Solar system computer model

Question

I'm interested in building a 3D model of our solar system for web use (probably with AS3 and papervision) and have been looking into how I would go about encoding the planetary positions. My idea was to download the already calculated positions from NASA as calculating the positions myself seems a but overcomplicated. I'm not sure though whether I should use a helio centric or an earth centric encoding.

I wanted to know if there are any one with any experience in this. Which approach would be better? The NASA JPL website seems to have the positions of all the major bodies in our solar system as earth centric. I can see this becoming a problem later on though when adding Voyager and Mars Lander missions to the model?

Any feedback, comments and links are very welcome.

EDIT: I have a rough model running that uses heliocentric coordinates, but I haven't been able to find the coordinates for all planets in this format.

UPDATE:

I don't have a lot of detail to provide for know because I really don't know what I'm doing (from the space point of view). I wanted to get a handle on 3D programming, and am interested in space. The idea was that I would make a rough solar system simulator with at first all the planets and their orbiters (maybe excluding satellites at first). Perhaps include a news aggregator and some links to news/resources and so on. The general idea would be to allow people to click around and get super excited about going to the moon and Mars (for a starter).

In the long run I hopefully would be able to add in satellites and the moon missions (scroll back in time to the 70's and see the moon missions).

So to answer Arrieta's question the idea was not to calculate eclipses but to build an easy to approach, interactive space exploratorium, and learn some 3D and space related stuff on the way.

Answer 1

Hi

I'd probably start (well, I did a while back) with heliocentric coordinates and get a few of the planets up and running. But sooner or later you'll want to write a heliocentric-to-geocentric coordinate conversion routine, and its inverse. For some bodies, such as artificial satellites the geocentric coordinates will be easier to deal with.

Regards

Mark

Answer 2

Glad you want to build your own simulator, but depending on what you want to do it may be far from an easy task. The simplest approach is as follows:

1. Download the JPL-DE405 ephemerides and the subroutines for retrieving the planetary positions (wrt Solar System Barycenter).
2. Request for timespan, compute the positions, and display them to the screen in a visually appealing manner
3. Done

Now, why would you want to do this? If you want to view the planet's orbits, that's it. You are done. If you want to compute geometric events (like eclipses, or line-of-sight, or ilumination) then you are in a whole different ball game. That's astronautics, and it is not simple.

Please be more specific. The distinction you make of "geocentric" or "heliocentric" coordinates really has no major difficulty involved. If you have all the states in heliocentric frame, you can compute the geocentric frame by simple vector subtraction. That's not the problem! The problems are a thousand more, but you need to be specific so we can provide more guidance.

JPL has provided high quality ephemerides for decades now, and we have a full team of brilliant people working on it. It is one of the most difficult things to get right!

Again, provide more details or check out other sources of information.

Please google "Solar System Simulator" (done here, at JPL) and see if it fulfills your needs.

Cheers.

Answer 3

It may be worth you checking out the ASCOM Platform (we also have a stack exchange site called ASCOM Answers).

The ASCOM Platform has several useful libraries for doing this sort of thing.

• USNO NOVAS (Naval Observatory Vector Astrometry)
• Kepler orbit engine

The USNO/NOVAS stuff was originally written in C and we've wrapped it up in .NET for ease of use from C# and VB.

As an added bonus (actually it's the raison d’être for ASCOM), the Platform makes it easy for you to control things like telescopes, it's used by Microsoft's World Wide Telescope for exactly that purpose. I tmight be a fun extension to your model to be able to point a telescope at things.