Observations from satellite

[MaximeJ]

Hi @jlipinski,

@jlipinski

I’m using DoubleDihedraFieldOfView but how spacecraft frame of reference is defined? PLUS_I is in the direction of movement, MINUS_K is towards Earth and J is perpendicular?

You can define S/C frame using a specific AttitudeProvider in your propagator.
For example, supposing that inertialFrame is the propagation frame and prop is the propagator:

AttitudeProvider attProv = new LofOffset(inertialFrame, LOFType.TNW);
prop.setAttitudeProvider(attProv);

This will align X (or PLUS_I) with velocity, Z (or PLUS_K) with the orbital momentum and Y will be perpendicular.
Here to see more about LOFTypes.

@jlipinski

And then I don’t really understand how to use InterSatDirectViewDetector. Ideally I would want to combine them using BooleanDetector like this (earth is defined earlier as OneAxisEllipsoid):

InterSatDirectViewDetector isdvd = new InterSatDirectViewDetector(earth, sPropagator);
BooleanDetector detector = BooleanDetector.andCombine(fovd, isdvd);

That could work but you have to negate the FieldOfViewDetector because it’s g function is negative when target is in FOV (see more for example here about combining detectors and sign of g).

@jlipinski

I don’t really undestand which propagator to use in those instances and if this approach is even correct for this problem.

You need to add the primary propagator (the one with the camera).
You cannot use PositionBuilder it will return the position of the primary.
You have to implement your own measurements and builder.
The structure of the measurement class would be just like an InterSatelliteRange but instead of computing the range you simply return the PV of the secondary object.

Does this help ?