The MIT Space Systems Laboratory developed Synchronized Position Hold, Engage, Reorient Experimental Satellites (SPHERES) formation flight testbed to provide the Air Force and NASA with a long term, replenishable, and upgradable testbed for the validation of high risk control, metrology, and autonomy technologies. The technologies are critical to the operation of distributed satellite and docking missions such as TechSat21, Starlight, Terrestrial Planet Finder, and Orbital Express.