SPHERES: Development of an ISS Laboratory for formation flight and docking research

The MIT Space Systems Laboratory (SSL) is developing the SPHERES (Synchronized Position Hold Engage Reorient Experimental Satellites) formation flight testbed to provide multiple investigators with a long term, replenishable, and upgradable testbed for the validation of high risk metrology, control, and autonomy technologies. These technologies are critical to the operation of distributed satellite and docking missions such as TechSat21, Starlight, Terrestrial Planet Finder, and Orbital Express. The development of SPHERES follows the guidelines set in a laboratory design philosophy created from lessons learned through the development and operation of prior microgravity testbeds by the MIT SSL. The philosophy ensures that the resulting laboratory provides a risk-tolerant and cost-effective environment that facilitates the design process and reduces the development costs of unproven technologies. The testbed consists of three free flyer units which can control their relative positions and orientations in six degrees of freedom. The testbed can operate in 2D on a laboratory platform and in 3D on NASA's KC-135 and inside the International Space Station. Flight tests aboard NASA's KC-135 and studies in the ground laboratory confirm the functionality of SPHERES.