Fig: Satellite link: earth station A transmits an uplink; the transponder relays a downlink to earth station BFig: Concentric orbit altitudes: LEO, MEO and GEO around the EarthFig: Kepler's laws: elliptical orbit with Earth at a focus and equal areas swept in equal times (left); the linear T^2-a^3 relation (right)Fig: Bent-pipe transponder: receive antenna LNA frequency converter channel filter HPA transmit antenna. A regenerative transponder additionally demodulates and remodulatesFig: Earth station: transmit chain (codec-conv) and receive chain (LNA-conv) sharing a duplexer, dish, tracking and monitor/controlFig: Spin versus three-axis stabilization and the closed-loop az/el tracking servoFig: VSAT topologies: star (remotes reach the hub in two hops) and mesh (remotes communicate directly in one hop)Fig: VSAT path: user IDU ODU (BUC/LNB/dish) satellite hub or remote VSATFig: Link-budget chain: uplink EIRP and losses to the satellite G/T and transponder, then downlink EIRP and losses to the earth-station G/T, combined as C/N_0