Spacecraft trajectories in the planet reference frame.

[MB]

I think that it would be interesting, at least for pedagogical point of view and specifically at present times with such titan flightby event, that an option allows to have the spacecraft trajectories drawn in the capturing body (planet) reference frame, begining , for example at the time of capture. This change of reference frame should be very easy to implement in the code, I guess.
It is highly probable that this point has been discussed in the past. Unfortunately I was not able to find a thread discussing it.
Our comon memory (Selden) should know, thanks for any info.
MB

[selden]

I'm not sure if I recall a discussion of such a transform being considered for inclusion in Celestia, although I might just be forgetting about it.

It is possible to define xyz trajectories relative to the planet. Unfortunately, the planet-centric coordinate system that Celestia uses for them are not the same as Horizons', unlike the heliocentric xyz coordinate system. I do recall that Grant recently described the transforms necessary to convert between them.

[HankR]

IIRC, when you define a spacecraft as a moon of a planet, the XYZ coordinates are interpreted by Celestia as relative to the planet's equatorial coordinate frame. So one could create multiple time-limited objects for a spacecraft with the appropriate time limits and coordinate transformations in segmented XYZ files to achieve something like this. It would be interesting to see the results if someone tried it. It would also be nice if eventually Celestia were able to do the transformations internally, so that the user could simply select which body the orbit shoud be displayed relative to, but I wouldn't expect to see that anytime soon.

- Hank