Space station SPHERES run circles around ordinary satellites

These are, in fact, the droids that NASA and its research partners are looking for. Inspired by a floating droid battling Luke Skywalker in the film Star Wars, the free-flying satellites known as Synchronized Position Hold, Engage, Reorient, Experimental Satellites (SPHERES) have been flying aboard the International Space Station since Expedition 8 in 2003.

Although there have been numerous SPHERES investigations held on the orbiting laboratory, four current and upcoming SPHERES projects are of particular significance to robotics engineers, rocket launch companies, NASA exploration and anyone who uses communications systems on Earth.

The SPHERES-Vertigo, Department of Defense (DOD) SPHERES-Rings, SPHERES-Slosh and SPHERES-Inspire II investigations all use the existing SPHERES space station facility of these self-contained satellites. Powered not by an astronauts use of the Force, but by AA batteries, the satellites act as free-flying platforms that can accommodate various mounting features and mechanisms in order to test and examine the physical or mechanical properties of materials in microgravity. Each satellite is an 18-sided polyhedron and is roughly the size of a soccer ball. NASA's Ames Research Center in Moffett Field, Calif., operates and maintains the SPHERES research facility aboard the space station, which is funded by the Human Exploration and Operations Mission Directorate at NASA Headquarters in Washington.

SPHERES provide a unique low risk, low-cost, long-term microgravity research facility that supports quick-reaction testing of technologies that can be repeated numerous times. Alvar Saenz Otero, Ph.D., associate director and SPHERES lead scientist at the Massachusetts Institute of Technology (MIT) Space Systems Laboratory describes the reusability of SPHERES for multiple microgravity investigations by saying, if anything goes wrong, reset and try again!

Operating intermittently since February 2013, the SPHERES Visual Estimation and Relative Tracking for Inspection of Generic Objects (SPHERES-Vertigo) investigation uses what looks like eye goggles and other new hardware and software on multiple satellites during testing. The purpose of the study is to build 3-D models of a target using mapping algorithms and computer vision-based navigation. These additions to the satellites help researchers create 3-D maps of a previously unknown object for navigation by flying the SPHERES in a path around that object while taking photos.

Brent Tweddle, a postdoctoral associate with the MIT Space Systems Laboratory, said the SPHERES-Vertigo project differs from previous SPHERES experiments by adding a pair of stereo cameras, which see, perceive and understand their world visually and can communicate with satellites using Vertigo goggles. The goggles act like their own little intelligence block that sticks on the front end of the SPHERES and allows them to see the rest of the world that they want to navigate through, explained Tweddle.

First, the SPHERES use their updated hardware and software to construct a 3-D model of a target object. Then, the satellites test their skills to perform relative navigation using only sensory reference to the 3-D model.

Imaging from projects like Vertigo could help refurbish old satellites by determining and mapping the specifications of the old satellites and repairing them as they orbit Earth. Other applications include NASAs future mission of visiting an asteroid, where thorough understanding of the size, shape and motion of an asteroid is necessary to navigate around it as it travels through space. Further, as robots become more autonomous, they will need a pair of eyes, similar to Vertigo, to provide them with navigational capabilities.

The DOD SPHERES-Rings investigation is the first demonstration of electromagnetic formation flight in microgravity, as well as of wireless power transfer in space. The study installs highly advanced rings to existing SPHERES. The crew places the rings around an individual satellite, consisting of resonant coils, coil housing with fans, batteries and support structure hardware. The Rings project demonstrates the use of electromagnetic coils to maneuver individual SPHERES with respect to one another. The current running through the ring of coils controls the satellites, so that two ring-outfitted SPHERES are able to attract, repel and rotate.

Using electrically-generated forces and torques is preferable to using fuel, since electricity can be generated by solar panels, but once fuel is expended, the mission is generally over, explained Kathleen Riesing, a graduate student with the MIT Space Systems Laboratory. The software used to control the rings will also demonstrate wireless power transfer, where one satellite sends power to another.

Visit link:
Space station SPHERES run circles around ordinary satellites