The Jet Propulsion Laboratory Developmental Ephemeris or JPL DE is actually a series of computer-based programs for the prediction of high precision coordinates for the Sun, Moon and planets. One of the principal puroses of the JPL DE's is to support both robotic and manned spacecraft missions from the 1960s through the present.

In the 1970s and early 1980s, much work was done in the astronomical community to update the astronomical almanacs from the theoretical work of the 1890s to modern, relativistic theory. 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. Among the most significant of them were the DE102 and DE200.

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 rotated to the J2000.0 reference frame, was adopted as the fundamental ephemeris for the new almanacs starting in 1984. The JPL ephemerides have remained the basis of the Astronomical Almanac to the present; the current Almanac is derived from DE405. Each such ephemeris was produced by numerical integration of the equations of motion, starting from a set of initial conditions.

Due to the precision of modern observational data, the analytical method of general perturbations could no longer be applied to a high enough accuracy to adequately reproduce the observations. 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. The initial conditions were both constants such as planetary masses, from outside sources, and parameters such as initial positions and velocities, adjusted to produce output which was a "best fit" to a large set of observations. A least-squares technique was used to perform the fitting.

The physics modeled include the mutual Newtonian gravitational accelerations and their relativistic corrections, the accelerations caused by the tidal distortion of the Earth, the accelerations caused by the figure of the Earth and Moon, and a model of the lunar librations.

The observational data in the fits has been an evolving set, including: ranges (distances) to planets measured by radio signals from spacecraft, direct radar-ranging of planets, two-dimensional position fixes (on the plane of the sky) by VLBI of spacecraft, transit and CCD telescopic observations of planets and small bodies, and laser-ranging of retroreflectors on the Moon, among others.

The table below lists some of the most important JPL DEs along with a brief description.

Note: Portions of this page come from Wikipedia and the Jet Propulsion Lab.