JWST Moving Targets in APT
Summary of how JWST Astronomer's Proposal Tool (APT) can be used by solar system observers, with description of current APT limitations and walk through examples for creating a proposal for various classes of solar system targets
The JWST Astronomer's Proposal Tool (APT) is used for designing JWST proposals and contains special options for solar system ("moving") target observations. Steps before APT are to estimate exposure times with the Exposure Time Calculator and to quick-look your target's visibility using JPL Horizons and the Moving Target Visibility Tool (MTVT). The latter tools could cut down the time you spend testing the schedulability of observations in APT. With these pre-steps complete, you will be ready to start designing your APT proposal. A typical workflow would be:
- Define the target. You have tremendous flexibility to identify specific targets and pointing positions relative to targets using a system of target Levels. Level 1 targets are solar system bodies directly orbiting the Sun (planets, comets, and asteroids), while Level 2 and Level 3 targets are moons of, or positions on or relative to, the specified Level 1 or Level 2 target. Moving targets are also divided in APT between Standard Targets and minor bodies (Asteroids and Comets). For Standard Targets, ephemerides can be computed using information directly accessible to and maintained by APT. For the minor bodies, you must supply orbital elements, either manually or by retrieving them from the JPL Horizons system using the built-in APT tool. See Tutorial on Creating Solar System Targets in APT.
- Define the observations. For each observation you must select a target, an instrument, and a science template. Note that moving targets can be observed with any instrument, any observing template, although not all templates are optimal for solar system observations; see the page on Instrument-Specific Considerations for Moving Targets. Also see Tutorial on Creating Solar System Observations in APT.
- Define scheduling constraints on the observations. These include date, time, separation from another body, apparent rate of motion, rotational phase, phase angle, etc. See also Tutorial on Creating Solar System Observations in APT.
- Evaluate the schedulability of observations.
- Submit your proposal.
You are advised to first read JWST Astronomers Proposal Tool for a general overview of APT. On this page, we describe APT's current limitations for moving targets and walk through the creation of moving target proposals.
APT limitations for solar system observations
APT is still under development and for moving targets some capabilities are not expected to be available until Cycles 1 or 2. The following list is not exhaustive. If you have questions please contact the help desk.
- APT does not (and is not planned to) provide sensitivity information. You must use the JWST Exposure Time Calculator (ETC). See JWST Moving Targets in ETC.
- Currently, APT does not allow observation visualization against all-sky images/catalogs for moving targets. This includes visualization of the object ephemeris. You must use a fixed target as a proxy to examine dithers, coverage, and orientation. A work-around is described in Tutorial on Visualizing Dithers of a Solar System Observation in APT. Accurate orientations for the Aladin viewer can be determined using the Moving Target Visibility Tool (MTVT).
General APT information
The most recent release of APT is available at http://apt.stsci.edu.
Begin a JWST proposal
Click on the New Document button in the upper left. You will have the option of starting either a new HST or new JWST proposal.
Edit proposal information
More extensive directions for filling out this form can be found at 2019-10-07_22-13-22_JWST Astronomers Proposal Tool Overview OLD. Moving target observers should select Solar System as either the Scientific Category or Alternate Category.
When you are ready to submit, click the paper plane icon, and fill in the form. Proposals can be re-submitted as needed up to the deadline. Any outstanding errors or warnings must be explained to complete the submission process.
Tutorials and tools
For additional information on APT, see JWST Astronomers Proposal Tool. The following will only concern the unique case of specifying a moving target observation.
Moving targets have unique parameters in APT. Some examples are illustrated in Tutorial on Creating Solar System Targets in APT.
Create observations and define scheduling constraints
Visualize dithers and mosaics using a fixed target as a proxy for your moving target
Currently APT does not have the capability to display a visualization of moving target dithers with the Aladin viewer. For a work-around, see Tutorial on Visualizing Dithers of a Solar System Observation in APT.
Target acquisition (TA) is not required (or recommended) for Standard Targets or numbered minor bodies for the IFU observing modes (MIRI MRS, NIRSpec IFU) or the NIRSpec MSA "long-slit" but may be necessary for other long-slit observing modes (MIRI LRS, NIRSpec fixed slit). NIRSpec TA for moving targets will use the 1.6” aperture and the observer can then put the target in any fixed slit, IFU, or MSA “long-slit.” This will be implemented for moving targets in Cycle 1.
More general information about APT target acquisition is in the article APT Target Acquisition.
Evaluate the schedulability of observations
APT has tools to visualize and check the schedulability of your observations (to visualize dithers, read this). You can also check for duplications and estimate the total time needed to execute your proposal.
Download the Astronomer's Proposal Tool
Go to the online JWST Exposure Time Calculator