WFSC Global Alignment Template Parameters
JWST's WFSC Global Alignment Template will be executed several times during commissioning to reduce the observed segment level Wavefront Error by refining the Secondary Mirror position and making coarse corrections for all Primary Mirror Segment Arrays.
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.
Red text indicates restrictions on a parameter.
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.
Wavefront Sensing and Control - Global Alignment will be executed several times during commissioning to reduce the observed segment level Wavefront Error by refining the Secondary Mirror position and making coarse corrections for all Primary Mirror Segment Arrays. Prior to the Global Alignment Measurements, the primary mirror segments are configured so that there is a separate image of the target star for each segment. There will be a total of 18 images per target placed in a pre-determined hexagonal array.
A typical observation will include the following:
- Enter FGS guide star tracking on one of the 18 guide star images
- Take a NIRCam image
- Perform the specified group of mirror moves
- Optional Small Angle Maneuver (SAM) to compensate for boresight changes due to the mirror moves
- Take another NIRCam image
- Take an FGS image to record new guide star PSFs
The following parameters are used to define Wavefront Sensing and Control Global Alignment Operations. A Wavefront Control File (provided by the WFSC Scientist) will be attached to each visit by the PPS Operator.
In addition to the following template parameters, this template will have the Special Requirement WAVEFRONT SENSING added with a default required 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 Global Alignment Template consists of the following parameters:
| Field | Details | Values | Notes |
|---|---|---|---|
| General Information | |||
| Observation Number | assign observation number | number | |
| Observation Label | provide observation label | text | optional |
| Observations Comments | provide observation comments | text | optional |
| Special Requirements | specify special requirements | choose from list | if needed |
| Template Specific Information | |||
| Target | enter target name | choose from list | |
| Global Alignment Iteration Type | select type | choose from list | |
| Expected Number of WFC Commands | specify Expected Number of WFC Commands | number | 1 - 2100 |
| NIRCam Parameters | |||
| Module | select Module | A, B | |
| Short Wavelength Filter | select Short Filter | F200W, F212N | |
| Long Wavelength Filter | select long filter | choose from list | |
| Readout Pattern | select readout pattern | RAPID, BRIGHT | |
| Number of Groups/Integration | specify number of groups/integration | number | |
| Number of Integrations/Exposure | specify number of integrations/exposure | number | |
| FGS Parameters | |||
| Number of Groups/Integration | specify number of groups/integration | number | |
| Number of Integrations/Exposure | specify number of integrations/exposure | number | |
General Information
The following parameters are generic to all templates, and are not discussed in this article: Observation Number, Observation Label, Observations Comments, and Special Requirements.
Target
Select the TARGET NAME from the list of targets previously entered.
Solar system targets may not be used with this template.
Global Alignment Iteration Type
GA ITERATION TYPE [GATYPE] = ADJUST1, ADJUST2, BSCORRECT, CORRECT, CORRECT+ADJUST
This field specifies the type of Global Alignment operation (see Table 1) to be executed in this observation. Select ADJUST1 or ADJUST2 to obtain more OTE status data. Select BSCORRECT to improve the wavefront error and modify the JWST boresight. Select CORRECT to improve the wavefront error without affecting the JWST boresight. Select CORRECT+ADJUST to improve the wavefront error followed by more OTE status data collection.
If GA ITERATION TYPE = BSCORRECT you will be prompted for the small angle maneuver (Delta X [delta_x] and Delta Y [delta_y] needed to re-center the boresight; each take values from -180 to +180 arcsec). Note that these offsets are in the FGS Ideal Coordinate System.
Table 1. Contents of Wavefront Control (WFC) Files for each GA type
| GA Type | WFC file contents |
|---|---|
| ADJUST1 | one group of diversity moves |
| ADJUST2 | two groups of diversity moves, one positive and one negative |
| BSCORRECT | one group of SM tilt and/or translations and any necessary PMSA moves |
| CORRECT | one group of corrections (not including SM tilt and/or translations) |
| CORRECT+ADJUST | one group of corrections (not including SM tilt and/or translations) and one group of diversity moves |
Expected Number of WFC Commands
EXPECTED NUMBER OF WFC COMMANDS = 1 - 2100
The number of WFC commands expected with this proposal. Default is 170.
NIRCam Parameters
The parameters listed below will be used for all NIRCam images in this observation.
Module
MODULE [MODULE] = A, B
This parameter specifies the MODULE to be used to obtain the data.
Short Wavelength Filter
SHORT FILTER [FILTSHORT] = F200W, F212N
Select the name of the SHORT FILTER [FILTSHORT] you wish to use.
Long Wavelength Filter
LONG FILTER [FILTLONG] = F322W2, F460M, F480M, F323N+F322W2
Select the name of the LONG FILTER you wish to use.
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
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] = 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. The value must be between 1 and 10.
Number of Integrations/Exposure
NUMBER OF INTEGRATIONS/EXPOSURE [NINTS] field specifies the number of times the integration is repeated. The value must be between 1 and 10.
FGS parameters
The parameters listed below will be used for all FGS images in this observation.
Number of Groups/Integrations
NUMBER OF GROUPS/INTEGRATON [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.
Note for developers: Visits created from this template should be marked as WFS visits by APT and as WFSC visit type in VSS.