Question re: SampledOrientation and .q file

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Topic author
BrianJ
Posts: 63
Joined: 17.07.2008
With us: 11 years 11 months

Question re: SampledOrientation and .q file

Post #1by BrianJ » 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:

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 0


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

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