as a summary: we are experimenting with a new poliastro.earth module, adding a class EarthSatellite that composes an Orbit and a new object Spacecraft. this class has one convenience method now, propagate, that takes the configuration of the perturbation directly, like this:

from astropy import units as u

from poliastro.examples import iss  # Orbit
from poliastro.earth.atmosphere import COESA76  # Moved!
from poliastro.earth.enums import EarthGravity  # New!
from poliastro.spacecraft import Spacecraft  # New!

sat = EarthSatellite(iss, Spacecraft(A=10 * u.m ** 2, C_D=2.2 * u.one, m=420e3 * u.kg)
sat.propagate(100 * u.min, gravity=EarthGravity.J2, atmosphere=COESA76())

The idea is that this Spacecraft can have properties like geometry, mass, and who knows? Propulsion, attitude... And EarthSatellite can offer some convenience methods that combine the orbital position and the properties of a spacecraft. Some parts of this can be generalized to arbitrary objects of the Solar System, we are using the Earth as a "playground" for new ideas.

This is highly experimental and we are not 100 % settled yet, so all feedback is more than welcome.

for the second part of GSOC, we'd like to focus on questions like:

• what's the area of the Earth that this satellite can observe?
• what's the area covered by this sensor on board of this satellite?
• does this site on Earth have visibility on this satellite?

so we need to explore a bit of geodesy and spherical trigonometry meuge

to have a clear end goal, I would focus on the first question: what's the area that this satellite can observe? and set some assumptions:

• this area is a polygon
• the coordinates of this polygon evolve with time
• the Earth is an ellipsoid (WGS84)
• for the moment, no notion of sensor, payload, attitude dynamics, or whatever: we assume the satellite can look in all directions

so, the first sub question is: given a (x, y, z) position in space and the WGS84 Earth ellipsoid, what's the area visible by the satellite?

• we need to understand how to represent it. I think a Shapely polygon https://shapely.readthedocs.io/ or a GeoPandas GeoSeries/GeoDataFrame https://geopandas.org/data_structures.html would be the first option
• and then, we need to understand how to compute it. I anticipate that libraries like GeographicLib https://pypi.org/project/geographiclib/ or pyproj https://proj.org/geodesic.html will be helpful

I said at the beginning that we would like to represent the area as a polygon. perhaps that's too ambitious and only useful for visualization purposes, and we could focus on:

the most relevant parameters of the coverage problem (i.e., ground-range angle, elevation angle, horizon-boresight angle)

I said at the beginning that we would like to represent the area as a polygon. perhaps that's too ambitious and only useful for visualization purposes, and we could focus on:

the most relevant parameters of the coverage problem (i.e., ground-range angle, elevation angle ε, horizon-boresight angle)

I said at the beginning that we would like to represent the area as a polygon. perhaps that's too ambitious and only useful for visualization purposes, and we could focus on:

the most relevant parameters of the coverage problem (i.e., ground-range angle Λ, elevation angle ε, horizon-boresight angle)