Avionics News May 2020 - 39

rockets between January 2017 and January 2019. To
precision system for air-traffic surveillance.
enable the Aireon system, Iridium hosted specially
This new prospect arises out of the existence today
designed receivers on each Iridium NEXT satellite to
of a global air-traffic surveillance system employing
provide 100% ADS-B coverage of the globe.
the same ADS-B connective technology used in most
With 66 active satellites and a batch of spares now in
of the world - and out of a desire to better track aircraft
orbit, Aireon's system today provides for 100% global
over water and the vast expanses of land lacking the
surveillance - still using the same ADS-B 1090 MHz
ground infrastructure for ADS-B: satellite-based ADS-B
extended squitter signal that many aircraft already
surveillance using the 1090 MHz extended squitter Mode
transmit.
S transponder frequency.
We'll get into the details next, but
You see, that's the rub. As accurate
as they are, today's ground-based
the satellite-based ADS-B revealed a
RELIABLE
ADS-B connection networks suffer
shortcoming in the existing systems
SERVICE USING
with the limitation of being terraininstalled in aircraft today.
based. As good as it is, ADS-B was
For American operators who
SPACE-BASED
developed around a ground-based
satisfied the Federal Aviation
ADS-B REQUIRES
infrastructure, with more than
Administration's mandate with a 978
THAT AN ADS-B
500 ground stations in the United
MHz universal access transceiver,
States providing the connection to
well, Aireon's satellites won't see
TRANSPONDER
relay aircraft ADS-B squawks to
them. Aireon is strictly a 1090ES
ANTENNA ALSO
controllers' display screens.
adopter, matching what every
The ADS-B system was
ADS-B adopting nation but the U.S.
conceived and built around existing
mandates.
technologies that mandated those
In the U.S., operators can use
ground stations. But a new ADS-B
1090ES solutions at all altitudes and
technology began to take shape
in all countries adopting ADS-B Out.
about midway through the nineThe 978 MHz UAT satisfies the U.S.
year adoption period that ended at midnight on New
mandate at altitudes below 18,000 feet mean sea level -
Flight Level 180 and below.
Year's Eve. And that's the basis for this new potential
And then there's the diversity issue.
surveillance system - one capable of providing coverage
over the entire planet.
Diversity in ADS-B: It's not a social issue
Aireon: It's up in the air - 485 miles up
As has been the practice for decades, the ADS-B
A company called Aireon developed its own spacetransponder antennas mount on the belly of aircraft
based global surveillance system - still using the
- thus providing line-of-sight connectivity between
same ADS-B technology already operating but flying
the aircraft and those ground stations, both radar and
on orbiting satellites instead of stationary in ground
ADS-B.
stations.
Reliable service using space-based ADS-B requires
Instead of utilizing traditional radio receiver towers on
that an ADS-B transponder antenna also sit atop the
the ground, Aireon redesigned the ADS-B transceivers
aircraft - again, to provide a clear line of sight between
into compact, lightweight, flexible and highly effective
the transponder antenna and the Aireon satellites flying
space-grade systems to ride on Iridium's secondin low-earth orbit about 485 miles above our planet.
generation satellite constellation, Iridium NEXT.
While unnecessary for ADS-B service over land
The backbone of Aireon's technology flies on the
equipped to provide coverage - like the continental
Iridium NEXT constellation of satellites. Aireon used
eight Iridium NEXT launches on Space-X Falcon 9
Continued on following page

SIT ATOP THE
AIRCRAFT.

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Avionics News May 2020

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