NASA, in cooperation with Scaled Composites, LLC, is conducting a new
phase of flight demonstrations of collision-avoidance systems to
develop the ability of unmanned aerial vehicles (UAVs) to eventually
fly routinely and reliably in the national civil airspace. Flights
on a test range near Mojave, Calif., in early April are evaluating a
Detect, See and Avoid (DSA) system that can identify non-cooperative
aircraft without operating transponders. This follows a series of
flight evaluations of a system to detect cooperative
transponder-equipped aircraft conducted in March 2002 at Las Cruces,
N.M.

The full potential of UAV systems cannot be realized until they
demonstrate the ability to operate safely and routinely within the
existing air traffic management system. NASA’s Environmental Research
Aircraft and Sensor Technology (ERAST) program has sought to apply
technology to scientific and commercial applications, particularly
the mission to study the Earth’s environment with high-altitude,
long-endurance UAVs.

“NASA’s interest is in getting UAVs to fly in national airspace as
general aviation aircraft do today,” said Glenn Hamilton, UAV
subsystems project manager at NASA’s Dryden Flight Research Center,
Edwards, Calif. “We need to establish an equivalent level of safety
for UAVs as manned aircraft have. Collision avoidance utilizing
reliable Detect, See and Avoid systems is one of the critical
technologies needed to enable UAVs to operate safely within the
national airspace structure.”

The surrogate UAV aircraft for the DSA tests is Scaled Composites’
optionally piloted Proteus. For the current flights, Proteus is
equipped with an Amphitech OASys high frequency radar system.
Originally developed to warn low-flying helicopter pilots of power
lines in their flight path, the 35 GHz (Ka band) radar is being used
to detect any approaching aircraft on a potential collision course
within a six nautical mile range, regardless of whether the intruder
is equipped with an operating transponder. As a backup sensor,
Proteus also is equipped with the Goodrich Skywatch HP traffic
advisory system it used successfully to detect transponder-equipped
aircraft at distances up to 35 nautical miles during last year’s
tests.

“We chose the Amphitech Ka band radar due to it being lightweight,
low cost and having low power requirements,” Hamilton added. “The
demonstration is to see if it will work in this application. We’re
trying to find the lowest cost solution that will work.”

Proteus and a variety of target aircraft, ranging from a hot-air
balloon to a high-speed NASA F/A-18 jet, are flying a series of 22
different simulated conflict scenarios over several days. Flights are
being conducted in a joint-use restricted test airspace zone
northwest of Edwards Air Force Base, Calif.

During the flight demonstrations, Proteus is controlled remotely by a
pilot in a ground station. Radar data is relayed to a ground station
via either a line-of-sight telemetry link or an over-the-horizon
Inmarsat satellite link, and the ground pilot then commands Proteus
to change course as needed. To enhance flight safety and mitigate
risk, a 500-foot “safety bubble,” including a minimum 200-foot
vertical separation, is being maintained throughout the tests and a
pilot is on board the Proteus who can take control at any time.

Douglas Shane, Scaled Composites’ vice-president of business
development and Proteus’ remote pilot for many of the test scenarios,
noted that flight safety is taken very seriously.

“A big component of safety in these tests is the fact that all
airplanes are piloted,” he said. “They have humans with rules of
engagement to ensure that we don’t proceed into an area that might
create a true conflict, or a true possibility of a mid-air collision.
That’s a big reason why the Proteus is a good developmental testbed,
because you have that human backup looking out the window.”

Russ Wolfe of Modern Technology Solutions, Inc., wrote the test plan
for the current flight demonstrations, which he cited as “a very
important step in proving enabling technologies for unmanned air
vehicles.”

“It’s something that the FAA deems as essential. They will not
approve a UAV to fly in the national airspace system without detect,
see and avoid capability. This test, (along with) many in the future,
will help to prove this enabling technology.”

“One of the biggest impediments to getting routine access to the
national airspace for unpiloted vehicles is the whole issue of see
and avoid,” Shane added. “That is one technology that is not mature
yet, (and) that is critical in order for the FAA and the general
public to accept an unpiloted airplane as being safe to
operate…with all the others. We believe these tests are absolutely
critical and fundamental to (enabling UAVs to have) routine access to
the national airspace”

Based at Scaled Composites’ facility at the Mojave Airport, the UAV
collision-avoidance flight demonstrations brought together a team of
pilots, engineers and technicians from NASA Dryden, Scaled
Composites, Modern Technology Solutions, (MTSI), Amphitech
International, New Mexico State University’s UAV Technical Analysis
Applications Center (TAAC) and the U.S. Navy Air Warfare Center
(NAWC).

NASA Dryden provided overall project management and two of the target
aircraft. Scaled Composites provided the Proteus test aircraft and
several of the intruder aircraft, as well as hardware and software
development and the ground control station. In addition to developing
the test plans and procedures, MTSI, based in Alexandria, Va.,
provided systems engineering and test coordination and will perform
the post-test data analysis. Amphitech, headquartered in Laval,
Quebec, Canada, furnished the 35 GHz OASys radar and engineering
support. TAAC, based at the NMSU campus at Las Cruces, N.M., assisted
with FAA airspace coordination. NAWC, China Lake, Calif., supported
the integration of the Amphitech radar and the Skywatch traffic
advisory system onto the Proteus.