This is a top-down (north-pole) 2D companion to the 3D constellation simulator, using the same real orbital mechanics:
- Kepler's third law sets the period from the altitude: T = 2π√(r³/μ), with r = Earth radius + altitude and μ = 398,600.4 km³/s² Earth's gravitational parameter. Lower orbits move faster.
- Each orbital plane is tilted by a fixed 53° inclination (a Starlink-style Walker Delta pattern) and spread evenly in right ascension, so from above the pole each plane traces its own ellipse.
- A satellite's footprint (coverage cone) has half-angle acos(Re/r) — higher altitude means a smaller r-based half-angle cosine but a wider footprint radius, since the satellite sees more of the curved Earth.
- The yellow marker is a fixed reference ground point (40°N). It counts as "visible" to a satellite the instant that satellite's footprint sweeps over it — exactly the same geometric test the 3D sim uses to shade its coverage zone.
- Global coverage % samples points evenly across the whole sphere (not just this 2D slice) and reports the fraction currently inside any satellite's footprint.