Get inclination in specified frame

Orekit usage
#1

Method getI() can be used to retrieve the inclination of a satellite from its SpacecraftState, eg. FramesFactory.getEME2000().

In which frame is it returned? I understand it is returned the frame in which the state is defined.

Is it possible to get the inclination in another, specified, frame, eg. FramesFactory.getTOD(IERSConventions.IERS_2010, false)? maybe using some transform method?

Thank you,
Alfredo

#2

Hi @acapobianchi,

Yes you need to perform a frame conversion of the orbit.
But there are built-in function that can help like SpacecraftState.getPVCoordinates(frame).

Example:

incInMyFrame = new CartesianOrbit(myState.getPVCoordinates(myFrame), myFrame, myState.getMu()).getI();

Hope this helps,
Maxime

2 Likes
#3

Hi All,(@MaximeJ )

Why should the inclination be different for a different frame, since it is the angle from orbit plane to equatorial plane?
( I am confused about this, since I am getting different inclination angles from TEME frame and GCRF frames)

#4

The equatorial plane is different in different frames. Some frames are at fixed dates (GCRF, EME2000) and consider the orientation that was active at that date. Some frame take into account only mean motion (i.e. precession) while other also take short periods (i.e. nutation) into account. The frames that depend on dates may use current date or epoch (this is a source of confusion for TEME with no official meaning and just general consensus following Vallado’s interpretation).

The main difference will come from frames with fixed date far in the past and “of date” or “of epoch” frames, because you get the build up for precession for decades.

#5

Thank you very much for the explanation !!