JPL Horizons On-Line Ephemeris System output values

JPL Horizons On-Line Ephemeris System provides access to key Solar System data and flexible production of highly accurate ephemerides for Solar System objects. Osculating elements at a given epoch (such as produced by the JPL Small-Body Database) are always an approximation to an object's orbit (i.e. an unperturbed conic orbit or a " two-body" orbit). The real orbit (or the best approximation to such) considers

perturbations Perturbation or perturb may refer to: * Perturbation theory, mathematical methods that give approximate solutions to problems that cannot be solved exactly * Perturbation (geology), changes in the nature of alluvial deposits over time * Perturbatio ...

by all planets, a few of the larger asteroids, a few other usually small physical forces, and requires

numerical integration In analysis, numerical integration comprises a broad family of algorithms for calculating the numerical value of a definite integral, and by extension, the term is also sometimes used to describe the numerical solution of differential equations ...

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(JPL) ephemerides do not use things such as periods, eccentricities, etc. Instead, JPL integrates the equations of motion in

Cartesian coordinates A Cartesian coordinate system (, ) in a plane is a coordinate system that specifies each point uniquely by a pair of numerical coordinates, which are the signed distances to the point from two fixed perpendicular oriented lines, measured i ...

(x,y,z), and adjusts the initial conditions in order to fit modern, highly accurate measurements of planetary positions. Since August 2013, Horizons has been using

ephemeris In astronomy and celestial navigation, an ephemeris (pl. ephemerides; ) is a book with tables that gives the trajectory of naturally occurring astronomical objects as well as artificial satellites in the sky, i.e., the position (and possibly ...

DE431. During the week of 12 April 2021, the Horizons ephemeris system was updated to replace the DE430/431 planetary ephemeris, used since 2013, with the new DE440/441 solution. 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. Inclusion of 30 new Kuiper-belt masses, and the Kuiper Belt ring mass, results in a time-varying shift of ~100 km in DE441's barycenter relative to DE431. In September 2021 JPL started transitioning from

common gateway interface In computing, Common Gateway Interface (CGI) is an interface specification that enables web servers to execute an external program, typically to process user requests. Such programs are often written in a scripting language and are commonly re ...

(CGI) to application programming interface (API).

Ejection

Objects (such as C/1980 E1) on an outbound ejection trajectory will show an eccentricity greater than 1, an apoapsis distance of AD= 9.99E+99 and an orbit period of PR= 9.99E+99. For objects orbiting the Sun, this is best computed at an epoch (date) when the object is outside of the planetary region of the Solar System and no longer subject to notable planetary perturbation. Due to the galactic tide and passing stars it is impossible to know if an object with a weak hyperbolic trajectory will truly be ejected or gently nudged back inward. The galactic tide and passing stars can also cause objects inbound from the Oort cloud to have a weakly hyperbolic trajectory.

Overview of usage

There are 3 ways to use the system and all of them can be automated: * Web (partial access) *

Email Electronic mail (email or e-mail) is a method of exchanging messages ("mail") between people using electronic devices. Email was thus conceived as the electronic ( digital) version of, or counterpart to, mail, at a time when "mail" mean ...

(full access) * Telnet (full access) The Horizons system was intended to be easy to use and should have a step-function learning curve.

References

{{Reflist, refs= {{cite web , author=Horizons output , url=https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%271980+E1%27&TABLE_TYPE=%27ELEMENTS%27&START_TIME=%271950-01-01%27&STOP_TIME=%272050-01-01%27&STEP_SIZE=%27100%20years%27&CENTER=%27@0%27&OUT_UNITS=%27AU-D%27 , title=Barycentric Osculating Orbital Elements for Comet C/1980 E1 (Bowell) Solution using the Solar System Barycenter. Ephemeris Type:Elements and Center:@0 (To be outside planetary region, inbound epoch 1950 and outbound epoch 2050)

External links

JPL Horizons On-Line Ephemeris SystemHORIZONS User Manual

HORIZONS Batch-Interface CGI

JPL SSD/CNEOS API
Astrometry Astronomy websites JPL online services