Spacecraft Orientation Problem: Velocity != planes

[selden]

aha: you're missing the FixedRotation {} statement.

Position and orientation each have two components: a coordinate system (OrbitFrame and BodyFrame) and a placement relative to that coordinate system

The defaults for the two components aren't always obvious. I usually try to specify both.

e.g.
OrbitFrame { ... }
FixedPosition [...]

BodyFrame {...}
FixedRotation {...}

[BrianJ]

Yes, that's it :-) Thanks again, Selden.

I'm reading this page:
http://en.wikibooks.org/wiki/Celestia/Reference_Frames

Hopefully I'll be able to get my head around it.

I'd like to:
(a) specify the spacecraft orientation such that y-axis points toward the Sun, and the spacecraft also rotates around the y-axis.

(b) specify the spacecraft trajectory relative to the Sun-Earth L2 point in a rotating frame (Sun-L2 line constant) - as per the classic "L2 halo orbit" illustration. I have some questions about this but I'll start a different thread for that.( Actually, I'm not sure I could extract the data from Horizons for this, so it may be a moot point!)

For the time being, any help with (a) is welcome.
Cheers,
Brian

[selden]

Brian,

Celestia's convention is for objects to rotate around their Z axis.

You can change the orientation of an SSC Mesh with respect to Celestia's axes by using the
Orientation directive. See http://en.wikibooks.org/wiki/Celestia/S ... _x_y_z_.5D
However, it might be easier to change the orientation of your model before exporting it from your 3D modelling program. Note that the axis labels within most 3D graphics programs do not correspond to the axes used by Celestia. There's usually a 90 degree rotation around the X axis.

[BrianJ]

Yes, that might make life simpler. Cheers.