http://defence-data.com/storypic/ultralite.jpg [not image]
Pop-up optics expand battlefield view
21 December 1999
Researchers at the Air Force Research Laboratory's Space Vehicles Directorate at Kirtland Air Force Base in New Mexico and their partners in industry and academia are working on a pop-up design to deploy the telescope mirrors of a large space-based optical system known as the Ultra-Lightweight Imaging Technology Experiments programme.
Ultra-Lightweight Imaging Technology Experiment
UltraLITE will eventually enable a wide variety of future surveillance missions involving laser, infrared, hyperspectral or visual imaging from space. And because of its size and precision optics, it will produce extraordinarily sharp, wide-angle, horizon to horizon, images of objects on Earth from very high orbits.
Because of their size, however, UltraLITE's mirrors must first be engineered to fold and flatten inside the relatively small space of a launch vehicle such as the Space Shuttle or expendable rocket.
"Like a child's pop-up book, our technology permits the pre-launch folding of UltraLITE's very thin mirrors into smaller configurations until the spacecraft reaches orbit," said AFRL's UltraLITE programme manager Mike Powers.
"Once in orbit," Powers explained, "UltraLITE's six huge mirrors, each measuring nearly two meters when folded, will automatically blossom open to eight meters across with the help of computer-assisted actuators into a very precise, pre-programmed shape. Think of it as the genetically-driven petals of a flower that pop open into a pre-arranged pattern."
The mirrors will collect, concentrate, and focus light onto light-gathering or light-transmitting optics which enable a telescope or other light-dependant devices to "see" more of the earth, specifically, more of a battlefield than ever before.
Because of critical alignment requirements that ensure high imaging resolution, the mirrors must "reassemble" themselves within the impossibly small tolerances of one ten-thousandth of an inch.
"Also, because launch costs run high, about $10,000 for each pound of payload put into space, reducing the mass of satellites like UltraLITE at launch is crucial if the Air Force is to maximise a launch vehicle's payload capacity," explained Powers. "For instance, with this technology, we could launch larger than Hubble Space Telescope-class optics with a medium launch vehicle-class rocket, which is much smaller then the Space Shuttle and cheaper to use. "
Compactly folded payloads means being able to launch satellites that, once in orbit, can have a greater unfurled size. This is particularly important for UltraLITE: the larger the mirror, the more expanded view. Simply, smaller optics on lower orbiting satellites cannot achieve the same result.
UltraLITE will also be cheaper than state-of-the-art systems. For example, six UltraLITE-based satellites with 8-meter-diameter lightweight mirrors could replace 75 current satellites that have 1-meter mirrors.
AFRL is developing many of the technologies needed for UltraLITE and must work out the details of how to integrate them all together into a package that meets Air Force mission goals.
"We have many customers for this technology," Powers added. "Right now we are partnered with NASA to build UltraLITE-type deployable optics to support NASA's Next Generation Space Telescope, which is the follow-on mission to replace the Hubble Space Telescope Observatory in 2007-08."
Defence Systems Daily