NIRSpec Focus Template Parameters
JWST's NIRSpec Focus template, available in the Astronomer’s Proposal Tool (APT), is used to perform Focus Sweeps and Focus Adjustments.
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.
These parameters are required to perform Focus Sweeps and Focus Adjustments. Note that this type of observation cannot be obtained as a parallel to normal science observations.
|assign observation number||number|
|Observation Label||provide observation label||text||optional|
|Observation Comments||provide observation comments||text||optional|
|select Target Name||choose from list||from Target List|
|specify special requirements||choose from list||if needed|
|Template specific information|
|MSA Configuration||select MSA configuration||ALLOPEN, ALLCLOSED|
|Readout Pattern||select readout pattern||choose from list|
|Number of Groups/Integration||select number of groups/integration||number|
|Number of Integrations/Exposure||select number of integrations/exposure||number|
|Relative Position||specify relative postion||number|
Select the TARGET NAME [TARGET] from the list of targets previously entered (see list of targets ).
MSA CONFIG = ALLOPEN, ALLCLOSED
Select the configuration for the micro-shutter assembly (MSA).
FILTER [FILTER] = F140X, F110W, F070LP, F100LP, F170LP, F290LP, CLEAR
Select the name of the filter you wish to use.
For each exposure to be executed, specify the READOUT PATTERN, NUMBER OF GROUPS/INTEGRATION, and the NUMBER OF INTEGRATIONS/EXPOSURE.
READOUT PATTERN [READOUT PATTERN] = NRS, NRSRAPID NRSIRS2, NRSIRS2RAPID
This field specifies the readout pattern to be used to obtain the data.
Note that NUMBER OF GROUPS/INTEGRATION x NUMBER OF INTEGRATIONS/EXPOSURE must be less than 256 for NRISIRS2 and 1024 for NRSIRS2RAPID.
Number of Groups/Integration
NUMBER OF GROUPS [NGROUPS] specifies the number of groups in an integration.
Number of Integrations/Exposure
NUMBER OF INTEGRATIONS [NINTS] field specifies the number of times the integration is performed.
Note to developers: while the SUBARRAY is not explicitly given, its value is FULL for the purposes of calculating photon collection time.
The Refocus Mechanism Assembly (RMA) is moved from the initial position to a number of specified positions, and a focus exposure is taken at each specified position. If only the RMA start position is specified (RELATIVE POSITION = "0"), a single focus exposure is taken without moving the RMA, providing the data needed to measure the current image quality. If RELATIVE POSITION contains a single nonzero value, the RMA is moved once, adjusting the focus. In this case, focus exposures are taken at the initial and final positions, providing the data needed to measure the change in image quality. Finally, if RELATIVE POSITION contains more than one value, the RMA is moved sequentially to each of the specified positions. Regardless of the number of positions and initial direction, a sweep will always end in the initial position. Focus exposures are taken at each RMA position, providing the data needed to measure image quality as a function of RMA position.
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 motor steps (the range is -18400 to +18400), and are offsets from the current position. The exact order in which the positions will be executed will be determined by onboard scripts. Note that for an adjustment to the focus, only 1 position can be specified.
Version 3 (April 19, 2019)
- Editorial change (moved change log to main article)
Version 2 (October 16, 2017)
- PR 88047 - added restriction on NGroups x NINTs for IRS2 readout pattern
Version 1 (June 15, 2017)