WFSC NIRCam Fine Phasing Template Parameters

JWST's WFSC NIRCam Fine Phasing Template, available in the Astronomer’s Proposal Tool (APT), is used for fine phasing and LOS jitter monitoring. 

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.

(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.


In WFSC NIRCam Fine Phasing the user may select two different types of activities. The user may both select Line-Of-Sight (LOS) jitter monitoring and Fine Phasing in a single visit, or either type may be selected separately.

In monitoring situations, both LOS and Fine Phasing would be selected.

  • A visit would start with a Target Acquisition in a 64 x 64 subarray, with target placement determined by the aperture paired to the subarray (see Acquisition Subarray).
  • Next, a series of 8 x 8 subarray LOS images will be taken, with target placement also determined by the aperture paired to the subarray (see LOS Subarray).
  • Lastly, the Fine Phasing activities would be executed. No additional Target Acquisition is needed for the Fine Phasing activities.

The WFSC NIRCam Fine Phasing Template consists of the following parameters: 

FieldDetailsValues Notes
General Information   
Observation Number assign observation number

number


  Observation Labelprovide observation labeltextoptional
Observations Commentsprovide observation commentstextoptional
 Targetselect Target Namechoose from listfrom Target List
 Special Requirementsspecify special requirementschoose from listif needed
Template Specific Information   
Sensing Type
select Sensing TypeChoose from list 
 Moduleselect ModuleA, B 
LOS Jitter Information (if SENSING TYPE = LOS JITTER or BOTH)
Acquisition Target
select Target Namechoose from listfrom Target List
Acquisition Subarray

based on selection of Module

Acquisition Filterdefault value

F212N


Acquisition Readout Pattern

default valueRAPID
Acquisition Number of Groups/Integrationselect number of groups/integrationchoose from list
Acquisition Number of Integrations/Exposuredefault value1
LOS Subarray

based on selection of Module
LOS Images Filtersdefault valueChoose from list
LOS Images Readout Patterndefault valueRAPID
LOS Images Number of Groups/Integrationspecify number of groups/integration1 - 1000
LOS Images Number of Integrations/Exposurespecify number of integrations/exposure1 - 65535
LOS Exposuresspecify number of exposures1 - 1024required
WESC Fine Phasing Information (if SENSING TYPE = FINE PHASING)

Diversity

select diversitychoose from list 
Expected Number of WFC Commandsspecify Expected Number of WFC Commandsnumber1 - 2100
Primary Dither Typeselect Primary Dither TypeNONE, WFSC

Plus/Minus 8 Waves Defocus (F212N) Imaging Parameters Information

Filters
see table
Readout Patternselect readout patternRAPID, BRIGHT1
Number of Groups/Integrationspecify number of groups/integrationnumber
Number of Integrations/Exposurespecify number of integrations/exposurenumber

Plus 12 Waves Defocus Imaging Parameters Information

Filters
see table.
Readout Pattern

select readout pattern

RAPID, BRIGHT1 
Number of Groups/Integrationspecify number of groups/integrationnumber
Number of Integrations/Exposurespecify number of integrations/exposurenumber

 Plus/Minus 4 Waves Defocus Imaging Parameters Information

Filters
see table
Readout Patternselect readout patternRAPID, BRIGHT1 
Number of Groups/Integrationspecify number of groups/integrationnumber
Number of Integrations/Exposurespecify number of integrations/exposurenumber

 Plus/Minus 8 Waves Defocus (F187N) Imaging Parameters Information

Filters
see table
Readout Patternselect readout patternRAPID, BRIGHT1
Number of Groups/Integrationspecify number of groups/integrationnumber
Number of Integrations/Exposurespecify number of integrations/exposurenumber

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,  and Special Requirements. 

Target 

Select the TARGET NAME from the list of targets previously entered. If a solar system target is selected, APT shows a warning.

Sensing Type

SENSING TYPE = FINE PHASING, LOS JITTER, BOTH

This parameter specifies the type of sensing observation to be executed.

A WAVEFRONT SENSING special requirement is required and is added by default. For required values see WAVEFRONT SENSING.

Note for developer: Do not duplicate the exposures when SENSING TYPE=BOTH.

Module

MODULE [ MODULE] = A, B

This parameter specifies the module to be used to obtain the data.

Beginning with APT 2024.7, target positioning on the A Module is changed from A3/FP1 to A1/FP6 (see Acquisition Subarray and LOS Subarray).

WFSC LOS Jitter Monitoring

If SENSING TYPE = LOS JITTER or BOTH, a target acquisition is performed to place the target star in the center of a 64x64 subarray. The center 8x8 pixels will be used for a series of NIRCam images.

Target Acquisition

The following parameters are used to define the Target Acquisition.

Acquisition Target

The default for this parameter is "Same Target as Observation." If an offset star is to be used for the target acquisition observation, select the TARGET NAME [TACQ TARGET] from the list of fixed targets previously entered. When the science target is a Solar System target, the acquisition target MUST be the science target. If no target acquisition is needed, select ACQUISITION TARGET to be NONE.

Note for developer: 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.

Acquisition Subarray

This parameter specifies the subarray used for acquisition images. Subarrays depend on the selected module and cannot be changed (see Table 1).

Table 1. Acquisition Subarrays

MODULESUBARRAYAperture
ASUB64FP6ANRCA1_FP6_SUB64
BSUB64FP1BNRCB4_FP1_SUB64

Acquisition Filter

The Target Acquisition FILTER is F212N.

Acquisition Readout Pattern

The READOUT PATTERN [TACQ PATTERN] for target acquisition is RAPID.

Acquisition Number of Groups/Integration

NUMBER OF GROUPS/INTEGRATION [TACQ NGROUPS] = 3, 5, 9, 17, 33, 65

This parameter specifies the number of groups in an integration.

Acquisition Number of Integrations/Exposure

NUMBER OF INTEGRATIONS/EXPOSURE specifies the number of times the integration is repeated, and is always 1.

 LOS Subarray

This parameter specifies the subarray used for LOS jitter images. Subarrays depend on the selected module and cannot be changed (see Table 2).

Table 2. LOS Image Subarrays

MODULESUBARRAYAperture
ASUB8FP6ANRCA1_FP6_SUB8
BSUB8FP1BNRCB4_FP1_SUB8

 LOS Images Filters

FILTER [FILTSHORT]= F200W, F210M, F212N

This parameter specifies the FILTER for the observation.

 LOS Images Readout Pattern

The READOUT PATTERN [PATTERN] for LOS Jitter is RAPID.

  LOS Images Number of Groups/Integration

NUMBER OF GROUPS/INTEGRATION [NGROUPS] = 1 - 1000

This parameter specifies the number of groups in an integration.

 LOS Number of Integrations/Exposure

NUMBER OF INTEGRATIONS/EXPOSURE [NINTS] = 1 - 65535

This parameter specifies the number of times the integration is repeated.

LOS Exposures

EXPOSURES=1 - 1024

This parameter specifies the number of exposures to be executed. This allows the total exposure time to exceed the maximum allowable time for a single exposure. All LOS  exposures are executed as dithers with zero offset and are written as dither records to  nircam_imaging_dither.

WFSC Fine Phasing

WFSC Fine Phasing will be executed several times during commissioning to measure OTE wavefront errors. It will also be executed approximately every 2 days during the mission to measure and optionally correct the wavefront error. Fine Phasing measurements consist of a series of steps that collect NIRCam images of a star using the Weak Lenses. Each step within the series consists of two exposures which may optionally be separated by a small (few pixel) dither. There are four types of exposures: Plus/Minus 8 Wave Defocus (F212N), Plus 12 Waves Defocus, Plus/Minus 4 Waves Defocus, and Plus/Minus 8 Waves Defocus (F187N). All the exposures of a given type use the same exposure parameters. The parameter DIVERSITY allows the user to select the types of exposures.

  • If a wavefront correction is required, then a Wavefront Control File containing one mirror control group should be uploaded prior to the execution of the observation.
  • A Wavefront Control File (provided by the WFSC Scientist) may be attached to each visit by the PPS Operator.
  • In addition to the following template parameters, this template will require a value be specified for the Special Requirement WAVEFRONT SENSING.

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

 Diversity

DIVERSITY [DIVERSITY] = ALL, ALL+187N, PM8

This parameter specifies the type of focus diversity images to obtain.

If ALL is specified, images with +8, -8, +12, -4, and +4 waves defocus (a total of 10 exposures) are obtained. These +8 and -8 waves defocused images use the F212N filter.

If ALL+187N is specified, the images described above are obtained, with the addition of images with +8 and -8 waves defocus using the F187N filter (a total of 14 exposures).

If PM8 (Plus and Minus 8 waves) is specified, only the +8 and -8 waves defocus images (using F212N) are obtained (a total of 4 exposures). Note that each step results in two exposures being obtained.

Expected Number of WFC Commands

EXPECTED NUMBER OF WFC COMMANDS = 0 - 2100

 The number of WFC commands expected with this proposal.

This parameter is affected by the WAVEFRONT SENSING special requirement:

  • When WAVEFRONT SENSING = ROUTINE, a value of 0 is allowed and is the default. For all other cases, 0 is not allowed and the default is 170.  
  • When WAVEFRONT SENSING = SENSING_ONLY, the EXPECTED NUMBER OF WFC COMMANDS parameter is removed. 

Primary Dither Type 

PRIMARY DITHER TYPE = NONE, WFSC (default)

Select the dither type for this observation. The WFSC dither type is specified in the NircamImagingSubpixel table in the PRD.

 Plus/Minus 8 Waves Defocus (F212N) Imaging Parameters

Filters

The following filters will be used to obtain the data.

Plus/Minus 8 waves defocus with F212N (DIVERSITY=ALL, ALL+187N, PM8)
Step number
SW PupilSW FilterLW PupilLW FilterSubarray

1 (-8 defocus)

WLM8

F212N

 CLEAR

F356W

FULL

2 (+8 defocus)

WLP8

F212N

CLEAR

F356W

FULL

Readout Pattern

READOUT PATTERN [READOUT PATTERN] = RAPID, BRIGHT1

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)The range is 1-10.

 Number of Integrations/Exposure

NUMBER OF INTEGRATIONS/EXPOSURE [NINTS] field specifies the number of times the integration is repeated. (warning)The range is 1-10.

   Plus 12 Waves Defocus Imaging Parameters

Filters

The following filters will be used.

Plus 12 waves defocus (DIVERSITY=ALL, all+187N)
Step numberSW PupilSW FilterLW PupilLW FilterSubarray

3 (+12 defocus)WLP8WLP4CLEARF356WFULL

Readout Pattern

READOUT PATTERN [READOUT PATTERN] = RAPID, BRIGHT1

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.

Number of Integrations/Exposure

NUMBER OF INTEGRATIONS/EXPOSURE [NINTS] field specifies the number of times the integration is repeated.

Plus/Minus 4 Waves Defocus Imaging Parameters

Filters

The following filters will be used.

Plus/Minus 4 waves defocus (DIVERSITY=ALL, ALL+187N)
Step numberSW PupilSW FilterLW PupilLW FilterSubarray

4 (-4 defocus)

WLM8

WLP4

CLEAR

F356W

FULL

5 (+4 defocus)

CLEAR

WLP4

CLEAR

F356W

FULL

Readout Pattern

READOUT PATTERN [READOUT PATTERN] = RAPID, BRIGHT

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.

Number of Integrations/Exposure

NUMBER OF INTEGRATIONS/EXPOSURE [NINTS] field specifies the number of times the integration is repeated.

 Plus/Minus 8 Waves Defocus (F187N) Imaging Parameters

Filters

The following filters will be used.

Plus/Minus 8 waves defocus with F187N (DIVERSITY=ALL+187N)
Step numberSW
Pupil		SW FilterLW
Pupil		LW
Filter		Subarray

6 (-8 defocus)

WLM8

F187N

CLEAR

F356W

FULL

7 (+8 defocus)

WLP8

F187N

CLEAR

F356W

FULL

Readout Pattern

READOUT PATTERN [READOUT PATTERN] = RAPID, BRIGHT1

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.

Number of Integrations/Exposure

NUMBER OF INTEGRATIONS/EXPOSURE [NINTS] field specifies the number of times the integration is repeated.

Change log

 

  1. PROPINSTJWST-91645 Added new subarray tables in Acquisition Subarray and LOS Subarray. Updated Introduction with new subarray information.


 

  1. PROPINSTJWST-91598 Added 0 as a legal value for Expected Number of WFC Commands.


December 16, 2022

  1. PROPINSTJWST-91549 In Filters sections, replaced LW filter F444W with F356W. Replaced F405M with CLEAR. In Introduction, added note that WAVEFRONT SENSING is required.
  2. PROPINSTJWST-91148 In Sensing Type section, rewrote developer note and added requirement for WAVEFRONT SENSING SR and its required values.


Version 7 (May 11, 2022)

  1. PROPINSTJWST-91468 Added developer note about warning for visit splitting distance to Acquisition Target Name section.


Version 6 (December 8, 2021)

  1. PROPINSTJWST-91490 Added constraint on solar system targets to Target parameter.


Version 5 (February 10, 2021)

  1. PROPINSTJWST-91471 - Added Primary Dither Type section.
  2. PROPINSTJWST-91469  - Added new filters to LOS Images Filters section.
  3. PROPINSTJWST-91476 - Added Exposures parameter to WFSC LOS Jitter Monitoring section.
  4. PROPINSTJWST-91389 - Added Expected Number of WFC Commands section.

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


Version 4 (September 24, 2019)

  1. PROPINSTJWST-88134 - Added description of TA=NONE option to Acquisition Target section.


Version 3 (April 19, 2019)

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


Version 2 (August 24, 2017)

  1. PR 87834 - add developer note to Sensing Type parameter


Version 1 (May 30, 2017)

  1. This is the converted Word File from Chapter 60.
  2. PR 87783 - revised TA NGroups
  3. PR 87895 - revised names of Number of Groups and Integrations