Does Universe Sandbox support ephemeris?

[Dan Dixon]

A user emailed me a good question:

I’ve did a search in the forums but the results did not confirm whether or not universe sandbox uses and supports ephemeris.

For example, when I run a simulation of the solar system for a certain time/date, are the planets on the exact position (and follow them in each time step) that I would find them using ephemeris tables?

Universe Sandbox does not use ephemeris. It includes some calculated ephemeris data from JPL's Horizon website:
http://ssd.jpl.nasa.gov/?horizons
which it uses for the staring position and velocities of certain simulations (Our Solar System, etc...), but as the simulation progresses after the initial load all positions are calculated using Newton's law of gravitation.

All of this pre-calculated ephemeris data can be found in the install folder (c:\program files\Universe Sandbox\data) in the horizon-xxxx-xx-xx.xml files. Units in horizon files are in km and km/sec.

With a small time step the results are going to be quite accurate, but I wouldn't use Universe Sandbox to determine the position of planets for launching probes.


What is ephemeris?
"Software that generates positions of the planets and often of their satellites, or of asteroids or comets at virtually any time desired by the user."
http://en.wikipedia.org/wiki/Ephemeris#Scientific_ephemeris