<p>I'm looking for accurate positions and velocities of the planets in the solar system over several decades. I want to simulate their trajectories using Newtonian laws of motion, and compare the precession of Mercury's perihelion with observed data. I used the <a href="http://ssd.jpl.nasa.gov/horizons.cgi" rel="noreferrer">JPL's HORIZONS system</a> but I can't manage to find these positions and velocities in the output data. </p>

<p>Could you explain how the data is formatted? (The HORIZONS web-interface Tutorial didn't help.) </p>

<solar-system><mercury>
What is the format of the data from the JPL's HORIZONS system?
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# What is the format of the data from the JPL's HORIZONS system?

(Asked by: username_0 on 2015-09-24)

I'm looking for accurate positions and velocities of the planets in the solar system over several decades. I want to simulate their trajectories using Newtonian laws of motion, and compare the precession of Mercury's perihelion with observed data. I used the [JPL's HORIZONS system](http://ssd.jpl.nasa.gov/horizons.cgi) but I can't manage to find these positions and velocities in the output data.

Could you explain how the data is formatted? (The HORIZONS web-interface Tutorial didn't help.)

**Tags:** solar-system, mercury

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