FITEL laser monitors space shuttle Discovery
Who can forget the replayed image of a piece of foam striking the shuttle Columbia during liftoff, and the disintegration of the shuttle upon re-entry in February 2003?
PEACHTREE CITY, GA and OTTAWA, ON, CANADA - Who can forget the replayed image of a piece of foam striking the shuttle Columbia during liftoff, and the disintegration of the shuttle upon re-entry in February 2003? In response to the tragedy, scientists at the National Aeronautics and Space Administration (NASA; Washington, DC) are working on a number of safety recommendations made by investigators of the Columbia accident.
For example, in an effort to prevent a breach of the thermal protection system for future launches, the space shuttle Discovery will carry aboard a new exterior inspection system designed to detect imperfections less than a millimeter in size on the thermal tiles of the shuttle’s hull. The three-dimensional (3-D) laser scanner system was developed by Neptec (Ottawa, ON, Canada) and is powered by a FITEL (Peachtree City, GA) pump laser that is manufactured by Furukawa Electric Co. (Tokyo, Japan).
Unlike a standard video camera working in the visible range, the 1500-nm wavelength of the FITEL laser is immune to the effects of changing lighting conditions-a critical advantage in orbit where the sun rises and sets many times each day. According to Isamu Oshima, product manager for Furukawa America (Clinton, NJ), the 1500-nm laser with a power output of 350 mW was selected for its ruggedized, radiation- and vibration-resistant packaging and its ability to deliver high output power with low power consumption, another important consideration for space-based instrumentation.
The FITEL laser is the source for the Neptec scanner, which enables transmission of detailed, three-dimensional models of the exterior surface of the shuttle using an auto-synchronous triangulation scanning technique. The pump laser is scanned across the underside of the shuttle and an indium gallium arsenide (InGaAs) linear detector array is part of the system used to measure the angle between the projected beam and the diffuse reflection, providing position information.
“The ability to scan intelligently and process the data intelligently allows you to gain more information with less data,” notes Iain Christie, Neptec’s vice president of research and development.
The Neptec system has demonstrated the ability to generate short-range and high-accuracy 3-D data in real-time. For objects moving in space, the system can provide position information at a rate fast enough to make autonomous satellite rendezvous and docking maneuvers a reality.
“We see the Discovery scanner as a beginning rather than an endpoint in our development of 3-D scanning intelligence,” adds Christie.
The scanner is mounted on an extension boom stored on the opposite side of the shuttle’s cargo bay from the Canadarm, a long arm that will connect with the extension boom and extend the reach of the scanner to enable viewing of hard-to-reach corners of the spacecraft.
- Gail Overton