Check optical visibility between graound station and a spacecraft

Orekit Python Wrapper usage
1

Hi,
I would like to check the visibility of a spacecraft from an optical ground station.
The propagator is already implemented, so now I have both the position of the satellite and the ground station in the same reference framen (actually EME2000).
How can I check visibility?

Thanks
Regards
Gaetano

2

Hi @Tanozar,

Welcome back to the forum!

You can use an ElevationDetector, see the tutorial VisibilityCheck.

Cheers,
Maxime

3

Hi Maxime,
thanks for answeirng. I’ll try it!!!

Cheers

4

Hi there,

The aforementioned tutorial shows how to detect starts of visibility windows (based only on an minimal elevation angle criterion) during orbit propagation. If you want to know the elevation at a specific epoch and you already have the position-velocity vector for the observable (as well as the geodetic coordinates of your sensor), you can simply define a TopocentricFrame like in the example and call the getElevation method with the right arguments. This however neglects light-time delay. Also note that there are other factors to take into account for observability with classical ground-based telescopes, such as eclipse conditions.

Cheers,
Romain.

5

Hi Serrof
I was controlling the tutorial suggested by @MaximeJ and, actually no information about sun position, eclipse conditions are reported. So, probably the tutorial is useful if one want to know if a satellite is above the horizon but for checking optical visibility something missing.
Do you have other suggestion?

Thanks

6

The two other observability conditions (assuming passive, visible-light telescopes whose images are post processed via astrometry) that you can check with Orekit are:

  • is the observable in sunlight?
  • is the sensor in nighttime?

They can both be assessed through
the sign of the so-called g function of their detectors (primarily designed for propagation events), respectively EclipseDetector and GroundAtNightDetector. I don’t think there are present in the tutorials (I may be wrong), but you can see how they are in used in the Javadoc or the unit tests.

7

Hi, if you are using the python version as indicated in your forum selection, there is a visibility example at examples/Event_Detectors.ipynb · master · Orekit Labs / Orekit Python Wrapper · GitLab
and examples · master · Orekit Labs / Orekit Python Wrapper · GitLab

Regarsd

8

Thanks @petrus.hyvonen
I’ll try your suggestions

Cheers
Gaetano