NASA JPL Development Ephemerides (DE441)

High-precision computation of planetary ephemerides

JPL planetary ephemerides are generally created to support spacecraft missions to the planets. Selected ephemerides are recommended for more general use.

The latest JPL ephemeris with fully consistent treatment of planetary and lunar laser ranging data is DE440 (Park et al., 2021). The dynamical model for DE440 includes a frictional damping between the fluid core and the elastic mantle. This damping term is not suitable for extrapolation more than several centuries into the past. In order to cover a longer time span, the ephemeris DE441 was integrated without the lunar core/mantle damping term. The positions of the planets for DE441 agree with the positions on DE440 to within one meter over the time covered by DE440. For the Moon DE441 differs from DE440 mainly in the estimated tidal damping term causing a difference in along-track position of the Moon of ~10 meters 100 years from the present and growing quadratically for times more than 100 years from present.

The JPL planetary ephemerides are saved as files of Chebyshev polynomials fit to the Cartesian positions and velocities of the planets, Sun, and Moon, typically in 32-day intervals. The positions are integrated in astronomical units (au), but with polynomials stored in units of kilometers. The integration time units are days of barycentric dynamical time (TDB). In DE440, similar to DE430, the astronomical units have been fixed to the value 149597870.700 km as adopted by the International Astronomical Union in 2012.

References:

Montenbruck O., and Gill E.; Satellite Orbits: Models, Methods, and Applications; Springer Verlag, Heidelberg; Corrected 3rd Printing (2005).

Vallado D. A; Fundamentals of Astrodynamics and Applications; McGraw-Hill, New York; 4th edition (2013).

Park et al.;The JPL Planetary and Lunar Ephemerides DE440 and DE441; (2021).

https://ssd.jpl.nasa.gov/ftp/eph/planets/ascii/de441/

https://celestrak.org/SpaceData/EOP-All.txt