jplephem

jplephem lets you consult a Jet Propulsion Laboratory ephemeris for the position and velocity of one of the planets, or the magnitude and rate-of-change of the Earth's nutation or the Moon's libration. To determine the position of Mars using the DE421 ephemeris, for example, you would start by installing two packages:

pip install jplephem
pip install de421

Then you can compute positions using a script like this:

import de421
from jplephem import Ephemeris

e = Ephemeris(de421)
jed = 2444391.5 # 1980.06.01
print e.compute('mars', jed)

The result should be a tuple providing the object's position in the Solar System given in kilometers, as well as its velocity in kilometers per second:

(x, y, z, xrate, yrate, zrate)

The ephemerides currently available as Python packages (the following links explain the differences between them) are:

- DE405 (May 1997)
- DE406 (May 1997)
- DE421 (February 2008)
- DE422 (September 2009)
- DE423 (February 2010)

What is new in this release:

• Deprecates the old compute() method in favor of separate position() and position_and_velocity() methods.
• Supports computing position and velocity in two separate phases by saving a "bundle" of coefficients returned by compute_bundle().
• From Marten van Kerkwijk: a second tdb2 time argument, for users who want to build higher precision dates out of two 64-bit floats.

Requirements:

• Python