Step-by-Step APT Guide for MIRI MRS Spectroscopy of a Late M Star

Instructions are provided for filling out JWST APT observing template for the MIRI MRS Spectroscopy of a Late M Star Example Science Program, where MIRI MRS is used to obtain a medium resolution spectrum of a late M star.

Dated material

This example was created pre-launch, and the APT has been updated since its creation. You may see differences in the appearance of the APT GUI and/or the warnings and errors in APT from what is shown herein.

Please refer to JWST Example Science Programs for more information.

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See also: MIRI Medium Resolution Spectroscopy, MIRI MRS APT TemplateJWST 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 MIRI MRS Spectroscopy of a Late M Star example science program.  

A filled out APT file can be accessed via the main menu via FileJWST Example Science Proposals MIRI 28 MIRI MRS Spectroscopy of a Late M Star in APT. The APT file was created with version 2020.4.1. There may be inconsistencies or additional warnings or errors with other versions of APT.

Fill out proposal information 

See also: JWST Astronomers Proposal Tool overview

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

After opening APT, we selected New JWST Proposal under the New Document pull-down field just above the tree editor (at the bottom-left of the top tool bar). On the active GUI window for the Proposal Information form, we entered the Title, Abstract, and Category of the proposal and kept Cycle at its default value.

Enter proposed targets

See also: APT Targets

Target forms are accessed by clicking on Targets in the tree editor. In this active GUI window, click on the New Fixed Target button to open the fixed target form. In the Name in the Proposal field, we entered SOMESTAR,  and for Category, we selected Star. The J2000 Coordinates entered were RA = 04 30 0.0000, Dec = +25 00 0.00.  For Description, we clicked the +/- button which opens a list of approved keywords and selected M stars.


See also: APT Observations

In the active GUI window for Observations, we clicked on the New Observation Folder button to specify the observing parameters for our program. In the Label field, we entered Late M Star. Note that while this label is not required, setting it is useful for visually organizing your observation folders in the tree editor when potentially many targets and/or instrument setups are used.

We clicked Observation 1 in the tree editor to open the observation template to be filled out. In the Instrument pull-down field in the active GUI window, we selected MIRI, and then selected MIRI MRS APT Template in Template. For Target, we selected SOMESTAR.

Filling out the APT observation template for MIRI MRS

See also: MIRI MRS APT Template, MIRI MRS Target Acquisition, MIRI MRS PSF and Dithering, MIRI MRS Simultaneous Imaging, MIRI MRS Recommended Strategies

Target acquisition

In the Target Acquisition Parameters panel, Acq Target is set to SOMESTAR (it is also possible to set the Acq Target to the target, as done in this example, or another nearby target), Acq Filter to FND, Acq Readout Pattern to FAST, and Acq Groups/Int set to 6.

MRS parameters

As discussed in the parent article and the Step-by-Step ETC Guide, a set of observations will be taken using all 3 grating settings for MIRI MRS: SHORT (A), MEDIUM (B), and LONG (C). Both short and long wavelength detectors are used.

The Primary Channel was set to ALL.

In order to set the dither pattern, we clicked the Add button under the Dithers panel, and chose a 4-Point dither pattern optimized for a POINT SOURCE in the NEGATIVE direction. 

The Simultaneous Imaging parameter was set to YES with Imager Subarray set to FULL.

In the Exposure Parameters panel, we clicked Add 3 times, each for the 3 available MRS grating settings. One click of the Add button brings up 3 rows: one each for the MIRI imager, MRS long wavelength detector, and MRS short wavelength detector.

Under the Wavelength Range column, for the first triplet of rows, the value was set to SHORT (A) for "MRSLONG" and "MRSSHORT" rows. For the second and third triplets of rows, the values were set to MEDIUM (B) and LONG (C), respectively. 

Under the Filter column, in the imager rows, F1130W was selected.

Under the Readout Pattern column, FASTR1 was selected.

Under the Groups/Int column, the values were set to 27 and 59 for the SHORT (A) and MEDIUM (B) gratings, respectively.  For the LONG (C) grating, for "MRSSHORT" the value is set to 49, while for "MRSLONG" the value is set to 98.  For the "IMAGER", the values are set to 27, 59, and 98 for the SHORT (A), MEDIUM (B), and LONG (C) gratings, respectively.

For the Integrations/Exp column, the values were set to 1 except for "MRSSHORT" for the LONG (C) grating, where the value is set to 2.

The values of Groups/Int and Integrations/Exp were determined by the iterative procedure described in the Step-by-Step ETC Guide.

Under the Exposures/Dith column, the value was set to 1 for all rows. 

Under the Dither column, the value was set to Dither 1 for all rows. 

Entries under the Total Dithers, Total Integrations, and Total Exposure Time columns were determined by APT from the previous entries.

The ID number of the ETC workbook used to calculate ETC parameters should be provided in the ETC Wkbk.Calc ID column, though an ETC workbook ID is not available for the Late M Star ETC sample workbook. 

The button in the last column, ETC, launches the JWST ETC.

Run Visit Planner

See also: APT Visit Planner

To determine the visibility window of our proposed observation, we ran the Visit Planner Tool.  First, click an observation in the tree editor. Then, click the Visit Planner button in the top tool bar, which changes the view in the active GUI window. Next, click the Run All Tools button at the right in the top tool bar. This shows us the observing window(s) for this target over the next ~19 months. APT assures us that all visits are schedulable.

Run Smart Accounting

See also: APT Smart Accounting

To minimize excessive overheads, we ran Smart Accounting from the Visit Planner page by clicking the Run Smart Accounting button at the bottom right of the page. This updated the Charged Time field in the Proposal Information form—the charged time for the observing program, including exposure time and overheads, is now accurately calculated.

Latest updates
    Updated to fix inconsistencies with the ETC Step-by-Step article that accompanies this example science program.
Originally published