NASA's goggle-eyed SPHERE robots create 3D maps on the fly
By David Szondy
April 27, 2013
Take the little floating ball that gave Luke Skywalker so much trouble during lightsaber practice, slap a pair of huge welder’s goggles on it and you start to get a picture of NASA’s latest foray into flying robots. Currently being tested aboard the International Space Station (ISS), MIT Space Systems Laboratory’s SPHERES-VERTIGO system is a free-flying robot with stereoscopic vision that is part of a program to develop ways for small satellites to autonomously create 3D maps of objects such as asteroids or disabled satellites.
The first part of the SPHERES-VERTIGO system is the Synchronized Position Hold Engage Reorient Experimental Satellites (SPHERES). Developed as part of a DARPA project, SPHERES may look like a plastic toy, but it hides some fairly sophisticated technology inside. It is designed as an experimental testbed for guidance, navigation and control algorithms and is being used for autonomous docking, formation flying and tele-operation tests.
Three of the free-flying robots have been aboard the ISS since 2006. Each one is 21.3 centimeters (8.3 in) in diameter, weighs about 4.16 kilograms (9.17 lb) and moves about by means of a carbon dioxide cold-gas system for both propulsion and attitude control. Navigation is achieved by means of a ”pseudoGPS” ultrasonic time-of-ﬂight sensing system that uses sonic beacons mounted on the inside of the ISS module’s hull, while onboard gyroscopes estimate the position, orientation, linear and angular velocity with respect to the interior of the ISS.
To help them accomplish its tasks, the SPHERES robots have a Texas Instruments C6701 Digital Signal Processor and a 900 MHz low-bandwidth modem for communication with a laptop. This is all powered by 16 AA non-rechargeable batteries.
The VERTIGO Goggles make up the other half of SPHERES-VERTIGO. VERTIGO stands for Visual Estimation and Relative Tracking for Inspection of Generic Objects and since October 2012, MIT Space Systems Laboratory and Aurora Flight Sciences have had astronauts putting the VERTIGO Goggles through their paces on the ISS.
Weighing 1.6 kilograms (3.5 lb), The VERTIGO Goggles are an add-on for SPHERES and are a self-contained, battery-powered unit made of a pair of cameras in a synchronized stereo configuration hooked to a 1.2 gigahertz Linux data processor, a 802.11n network card and a 128 GB flash drive. The unit is intended to be easily modified with different sensors and configurations.
Put together, SPHERES-VERTIGO is designed to perform research on the inspection of unknown, non-cooperative targets that may be moving and tumbling in space. The SPHERES robot’s job is to navigate around an object while the VERTIGO Goggles uses its cameras to build up a 3D model of the object by matching up the images taken against “feature steps,” such as corners. It does this autonomously in order to avoid delays that occur in communicating with ground control or a space station during an actual mission. All data processing is done by the VERTIGO goggles and it can stream video to the astronaut operator by Wi-Fi or ethernet in real time.
NASA sees SPHERES-VERTIGO as the precursor to a number of possible missions, including the recycling of old aperture satellites, mapping of an asteroid for exploration, simpler docking techniques, better satellite station keeping for formation-flying missions, and Earth-based applications in surveillance, mapping, communications and navigation.
The ISS tests are under the Defense Advanced Research Projects Agency-funded International Space Station SPHERES Integrated Research Experiments (InSPIRE) program, which uses astronauts to carry out “rapid, iterative experimentation and design of space capabilities.” The aim of the program is to speed up technology development and, through the ZERO Robotics Competition, provide the next generation of scientists with experience in space experiments quickly and cheaply.
The MIT video below shows a SPHERES-VERTIGO’s-eye view a target.