S-band Multiple Access
S-band Multiple Access, also known as SMA, is a radio wave transmission technology used by the Tracking and Data Relay Satellite System (TDRSS) to facilitate communications between multiple spacecraft. It uses a phased array consisting of two antennae. One antenna is dedicated to the simultaneous reception of S-band microwave radio transmissions from up to five spacecraft. The other antenna is used for sending data to a single spacecraft.