NIRSpec MPT - Plans
The Plans pane in the MSA Planning Tool provides the user with a view of observation planning results from the MPT, including statistical information about the generated configurations. It is in this pane where plans can be merged and observations are finally created.
Once a plan is created using the Planner or in the MSA Planning Tool (MPT), or the Manual Planner, the user can review the results with the help of the information in the Plans tab. This tab contains information to help assess the merit of the created configurations and it also provides some statistics that users might find useful before creating a final observation.
The MPT Plans tab has the format shown in Figure 1, where 5 sections are highlighted. These are described in detail below.
- Section 1: Plan & Description
- Section 2: Pointings
- Section 3: Targets and Coverage
- Section 4: Timing
- Section 5: Plan operations and Observation creation
MPT Section 1. Plan and Description
This section contains a pull-down selection of the plans generated in your APT session or saved in your APT file from an earlier session, and a Description box listing the parameters used in the particular Plan selected from the pull-down menu. Since several plans can be saved in the same APT file, the user should first select a Plan by name.
MPT Section 2. Pointings
The MPT generates configurations based on the parameter 'Number of Configurations'1 defined in the Planner pane. For the example shown in Figure 1, four exposures were generated, each with a slightly different pointing and different MSA configuration. These four exposures are listed in the Pointings table (Figure 1, Section 2) with names that concatenate the MSA configuration ID and exposure ID. For example, in this case we have four configurations c0, c1, c2, c3 each with one exposures e0, so the names are c0e0, c1e0, c2e0 and c3e0. For each exposure listed here, the Right Ascension, Declination, and Aperture Position Angle (shown as "Orient"), are shown (see Figure 2).
- Page not found for multiexcerpt macro.
NIRSpec MPT: Plans, Video 1: Plan Description and Pointings
Figure 3 shows the MSA Shutter View of configuration c0e0. This is a pop-up window that appears after clicking the Show button. It may take a few seconds to generate. In the MSA Shutter View, the four MSA quadrants are shown. From left to right and top to bottom, the quadrant ID is : 3, 1, 4, 2. Over-plotted are the Primary sources (green), the Filler sources (blue), and the Contaminants (black). A source is classified as a contaminant if it is a source in the Catalog, falling into an open shutter but is not the source that the shutter was intended for.
Tables 1 and 2 explain the color codes for shutters and sources, respectively.
Clicking on a Catalog or Candidate Set in the list will display it (if it is not already there). In order to remove the Catalog from the display simply command-click on the Catalog that you want to remove from view.
Zooming to shutter level, as shown in Figure 4, it is possible to view individual sources and slitlets.
Note that hovering with the mouse over a shutter will display the shutter location in the MSA (quadrant, shutter ID in dispersion, shutter ID in cross-dispersion). Hovering the mouse over a target symbol will display the Source ID from the input Catalog.
It is possible to save a completed MSA configuration using the Export to CSV button. Export to CSV produces an ASCII file of comma-separated values. The exported csv file has values of '0', '1', 's', or 'x' for each commanded open, commanded closed, failed open, or failed closed shutter, respectively. These exported MSA configuration files can be imported to the MSAViz tool to view of how the spectra will look on the detector, for example. Expert users can modify these MSA configuration csv files outside of APT, and later import them into the Manual Planner with Import to CSV. That workflow is not recommended for the general user, however.
An image of the configuration can additionally be saved from the MSA Shutter View in SVG format.
The failed shutter positions are inherited from the current MSA operability reference data that the MPT utilizes during plan creation.
Table 1. Shutter color and meaning
|Shutter color||Description/ meaning|
This color indicates shutters that were masked during the creation of the MSA configuration.
Adding a new source slitlet anywhere in this area will cause spectral contamination on the detector of the added source's spectrum and spectra of other existing targets in the MSA configuration.
The number of shutters in light orange indicates how complete is the utilization of the MSA.
|orange||The shutter is commanded open and part of the slitlet.|
|light red||The area marked in this color is impacted by the presence of a failed opens shutter (several rows may be impacted completely or partially.)|
|red||Shutter is failed open.|
|gray||Shutter is either failed closed, vignetted, or is in a shorted row or column. These types of shutters are avoided during planning. They cannot be used in any observation.|
This area is available. MPT did not find sources to fill this space.
Only the white areas of the MSA configuration would be available to add extra background shutters, for example, with the Manual Planner.
Table 2. Symbol color and meaning
|green dot||Source from the Primary Candidate List that is a successful MSA target in the displayed exposure.|
|green plus symbol||Source from the Primary Candidate List that is a successful MSA target in another exposure of the plan.|
|blue dot||Source from the Filler Candidate List that is a successful MSA target in the displayed exposure|
|blue plus symbol||Source from the Filler Candidate List that is a successful MSA target in another exposure of the plan.|
|black dot||Contaminant source present on this exposure.|
|black plus symbol||Contaminant source present in another exposure of the plan.|
There is a second exposure view present in the pop-up window called the Collapsed Shutter View which can be seen by clicking Collapsed Shutters icon as shown in Figures 3 and 5. This view (Figure 5) shows each target's position in its own shutter in an exposure, all plotted together in a single virtual shutter. Clicking on a symbol will indicate the source ID and will highlight it in the color magenta. It will also highlight the same source if it is present in a second pop-up exposure view of this or another exposure in the plan.
NIRSpec MPT: Plans, Video 2. Aladin Viewer
The Add shutters plane to Aladin button located at the bottom of the MSA shutter view will draw a sketch of the shutters that comprise the target slitlets on the Aladin sky view, as shown in Figure 6. The shutters in this case are drawn in green while the sources from two candidate sets are shown as red and blue crosses.
Downloading images from the server to Aladin can sometimes cause APT to come to a halt if the image is large. Make sure to save your APT session before attempting to load an image, or load the image before running MPT.
MPT Section 3. Targets and Coverage
Section 3 (Figure 1) contains basic statistics about the Plans and target sets. A target set is the subset of sources from the input Catalog that are observed over a complete set of dithers specified in the plan. During plan generation, one or more target sets may be created depending on the number of MSA configurations the user specified. For example, if a set of dithers requires 3 MSA configurations to complete a target set, then if the user had specified 6 MSA configurations as the Number of Configurations in the NIRSpec MPT - Planner, the final plan would contain two target sets.
Target results can be filtered in different ways to help users assess their plans. First, click to highlight exposures you are interested in within the Pointings table (Section 2) (e.g., all exposures for the first target set, or, one set of dithers). The NIRSpec MOS observation sequences are ordered to minimize the reconfiguration of the MSA, with nod position changing most frequently from row to row in the table, then grating, then MSA configurations (for each primary dither).
When you first land in the Plans pane, by default all exposures are selected at once. Next, select the Target Set Operation that you would like to perform on the selected exposures, along with a Target type (see Figure 9). For example, suppose you have a plan constructed with a single primary dither, and a set of 3-shutter nods at each primary pointing. It would have 2 MSA configurations, each with 3 exposures. If you are interested in seeing all of the Primary targets that are successfully observed through the dithers, highlight all the exposures, choose Target Set Operation = "Targets in all selected exposures", and select Target type = "Primary targets".
The results of filtering will be shown in the space below the filters. The number of targets will be summed and displayed, followed by a table with an "x" indicating which exposure contain a given target.
A histogram depicting number of targets as a function of its number of exposures (the coverage) is also plotted at the bottom of the Plans Tab. This plot is useful to rapidly assess the completeness of the configuration. The Send to Aladin button shows the targets using the Aladin interface as described in Section 2.
MPT has an added feature that could be useful for visualizing the location of sources on the MSA or within slitlets: If the MSA Shutter View or Collapsed Shutter View are open, clicking a source in the target table will highlight it in magenta on the viewer. (This feature will not work correctly if the user has re-ordered the targets in the Targets table by clicking on one of the column labels. Doing so will cause the target info to get out of sync between windows. Re-load the Plan in the pull-down menu on the Plans pane to re-initialize the ordering of targets in the Plan.)
MPT Section 4. Timing
Section 4 is primarily for testing purposes. It lists the number of configurations that were generated in the Plan, the number of targets that are observed, the durations, and a score for the Plan. The iteration duration is the time it took to create the first target set, and the Planning Duration gives the total time it took to make the Plan. The score is a number used by MPT to quantify and select the most successful plan. The higher the score the better.
MPT Section 5. Plan operations and Observation creation
Section 5 contains four buttons:
- Delete Plan
- Manual Editing
- Merge Plans
- Create Observation
This button allows the user to discard the selected plan. In cases where many test plans have beed created, deleting unused plans can improve APT performance. In particular, opening a saved APT file can take long time when it contains many MPT plans.
By definition, an observation is created from a single plan. The Merge Plans button was added to allow observers to put one or more independently developed Plans into a single Plan, in order to create one Observation. This is especially useful for minimizing overheads for guide star and target acquisitions when all plan pointings are in close proximity (within the visit splitting distance).
Before creating an observation, users will create several plans and assess their quality and completeness. It is then possible to merge the best plans into one single plan. This might be done, for example, if prism and grating MOS observing plans were generated separately to ensure high multiplexing with no spectral overlap in any exposures. By clicking on the Merge Plans button, the user is prompted to select which plans to merge, as shown in Figure 10. Simply select the plans that you want to merge, and assign a name to the resulting plan.
it is not possible to merge a manual plan and one created automatically in MPT. The workaround is to port the automatic plan to the Manual Planner, save it as a manual plan, and merge it there with another manual plan.
The purpose of the Create Observation button is to gather all the information from the current plan, and send it to the MOS observation template to populate pointings, MSA configurations, instrument and exposure parameters. Doing this will also construct Visits within the Observation. The visit structure will depend on the list and order of pointings in your observation, and the Visit splitting distance for the observation pointing. You may learn more about this in the article APT Visit Planner.
The user may notice that there is a "dummy" Observation that is initially created by APT. This observation is extraneous and should be deleted prior to running MPT. MPT will instead populate a new Observation with observation parameters created from MPT.
There are some known problems with manipulating MPT-created Observations in APT.
- MPT-created observations are linked to the Plans used to make them. The Plan used to make an Observation should not be deleted without first removing the Observation.
- MSA Observations created with MPT cannot be successfully copied and pasted to another Observation in the same APT folder. The AUTO-Target from the parent is not copied to the new Observation.
- MSA Observations created with MPT cannot be successfully copied to another APT Folder. The Plans of the parent folder will not be copied to the new folder.
- Once an Observation is created with MPT, its exposure parameters, including the exposure time, cannot be altered. A new Plan is required.
After the Plan is saved, and an Observation is created from it, there is also a mechanism for saving the planned target info from exposures made with the Manual Planner or those automatically-generated using the MPT. The target positions, pointing, and shutter information can be saved to a .csv file. To do so, click on the File item from the main menu at the very top of the computer screen. From the pull-down menu, select Export → MSA Target Info. This mechanism makes it possible to track target coverage through all exposures of an Observation outside of APT. These files are ASCII and readable by Excel, for example.
Completing the Observation parameters
Finally, after a MOS Observation is created, return to the Observation Summary view in APT. At the Observation level in the tree, you will need to complete the observation form by selecting Confirmation Image parameters, if desired, and filling in the Observation Special Requirements needed for MOS observations - There are timing and ON Hold special requirements to add. More details can be found in the MOS Roadmap.
Karakla, D. et al. 2014, Proc. SPIE 9149
The NIRSpec MSA Planning Tool for multi-object spectroscopy with JWST
Updated March 29, 2018
Added tip to merge plans
Updated July 6, 2017
Added Video 1: Plan description and pointings
Added video 2: Aladin viewer
Added video: Using the Aladin viewer in MPT
Published June 2, 2017