The Cassini/Huygens Navigation Ground Data System: Design, Implementation, and Operations

Abstract

The highly successful Cassini/Huygens mission conducted almost 20 years of scientific research in both its journey across the solar system and its 13-year reconnaissance of the Saturnian system. This operational effort was orchestrated by the Cassini/Huygens Spacecraft Navigation team on a network of computer systems that met a requirement for no more than two minutes of unplanned downtime a year (99.9995% availability). The work of spacecraft navigation involved rigorous requirements for accuracy and completeness carried out often under uncompromising critical time pressures and resulted from a complex interplay between several teams within the Cassini Project, conducted on the Ground Data System. To support the Navigation function, a fault-tolerant, secure, high-reliability/high-availability computational environment was necessary to support operations data processing. This paper discusses the design, implementation, re-implementation, and operation of the Navigation Ground Data System. Systems analysis and performance tuning based on a review of science goals and user consultation informed the initial launch and cruise configuration requirements, and then those requirements were subsequently upgraded for support of the demanding orbital tour of the Saturn System. Configuration management was integrated with fault-tolerant design and security engineering, according to cornerstone principles of Confidentiality, Integrity, and Availability, and strategic design approaches such as Defense in Depth, Least Privilege, and Vulnerability Removal. Included with this approach were security benchmarks and validation to meet strict confidence levels. The implementation of this computational environment incorporated a secure, modular system that met its reliability metrics and experienced almost no downtime throughout tour operations.