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JPL Horizons On-Line Ephemeris System

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JPL Horizons On-Line Ephemeris System provides easy access to key solar system data and flexible production of highly accurate ephemerides for solar system objects.

Osculating elements at a given epoch are always an approximation to an object's orbit (i.e. an unperturbed conic orbit or a "two-body" orbit). The real orbit (or the best approximation to such) considers perturbations by all planets, a few of the larger asteroids, a few other physical usually small forces, and requires numerical integration.

Jet Propulsion Laboratory (JPL) ephemerides do not use things such as periods, eccentricities, etc.[1] Instead, JPL integrates the equations of motion in Cartesian coordinates (x,y,z), and adjusts the initial conditions in order to fit modern, highly accurate measurements of planetary positions.[1]

As of August 2013, Horizons now uses ephemeris DE431.[2]

Introduction

There are 3 ways to use the system:

References

  1. ^ a b Alan B. Chamberlin (2006-02-28). "Frequently Asked Questions (FAQ): What's the exact value of..." JPL Solar System Dynamics. Retrieved 2011-01-20.
  2. ^ Acton (2013). "README.txt". file at the NAIF website.[dead link]
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