MIT Lincoln Laboratory is first to demonstrate next-generation antenna for airborne communication with Milstar

MIT Lincoln Laboratory continued its successful testing of protected military satellite communications by flying the first Advanced Multiband Communications Antenna System (AMCAS) delivered to the government. The new antenna system, designed for wide-body aircraft, flew on the Paul Revere, a heavily modified Boeing 707 the Laboratory operates for the Air Force as a communications and sensor testbed used in the development of integrated networking and airborne sensing. The June 2009 flight test represents the most recent phase in Lincoln Laboratory's secure extremely high frequency (EHF) satellite communications testing program.

Paul Revere aircraft with antennaThis photograph of the Paul Revere shows the position of the Large Aircraft Antenna (LAA) radome, the dark-grey radome housing the AMCAS antenna just aft of the wings.

The goal of the AMCAS program is to develop low-profile antennas that are capable of a few million bits per second (Mbps) when operating with military communication satellites, such as the Wideband Gapfiller or Milstar. The program seeks to validate link analysis, qualify hardware for flight, and establish a realistic production specification by demonstrating the antennas in an operational environment. The first antenna to reach the flight-test stage was the Variable Inclination Continuous Transverse Stub (VICTS) antenna—a result of a successful collaboration between Thinkom, Raytheon, Lincoln Laboratory, and the Air Force Electronic Systems Center. The antenna performed as expected throughout the mission, receiving data at 1.5 Mbps from Milstar at 20 GHz. "While this flight test represents a very important step in the development of EHF antennas for military aircraft, it more importantly demonstrates how industry, academia, and the Pentagon can collaborate to develop needed technology quickly and affordably," says Dave Snider, AMCAS program leader and senior staff in the Laboratory's Communications and Information Technology Division.

AMCAS antenna systemAlong with the AUST-T, the AMCAS antenna system used on the Paul Revere provides airborne connectivity to Milstar.

The successful June flight test with the system originated at Hanscom Air Force Base, Massachusetts. The flight pattern consisted of a flight down the coast to the southern tip of New Jersey. Several racetrack loops were made in the Atlantic Ocean, southeast of Cape May, New Jersey, before the aircraft returned to base.

"Nothing beats an actual flight test," says lead systems engineer, Tim Gallagher. "It's one thing to say that a system can receive data based on a link analysis. It's quite another thing to be able to say 'yes, we bolted the system to a big airplane, took off, and flew to New Jersey and back again while receiving data at rates that max out the satellite's capability.'"

Flight test route mapFor the 8 June 2009 flight test, the Paul Revere flight path originated at Hanscom Air Force Base and continued down the Atlantic coast to the southern tip of New Jersey.

The current AMCAS flight test is on the heels of another successful series of EHF flights in August and September 2008 using the same Advanced EHF Universal System Test–Terminal (AUST-T) terminal. At that time, Lincoln Laboratory ruggedized and installed on the Paul Revere an AUST-T, which was developed by the Laboratory as a "gold standard" terminal for use by contractors to test Advanced EHF satellite payloads. This terminal, along with a conventional parabolic dish antenna, was successfully flown in August and September of that year using the AUST-T as its Milstar modem. AMCAS replaces the parabolic dish and its relatively high profile with a unit that is externally attached but is low profile and so requires a much smaller radome.

"Success for us was at first considered our ability to integrate the AMCAS antenna with the AUST-T and track Milstar satellites for a while with some expected performance. It soon became clear that given the team we had, we could do so much more," says Gallagher. From takeoff to landing, the antenna/pedestal system continually tracked several beams on a Milstar satellite. Being a receive-only system, the flight system required cooperation from a terminal on the ground to show its ability to receive data with expected performance. A medium-data-rate (MDR) network was maintained for the entire flight. For the last 60 minutes, the highest-order MDR modulation was used at the highest allowable data rate. A terminal at the Laboratory acted as a cooperating terminal transmitting the 1.5 Mbps data stream. 

"Taking advantage of assets across the Laboratory and working hard towards a common goal are what we do," says 25-year veteran of Milstar operations and cooperating terminal operator Mike Coyne. Coyne worked closely with Raj Viswanathan, who spent his time moving from lab through ground and through flight testing, making the whole system go.

"We wanted to show a little more, but that required some help from across the Lab and the country," says Viswanathan. In early testing, links were set up with a terminal at Schriever Air Force Base. "The personnel at that site were important in working out the basic issue with a receive-only terminal like ours." On flight test day, it was Viswanathan, Coyne, Milstar, and a lot of random, but well received, data.

"Our goal is always to provide the government with advanced airborne communications test capabilities and this is a significant addition to our arsenal," says Kevin Kelly, assistant leader of the Net-centric Integration Group.

Posted July 2009

top of page