Jet Propulsion Laboratory Development Ephemeris (abbreviated JPL DE(number), or simply DE(number)) designates one of a series of mathematical models of the Solar System produced at the Jet Propulsion Laboratory in Pasadena, California, for use in spacecraft navigation and astronomy.
The models consist of numeric representations of positions, velocities and accelerations of major Solar System bodies, tabulated at equally spaced intervals of time, covering a specified span of years.
There have been many versions of the JPL DE, from the 1960s through the present,[2] in support of both robotic and crewed[3] spacecraft missions.
From 1975 through 1982, six ephemerides were produced at JPL using the modern techniques of least-squares adjustment of numerically-integrated output to high precision data: DE96 in Nov. 1975, DE102 in Sep. 1977, DE111 in May 1980, DE118 in Sep. 1981, and DE200 in 1982.
[6] DE102 was the first numerically integrated so-called Long Ephemeris, covering much of history for which useful astronomical observations were available: 1141 BC to AD 3001.
DE200, a version of DE118 migrated to the J2000.0 reference frame, was adopted as the fundamental ephemeris for the new almanacs starting in 1984.
DE440 and DE441 were published in 2021, with improvements in the orbits of Jupiter, Saturn and Pluto from more recent spacecraft observations.
)[8][9] Each ephemeris was produced by numerical integration of the equations of motion, starting from a set of initial conditions.
The method of special perturbations was applied, using numerical integration to solve the n-body problem, in effect putting the entire Solar System into motion in the computer's memory, accounting for all relevant physical laws.
[10] The ephemerides are now available via World Wide Web and FTP[13] as data files containing the Chebyshev coefficients, along with source code to recover (calculate) positions and velocities.
[14] Files vary in the time periods they cover, ranging from a few hundred years to several thousand, and bodies they include.
The use of Chebyshev polynomials enables highly precise, efficient calculations for any given point in time.
Note that these precision numbers are for the interpolated values relative to the original tabulated coordinates.
The new DE440 / 441 general-purpose planetary solution includes seven additional years of ground and space-based astrometric data, data calibrations, and dynamical model improvements, most significantly involving Jupiter, Saturn, Pluto, and the Kuiper Belt.
DE403[21] was created 1993, released in 1995, expressed in the coordinates of the International Earth Rotation Service (IERS) reference frame, essentially the ICRF.
Telescopic observations remained important for the outer planets because of their distance, hence the inability to bounce radar off of them, and the difficulty of parking a spacecraft near them.
While both DE403 and DE404 were integrated over the same timespan, the interpolation of DE404 was somewhat reduced in accuracy and nutation of the Earth and libration of the Moon were not included.
The orbits of the Pioneer and Voyager spacecraft were reprocessed to give data points for Saturn.
DE410[28] was also released in 2003 covered 1901 - 2019, with improvements from DE409 in the masses for Venus, Mars, Jupiter, Saturn and the Earth-Moon system based on recent research.
DE413 was fit to new CCD telescopic observations of Pluto in order to give improved positions of the planet and its moon.
The numerical integration software was updated to use quadruple-precision for the Newtonian part of the equations of motion.
Some ranging data to the NEAR Shoemaker spacecraft orbiting the asteroid Eros was used to derive the Earth/Moon mass ratio.
New observations of Pluto, which took advantage of the new astrometric accuracy of the Hipparcos star catalog, were included in the fit.
was created in 2013 and is intended for analysis of earlier historical observations of the Sun, Moon, and planets.
DE432 is a minor update to DE430, and is intended primarily to aid the New Horizons project targeting of Pluto.
[42] DE436[43] was created in 2016 and was based on the DE430, with improved orbital data for Jupiter specifically for the Juno mission).