What is elevation angle?
Elevation angle (or look angle) is the angle measured upward from the local horizontal plane to the direction of a satellite as seen from a ground station or user terminal. At 0° elevation, the satellite is on the horizon; at 90°, it is directly overhead (zenith). The elevation angle determines the atmospheric path length the signal must traverse and has significant practical consequences for link quality and terminal installation.
Effect on link performance
At low elevation angles (0–10°), radio signals must pass through much more atmosphere than at high elevations — increasing atmospheric absorption, rain attenuation, and multipath reflection from terrain and buildings. A signal at 5° elevation traverses approximately 10× more troposphere than at 90°. For Ka-band GEO services, the rain fade margin must be much larger at low elevation angles. Most commercial VSAT systems specify a minimum operational elevation angle of 5–15° for GEO satellites, and many residential satellite installations require even higher minimums (20–25°) to ensure reliable performance.
GEO vs. LEO elevation geometry
GEO satellites appear at fixed elevation angles that depend on the user's latitude and the satellite's longitude. A UK user viewing Astra at 28.2°E sees it at approximately 27° elevation — adequate for VSAT but lower than users in equatorial regions who see GEO satellites near zenith. For LEO satellites, elevation angle varies continuously as the satellite passes overhead; the maximum elevation (the transit's 'peak') determines the duration of usable contact. At 550 km altitude, a pass at 0° minimum elevation lasts about 10 minutes; a direct overhead pass lasts about 12 minutes.