Formation flying system design for a planet-finding telescope-occulter system

The concept of flying an occulting shade in formation with an orbiting space telescope to enable astronomical imaging of faint targets while blocking out background noise primarily from starlight near distant Earth-like planets has been studied in various forms over the past decade. Recent analysis has shown that this approach may offer comparable performance to that provided by a space-based coronagraph with reduced engineering and technological challenges as well as overall mission and development costs. This paper will present a design of the formation flying architecture (FFA) for such a collection system that has potential to meet the scientific requirements of the National Aeronautics and Space Administration's (NASA's) Terrestrial Planet Finder mission. The elements of the FFA include the relative navigation, intersatellite communication, formation control, and the spacecraft guidance, navigation, and control (GN&C) systems. The relative navigation system consists of the sensors and algorithms to provide necessary range, bearing or line-of-sight, and relative attitude between the telescope and occulter. Various sensor and filtering (estimation) approaches will be introduced. A formation control and GN&C approach will be defined that provides the proper alignment and range between the spacecraft, occulter, and target to meet scientific objectives. The state of technology will be defined and related to several formation flying and rendezvous spacecraft demonstration missions that have flown.