System aspects on clusters of small sensor satellites

A single large satellite can be replaced with a configuration of several smaller satellites which together performs the same function as a larger satellite. The report deals with how such "formation-flying" satellites can be used for military applications and what sensor system then can be used. Sensor systems discussed are SAR, SIGINT (passive interception), and optical systems. An overview of a few of the multitude of on-going projects around the world is given. A short review of orbits for formation-flying satellites is also given. The advantages with systems of satellites in comparison to solitary satellites are presented. One of the main ideas behind the concept of formation flying is that by using several small satellites the costs are reduced and the reliability of the system is increased. The costs may diminish when the microtechnology is mature enough for massproduction of microsatellites. The report shows that it is primarily the SAR technology which is useful for military applications; secondly, it is SIGINT. Using formation-flying SAR systems, detection of moving objects can be improved; stealth objects can more easily be detected; and the creation of elevation maps is facilitated. A number of proposals on how a continued investigation of the possibilities to use small co-operating satellites can be executed are presented.