I added support for satellite footprints using a spherical earth model approximation. I added the bare-minimum code and configuration options required to do this. You can control footprint visibility and color using two new configuration options: show_footprints and footprint_color.
When show_footprints is true, each satellites footprint is rendered. Below is a snapshot of SRMSat with footprints enabled.
Ground station line of site indicators can be rendered simultaneously. Below you can observe two example ground stations within the footprint of SRMSat. Both ground stations are displaying their line of sight indicators.
After a few seconds, I took another shot from the top. Notice how the ground stations are right near the edge of the footprint and line of sight indicators are still enabled (as expected).
As the footprint moves away from the ground stations, we would expect to lose line of sight. Below, you can observe an example ground station right on the edge of the footprint.
Eventually, the ground station will sit right outside of the footprint and line of sight will be lost.
Now that basic footprint functionality is complete, we have many more possibilities. The next step could be to plot collections of ground station networks and plan telemetry collection schedules. But before doing this, I am going to finish implementing the same type of visualization but for ground station visibility.