This publication describes the giant-capacity space communications installation called the "Tracking and Data Relay Satellite System" (TDRSS). Chapters include: (1) "A New Communications Bridge to Orbit" (illustrating what it is and how it looks); (2) "TDRSS Goes to Work" (describing how it functions); (3) "The Ground Segment" (discussing the system's link with Earth); (4) "Why TDRSS is Needed" (its history and rationale); and (5) "The Space Network Today and Tomorrow." The technical information on the TDRSS, including frequency bands and ground terminal equipment, is appended. (YP)