This article describes how to discover MAST mission observations of solar system bodies.

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Searching for observations of solar system bodies (planets, moons of planets, dwarf planets, comets, asteroids) is useful to:

  • identify data for archival research
  • identify observations that might duplicate future observations (e.g., with HST or JWST) you are contemplating
  • chart the past history of positions, brightness, or other properties of individual objects

Crafting queries of such targets with MAST interfaces requires special attention because:

  • searching by time-dependent coordinates is not well supported
  • object names for solar system bodies are not resolvable to positions by standard catalog services (e.g., Simbad, NED)
  • targets where the original observer specified a name that may not correspond to an IAU standard name

There are a few approaches to overcoming these challenges, which are described below.

This article does not address determining future target positions for the purpose of planning observations. See the article Solar System Targets in the Astronomer Proposal Tool (APT) documentation for guidance in this area.

Search by Target

The most straightforward approach to search for fixed targets in MAST is by name and (optionally) other metadata. Searching for moving targets (solar system bodies) is different, and requires you to specify additional metadata. The values for metadata in MAST (HST and JWST only) related to solar system bodies are taken from database fields in the Astronomers Proposal Tool (APT), where observers provide their detailed observing plans. Note: some of these fields are auto-populated for APT standard targets (e.g., planets and their major moons), but not for minor bodies—e.g., less famous asteroids and recently discovered comets. There are complications, however:

  • the target names in MAST may or may not include ancillary information (such as annotations related to offsets or of particular features on an extended target) included in the value string
  • the target name for minor bodies is chosen by the observer, and may or may not match a standard name

Searches in MAST distinguish between

  • Object Name, where the name is matched to external catalogs and, if successful, determines source coordinates 
  • Target Name, which performs a string match of Observation metadata that are derived from observing programs 

The Target Name field is not guaranteed to be populated for any MAST mission except for HST and JWST.

The equivalent astroquery.mast Observation.query_object() class parameter names are objectname and target_name, respectively.

Below are strategies to employ when searching MAST for sources by name. 

It is not especially helpful to search MAST for observations where the Moving Target field has the value 1 (i.e, True): There are thousands of results for both HST and JWST. 

Portal searches

See the Portal Guide chapter Advanced Search to learn about searching MAST with the Portal. In all cases, it is helpful to surround filter values with wildcard characters (use an asterisk: *) to ensure it matches relevant values in the associated database field.

Advanced search

  1. Select the MAST Observatinos by Object Name or RA/Dec collection from the drop-down menu.
  2. Click the Advanced Search link in the Portal search area.
  3. In the Advanced Search window select and populate one or both of the filter dialogs for Target Name and Target Classification. The example at right shows the filter dialogs for Target Name (*didymos*) and Target Classification (*asteroid*). Remember to enter <Return> or <Tab> on your keyboard to include text filters in the search criteria.
  4. Click the Search button.

JWST keyword search

  1. Select the JWST Instrument Keywords collection from the drop-down menu.
  2. Click Advanced Search in the Portal search area.
  3. In the Advanced Search window select and populate one or both of the filter dialogs for targname, targcat, and targdesc. The examples at right show the filter dialogs for targname (*didymos*), targcat (*solar system*) , and targdesc (*asteroid*). 
  4. Remember to enter <Return> or <Tab> on your keyboard to include text filters in the search criteria.
  5. Click the Search button.

Portal filter dialogs for targname and targcat

Portal filter dialog for targdesc

JWST/HST mission search

See the Mission Search Guide chapter Search Parameter Overview to learn about searching MAST with the mission-specific searches. 

  1. From the HST or JWST Mission search, add additional columns to match one or more of Target Name, Target description from APT, and Target category from APT. 
  2. Click the Search button.

Mission MAST conditions for the column "Target Name", "Target description" and "Target Category"

It may be instructive to search solely on Target Classification (or Target Description) with the value *asteroid* just to see the variety of target names that appear in the results table. 

Search by Coordinates

Discovering observations in MAST of some targets, particularly for missions other than HST and JWST, requires searching by position. The coordinates as a function of time for known solar system bodies can be found from the NASA JPL Horizons System. As shown below, the interface will generate an ephemeris over a range of time for a given body, the observer location; the information provided in the output table is configurable. 


JPL Horizons System web application interface

Figure 1 – NASA/JPL Horizons System web interface, with selections to request the ephemeris for the asteroid Didymos as observed from JWST in the time interval 2022-09-26 through 2022-10-15 (i.e. starting just before the date of the DART impact), in time steps of 6 hours. The apparent position of near-Earth asteroids can change quite rapidly. 

If you are suspect that a particular solar system body has been observed and know the approximate time, finding Observations in MAST is straightfoward. 

  1. Navigate to the JPL Horizons System app, enter the target name, the observer location and time window
    1. be sure to set the time step to a sufficiently small interval
  2. Generate an ephemeris
  3. Use the coordinates from the dates/times of interest, and conduct a search by position in a MAST web tool
    1. be sure to set a sufficiently large search radius to ensure a match with the MAST mission/instrument observing aperture

A detailed search of Pan-STARRS

The Pan-STARRS survey includes both images and a catalog; these products are hosted at MAST (see the Pan-STARRS1 data archive). Many images over 3/4 of the sky were obtained in 5 optical passbands over the course of the ~5 year survey, so there is a very good chance that sufficiently bright solar system bodies were detected, often multiple times, in this survey.

A tutorial has been developed (with an accompanying Jupyter notebook) to search for a known, but faint, asteroid in the Pan-STARRS catalog and to extract cut-out images from the survey images. To replicate this technique for other know solar system bodies, you will need: 

The results show how the position and brightness of the source can be tracked.

The Solar System Object Image Search tool can also search for images obtained by many of the HST instruments, the SDSS surveys, and many other non-MAST missions and observing facilities. The techniques described in the Pan-STARRS tutorial should be equally applicable. 

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