AOPA Pilot Magazine - January 2018 - 90

P&E

ADS-B

A SPACEX FALCON 9 rocket lofts the first 10 Iridium NEXT satellites into space. They were

delivered into low Earth orbit about one hour after the January 14, 2017, launch from
Vandenberg Air Force Base in California.

"We're now receiving
3 billion ADS-B
position messages per
month-with 13
operational payloads."

-Jessie Hillenbrand,
Aireon director of marketing
and public relations

90 | AOPA PILOT January 2018

PHOTO COURTESY OF SPACEX

about 1,900 pounds. They're orbiting at
an altitude of 780 kilometers, or about 485
miles. When completed, the constellation will include 66 active satellites in six
orbital planes, and nine spares. "It's the
magic number based on the altitude we're
at to achieve global coverage," explained
Chris Jones, Iridium's director of mission operations. Each satellite orbits the
Earth in 100 minutes, making 14 revolutions per day.
Each satellite has a footprint about 250
miles in diameter. "We always describe our
network as an inverted cellphone tower,"
he said. "The idea is your cell towers are
moving above you. It will transfer you from
beam to beam, and eventually satellite to
satellite." Even if you're flying a fast jet,
you're essentially stationary with respect
to the satellites, he added.
The constellation is managed from
Iridium's Satellite Network Operations

Center near Leesburg, Virginia, where
seven operators per shift were controlling 90 space vehicles during a recent visit.
Some of the 20-year-old Block 1 satellites-
never expected to operate this long-need
increased maintenance, while new satellites must be tested and moved into mission
orbits. "We'll put it right behind an existing
satellite," Jones said. "We'll slide it in about
30 miles behind." Deactivation of the first
Block 1 satellite began October 31.
Next to the Iridium controllers sit a
hosted payload controller. Hosted payloads, like the Aireon ADS-B hardware, are
a new concept for Iridium with its NEXT
satellites, said Brian Patti, Iridium's program manager for hosted payloads. "So
what happened was a kind of a homegrown idea to do satellite-based aircraft
surveillance," he explained. ADS-B veteran
Harris Corp. built the receiver.
Iridium provides Aireon with the datalink, as well as hosting the payload. The
data goes to Iridium's Hosted Payload
Operations Center, and is then forwarded
to Aireon Processing and Distribution-
which creates aircraft tracks, parsing the
data according to the requirements of the
air navigation service providers, and then
forwards it to those customers. The data can
be filtered by altitude and other parameters.
"We're now receiving 3 billion ADS-B
position messages per month-with 13 operational payloads," said Jessie Hillenbrand,
Aireon's director of marketing and public

relations. "Right now we're working with the
FAA towards deploying the system. They've
been a collaborator from the get-go."
The FAA has been testing the system
with a specially instrumented Bombardier
Global Express, evaluating the receivers
in space with top- and bottom-mounted
ADS-B antennas at specific power settings. Its first test flight was March 30,
2017, when only three of the Aireon payloads were operational.
Four aircraft are involved in testing the
system. The FAA's Global Express has primarily been flying in oceanic airspace. Nav
Canada has been conducting test flights in
a Canadair Regional Jet and a Bombardier
Dash 8 turboprop-and Patti has been testing with his 1966 Beechcraft Debonair.
"Because of the capabilities of the aircraft,
they've tailored the test cases. I'm doing
exactly the same kind of tests the FAA is
doing. The scope of this is just astronomical," he explained. "As a pilot I'm proud to
be a part of it."
His Debonair is equipped with an L3
Lynx NGT-9000 1090ES transponder with
diversity-meaning that there are transponder antennas on both the belly and top
of the airplane, alternating transmissions-
and data-logging equipment.
Because of its footprint, an ADS-B
receiver in space can see the entire United
States. Other 1090 MHz transmissions, such
as responses to secondary surveillance radar
interrogations or those from traffic collision
avoidance systems, can look like interference that can be quantified as False Returns
Unsynchronized in Time, or FRUIT. Patti's
assignment is to conduct test flights in highFRUIT environments. "I'll typically fly
Arizona to Oklahoma, Kansas, Texas. We plan
my flight tests to be in high FRUIT areas."
Because the constellation is not complete, his flights are carefully scheduled to
ensure he will be in ADS-B satellite coverage. They're flown under instrument
flight rules, and only during the day. Before
departing, he connects a laptop to his transponder through a maintenance port and
begins to record; he can capture up to four
hours of data on a flight. After landing, Patti
shuts down, powers up the avionics with
an external power source, and downloads
the data-which can take 30 or 40 minutes.
AOPA Pilot Magazine - January 2018

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