Planning for the upgrade and/or replacement of Deep Space Network (DSN) assets that typically operate for forty or more years necessitates understanding potential customer needs as far into the future as possible. This paper describes the methodology Deep Space Network (DSN) planners use to develop this understanding, some key future mission trends that have emerged from application of this methodology, and the implications of the trends for the DSN's future evolution. For NASA's current plans out to 2030, these trends suggest the need to accommodate: three times as many communication links, downlink rates two orders of magnitude greater than today's, uplink rates some four orders of magnitude greater, and end-to-end link difficulties two-to-three orders of magnitude greater. To meet these challenges, both DSN capacity and capability will need to increase. I. Introduction: The Mission-Driven Evolution of the Deep Space Network INCE its inception, the Deep Space Network has had to evolve its capability and capacity in anticipation of the increasingly challenging missions needing it for communication and navigation support. The Network began under U.S. Army auspices in 1958 with the Jet Propulsion Laboratory's (JPL's) efforts to develop and operate the nation's first satellite, Explorer 1. To receive telemetry and plot the orbit of this satellite, JPL developed the "Microlock" tracking and data acquisition system-a set of somewhat portable tracking stations located at each of four sites: Cape Canaveral, Nigeria, Singapore, and San Diego. 1 Meanwhile, the Department of Defense established the Advanced Research Projects Agency (ARPA) to "promote, coordinate, and manage all existing military and civilian space activities." As part of this responsibility, ARPA was directed to oversee a lunar space program called Pioneer. Understanding that the existing "Microlock" system was inadequate for tracking spacecraft at lunar distances, ARPA approved a JPL plan to adapt an existing 26m radio astronomy antenna design to the tracking of the Pioneer probes at L-band. Three of these antennas were to be procured to form what ARPA referred to as the Tracking and Communications Extraterrestrial Network (TRACE). However, as JPL began construction on the first 26m antenna, the civilian space program was transferred to the newly formed National Aeronautics and Space Administration, and JPL's transfer from the Army to NASA quickly followed. Under this new organizational arrangement, JPL completed the first 26m antenna at the end of 1958-located at Fort Irwin in Goldstone, California. The antenna was named Pioneer Station after the first two spacecraft with which it communicated, Pioneers 3 and 4. As NASA pursued increasingly ambitious robotic reconnaissance of the moon, construction of other stations followed. In 1960, JPL supervised the construction of NASA's first overseas station in Woomera, Australia. NASA's second and third overseas stations were constructed near Johannesburg, South Africa (1961) and about 40 miles west of Madrid, S...