Cassini/Saturn Moon Tracker Help

This form enables you to generate a diagram showing the east-west motion of the inner satellites of Saturn across the planet's disk. The distance of each selected moon from the planet's axis is plotted in units of either arcsec or planetary radii. Positive values correspond to bodies on the "morning" side of the planet (moving toward the observer) and negative values by the "evening" side. In the diagram, the planetary limbs are indicated by a dark gray stripe down the middle. Optionally, the locations of the rings can be added as bands in lighter gray. Time increases downward on the plot.

The Moon Tracker tool also allows you to download an ASCII table containing the numeric values that went into the diagram. The file contains a single header line followed by the numbers. Columns are as follows:

Modified Julian Date (UTC)
Year
Month
Day
Hour
Minute
Projected equatorial radius of planet (arcsec)
Distance of first moon from planet's axis (arcsec)
Distance of second moon from planet's axis (arcsec)
etc.

Change History

1.0 (July 21, 2001): Original Cassini/Saturn Moon Tracker, based on the Earth-based Saturn Moon Tracker.
1.1 (January 2, 2002): Updated for the official Cassini tour as of 1 December 2002.
1.2 (January 9, 2003): Phoebe added as a satellite choice. An option added for second accuracy in time tags.
1.3 (August 30, 2007): Added Cassini-discovered moons and the latest ephemeris options. Also added the tour for the Cassini extended mission.
1.4 (December 1, 2009): Updated the default ephemerides. To reduce confusion, we have removed the choice about what ephemeris to use.
2.5 (January 23, 2013): Anthe and Aegaeon added. Renumbered for consistency across all the Moon Tracker tools. Ephemeris updates.
2.6 (January 4, 2016): Ported to new server. Ephemeris updates.
2.7 (October 14, 2020): Ephemeris updates, including the final Cassini tour reconstruction.
2.8 (June 20, 2021): Ephemeris updates.
3.0 (August 2, 2022): Major new features:
- JWST, HST, and Earth-based observatories are now supported.
- Moon Tracker requests can now be bookmarked.
- the new Output option lets you jump directly to the table, bypassing the web page.

Time Limits

The start and stop times (UTC) of the table can be entered in a variety of formats. For example, the following all parse to 0:01:02 UTC on July 4, 1976:

1976-JUL-04 00:01:02.00
July 4, 1976 12:01:02 am
12:01:02 am July 4, 1976
1976-07-04T00:01:02Z (ISO format)
MJD 42963.00071759259
JD 2442963.50071759259

If you want the gory details of how times are interpreted, click here.

Interval: Enter the time interval to be used for the tabulation as a number in the box, and select the time unit from the choices provided. Start times and intervals are rounded to the nearest minute.

Moon Selection

Click on the box to the left of each moon that you wish to include in the diagram and in the tabulation.

Ring Selection

Click on the box to the left of each ring that you wish to include in the diagram. Rings appear as gray vertical stripes on the plot. For plotting purposes, the rings are shown extending all the way down to the planet.

Plot Options

Scale: Enter the numeric range and units of the horizontal axis. The value you enter is actually half the width of the diagram; for example, if you enter 10 planetary radii, then the axis will run from -10 to 10. Zero always falls at the middle of the plot.

Title: Enter a title for the plot in this box. It will appear centered above the diagram.

Output

By default, when you click on "Submit", you are directed to a web page that lists the details of the request, a small preview of the diagram produced, and options to view or download that diagram as PDF, JPEG, Postscript, or as an ASCII table. Optionally, you can choose to bypass the web page and go directly to any one of these four formats.