DE436

DE436
Name	DE436
Type	Planetary ephemeris
Developer	Jet Propulsion Laboratory
Release date	2019
Latest version	DE436
Predecessor	DE430
Successor	DE441
Primary objects	Mercury (planet), Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto (dwarf planet)
Time standard	Barycentric Dynamical Time
Reference frame	International Celestial Reference Frame

DE436

DE436 is a numerical planetary and lunar ephemeris produced by the Jet Propulsion Laboratory for high-precision solar system dynamics and navigation. It provides positions and velocities of major solar system bodies relative to the International Celestial Reference Frame and uses Barycentric Dynamical Time for temporal parameterization. DE436 serves scientific communities such as planetary astronomers, spacecraft mission designers, and pulsar timing analysts.

Overview

DE436 tabulates the barycentric and geocentric state vectors and analytic/chebyshev representation for bodies including Mercury (planet), Venus, Earth, Moon, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto (dwarf planet). The model is anchored to observational reference frames established by Very Long Baseline Interferometry networks and the International Celestial Reference Frame, and it supports navigation for missions by agencies like NASA, ESA, JAXA, and Roscosmos. DE436 complements auxiliary products such as planetary constants from the International Astronomical Union and time-scale realizations like Terrestrial Time and Coordinated Universal Time for cross-disciplinary applications. The ephemeris is distributed in machine-readable formats for integration with mission planning systems used by Deep Space Network operations and pulsar timing arrays including NANOGrav.

Development and Data Sources

Development of DE436 synthesized radiometric and optical measurements drawn from spacecraft tracking and ground-based observations. Key spacecraft contributors include range and Doppler data from Mars Reconnaissance Orbiter, Cassini (spacecraft), Messenger (spacecraft), Juno (spacecraft), and New Horizons, adding high-precision constraints on Mars and the outer planets. Ground-based inputs derive from Very Long Baseline Interferometry sessions tied to quasars cataloged in the International Celestial Reference Frame, optical astrometry from observatories such as Palomar Observatory and Kitt Peak National Observatory, and lunar laser ranging from Apache Point Observatory and Observatoire de la Côte d'Azur. Planetary radar echoes from facilities including Arecibo Observatory and Goldstone Deep Space Communications Complex provided distance and line-of-sight velocity constraints for Mercury (planet), Venus, and Mars. DE436 also incorporated masses and dynamical constants refined by missions like Juno (spacecraft) for Jupiter and by ring and satellite studies of Saturn from Cassini (spacecraft).

Ephemeris Model and Computational Methods

The ephemeris integrates the coupled N-body equations of motion using relativistic formulations consistent with General Relativity in the parametrized post-Newtonian framework. Perturbations modeled include gravitational influences from major planets and selected asteroids, solar oblateness characterized by J2, tidal interactions between Earth and Moon, and relativistic light-time corrections for radiometric tracking. Numerical integration employed variable-step Gauss–Radau or Adams–Bashforth–Moulton schemes implemented in software environments used by the Jet Propulsion Laboratory navigation analysts. State vectors are represented as Chebyshev polynomial coefficients over standard time intervals to facilitate interpolation for applications in Spacecraft (spacecraft) navigation and astronomical software such as the SPICE (spacecraft navigation) toolkit. The ephemeris aligns with coordinate transformations provided by standards from the International Astronomical Union and timing conventions from International Earth Rotation and Reference Systems Service.

Accuracy and Validation

Validation of DE436 involved residual analysis against independent tracking datasets and comparisons with predecessor ephemerides like DE430 and DE432. Typical post-fit residuals for radiometric range and Doppler vary by target and dataset: ranges to inner planets achieved meter-level or sub-meter agreements for well-tracked intervals, while outer-planet positional uncertainties are dictated by optical astrometry and spacecraft flyby geometry. Lunar position and libration accuracy benefitted from lunar laser ranging residuals tied to arrays at McDonald Observatory and Lunar Laser Ranging Retroreflector measurements, constraining Earth–Moon dynamics. Cross-validation included comparisons with ephemerides produced by other groups such as INPOP and EPM to quantify systematic frame and mass-parameter differences. Uncertainty budgets consider observational errors, model truncation, asteroid mass uncertainties from studies involving Minor Planet Center data, and spacecraft non-gravitational accelerations characterized in mission-specific telemetry.

Applications and Usage

DE436 underpins navigation and targeting for interplanetary missions, orbit determination for planetary satellites, and computation of barycentric corrections for high-precision timing in pulsar and exoplanet studies conducted by collaborations like European Pulsar Timing Array and Pulsar Timing Array consortia. Astronomers use DE436 for ephemerides in observational planning at facilities including Hubble Space Telescope, Very Large Telescope, and Atacama Large Millimeter/submillimeter Array to predict occultations, transits, and conjunctions. Geodesists and relativistic experiments reference DE436 for spacecraft-based tests of gravitational theory and for providing solar system barycenter coordinates required by initiatives at Jet Propulsion Laboratory and agencies such as NASA and European Space Agency. Software libraries, mission design tools, and databases integrate DE436 coefficients for simulation, catalog cross-matching, and archival data reduction workflows at institutions like Harvard–Smithsonian Center for Astrophysics.

Release History and Versions

DE436 was released by the Jet Propulsion Laboratory as part of an ongoing series of planetary ephemerides updates following DE430 and preceding DE441. Each release incorporates new spacecraft tracking, revised planetary constants endorsed by the International Astronomical Union, and improved modeling of small-body perturbations informed by surveys cataloged at the Minor Planet Center and missions such as Gaia (spacecraft). Version notes document time span coverage, dynamical model changes, and recommended usage domains; distribution channels include institutional data repositories used by NASA and mission teams. Future updates continue through collaborative efforts among agencies and observatories including European Space Agency and national research centers to maintain compatibility with evolving reference frames and timing realizations.

Category:Planetary ephemerides