PyEphem under the hood - how does it calculate the position of the planets?

Question

In SE space, it was suggested I use PyEphem to calculate the orbits of two-line elements. Now I'm curious how he calculates the “embedded” objects of the solar system, such as planets and their satellites. Does it use one of the standard jpg ephemerides (also here ) or something else?

So far, I have not been able to find out what PyEphem or XEphem looks like .

For example, JPL ephemeris are generated (fluently) by integrating orbits over a limited period of time, and compared with a large amount of observable data, to achieve a set of orbit parameters. Then it integrates into the future and the past, and the results are tabulated at a fixed time. This table of positions (and other things) can be called ephemeris.

Ephemeris are then used by interpolation between time periods - in this case, using the Chebyshev polynomial coefficients given in the table.

JPL DE405 ephemeris, for example, can be read using the python de405 module

@Mattexx pointed out below that XEphem uses a procedure called libastro, and that PyEphem probably does the same. Therefore, I would like to know what it uses to calculate positions - the algorithm and the observed data set.

Answer 1

According to PyEphem Readme

Suitable numerical procedures are encoded in C and are the ones that cite the popular astronomy application XEphem, whose author, Elwood Charles Downey, generously gave permission to use them in PyEphem.

The C library is called libastro. A survey of the libastro source shows that it actually uses VSOP 87.