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James Webb Space Telescope User Documentation

 

 

JWST's FGS Internal Flat template, available in the Astronomer’s Proposal Tool (APT), has parameters for specifying and scheduling observations.

Introduction

The FGS Internal Flat template is to be used for all observations using the internal flat mode of the FGS, and this article describes allowed values for all parameters. Note that this type of observation cannot be obtained as a parallel to normal science observations.  There is an implicit PCSMODE = COARSE for these observations.

Internal flats are obtained with illumination from one of the FGS calibration lamps (although the sky is being detected since there is no shutter). Exposures with predefined parameters are taken at each pointing in the specified dither pattern.

The FGS Internal Flat template consists of the following parameters:

FieldDetailsValues Notes
General Information   
Observation Numberassign observation number

number


Observation Labelprovide observation labeltextoptional
Observation Comments
provide observation commentstextoptional
Target Nameselect Target Namechoose from listfrom Target List
Special Requirementsspecify special requirementschoose from listif needed
Template Specific Information   
Target Nameselect Target Namechoose from listfrom Target List
Detectorselect detectorGUIDER1, GUIDER2
Calibration Type
select calibration typeFULLONLY, WITHSUBARRAYS
Primary Dithersselect number of steps1, 2
Subpixel Positionsselect subpixel position1, 2

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).

Detector 

DETECTOR [DETECTOR] = GUIDER1, GUIDER2

This field specifies the detector to be used to obtain the data.

Calibration Type 

CALIBRATION TYPE [CALIB_TYPE] = FULLONLY, WITHSUBARRAYS

This field specifies the calibration type to be performed.  If FULLONLY is selected, only full-frame exposures will be taken.  If WITHSUBARRAYS is selected, exposures of a set of 9 calibration subarrays will also be taken along with the full-frame exposures at each pointing in the dither pattern.

Primary Dithers

PRIMARY DITHERS [PRIMARY_DITHERS] = 1, 2

This parameter specifies the number of primary dither points.

Subpixel Positions

SUBPIXEL POSITIONS [SUBPIXEL_POSITIONS] = 1, 2

This parameter specifies the secondary dither points used for every primary dither point.

Note for developer: The table below specifies the sequence of exposures at each pointing when the calibration type is WITHSUBARRAYS.  The NUMBER OF INTEGRATIONS/EXPOSURE is 5 and the NUMBER OF GROUPS/INTEGRATION is 10 for all Internal Flat exposures.  The placeholder character n in aperture names refers to the guider in use (1 or 2).  For the FULLONLY calibration type, only the first (full-frame) exposure is performed at each pointing.  The list of FGS apertures can be found in Appendix H4 and the readout pattern definitions can be found in Appendix D.

Exposure #

SUBARRAY

APERTURE

READOUT PATTERN

1

FULL

FGSn_FULL

FGSRAPID

2

SUB128LLCORNER

FGSn_SUB128LL

FGS60

3

SUB128DIAGONAL

FGSn_SUB128DIAG

FGS60

4

SUB128CENTER

FGSn_SUB128CNTR

FGS60

5

SUB32LLCORNER

FGSn_SUB32LL

FGS840

6

SUB32DIAGONAL

FGSn_SUB32DIAG

FGS840

7

SUB32CENTER

FGSn_SUB32CNTR

FGS840

8

SUB8LLCORNER

FGSn_SUB8LL

FGS8370

9

SUB8DIAGONAL

FGSn_SUB8DIAG

FGS8370

10

SUB8CENTER

FGSn_SUB8CNTR

FGS8370

Change log

 Click here to expand...

Version 3 (April 19, 2019)

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


Version 2 (January 18, 2018)

  1. PR 89639 - Add Primary Dithers and Subpixel Positions.


Version 1 (May 8, 2017)

This is the converted Word file from Chapter 59.

 

Related links

Other FGS Templates:

FGS External Calibration

FGS Focus

Keywords

JWST FGS Internal Flat template

JWST FGS Internal Flat template parameters

Format definitions

Boldface italics type indicates the name of an APT parameter or a value for a parameter.

Green text indicates the name of the parameter used by Commanding.

On this page

JWST Proposal Parameters

Change log

Change log