PACKET TELEMETRY AND PACKET TELECOMMAND: THE NEW GENERATION OF SPACECRAFT DATA HANDLING TECHNIQUES

Abstract

During twenty-five years of space exploration by NASA, the formats and protocols used within the flow of spacecraft telemetry and telecommand data have usually been customized from mission-to-mission. Consequently, considerable resources are often expended by each project in redesigning and testing significant elements of the spacecraft and ground network hardware and software. This high degree of customization tends to inhibit automation of the data handling processes, thus raising costs and potentially reducing reliability. The concepts of standardized “Packet Telemetry” and “Packet Telecommand” are emerging as viable alternatives to the constant cycle of redesign. Within each concept, autonomous “packets” of data are created within space or ground application processes, using standard formatting techniques. These packets are then switched end-to-end through the space data network to their destination application processes, using standard transfer protocols. As a result the intermediate data networks may be designed to be completely mission-independent, thus facilitating a high degree of automation and interoperability. The Packet Telemetry protocols are currently mature and are in a final review cycle; the Packet Telecommand protocols are more developmental, but essentially form symmetrical “mirror-images” of the telemetry formats. This paper reviews both sets of standard protocols.