Constellation Design Calculator

This calculator sizes a Walker-style satellite constellation for continuous coverage using simplified spherical geometry rather than a full orbital-mechanics simulation. It starts from Earth's angular radius as seen from orbit — a function purely of altitude, since a satellite farther out sees a smaller slice of Earth's disk — and combines that with your minimum usable elevation angle (how high above the local horizon a satellite must sit before its signal counts as usable) to derive a half-swath coverage angle on the ground. Satellites-per-plane and number-of-planes are then back-calculated so each satellite's ground footprint just overlaps the next, closing gaps along both the along-track and cross-track directions; the coverage-overlap-margin input deliberately shrinks the usable swath to build in redundancy against an unplanned satellite loss. Orbital inclination sets the maximum latitude actually covered — a 53° inclination, similar to much of Starlink's constellation, reaches mid-latitudes but leaves the poles dark, while a 90° polar inclination is needed to reach the poles at all.

Note that this model's plane count and satellites-per-plane come entirely from altitude, minimum elevation, and overlap margin — inclination only determines which latitudes get covered, not how many planes the swath math calls for, so a polar and a mid-inclination constellation at the same altitude come out needing the same plane count here. The calculator's own documentation flags its key limitation plainly: it uses idealized spherical trigonometry and ignores both J2 perturbation (the orbital drift real satellites experience from Earth's oblateness) and the phasing optimization real constellation designers rely on to minimize satellite count — so treat the total-satellites figure as a first-order sizing estimate for early trade studies, not a final architecture. Raising altitude shrinks the required constellation size but raises both launch cost and per-satellite link complexity, a trade every constellation designer has to weigh.