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 {...}
Spacecraft Orientation Problem: Velocity != planes
Re: Spacecraft Orientation Problem: Velocity != planes
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
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
Re: Spacecraft Orientation Problem: Velocity != planes
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.
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.
Selden
Re: Spacecraft Orientation Problem: Velocity != planes
Yes, that might make life simpler. Cheers.