Non-Earth Based Solar System Ephemerides Available

The Horizons on-line solar system ephemeris program has been generalized to allow observing sites on other planets, satellites, some asteroids & comets, and some spacecraft. This new capability is accessible from telnet or e-mail interfaces.

Documentation (explains how to access system):

            Web:   http://ssd.jpl.nasa.gov/horizons_doc.html
     PostScript:   ftp://ssd.jpl.nasa.gov/pub/ssd/Horizons_doc.ps

Examples of new applications, considering the extension to non-Earth sites:

• When does the Earth rise as seen from a site on Io?
• What are the eclipse circumstances of Deimos as seen from a landing site on Phobos?
• When is sun-rise as seen from Viking 1 landing site?
• What is the azimuth and elevation of asteroid Ceres from a site on the Moon?

A database of spacecraft landing sites on Venus, the Moon and Mars has been defined. Users may define their own topocentric sites on any body with a known rotational model. There are 750+ sites predefined for the Earth.

Horizons provides comprehensive access to solar system data and production of highly accurate ephemerides for solar system objects. This includes 25000+ asteroids & comets, 63 natural satellites, 9 planets, the Sun, spacecraft, and several dynamical points.

Users connect and generate customized parameter searches OR tables of up to 70 dynamic, geometric and sky circumstance quantities, as a function of time.

Computations are based on the latest physical models used at JPL for spacecraft navigation, mission planning and radar astronomy. Output is suitable for researchers, observers, mission planners and others who need accurate numerical data, but the system is open to the public and is intended to be easy to use. A forms-based web interface offers access to a subset of program capabilities.

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Jon Giorgini                       |  Navigation & Flight Mechanics Section
jdg@tycho.jpl.nasa.gov             |  Solar System Dynamics Group
Jon.D.Giorgini@jpl.nasa.gov        |  Jet Propulsion Laboratory
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