SPHERES

The Synchronized Position Hold Engage and Reorient Experimental Satellite (SPHERES) are a series of miniaturized satellites developed by MIT's Space Systems Laboratory for NASA and US Military, to be used as a low-risk, extensible test bed for the development of metrology, formation flight, rendezvous, docking and autonomy algorithms that are critical for future space missions that use distributed spacecraft architecture, such as Terrestrial Planet Finder and Orbital Express.

The battery-powered, self-contained units can operate semi-autonomously, using CO2-based cold-gas thrusters for movement and a series of ultrasonic beacons for orientation.

[4] The initial development of SPHERES started in 1999, by a team of students at Massachusetts Institute of Technology, as part of an aerospace engineering program.

Several prototypes were developed during the course of the program, and were tested in ground laboratories as well as in parabolic flights using NASA's reduced gravity aircraft.

In collaboration with Aurora Flight Sciences, the design was refined and six flight-ready satellites were built, out of which three were delivered to the International Space Station.

[6] SPHERES satellites are able to connect to the International Space Station's on-board Wi-Fi network for tasks that require a higher data bandwidth.

The laboratory is able to provide a navigational reference frame in a similar configuration as in the International Space Station using five ultrasonic beacons, and the output of cold gas thrusters are analysed to simulate the expected movement in a micro-gravity environment.

[8][9] The Flight Assembly Laboratory is used to prepare and test consumables – battery packs and liquid CO2 containers – used by the SPHERES units.

Spent CO2 containers are returned to the Flight Assembly Laboratory for re-filling and safety testing before being flown back to the International Space Station.

Each satellite was enhanced through the use of processing power, wireless networking, camera, sensors and the touch sensitive display of the connected smartphone.

The availability of the Android operating system's source code enabled the devices to be used as a compact, low-cost, low-power computers.

[11][12] The experiment studies the use of SPHERES satellites to conduct autonomous and remotely operated environmental and inventory surveys aboard the Space Station, with the aim of reducing the astronaut's time spent on routine tasks.

[11] The SmartSPHERES experiment is managed by the Intelligent Robotics Group of the Ames Research Center with funding from Enabling Technology Development and Demonstration program of NASA's Exploration Systems Mission Directorate.

[13] DOD SPHERES-RINGS (Department of Defense SPHERES-Resonant Inductive Near-field Generation System) experiment aims to develop software and hardware capable of Electromagnetic Formation Flight (EMFF) and wireless power transfer in microgravity environment.

[14] Individual SPHERES units are maneuvered with respect to each other by generating controlled attractive, repulsive and shear forces using the electromagnetic coils.

Zero Robotics is an annual international competition conducted by MIT, where participating student teams program the SPHERES satellites to solve a specific challenge.