Celestia Forums

Fridger - Thanks for taking the time to post such a detailed reply. It looks like you a lot of hard -- and excellent -- work here! I am concerned about the Earth-Moon system, but that is mitigated quite a bit by the option Selden mentioned to use the JPL ephemerides in Celestia 1.5 -- once I figure ...

...Meanwhile, here's a tweaked version on Steve's Apollo free return mission, in Celestia: ... and a different view as the return to Earth starts: ... What about those hard edges in the trajectory? not enough data? Yes. During the transfer orbit, the data points are about 45 minutes apart. We can s...

... To repeat: accuracy for the planets, accuracy for the moon (which is a special issue!) , easyness in handling AND speed considerations. And more recently, there is the fact that SPICE and GMAT do NOT use VSOP87. ... Bye Fridger Do you remember roughly how different the VSOP87 and VSOP2000 were ...

Would there be some menpower ready to actively promote also the development of Celestia, for example? This I doubt in case of the commercial contractors ;-) Well, I can't speak to most of what was asked in this original message, since I'm not a NASA employee. But as the -- currently only -- commerc...

Not a problem at all on the Thinking Systems site. That one I control. :) I don't remember where I got the Earth in the Thinking Systems banner -- that image was made 4 or 5 years ago, IIRC. I remember spending hours in the GIMP trying to get something I liked... The Earth image very well may have c...

It's a fictional orbit. Basically, I took GMAT's "default" mission -- the first one we use to sanity test a new build -- added a couple of maneuvers and some propagation, and wrote the results to a file. That part took about a minute. Then I edited the file to set the epoch correctly -- we use a mod...

That piece is pretty simple -- I did a hand edit of some GMAT data (we write out a modified Julian data, but full Julian a simple thing to add). Here's a GMAT generated orbit, viewed in Celestia:

Right now GMAT does not write SPICE formatted data. It can generate a text ephemeris, though -- epoch, X, Y, Z, for example. I suspect that one way we may be able to work together is to have Celestia read and display a GMAT trajectory by importing that type of data. I haven't looked for it yet -- is...

Thanks for the response. I'm one of GMAT's developers, so Steve asked me to post a reply. We actually do build GMAT on all three supported platforms (Mac, Windows, Linux) using GNU-Make. The makefiles you see in the source distribution have the suffix ".eclipse" as an artifact -- we used to have sep...