Spacecraft monitoring and control a pragmatic evaluation through the eyes of the CAP theorem

Abstract

The CAP theorem has detected and proven universal limitations on distributed systems design and implementation. It states that it is impossible for a distributed computer system to simultaneously be Consistent (all nodes output the same information at all times), Available (every request receives a response about whether it was successful or failed) and Partition tolerant (the system continues to operate despite arbitrary message loss or failure of part of the system). These proven limitations affect how systems are implemented and therefore must be tackled early in the design stage. Using the CAP theorem as a known limitation we analyzed how its restrictions were negotiated in current spacecraft systems and evaluated its use for future more complex missions. NomenclatureCAP = Consistency, Availability and Partition-tolerance CCSDS = Consultative Committee for Space Data Systems DTR = Data Transmission Relay ECSS = European Cooperation on Space Standardization EDRS = European Data Relay System ESA = European Space Agency ESOC = European Space Operations Centre HFA = History Files Archiver MCCM = Multi-Mission Configuration and Central Monitoring OBQM = On-Board Queue Model PARC = Packet ARChive PUS = Packet Utilization Standard SCOS = Spacecraft Control and Operation System (ESA Software) SMCS = Spacecraft Monitor and Control System (any software for monitor and control of spacecrafts)