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| UAT Puts UAVs on the Radar June 2008
Soon, thanks to the efforts of MITRE engineers, UAVs—as well as balloons, sky-divers, and sailplanes—will become detectable to other aircraft in the sky. This ability for small craft to be seen isn't a small thing. For example, the Air Force's Global Hawk unmanned aerial vehicle (UAV) flew its first domestic mission providing imagery of Southern California's wildfires in October 2007. Before it could take off, however, the Federal Aviation Administration (FAA) had to grant permission for the flight, even though it was flying at 50,000 feet plus, well above commercial airspace. So why does a high-altitude flying Global Hawk have to ask for FAA permission when a recreational pilot in his hill-hugging Piper J-3 Cub does not? The answer: situational awareness. At the moment, pilots in Cubs have it. UAV pilots do not. But that's changing, as UAV manufacturers, government researchers, and the FAA work out how to meet an objective of a 500-foot safety bubble around each and every aircraft. The C4ISR Journal summed it up as, "The research and development focus today is on three streams of bolt-on technology to sense and avoid cooperative and non-cooperative threats in the National Airspace System: electro-optics, radar, and acoustics." In short: see me, hear me, avoid me. These technologies allow UAVs to "see" other aircraft, but do little to enable other aircraft to see UAVs. Lacking the need to provide space for a pilot, UAVs such as the Scan Eagle, Puma, and Wasp are small and largely made out of composite materials. Their very design makes them not only difficult to observe visually and by radar, but limits how much weight can be carried aloft. A Solution for the Smallest Flyers Currently, radar transponders and commercial-grade Automatic Dependent Surveillance-Broadcast (ADS-B) avionics are relatively large, heavy, and costly and require aircraft electrical systems. According to Robert Strain, a MITRE principal communications engineer, "We are miniaturizing ADS-B and providing small UAVs with the electronic equivalent of a red blinking beacon light that exists on manned aircraft."
ADS-B uses GPS technology to determine a plane's exact location (including altitude), and whether it is climbing, descending, or turning, broadcasting it once a second. This information is available to pilots, air traffic controllers, and other suitably equipped aircraft in the area. MITRE has been involved in developing ADS-B since the early 1990s and invented the Universal Access Transceiver (UAT), which is the ADS-B technology to be used by small aircraft and aircraft operating in the lower altitudes of the U.S. National Airspace System. A solution for UAVs would be the same type of technology in a much smaller package—about the size of two decks of cards. The result, MITRE's UAT Beacon Radio (UBR), can operate with its own power supply or, given UAT's very low power requirements, may use the aircraft's own battery power. The device's modular architecture enables it to stand alone or be integrated with other electronics or sensors. Despite Accomplishments, Development Continues MITRE's "Lightweight Beacon System for Unmanned Aerial Systems" research project involves staff from across the corporation. Strain is the project's principal investigator, and Perry Hamlyn, head of MITRE's Advanced Wireless Electronics Department, is the radio development lead. The challenge is to downsize the technology while keeping it tough and creating minimal drain on electrical power, yet enabling it to transmit to all involved. It also has to be inexpensive. The project team is focused on something PDA in size with a 12-hour battery life and component cost of less than $200. Clipped to the visor or glare shield mount, the device would also be as useful and portable for balloons, sky-divers, and small aircraft that don't have engine-powered electrical systems. For example, there are roughly 12,000 sail planes in the United States that need a UBR.
Hamlyn says the UAT Beacon Radio Development Team has accomplished much, but still has much left to accomplish. "The hardware team has moved from developing the UBR with just a transmitter to developing a full transceiver. The goal is to demonstrate that we can provide both transmit and receive capability in a small, low-cost design. In order to accomplish this, we need to reduce the size and weight beyond the level that we achieved with the UBR. This is a very formidable task," says Hamlyn. "But the team has a lot of enthusiasm and some very creative ideas. They have made great progress so far this year and I'm sure they will succeed." The UBR transceiver, called a UBR-TVR, is expected to be available in late 2008. MITRE has signed collaborative agreements to demonstrate the operations and benefits of UBR technology and is working with industry to commercialize the technology. So it will not be long before, up in the sky—among the birds, the sailplanes, and balloons—there will be UAVs, all with UBRs. —by Robin Hartford Related Information Articles and News
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| Page last updated: June 6, 2008 | Top of page |
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