Space Station Relay Link Coverage

A space station in low Earth orbit spends most of its time out of sight of any single ground antenna — the planet's curvature blocks the line of sight for long stretches. This simulator renders the real fix: a network of geostationary relay satellites (modeled on NASA's TDRS constellation) positioned high enough to see nearly half the Earth at once, plus a direct ground antenna with an elevation mask. A true ray–sphere intersection test against Earth decides, every frame, whether the station can see each relay or the ground station, so you watch the active link hop between TDRS-East, TDRS-West and the ground antenna in real time — and watch it drop out entirely when you switch a relay off and the orbit carries the station into the resulting "zone of exclusion". Live readouts track the current link, time to the next hand-off or loss of signal, and coverage percentage over the trailing orbit, exactly the numbers a real mission communications planner works from.