NIRSpec Focus Template Parameters

JWST's NIRSpec Focus template, available in the Astronomer’s Proposal Tool (APT), is used to perform Focus Sweeps and Focus Adjustments.


 Format definitions...

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.

These parameters are required to perform Focus Sweeps and Focus Adjustments. Note that this type of observation cannot be obtained as a parallel to normal science observations.

FieldDetailsValueNotes
General Information
Observation Numberassign observation numbernumber
Observation Labelprovide observation labeltextoptional
Observation Commentsprovide observation commentstextoptional
Target Nameselect Target Namechoose from listfrom Target List
Special Requirementsspecify special requirementschoose from listif needed
Template specific information
MSA Configurationselect MSA configurationALLOPEN, ALLCLOSED
Readout Patternselect readout patternchoose from list
Number of Groups/Integrationselect number of groups/integrationnumber
Number of Integrations/Exposureselect number of integrations/exposurenumber
Relative Positionspecify relative postionnumber

 General information  

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

Target Name

Select the TARGET NAME [TARGET] from the list of targets previously entered (see list of targets ).

MSA Configuration

MSA CONFIG = ALLOPEN, ALLCLOSED

Select the configuration for the micro-shutter assembly (MSA).

Filter

FILTER [FILTER] = F140X, F110W, F070LP, F100LP, F170LP, F290LP, CLEAR

Select the name of the filter you wish to use. 

Exposure Specifications

For each exposure to be executed, specify the READOUT PATTERN, NUMBER OF GROUPS/INTEGRATION,  and the NUMBER OF INTEGRATIONS/EXPOSURE.

Readout Pattern

READOUT PATTERN [READOUT PATTERN] = NRS, NRSRAPID NRSIRS2, NRSIRS2RAPID

This field specifies the readout pattern to be used to obtain the data.

 

(warning)Note that NUMBER OF GROUPS/INTEGRATION x NUMBER OF INTEGRATIONS/EXPOSURE must be less than 256 for NRISIRS2 and 1024 for NRSIRS2RAPID.

Number of Groups/Integration

NUMBER OF GROUPS [NGROUPS] specifies the number of groups in an integration.

Number of Integrations/Exposure

NUMBER OF INTEGRATIONS [NINTS] field specifies the number of times the integration is performed.  

Note to developers: while the SUBARRAY is not explicitly given, its value is FULL for the purposes of calculating photon collection time.

Relative Position

The Refocus Mechanism Assembly (RMA) is moved from the initial position to a number of specified positions, and a focus exposure is taken at each specified position. If only the RMA start position is specified (RELATIVE POSITION = "0"), a single focus exposure is taken without moving the RMA, providing the data needed to measure the current image quality. If RELATIVE POSITION contains a single nonzero value, the RMA is moved once, adjusting the focus. In this case, focus exposures are taken at the initial and final positions, providing the data needed to measure the change in image quality. Finally, if RELATIVE POSITION contains more than one value, the RMA is moved sequentially to each of the specified positions. Regardless of the number of positions and initial direction, a sweep will always end in the initial position. Focus exposures are taken at each RMA position, providing the data needed to measure image quality as a function of RMA position.

The RELATIVE POSITION [DELTARRAY] parameter specifies an array of 1 to 20 positions that the focus is to be moved to; note that each position must be unique (i.e. a given value can only appear once in the list). The positions are given in motor steps ((warning)the range is -18400 to +18400), and are offsets from the current position. The exact order in which the positions will be executed will be determined by onboard scripts. Note that for an adjustment to the focus, only 1 position can be specified.

Change log

 Click here to expand...

Version 3 (April 19, 2019)

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


Version 2 (October 16, 2017)

  1. PR 88047 - added restriction on NGroups x NINTs for IRS2 readout pattern


Version 1 (June 15, 2017)

  1. This is the converted Word File from Chapter 39.
  2. PR 87895 - revised names of Number of Groups and Integrations
  3. To match GUI - removed restriction on NINTs when Readout Pattern is IRS2