Question re: SampledOrientation and .q file
Posted: 06.12.2009, 23:53
Hi,
I'm having trouble using the SampledOrientation parameter together with a .q file.
I made a "testvessel" spacecraft (in Geosynchronous orbit) that uses the following .ssc file:
The .q file "testvessel.q" is as follows:
I thought that the quaternions used (1 0 0 0) implied no rotation, and thus the spacecraft body axes would be aligned with the frame (Ecliptic) axes, but this is not the case.
Using the above .ssc and .q gives the following transformation:
Ecliptic X = Body -X
Ecliptic Y = Body Z
Ecliptic Z = Body Y
Here's a link to a screen shot showing the Ecliptic grid and spacecraft Frame axes:
http://img19.imageshack.us/img19/8297/testframeaxes.gif
...and here's one showing Ecliptic grid and spacecraft Body axes:
http://img43.imageshack.us/img43/6051/testbodyaxes.gif
What should my BodyFrame{} parameter and .q file quaternions be in order to set the spacecraft body axes to the same orientation as the frame(ecliptic) axes? (or is this a bug?)
I'm using Celestia 1.6.0 and Windows XP.
Many thanks,
Brian
I'm having trouble using the SampledOrientation parameter together with a .q file.
I made a "testvessel" spacecraft (in Geosynchronous orbit) that uses the following .ssc file:
Code: Select all
"Testvessel" "Sol/Earth"
{
Class "spacecraft"
Radius 0.0075
Beginning 2453635.8061092
Ending 2453636.9029765
OrbitFrame { EclipticJ2000 { Center "Sol/Earth" } }
SampledOrbit "testvessel.xyzv"
BodyFrame { EclipticJ2000{ Center "Sol/Earth" } }
SampledOrientation "testvessel.q"
FixedRotation{}
Albedo 0.10
}The .q file "testvessel.q" is as follows:
Code: Select all
2453635.8061092 1 0 0 0
2453636.9029765 1 0 0 0I thought that the quaternions used (1 0 0 0) implied no rotation, and thus the spacecraft body axes would be aligned with the frame (Ecliptic) axes, but this is not the case.
Using the above .ssc and .q gives the following transformation:
Ecliptic X = Body -X
Ecliptic Y = Body Z
Ecliptic Z = Body Y
Here's a link to a screen shot showing the Ecliptic grid and spacecraft Frame axes:
http://img19.imageshack.us/img19/8297/testframeaxes.gif
...and here's one showing Ecliptic grid and spacecraft Body axes:
http://img43.imageshack.us/img43/6051/testbodyaxes.gif
What should my BodyFrame{} parameter and .q file quaternions be in order to set the spacecraft body axes to the same orientation as the frame(ecliptic) axes? (or is this a bug?)
I'm using Celestia 1.6.0 and Windows XP.
Many thanks,
Brian