de422 2009.1

This is the most recent long-period ephemeris published by the Jet Propulsion Laboratory. While requiring more than half a gigabyte of space, it achieves quite high accuracy.

Name:	DE422 (September 2009)
Years:	-3000 through 3000
Planets:	Yes
Sun/Moon:	Yes
Nutations:	Yes
Librations:	Yes
Report:	Jones, Fomalont, Dhawan, Romney, Folkner, Lanyi, Border, Jacobson (2010) [PDF]
Size:	531 MB

This ephemeris incorporates ranging data from recent spacecraft missions, including the Cassini mission to Saturn, which results in an accuracy for Saturn of a few milliarcseconds for positions over the past decade. If this ephemeris is too large for your application, take a look at DE421 and DE423 as alternatives.

To compute using this ephemeris in Python, see the jplephem package.