WFSC Commissioning Template Parameters

JWST's WFSC Commissioning Template, available in the Astronomer’s Proposal Tool (APT), is used for any commissioning activity that uses NIRCam exposures alternating with mirror moves.


 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.

This method will be used during any commissioning activity that uses the following sequence, containing NIRCam exposures alternating with mirror moves.

  • Take a NIRCam image
  • Perform a group of mirror moves
  • Take another NIRCam image
  • Perform the next group of mirror moves


  • Take a final NIRCam image

The length of the sequence is determined by the contents of the Wavefront Control File. There can be multiple mirror move groups in a Wavefront Control File.

The following parameters are used to define Wavefront Sensing and Control Commissioning Operations. A Wavefront Control File (provided by the WFSC Scientist) will be attached to each visit by the PPS Operator.

Currently, this method is specified for the following commissioning steps:

  1. Secondary Mirror Focus Sweep
  2. Segment ID
  3. Segment Image Array
  4. Pupil Imaging
  5. Coarse Phasing
  6. Segment Piston Scan

Note: A NIRCam Image will be taken before and after each set of mirror moves. All images will be Full frames using the same parameters on all the specified NIRCam detectors.

In addition to the following template parameters, this template will have the Special Requirement WAVEFRONT SENSING   added with a default value of SENSING_CONTROL .

Note that this type of observation cannot be obtained with other parallel observations or as a parallel to normal science observations.

 Note for developers: the default PCS MODE should be COARSE. If the user overrides this value, a warning should be given, unless the SEGMENT GUIDE STAR special requirement is used.

 The WFSC Commissioning template consists of the following parameters:

FieldDetailsValues Notes
General Information   
Observation Numberassign observation number


Observation Label provide observation labeltextoptional
Observation Commentsprovide observation commentstextoptional
Target Nameselect Target Namechoose from listfrom Target List
Special Requirementsspecify special requirementschoose from listif needed
Template Specific Information   


select moduleA, B
Short Wavelength Filterselect short filterF200W, F212N
Option for Long Wavelength Filtercheckbox

Long Wavelength Filterselect long filterchoose from listif Option for Long Wavelength Filter is checked
Readout Patternselect readout patternFAST, SLOW
Number of Groups/Integrationspecify number of groups/integrationnumber
Number of Integrations/Exposurespecify number of integrations/exposurenumber
Reacquisitionselect reacquisitionREAC, NOREAC
Expected Number of WFC Groupsspecify number of groupsnumber

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 [TBD] from the list of targets previously entered (see list of targets).



 This parameter specifies the module(s) to be used to obtain the data.


Short Filter


Select the name of the SHORT FILTER you wish to use. The same filter will be used in both modules, if both modules are specified.

Option for Long Wavelength Channel

Select USE LONG WAVELENGTH CHANNEL if long wavelength images of the sky will also be collected. If not selected, the long wavelength pupil wheel will by default be placed in the FLAT position (as it is for Dark Frames).

Long Filter

FILTER  [FILTLONG] = F322W2, F460M, F480M. F323N+F322W2

Select the name of the LONG FILTER [FILTLONG]you wish to use. The same filter will be used in both modules, if both modules are specified.

Developer note: In the database the default of FLAT will be stored in PUPILLONG. If long wavelength filter(s) are chosen (including F323N_F322W) they will be stored in the FILTLONG, and the PUPILLONG will be null.

Exposure Duration


 Readout Pattern


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

Number of Groups/Integration

NUMBER OF GROUPS/INTEGRATION [NGROUPS] specifies the number of groups in an integration. (warning)If MODULE = A or B, the value must be between 1 and 10. If MODULE = ALL, the value must be between 1 and 4.

Number of Integrations/Exposure

NUMBER OF INTEGRATIONS/EXPOSURE [NINTS] field specifies the number of times the integration is repeated. (warning)If MODULE = A or B, the value must be between 1 and 10 If MODULE = ALL, the value must be 1.



RThis parameter specifies if the guide star is to be re-acquired after each mirror move group is executed.

Note for developers: Visits created from this template should be marked in the database as WFS visits by APT (visit.wavefront_sensing) and as WFSC visit type in VSS.

Expected Number of WFC Groups

The expected number of WFC groups [NWFCGROUPS] specifies the expected number of mirror move groups in the WFC file to be associated with this observation. The number of groups controls the number of images taken through the iterative process described above. Note that this parameter is purely advisory for use in PPS calculations of visit duration and data volume; the number of groups executed on orbit will depend solely on the contents of the WFC file and not on this parameter. (warning)This parameter is an integer and must be in the range 1 to 200: the default value is 1.

Note for developers: The estimated duration of the observation should be calculated as follows:

estimated_duration = (NWFCGROUPS +1) * (duration of one NIRCam image including overheads) + NWFCGROUPS * T_MIRROR_MOVE,

where T_MIRROR_MOVE is time for a segment mirror move.

If REACQ then estimated_duration = NWFCGROUPS * (FGS overhead to get into tracking)

The estimated data volume should be calculated as (NWFCGROUPS + 1) * (the data volume for an individual exposure).

Throughout most of OTE commissioning the expected number is known in advance for each observation, and in the handful of cases where the WFC file may differ from the expected value it should not be necessary to reprocess this parameter in APT and reprocess the visits.

Change log

 Click here to expand...

Version 3 (April 16, 2019)

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

Version 2 (May 7, 2018)

  1. PR 89947 - updated note to developer in Introduction section.

Version 1 (May 30, 2017)

  1. This is the converted Word File from Chapter 60.
  2. PR 87895 - revised names of Number of Groups and Integrations