The NASA Space Network Demand Access System (DAS)

The Demand Access System (DAS) of the NASA Space Network offers a new and innovative service for space operations by providing continuous and automated communication links via the Tracking and Data Relay Satellite System (TDRSS). Operational in October 2002, the Demand Access System expands the TDRSS Multiple Access return (spacecraft-to-ground) capabilities by building on the availability of ground-based Commercial Off-the-Shelf (COTS) systems, such as the Third Generation Multiple Access Beamformer Subsystem (TGBFS) and the Programmable Telemetry Processor (PTP), and by using networking standards, including TCP/IP and web-based interfaces. This paper reviews the DAS architecture, noting the use of COTS hardware components, as well as its automated approach to space operations for Earth-science and space science missions.