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.


Purple text indicates the parameter is Limited Access.

Boldface italics type indicates the name of an APT parameter or a value for a parameter.

(warning)Red text indicates restrictions on a parameter.

(red star) 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:

FieldDetailsValues Notes
General Information   
Observation Numberassign observation number


Observation Label provide observation labeltextoptional

Observation Comments

provide observation commentstextoptional
Target Nameselect Target Namechoose from listfrom Target List

ETC Wkbk. Calc. ID

specify ETC Workbook Calculation IDnumberfor science exposures (optional) and target acquisition exposures
Special Requirementsspecify special requirementschoose from listif needed
Template Specific Information   
Target Acquisition Exposure
select acquisition target

choose from list

Acquisition Filterdefault valueF480M
select acquisition mode


select acquisition readout pattern


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


specify number of integrations per exposure


Include F277W Exposure?select checkboxcheckbox
F277W Exposure

     F277W Exposure(same parameters as SOSS Exposure)
available only if Include 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  

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 


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 


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. An optional second exposure using the F2770W filter may be selected. 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.

Note for developers: only 1 SOSS exposure and only 1 F277W exposure are allowed in an observation.

SOSS Exposure



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 


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. (warning)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. (warning)The range is 1-65535.

Include F277W Exposure?


The F277W Exposure parameters are hidden when this checkbox is not selected, and displayed when the checkbox is selected.

F277W Exposure

The F277W Exposure is a second exposure using the F277W filter. Exposure specification parameters are identical to  SOSS Exposure parameters and are only displayed when the Include F277W Exposure? checkbox is selected.

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.

Change log

The initial version of this chapter was provided by Lily Liu.

August 11, 2022

  1. PROPINSTJWST-91523 Added GROUP VISITS NON INT exception to the F277W Exposure section.

Version 10 (May 6, 2022)

  1. PROPINSTJWST-91468 In Acquisition Target section developer note, changed "error" to "warning" for visit splitting.

Version 9 (August 9, 2021)

  1. Editorial change - Anchor links fixed in parameter table by removing pagename from link.

Version 8 (November 22, 2019)

  1. PROPINSTJWST-91226 - added new section for F277W checkbox and F277W exposure.

Version 7 (April 18, 2019)

  1. Editorial change (moved change log to main article).

Version 6 (December 21, 2018)

  1. PROPINSTJWST-91122 - Added developer note  in Acquisition Target section restricting acquisition target options for fixed vs. solar system observations.

Version 5 (December 27, 2017)

  1. PR 89483 - added restriction on Acq Target for SS observations
  2. PR 88411 - added developer note about TSO and NO PARALLEL requirements

Version 4 (November 15, 2017)

  1. PR 87895 - updated Exposure field labels to Groups/Integration and Integrations/Exposure
  2. PR 87961 - updated TA Readout Pattern options to include NIS
  3. PR 87198 - added note that NIS is only available when SUBARRAY=FULL
  4. PR 88816 - updated text for Acquisition Mode

Version 3 (February 21, 2017)

  1. PR 87071 - removed mosaics option

Version 2 (December 20, 2016)

  1. PR 85863 - updated developer note for Acquisition Target
  2. PR 85608 - removed statement about Acq Flux, and added new section to state default Acq Filter

Version 1 (March 29, 2016)

This is the converted Word File from Chapter 42.