Space Station Ground Track and Relay 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 2D top-down companion to the 3D relay 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. The same 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. Drag the view to pan and scroll to zoom in on any part of the geometry.