Spacecraft Position IAU_Earth Reference Frame

[Luca Pascali]

Hi, 

I've set a simulation creating the Earth through the Spice interface.

Does anybody know if it is possible to get the spacecraft state with respect to the Earth fixed rotating frame (IAU_Earth) or it is only possible to get the state relative to the inertial frame (r_BN_N) ?

The only thing that I've found is that the SpicePlanetStateMsgPayload has J20002Pfix as one of the outputs but I if I try to make the matrix vector multiplication for each saved inertial position vector to get the ones in the planet fixed frame it takes a lot of time. For this reason I was wondering if there is any message or any way that I've not found yet that directly gives the r_BP_P position of the spacecraft.

Thank you in advance!

[Hanspeter Schaub]

See this multi-body gravity example script that uses Spice.  

http://hanspeterschaub.info/basilisk/_modules/scenarioOrbitMultiBody.html#run

It talks about setting `zeroBase` value to make Spice output all states relative to this planetary body.  

However, it won't do it relative to a rotating planet fixed frame to the best of my knowledge.  There you'd have to do some post-processing.

[Luca Pascali]

Thanks a lot for the answer! 

Actually I had already set Earth as zero base and was just wondering if it was possible to get directly a state in a rotating planet fixed frame. I will just do some post-processing exploiting the J20002Pfix matrix.