Modelling planet positions, now with VSOP87

[evilfer]

Hi,

I'd like to ask for a recommendation for a open source c/c++ implementation of VSOP87 (preferably cartesian coordinates relative to solar system barycenter), that computes the position of planet satellites as well.

I've found the one of Stellarium, but I thought there might a specific library for this.

Besides and out of curiosity, when using VSOP87, are satellite positions calculated from orbit parameters (assuming 2-body problem)?

 

[martins]

Aren't the VSOP data and sample codes freely available anyway? If I remember correctly, the original code may be in Fortran, but it is fairly simple, so if you don't like Fortran, a conversion to C should be trivial (or use f2c).

By "planet satellites", do you mean moons? Most moons in orbiter use their own series expansion solutions, from various sources. If no perturbation solutions are available, then orbiter falls back to a 2-body solution as a last resort.

If you mean artificial satellites, then they are propagated by numerical integration, taking into account all relevant gravity sources at the given vessel location.

 

[evilfer]

Aren't the VSOP data and sample codes freely available anyway? If I remember correctly, the original code may be in Fortran, but it is fairly simple, so if you don't like Fortran, a conversion to C should be trivial (or use f2c).

By "planet satellites", do you mean moons? Most moons in orbiter use their own series expansion solutions, from various sources. If no perturbation solutions are available, then orbiter falls back to a 2-body solution as a last resort.

If you mean artificial satellites, then they are propagated by numerical integration, taking into account all relevant gravity sources at the given vessel location.

Yes, I meant just moons, natural satellites :S. The thing is I found the VSOP87 data and code for the planets, but not the moons. And then I saw the ELP82 file for the Moon in the Orbiter distribution, and references to GALSAT ephemerids (couldn't find the data source for Mars moons though)...

I don't want to sound lazy, but if there were a programming library to access all these data in the same way (as in the CSPICE API), it'd be very convenient, and I feel this must be a recurrent need for developers. Otherwise I think I'll reuse one of the current implementations for planet/moon position from some software at sourceforge, so I wanted to ask for advice on which one to use .