RE: [Orekit Users] Correct values for DihedralFieldOfViewDetector axis1, axis2, and center

[Carlos Krefft <ckrefft@rsmas.miami.edu>]

Thanks Luc,

I'm using the TLEPropagator. Do you know if this insures earth is at a MINUS_J direction? If so, I should be okay right?

Carlos K.



-----Original Message-----
From: orekit-users-request@orekit.org [mailto:orekit-users-request@orekit.org] On Behalf Of MAISONOBE Luc
Sent: Friday, March 14, 2014 4:31 PM
To: orekit-users@orekit.org
Subject: Re: [Orekit Users] Correct values for DihedralFieldOfViewDetector axis1, axis2, and center

Hi Carlos,

Carlos Krefft <ckrefft@rsmas.miami.edu> a écrit :

> Can anyone tell me what the correct values for axis1, axis2, and 
> center would be for a  target on earth?
>
> I've modefined the DihedralFieldOfViewDetectorTest file
> (\orekit-6.1\src\test\java\org\orekit\propagation\events\DihedralField
> OfViewDetectorTest)
>
> To have a target on earth but not sure what Vector3D parameter values 
> should be used for ground pointing:
>
> ...
> GeodeticPoint point = new
> GeodeticPoint(FastMath.toRadians(25.61379),
> FastMath.toRadians(-80.38402), 0.0);
>                 TopocentricFrame stationFrame = new 
> TopocentricFrame(earth, gPoint, "AOI");
>                 final PVCoordinatesProvider aoiTarget = stationFrame;
>
> final double maxCheck  = 1.;
>
> final Vector3D center = Vector3D.MINUS_J; final Vector3D axis1 = 
> Vector3D.PLUS_K; final Vector3D axis2 = Vector3D.PLUS_I;

It really depends on the attitude you have, because these vectors are defined in the spacecraft frame.

If you have an attitude provider that ensures the Earth is in the MINUS_J direction, then you should be fine. The "center" vectors defines the center of the field of view, i.e. the pointing direction of the instrument with respect to spacecraft frame, and the attitude provider defines the way the spacecraft frame is oriented with respect to the inertial frame. So it is basically a two step definition and you have to get both steps right.

Hope this helps
Luc

>
> final double aperture1 = FastMath.toRadians(28); final double 
> aperture2 = FastMath.toRadians(120);
>
> final EventDetector sunVisi =
>            new DihedralFieldOfViewDetector(maxCheck, aoiTarget, 
> center, axis1, aperture1, axis2, aperture2).
>            withHandler(new DihedralSunVisiHandler()); ...
>
> Any help would be greatly appreciated.
>
> Thanks,
> Carlos Krefft
>
>
>



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