Very small satellites can be put in ready-and-waiting parking orbits, then called to action to inspect or intercept a troublemaking asteroid. Photo shows PICOSat, a 147-pound (67-kilogram) microsatellite developed for the US Air Force Space Test Program (STP) by Surrey Satellite Technology Limited (SSTL) in the UK. Satellite was launched successfully from Alaska last year. CREDIT: SSTL
