FGS External Calibration
JWST's FGS External Calibration template, available in the Astronomer’s Proposal Tool (APT), has parameters for specifying and scheduling observations.
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.
The FGS External Calibration template is to be used for all observations using the external calibration mode of the FGS, and this article describes allowed values for all parameters. If this template will be used for Multi-Instrument Multi-Field (MIMF) observations, you will need to add the Special Requirement WAVEFRONT SENSING with a value of SENSING_ONLY.
The FGS External Calibration 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 |
| Observation Comments | provide observation comments | text | optional |
| Target Name | select Target Name | choose from list | from Target list |
| Mosaic Properties | specify mosaic parameters | number | only available if TARGET TYPE is IMAGE |
| Special Requirements | specify special requirements | choose from list | if needed |
Template Specific Information | |||
| Target Name | select Target Name | choose from list | from Target list |
| Calibration Exposures | |||
| Pointing Type | select Pointing Type | PRIME, PARALLEL | |
| Target Type | select target type | IMAGE, DARK, SKYFLAT | |
| Dither | |||
| Primary Dithers | specify number of steps | 1-25 | |
| Subpixel Positions | select number of secondary dither positions | 1, 4 | |
| Detector | select detector | GUIDER1, GUIDER2 | |
| Readout Pattern | select readout pattern | FGS, FGSRAPID | |
| Number of Groups/Integration | specify number of groups per integration | number | |
| Number of Integrations/Exposure | specify number of integrations per exposure | number | |
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, Mosaic Properties, and Special Requirements.
Target Name
Select the TARGET NAME [TBD] from the list of targets previously entered (see list of targets).
Calibration Exposures
Pointing Type
POINTING TYPE = PARALLEL, PRIME (default)
This parameter enables the user to control whether the data will be obtained in parallel like other calibrations, or as a primary observation like regular science.
Note for developers:
- This field is not saved directly into the database.
- If PRIME, make TARGET NAME required, remove the NONE option, and make the default "None Selected." If a PARALLEL special requirement is present, remove it.
- If PARALLEL, set TARGET NAME = NONE (not changeable) and hide the Dither fields. If a PARALLEL special requirement is not present, add it.
Target Type
TARGET TYPE [TARG_TYPE] = IMAGE, DARK, SKYFLAT
This field specifies the how the ground system should process the data. Mosaics are available when Target Type is IMAGE.
Dither
Note for developers: Dither options are not available when used as a parallel.
Primary Dithers
PRIMARY DITHERS [PRIMARY_DITHERS] = 1, 2, 3, 4, 5, 6, 7, 8, . . .23, 24, 25
This parameter specifies the number of primary dither points.
Subpixel Positions
SUBPIXEL POSITIONS [SUBPIXEL_POSITIONS] = 1, 4
This parameter specifies the secondary dither points used for every primary dither point.
Note that selecting a value of 1 for both PRIMARY DITHERS and SUBPIXEL POSITIONS will result in a single image with no offset images.
Note for developers: see FGS Dither Parameters for dithering details.
Detector
DETECTOR [DETECTOR] = GUIDER1, GUIDER2
This field specifies the detector to be used to obtain the data.
For each exposure to be executed at each position in a dither pattern, specify the READOUT PATTERN, NUMBER OF GROUPS/INTEGRATION, and the NUMBER OF INTEGRATIONS/EXPOSURE.
Note for developers: A Guide Star special requirement is required and is added when DETECTOR is selected. The special requirement may not use the same guider as the DETECTOR.
Readout Pattern
READOUT PATTERN [READOUT PATTERN] = FGS, FGSRAPID
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.