High-Integrity GPS, or iGPS, Advances

GNSS System
High-Integrity GPS, or iGPS, Advances
http://www.gpsworld.com/gnss-system/news/high-intregity-gps-or-igps-advances-8587

July 28, 2009

Iridium and Boeing have demonstrated capability steps along the way to the High
Integrity
GPS program for the U.S. Naval Research Laboratory. The companies completed an
enhanced
narrowband software modification to computers on Iridium satellites, enabling
second-generation GPS-aiding signals to be broadcast through the entire Iridium
constellation. The GPS-aiding signals will provide appropriately equipped
warfighters
significantly improved capabilities for quickly locking on and maintaining a GPS
signal,
even while operating in restrictive environments and under jamming. They also
demonstrated
acquisition of a GPS signal under substantial jamming while moving in a vehicle.

On July 13, Iridium Satellite LLC announced that, in conjunction with Boeing,
the
companies had achieved two milestones in development and demonstration of
capability
enhancements to the High Integrity GPS (iGPS) program for the U.S. Naval
Research Laboratory.

Completion of an Enhanced Narrowband (ENB) software modification to computers on
Iridium
satellites enables second-generation GPS-aiding signals to be broadcast through
the entire
Iridium constellation. These broadcasts will enable rapid, more accurate GPS
position
fixes than are available with current technology, according to the companies The
GPS-aiding signals will provide appropriately equipped warfighters significantly
improved
capabilities for quickly locking on and maintaining a GPS signal, even while
operating in
restrictive environments such as urban areas, forests, mountains and canyons, as
well as
under enemy jamming attempts or amid battlefield radio frequency noise. This
will provide
warfighters with improved GPS anti-jam and time-stability transfer capabilities.

Secondly, the companies demonstrated to their government sponsor the acquisition
of a GPS
signal under substantial jamming while moving in a vehicle.

The iGPS principle uses satellite signals from the Iridium low-Earth orbiting
(LEO)
satellite communications system and GPS mid-Earth orbit navigational satellites.
Iridium
provides a high-power signal and rapidly changing ground track to accelerate an
initial
position fix by users. The GPS system provides navigational data in time,
location and
velocity. The result is an augmentation to GPS that provides iGPS receivers with
improved
navigation, higher signal integrity, precision accuracy and more jam-resistant
capabilities. iGPS also has the potential to provide geographic positioning data
to within
centimeters, an improvement over current meter-level standalone GPS.

The iGPS team includes Iridium, Boeing Phantom Works' Advanced Network and Space
Systems,
Rockwell Collins, Coherent Navigation and experts from academia.

In March 2007, the Boeing Co. announced concepts for combining the GPS network
with the
Iridium low-earth orbit telecommunication network to improve accuracy, and
signal
acquisition in urban environments. Boeing executives delivered the briefing at
the
National Space Symposium for Pentagon and industry officials. "In any event,
this would
not obviate the need for GPS upgrades in any way," said retired Maj. Gen. Craig
Cooning,
vice president and deputy general manager of space and intelligence systems at
Boeing.
"What it does represent is an elegant solution for augmentation of GPS."

Iridium is a constellation of LEO communication satellites originally developed
by
Motorola Inc. in the late 1990s. When the system proved uneconomical, it was
almost
de-orbited early in the decade, until the Defense Department and private
investors put in
new money to keep the systems in orbit. According the Boeing statements in
20008, the
Iridium constellation would have to be replenished in order to support the IGPS
concept,
but an upgrade of the system would be necessary in any event by 2014.