FGS Focus

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

Introduction

 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.

The FGS Focus template is to be used for all observations using the focus 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.

The focusing mechanism will be scanned through a specified number of relative positions centered on the expected focus, and then returned to the starting position.  At each point in the focus sweep, a wide-band image will be obtained for analysis. If only one position is specified, the focus is maintained at this new position (i.e. the focus is reset).

The FGS Focus template consists of the following parameters:

FieldDetailsValues Notes
General Information   
Observation Number
assign observation number

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   
Detectorselect detectorGUIDER1, GUIDER2
Readout Patternselect readout patternFGS, FGSRAPID
Number of Groups/Integrationspecify number of groups per integrationnumber
Number of Integrations/Exposurespecify number of integrations per exposurenumber
Relative Positionsspecify array of positionsarray of 1-20 positions

General Information 

Target Name   

Detector 

DETECTOR [DETECTOR] = GUIDER1, GUIDER2

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

Exposure Specifications

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] = 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.

Relative Positions 

The RELATIVE POSITION [DELTARRAY] parameter specifies an array of 1 to 20 positions that the focus is to be moved to; note that each position must be unique (i.e. a given value can only appear once in the list).  The positions are given in millimeters (range +26.73 to -26.73) in the OTE frame, and are offsets from the current position. The exact order in which the positions will be executed will be determined by the onboard scripts.  There are 3 unique cases:

  1. to perform a focus sweep (returning to the original focus), enter from 2 to 20 positions
  2. to reset the focus, specify only 1 position
  3. to use the default scan (10 steps of 0.4mm from -2.0 to +2.0), select the checkbox

Note for developers: when the checkbox for default scan is selected, the Relative Position input area should be inactive.

Change log

 Click here to expand...

Version 3 (April 19, 2019)

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


Version 2 (September 18, 2017)

  1. PR 87895 - updated Exposure field labels to Groups/Integration and Integrations/Exposure


Version 1 (May 8, 2017)

This is the converted Word file from Chapter 59.