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Ephemerides
High precision ephemerides for solar-system bodies
are available on-line
using JPL's HORIZONS system.
Most optical and radar observers will be best served by using
our HORIZONS system to generate custom observer-table ephemerides.
Our on-line HORIZONS system can also be used to output
ephemerides in the form of osculating orbital elements and/or Cartesian vectors
(position, velocity, and acceleration).
However, there are some ephemeris data files available for export (see below)
for those rare cases when HORIZONS will not suffice.
Professionals requiring high-precision ephemerides readable from their own
software may find ephemeris data files (in SPK format) and a
software toolkit
needed to read those files from JPL's
NAIF web-site.
SPK files
for planetary and planetary satellite ephemerides are available
from NAIF.
Comet and asteroid SPK files may be generated using our HORIZONS system.
Planets
Planetary ephemerides are available using JPL's HORIZONS system.
Although the HORIZONS system will be sufficient
for the vast majority of ephemeris requests, JPL
planetary and lunar ephemeris files
(e.g. DE406) are also available.
The use of these ephemeris files is recommended only for professionals
whose needs are not readily met by the HORIZONS system.
Alternatively, you may use the
NAIF SPICE toolkit
and planetary ephemerides in
SPK format from
JPL's NAIF web-site.
As a low-precision alternative suitable for many applications,
approximate positions of the planets
can be computed from their orbital elements as described in a
separate page.
Summary of available planetary ephemerides:
Planetary Satellites
Ephemerides for planetary satellites are available from
JPL's HORIZONS system.
Although mean orbital elements are also available for
planetary satellites, you are strongly discouraged from
using them to generate your own ephemerides, as they will be highly inaccurate
for many bodies.
The list of planetary satellite ephemerides available
via HORIZONS is available in this table.
SPK ephemeris files are available from JPL's NAIF
site under the "data" section.
These data will be useful to users of the
NAIF SPICE toolkit.
Comets & Asteroids
Ephemerides for comets and asteroids
are available from JPL's HORIZONS system.
SPK ephemeris files can also be custom generated using HORIZONS for use with JPL's
NAIF SPICE toolkit.
Spacecraft
The Solar System Dynamics Group does not create spacecraft ephemerides.
However, JPL's HORIZONS system can access trajectory solutions
provided by the navigation teams of many missions and derive many ephemeris
quantities related to position and velocity.
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