NIRISS Aperture Masking Interferometry (AMI) Template Parameters
JWST's Aperture Masking Interferometry (AMI) template, available in the Astronomer’s Proposal Tool (APT), has parameters for specifying and scheduling observations.
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.
The NIRISS Aperture Masking Interferometry (AMI) template is used for the AMI mode of NIRISS, and this article describes allowed values for all parameters. The AMI template includes an option to take direct images; the direct imaging mode of NIRISS is discussed in more detail in NIRISS Imaging Template Parameters and the NIRISS Imaging APT Template article. Advice on how to choose values which optimize your science can be found in the NIRISS Aperture Masking Interferometry APT Template article.
The NIRISS AMI 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 |
| specify ETC Workbook Calculation ID | number | ||
| Special Requirements | specify special requirements | choose from list | if needed |
| Template Specific Information | |||
Target Acquisition Parameters | |||
| select acquisition target | choose from list | ||
| Acquisition Filter | default value | F480M | |
| select acquisition mode | AMIBRIGHT, AMIFAINT | ||
| select acquisition readout pattern | NIS, NISRAPID | ||
| select number of groups per integration | choose from list | ||
AMI Exposures | |||
| select subarray | choose from list | ||
| select number of steps | choose from list | ||
| select number of positions | choose from list | ||
| select filter name | choose from list | ||
| specify whether a direct image should be taken | checkbox | ||
| select readout pattern | choose from list | ||
| specify number of groups per integration | number | ||
| specify number of integrations per exposure | number | ||
Direct Imaging Parameters (optional) | |||
| select number of steps | choose from list | ||
| select readout pattern | choose from list | ||
| specify number of groups per integration | number | ||
| specify number of integrations per exposur | number | ||
| PSF Reference Observations | |||
| This is a PSF Reference Observation | indicate if PSF | ||
| PSF Reference Observations | select PSF Observations | choose from list | |
| Additional Justification | indicate that there will be no specific PSF Obs | ||
General Information
The following parameters are generic to all templates, and are not discussed in this article: Observation Number, Observation Label, Observations Comments, Target Name, ETC Wkbk. Calc. ID, and Special Requirements.
Target Acquisition Parameters
Acquisition Target
If an offset star is to be used for the target acquisition observation, select the ACQUISITION TARGET [TACQ TARGET] from the list of targets previously entered. When the science target is a Solar System target, the acquisition target MUST be the science target. Or, if no target acquisition is needed, select ACQUISITION TARGET to be NONE; the latter option is only allowed if SUBARRAY is FULL see Subarray in the NIRISS Aperture Masking Interferometry APT Template article).
Notes for developers:
- The ACQUISITION TARGET NAME field should always be present, but should be defaulted to the SAME TARGET AS OBSERVATION.
- If the acquisition target is different from the science target, APT should provide a warning if the distance between the ACQ and Science targets is greater than the Visit splitting distance found in the PRD. Also, if there are multiple pointings within a visit, then the rules have to apply to the greatest separation between acq target and pointing within the visit.
- If the observation target is a fixed target, remove solar system targets from the acquisition target options. If the observation target is a Solar system target, remove all options from the acquisition target list except for the observation target and NONE.
Acquisition Filter
The Target Acquisition FILTER is F480M.
Acquisition Mode
ACQUISITION MODE [TACQ MODE] = AMIBRIGHT, AMIFAINT
This field specifies the target acquisition mode to be used to obtain the acquisition data for a “bright” or “faint” target. In this context, "bright" refers to M-band magnitudes in the range 3.0 ≤ M ≤ 9.3 (in the Vegamag system), while "faint" refers to 9.3 ≤ M ≤ 14.5.
Acquisition Readout Pattern
READOUT PATTERN [TACQ PATTERN] = NIS, NISRAPID
This field specifies the readout pattern to be used to obtain the acquisition data.
Note for developer: The NIS option is only available when TACQ MODE = AMIFAINT.
Acquisition Number of Groups/Integration
NUMBER OF GROUPS/INTEGRATION [TACQ NGROUPS] = 3, 5, 7, 9, 11, 13, 15, 17, 19
This parameter specifies the number of groups in an integration.
Note that the NUMBER OF INTEGRATIONS/EXPOSURE is set to 1 for target acquisition observations.
AMI Parameters
Dither Pattern
The following parameters are used to define dithers (or dither patterns). Dithers for AMI science exposures are specified independently of direct images. For more details about dither patterns, see Direct image in the NIRISS Aperture Masking Interferometry APT Template article.
Primary Dithers
PRIMARY DITHERS [PRIMARY DITHERS] = NONE, 2, 3, 4 (default)
This parameter indicates the number of steps in the primary dither pattern.
Subpixel Positions
SUBPIXEL POSITIONS [SUBPIXEL POSITIONS] = NONE (default), 5, 9, 25
This parameter indicates the number of subpixel positions, which will be executed at each step of the primary dither pattern.
Note for developers: see NIRISS Dithering Details for dithering details.
Subarray
SUBARRAY [SUBARRAY] = SUB80 (default), FULL
This parameter specifies the region of the SCA detector that is to be read out. For more details about these subarrays, see Subarray in the NIRISS Aperture Masking Interferometry APT Template article.
Filter(s)
Exposures are grouped by filter. For each set of exposures, specify the FILTER, DIRECT IMAGE, READOUT PATTERN, NUMBER OF GROUPS/INTEGRATION, and the NUMBER OF INTEGRATIONS/EXPOSURE. For more information on defining an exposure specification, see Filters in the NIRISS Aperture Masking Interferometry APT Template article.
Filter Names
FILTER [FILTER] = F277W, F380M, F430M, F480
This parameter specifies the filter to be used for the exposure. For the filter bandpasses, see NIRISS Filters.
Direct Image
DIRECT IMAGE [DIRECT_IMAGE] = FALSE (default), TRUE
Select the DIRECT IMAGE checkbox to specify that a direct image exposure should be taken corresponding to the selected AMI exposure. The default is for the checkbox to be not selected. When DIRECT IMAGE is selected, a new exposure is added to Direct Image Exposures on the template form.
Readout Pattern
READOUT PATTERN [READOUT PATTERN] = NISRAPID (default), NIS
This field specifies the readout pattern to be used to obtain the AMI image. The NIS option is only available when SUBARRAY = FULL.
Number of Groups/Integration
NUMBER OF GROUPS/INTEGRATION [NGROUPS] specifies the number of groups in each AMI image integration. For readout pattern NIS, the range is 1-200, while for NISRAPID the range is 1-800.
Number of Integrations/Exposure
NUMBER OF INTEGRATIONS/EXPOSURE [NINTS] field specifies the number of times the AMI image integration is repeated within an exposure. The range is 1-10000
Direct Imaging Parameters
Displays all direct image exposures for the filter group selected under AMI Parameters. Each direct imaging exposure corresponds to a selected AMI exposure.
- To add a direct image exposure, select the Direct Image checkbox in an AMI exposure.
- Direct Image Exposures are numbered with the same number as the corresponding AMI exposure.
- All exposure specifications must be entered for the direct image.
- To remove the direct image exposure, de-select the Direct Image checkbox for the corresponding AMI exposure.
Image Dithers
IMAGE DITHERS [IMAGE DITHERS] = NONE, 2, 3, 4 (default)
This field specifies the number of steps in the dither pattern used to obtain the direct image.
Readout Pattern
READOUT PATTERN [READOUT PATTERN] = NISRAPID (default), NIS
This field specifies the readout pattern to be used to obtain the direct image. The NIS option is only available when SUBARRAY = FULL.
Number of Groups
NUMBER OF GROUPS [NGROUPS] specifies the number of groups in each direct image integration. For readout pattern NIS, the range is 1-200, while for NISRAPID the range is 1-120.
Number of Integrations
NUMBER OF INTEGRATIONS [NINTS] field specifies the number of times the direct image integration is repeated within an exposure. The range is 1-65535
Note for developer: The direct image flag should be set to YES for each direct image exposure specification in the database to distinguish between the required AMI image and direct image. The order of operation is all the AMI exposures are executed, followed by all the Direct Images. Since the same fields in the database are used for both AMI and Direct, APT needs to populate the exposures in this order.
PSF Reference Observations
AMI observations generally have associated PSF reference observation(s). These observations should be done back-to-back using the SEQUENCE NON-INT special requirement. Warning and errors will help guide the user to correctly set up these links.
This is a PSF Reference Observation
Choosing this option indicates that this observation is a PSF observation.
Note to developer: If this option is chosen, display on the GUI "exclusive access period will be 0 months".
PSF Reference Observations
If this is a science observation, designated PSF Reference Observations must be selected from this list. (The exception is for a "self reference survey" where all observations serve as PSF observations for each other. In this case select the science observations which will be used.)
Note to developer: Only list observations which use the same instrument and same filter (ordered so that ones with the PSF Reference Observation checked come first and then the ones without the check).
Additional Justification
Choosing this option indicates that this observation will not have a separate designated PSF observation because it is part of a self reference survey which will be described in the science justification.
Note to developer: It is an error to have nothing checked in the PSF Reference Observations. And it is still an error for a science observation to only choose other science observations and not choose a designated PSF observation, but in that case choosing the Additional Justification option replaces that error with a warning that a self reference survey must be justified.