NIRSpec MSA Masking Template Parameters

JWST's NIRSpec MSA Masking template, available in the Astronomer’s Proposal Tool (APT), is used to apply one or more masks to the micro-shutter assembly (MSA).

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.

This engineering feature allows the user to apply a set of zero-potential or tri-state masks to the MSA; one each for the 171-side and the 365-side of the specified quadrants. Masking of multiple quadrants can be done in a single visit by specifying multiple quadrant numbers.

Note to developer: Add a NO PARALLEL special requirement by default. If the special requirement is removed, give an error. 

Note to developer: Add a SPECIAL COMMANDING special requirement by default with the following text: "Special Commanding Approval will indicate confirmation that the MCE resolver conversion, tri-state, zero-potential masks and the predefined MSA configuration (allopen/allclosed) files needed for this visit will be in the ISIM file store before it begins". If the special requirement is removed, give an error. 

The following parameters define MSA Masking.

General Information
Observation Numberassign observation numbernumber
Observation Labelprovide observation labeltextoptional
Observation Commentsprovide observation commentstextoptional
Special Requirementsspecify special requirementschoose from listif needed
Template specific information
Mask Typeselect a mask typeZERO_POTENTIAL, TRI_STATE
Quadrant Listselect a quadrantchoose from list

 General information  

The following parameters are generic to all templates, and are not discussed in this article: Observation Number, Observation Label, Observation Comments,  and Special Requirements.

Mask Type


This parameter specifies the type of mask to update.

Quadrant List


This parameter specifies the quadrant(s) to be masked. You may specify one to four unique quadrants. Specifying a list of multiple quadrants will execute the procedure on the quadrants one-by-one in the order specified.

Change log

Version 5 (August 4, 2021)

  1. Editorial change - fixed anchor links in table.

Version 4 (January 22, 2020)

  1. Editorial change - previous published edit was left with some orange highlighting for review.

Version 3 (September 18, 2019)

  1. PROPINSTJWST-83804 - Added developer note to require PARALLEL SLEW ONLY. Added developer note to require SPECIAL COMMANDING. Removed requirement that both should be implicit SRs.

Version 2 (April 19, 2019)

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

Version 1 (June 15, 2017)

  1. This is the converted Word File from Chapter 39.