Step-by-Step APT Guide for NIRISS AMI Observations of Extrasolar Planets Around a Host Star

Instructions are provided for filling out the AMI observing template in the Astronomer's Proposal Tool (APT) for the JWST NIRISS AMI Example Science Program.

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See also: NIRISS Aperture Masking Interferometry, NIRISS AMI Template APT Guide, JWST APT Video Tutorials

The Astronomer's Proposal Tool (APT) is used for submitting JWST proposals. There are multiple components to an APT submission: generic proposal information, target information, and exposure specifications for the proposed program. This guide discusses how to fill out the APT observing template for the "NIRISS AMI Observations of Extrasolar Planets Around a Host Star" Example Science Program

A filled out APT file can be accessed, after Aug. 24, '23, via the menu options FileJWST Example Science Proposals → NIRISS23 NIRISS AMI Observations of Extrasolar Planets Around a Host Star in APT. The APT file was created with version 2023.5 (release date Aug. 24, '23). There may be inconsistencies or additional warnings or errors with other versions of APT.

Fill out Proposal Information

Words in bold are GUI menus/
panels or data software packages; 
bold italics are buttons in GUI
tools or package parameters.

See also: JWST Astronomers Proposal Tool Overview

After opening APT, we selected New JWST Proposal under the New Document pull-down menu. On the Proposal Information page, we entered TitleAbstract, and Category of proposal and kept Cycle number at its default value.

Enter proposed Targets

See also: APT Targets, APT Target Confirmation Charts

Target information is entered by selecting Targets in the tree editor, which provides options in the active GUI window.  If a target has significant proper motion (> 10 mas /yr), we recommend fetching the coordinates and proper motion from the Gaia DR2 archive and inputting this information manually into APT. Note that the coordinate epoch from Gaia is 2015.5, so this needs to be added into the Epoch box.

We chose the New Fixed Target button so that we could add in the Gaia coordinates (J2000 CoordinatesRA = 23 07 28.8327; Dec = +21 08 2.53) and proper motion (Proper Motion RA = 108.30 mas/yr; Dec = -49.48 mas/yr). We updated the Category to Star and inserted Exoplanet System and F stars into the Description box.

We created a New Fixed Target for the PSF reference star (HD 218172) and entered the Gaia coordinates (J2000 Coordinates RA = 23 05 35.3371; Dec = +20 14 27.69) and proper motion (Proper Motion RA = 7.81 mas/yr; Dec = 20.86 mas/yr). We updated Category to Calibration and added Point spread function to Description.

We note that by clicking on Target Confirmation in the top tool bar, you can create target confirmation charts to verify that the target coordinates are correct and the telescope will be positioned in the expected place. The observations can be visualized onto various sky location using the Aladin visualization tool.


See also: APT Observations

Selecting Observations in the tree editor, we clicked on the New Observation Folder, and in the Label field, we entered Exoplanets in HD 218396 with NIRISS AMI.

Create observation for source (HD-218396)

We next clicked Observation 1 in the tree editor to open the observation template in the active GUI window. In the Instrument pull-down menu, we selected NIRISS, and then selected the NIRISS Aperture Masking Interferometry template in the Template pull-down menu.  Note that only parameters of interest to NIRISS AMI are shown in the GUI.  In the Target pull-down menu, we selected HD-218396 which we defined above. We added HD-218396 into the Label field.

Create observation for PSF reference star (HD-218172)

We returned to the observation template and clicked Add to create an observation template for the PSF reference star. Similar to the steps above, we selected NIRISS from the Instrument pull-down menu and selected the NIRISS Aperture Masking Interferometry template. In the Target pull-down menu, we selected HD-218172. We added HD-218172 into the Label field.

Complete APT observation template for NIRISS AMI

See also: NIRISS AMI Template APT Guide, APT Target Acquisition

Fill out APT template for PSF reference star (HD-218172)

Target acquisition

For this science program, we perform the TA on the target, so in the NIRISS AMI APT Observation Template we kept the acquisition target in the Target ACQ pull-down menu at its default value of SAME TARGET AS OBSERVATION. Using the results from the ETC calculations, we selected AMIBRIGHT for Acq ModeNISRAPID for Acq Readout Pattern, and Acq Groups/Int. For your own tracking purposes, it is recommended you include the ETC workbook and calculation ID number in the Acq ETC Wkbk Calc ID field so the TA SNR calculations can be verified by Instrument Scientists during technical reviews after the proposal is accepted.  In this example, we do not include an ETC workbook ID number in the provided APT file since a unique ID number is generated when an example workbook is added to a user's list of workbooks.

AMI Parameters

We selected NONE for both Primary Dithers and Subpixel Positions, and selected the SUB80 Subarray. We selected the F480M Filter and updated Groups/Int to 9 and Integrations/Exp to 9899, based on our ETC calculations; the only available Readout Pattern is NISRAPID since we chose a subarray. 

We selected False for Direct Image since we are not taking a direct image with this program. In the PSF Reference Observations box, we click the checkbox next to This is a PSF Reference Observation.

Fill out APT template for source (HD-218396)

Target acquisition

Similar to the PSF reference star, we perform target acquisition on the source, so we choose SAME TARGET AS OBSERVATION in the Target ACQ pull-down menu. We selected AMIBRIGHT for Acq ModeNISRAPID for Acq Readout Pattern, and Acq Groups/Int,based on results from the ETC calculation.

AMI parameters

We selected NONE for both Primary Dithers and Subpixel Positions, and selected the SUB80 Subarray. We selected the F480M Filter. Based on our ETC calculations, we need 5 Groups/Int and 10537 integrations in order to detect an adequate number of photons for analysis. Since there is a limit on the number of integrations of 10000, we break the observation up into 2 exposures. We define an exposure with the NISRAPID Readout Pattern (the only one available since we chose a subarray), 5 Groups/Int, and  5269 Integrations/Exp. We then Duplicate that exposure so we have 2 exposures with the same exposure parameters that add up to the needed exposure time to detect 1010 photons.

We selected False for Direct Image. In the PSF Reference Observations box, we selected the checkbox next to HD-217783 to associate the target with the PSF reference star so that the JWST pipeline will calibrate HD-218396 with HD-218172.

Define special requirements

See also: APT Special Requirements

The observations of the target and the PSF reference star now need to be linked together (for reasons explained in the introduction for this science program), using special requirements. After clicking on the Special Requirements tab, we added a Timing requirement of Group/Sequence Observations Link, selected both the target (HD-218396 (Obs 1)) and PSF reference star (HD-218172 (Obs2)), and chose the Non-interruptible option. 

Run Visit Planner

See also: APT Visit Planner

The APT Visit Planner checks the schedulability of an observation and whether guide stars can be found to support the observation. To check the schedulability of these linked observations, we made sure one of the observations was selected in the Tree editor, we clicked on the Visit Planner icon in the top tool bar, and then clicked on Update Display in the active GUI. The Visit Planner returned with a confirmation that the set of observations is schedulable (green check next to both observations).

Run Smart Accounting

See also: APT Smart Accounting

To minimize excessive overheads, we ran Smart Accounting from the Visit Planner page by selecting the Run Smart Accounting option. The charged time for the observing program, including exposure time and overheads, is now accurately calculated.

Latest updates
    Updated with new ETC 3.0 sensitivities (ETC 3.0 release: 24 Aug. '23).

Originally published