Distributed spacecraft systems is envisioned to Other modular and flexible efforts providing Lego-like provide the technology platform to extend, improve and construction capability similar to the aforementioned projects enable mission concepts such as wide aperture radars for are inflatable antennas [2], [3] and the Non Contacting high-precision space-borne surveillance, 3D mapping of Modular Reconfigurable Spacecraft Project [4]. The DARPAEarth's magnetic field and even deep-space interferometry NASA Orbital Express on-orbit servicing mission is in a to better understand the origins of the universe. However, a similar spirit to these projects since it demonstrates automated mission with a fully autonomous spacecraft fleet flying in rendezvous and docking technology and performs physical close-proximity or in a tightly kept configuration has yet to exchange of parts. This mission will play a central role in space be realized. experimentation of modularity, reconfigurability and longevity In this work, we review the major technology drivers and for future missions. challenges for such next generation systems across a selective set of on-going, cancelled or proposed spaceThe second category of formation flight is envisioned to missions. Our analyses identify five main classes of provide innovative approaches in applications such as technology drivers from navigation and control distributed imaging capabilities both in planetary orbits and perspective. These drivers are enumerated for a typical deep space, mapping of the Earth's magnetic field accurately, interferometric SAR example. The example illustrates steep and large scale testing of physical phenomena in the technological challenges such as the need for sub-millimeter foreseeable future. This category is the main focus of this relative navigation solution accuracy for even decimeter paper. level vertical image resolution. We conclude with an initial effort at outlining a cost effective and robust roadmap for Advantages of distributed space systems include flight maturation of the key technologies to deem such improvement of observation resolution, thus scientific return, missions and goals achievable.prevention of a single point of failure and suitability to supporting living environments. Without such systems, these I. INTRODUCTION would be either unlikely or impossible goals. Some enabling technologies for distributed systems have been demonstrated so Recent successes in missions such as EO-1 EFF, Cluster II, far. These include on-board orbit control [5], autonomous ST5, and with many more projects such as Laser Interferometer simple constellation keeping [6], somewhat accurate relative Space Antenna (LISA), PRISMA, MMS on the drawing board, motion modeling [7],[8], CDGPS [9],[10], formation distributed spacecraft concepts has attracted a sustained interest algorithms [32] various payloads, basic spacecraft autonomy from space organizations and scientists.[11], on-board processing. The reader is referred to references[12] and [13] for a survey of state o...
