NIRISS Single-Object Slitless Spectroscopy (SOSS) Template Parameters
JWST's NIRISS Single-Object Slitless Spectroscopy (SOSS) imaging template, available in the Astronomer’s Proposal Tool (APT), has parameters for specifying and scheduling observations.
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 NIRISS Single-Object Slitless Spectroscopy (SOSS) template is used for the SOSS mode of NIRISS, and this article describes allowed values for all parameters. Advice on how to choose values which optimize your science can be found in the NIRISS Single-Object Slitless Spectroscopy APT Template article.
The NIRISS SOSS 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 |
| provide observation comments | text | optional | |
| Target Name | select Target Name | choose from list | from Target List |
| specify ETC Workbook Calculation ID | number | for science exposures (optional) and target acquisition exposures | |
| Special Requirements | specify special requirements | choose from list | if needed |
| Template Specific Information | |||
| Target Acquisition Exposure | |||
| select acquisition target | choose from list | ||
| Acquisition Filter | default value | F480M | |
| select acquisition mode | SOSSBRIGHT, SOSSFAINT | ||
| select acquisition readout pattern | NIS, NISRAPID | ||
| select number of groups per integration | choose from list | ||
| SOSS Exposure Parameters | |||
| select subarray | choose from list | ||
| SOSS Exposure | |||
| select readout pattern | choose from list | ||
| specify number of groups per integration | number | ||
| specify number of integrations per exposure | number | ||
| Include Short First Exposure and F277W Exposure? | select checkbox | checkbox | |
| F277W Exposure | |||
| Short First Exposure | (same parameters as SOSS Exposure) | available only if Include Short First Exposure and F277W Exposure? checkbox is selected. | |
| F277W Exposure | (same parameters as SOSS Exposure) | available only if Include Short First Exposure and F277W Exposure? checkbox is selected. | |
Note for developer: This template cannot be used in parallel and cannot have parallels attached to it; the NO PARALLEL special requirement should be added. The TIME SERIES OBSERVATION special requirement should also be added.
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, ETC Wkbk. Calc. ID, and Special Requirements.
Target Acquisition Exposure
Acquisition Target
If an offset star is to be used for the target acquisition observation, 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; the latter option is only allowed if SUBARRAY is FULL (see Subarray in the NIRISS Single-Object Slitless Spectroscopy APT Template article).
Notes for developers:
- The ACQUISITION TARGET name field should always be present, but should be defaulted to the SAME TARGET AS OBSERVATION.
- 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
This field specifies the target acquisition mode to be used to obtain the acquisition data for a “bright” or “faint” target. In this context, "bright" refers to M-band magnitudes in the range 3.0 ≤ M ≤ 6.1 (in the Vegamag system), while "faint" refers to 6.1 ≤ M ≤ 14.5.
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 developer: The NIS option is only available when TACQ MODE = 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.
SOSS Exposure Parameters
SOSS exposures are spectroscopic exposures using the GR700XD grism. For each exposure specify the SUBARRAY, READOUT PATTERN, NUMBER OF GROUPS/INTEGRATION, and NUMBER OF INTEGRATIONS/EXPOSURE. For more information on defining an exposure specification, see Exposure Time in the NIRISS Single-Object Slitless Spectroscopy APT Template article.
Two additional exposures may be specified together (see Include Short First Exposure and F277W Exposure).
SOSS Exposure
Subarray
SUBARRAY [SUBARRAY] = SUBSTRIP256 (default), SUBSTRIP96, FULL
This parameter specifies the region of the SCA detector that is to be read out. For details see Subarray in the NIRISS Single-Object Slitless Spectroscopy APT Template article.
Readout Pattern
READOUT PATTERN [READOUT PATTERN] = NISRAPID (default), NIS
This field specifies the readout pattern to be used to obtain the SOSS science data. Note that NIS is only available when SUBARRAY = FULL.
Number of Groups/Integration
NUMBER OF GROUPS/INTEGRATION [NGROUPS] specifies the number of groups in each integration. For readout pattern NIS, the range is 1-200, while for NISRAPID the range is 1-30
Number of Integrations/Exposure
NUMBER OF INTEGRATIONS/EXPOSURE [NINTS] field specifies the number of times the integration is repeated. The range is 1-65535.
Include Short First Exposure and F277W Exposure?
INCLUDE SHORT FIRST EXPOSURE AND F277W EXPOSURE = TRUE, FALSE (default)
The Short First Exposure and F277W Exposure parameters are hidden when this checkbox is not selected, and displayed when the checkbox is selected.
Short First Exposure
This short exposure uses the element GR700XD in the pupil wheel and CLEAR in the filter wheel, and is the first exposure to execute in the observation.
- Subarray is set to NISRAPID and may not be changed.
- NUMBER OF GROUPS/INTEGRATION and NUMBER OF INTEGRATIONS/EXPOSURE is set to 1 and may not be changed.
F277W Exposure
The F277W Exposure uses the same parameters as the SOSS Exposure and allows selection of values. This exposure uses the F277W filter and the element GR700XD in the pupil wheel, and is the last exposure to execute in the observation.
- Any allowable value may be selected for SUBARRAY, READOUT PATTERN, NUMBER OF GROUPS/INTEGRATION and NUMBER OF INTEGRATIONS/EXPOSURE.If the total Exposure Duration causes the observation to be split into two visits, the GROUP VISITS NON INTERRUPTIBLE special requirement is added as an implicit special requirement.