Instrument coverage for LEO satellites

[lalligagger]

Hi all,

I've been getting started with skyfield over the last month to map the coverage of LEO satellites. To do this I'm projecting an instrument FOV using a pseudo-conversion to local vertical, local horizontal (LVLH) frame. Here is the repo. There are many refinements/ optimizations to make but the basics are there.

The FOV projection requires scipy.spatial.transform.Rotation which could potentially be replaced by implementing Euler-Rodrigues formula. For coverage statistics and mapping I have used geopandas and folium/leaflet.

I wanted to thank @brandon-rhodes for his work on skyfield and python-sgp4 to make this possible, and maybe link up with others who are interested in improving this functionality. I found the following related issues as I worked through this:

• extend subpoint() to off-nadir #195
• Support for local satellite reference coordinate system #492

Cheers,
Kevin

PS - attached are two html outputs which show the FOVs and coverage statistics for Landsat 8 & Landsat 9, over 3 day period.
samples.zip