Ground station implementation

[gomezzz]

Description

Summary of changes

• Implemented ground station actor with vision cones etc.
• Some bugfixes along the way from bugs introduced in Set position only once #45
• Added some missing docstrings
• Added skyfield

Resolved Issues

• fixes Add ground stations #16

How Has This Been Tested?

• pytest
• test driven development

Related Pull Requests

N/A

[GabrieleMeoni]

I still need to test it, but I would like to understand it better first.

[gomezzz]

@GabrieleMeoni I am waiting on a review of this if you find a second 🙏 (starting to accumulate a lot of PRs :D )

[GabrieleMeoni]

Everything works fine for me, but I would add:

-) Comments to explain the rationale of tests (at a first glance, satellites with 0 velocity are weird. Also, it is not immediate to understand why satellites becomes visible over time).

-) Test to check GS visibility with non-zero satellite velocity. Maybe S2 (tle are notes and GS positions should be retrievable) and check how long the satellite is visible. This should give us a reasonable Ground-truth.

[gomezzz]

@GabrieleMeoni

-) Test to check GS visibility with non-zero satellite velocity. Maybe S2 (tle are notes and GS positions should be retrievable) and check how long the satellite is visible. This should give us a reasonable Ground-truth.

Do you have this data? I don't have it, especially the altitude angle at which the station are able to talk to S2 and window length I can't find online and I don't wanna spend hours searching.

[gomezzz]

Added test for groundstation window length