specified or NONE.
Note for developers: DITHER should be a required field, and there should be no default value (i.e. do not make NONE the default)
Version 11 (June 7, 2019)
- PROPINSTJWST-91381 - updated Acquisition Number of Groups/Integration section.
Version 10 (April 18, 2019)
- Editorial change (moved change log to main article).
Version 9 (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 8 (August 14. 2018)
- PR 89798 - Updated Acquisition Number of Groups/Integration section.
- PR 90970 - revised warning to Wavelength Range section.
Version 7 (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
- PR 86951 - added restricted filters and updated developer note Filter Name section
Version 6 (December 26, 2017)
- PR 88480 - revised the WAVELENGTH parameter
- PR 89483 - added restriction on Acq Target for SS observations
- PR 86278 - added option for no target acquisition
Version 5 (September 27, 2017)
- PR 88372 - revised the WAVELENGTH parameter
- PR 87895 - updated Exposure field labels to Groups/Integration and Integrations/Exposure
- PR 88896 - made TA Number of Groups/Integration be a picklist
Version 4 (May 11, 2017)
- PR 87747 - revised Readout Pattern for wait period
Version 3 (December 20, 2016)
- PR 80734 - added Number of Exposures parameter
- PR 85174 - revised Dither Types
- PR 85823 - added Primary Channel parameter
- PR 85925 - added simultaneous MIRI imaging
- PR 85925 - added restrictions on Readout Pattern, Num Groups
- PR 85925 - added default for Num Ints
- PR 85608 - updated TA parameters
- PR 85929 - added Imager Subarray restriction
- PR 85863 - updated developer note for Acquisition Target
- PR 83015 - updated Optimized For parameter
Version 2 (July 16, 2016)
- PR 84810 - updated text for WAVELENGTH REGION to clarify that 3 sets of exposures will be obtained when ALL selected
Version 1 (May 2, 2016)
his is the converted Word File from Chapter 12.