The Future Challenge Assured Position, Navigation and Timing: Northrop Grumman ...
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Assured Position, Navigation and Timing:
The Future Challenge
Northrop Grumman has a long and
distinguished history of supplying trusted
navigation and positioning systems for a
wide range of US ships and aircraft
(US Navy/Lt j.g. James Griffin)
the use of global navigation Satellite markets, utilities and transport all rely on its has never been usable underwater or in
Systems (gnSS), largely through the uS capabilities. deep space.
global Positioning System (gPS), pervades
almost every area of modern life, and However, there is now increasing concern There is therefore a need for devices to
this is particularly true of the military. about overreliance on GPS given the replicate the integrity and reliability of GPS
there are few, if any, aspects of military fragility of the signal. GPS is vulnerable to to provide an alternative Assured PNT
operations that are not dependent on jamming, interference and “spoofing” – (APNT) capability which will provide positional
Pnt: Position (knowing where you are), the attempted deception of the receiver data with the same accuracy as GPS, and
navigation (how you are going to get to by the broadcasting of incorrect signals. timing with the equivalent traceability to that
where you want to be) and timing. During the Russian exercise “Zapad derived from the atomic clock. This must not
2017” GPS signals were reportedly lost by only address the requirements of GPS users
It is unlikely that any modern military mission commercial aircraft and other platforms who are temporarily denied its use because
could be successfully executed without over the eastern Finnmark region of of physical circumstances or human
accurate PNT. This is currently supported Norway as far as 250 km from the Russian interference but also extend the benefits of
largely by GPS, which provides supremely border, with similar large-scale interference APNT to those who have never had access
accurate position and timing, with the latter experienced over land and sea across to the GPS signal.
linked to atomic clocks monitored by the northern Finland and Sweden. And earlier
GPS ground control segment and traceable in the same year it was reported that Northrop Grumman Mission Systems has a
to Universal Coordinated Time (UTC) at GPS anomalies affected the navigation of strong history of over 50 years of delivering
the US Naval Observatory. PNT provided some 20 vessels in the Black Sea, which trusted navigation and positioning systems,
by GPS is fundamental to precision-guided was suspected to have been caused by a rooted in its Litton Industries heritage of
weapons; the provision of synchronised spoofing attack. the development of lightweight inertial
situational awareness; unmanned platforms; navigation systems (INS) for aircraft in the
in fact almost every area of military GPS is also not always universally available late 1950s. By 1983 Litton had produced
activity. GPS has been so successful that simply because of physical factors. Being 20,000 aircraft INS. Litton was acquired
it now pervades much of civil society, and inside buildings, under dense foliage or by Northrop Grumman (NG) in 2001 and
commercial activities such as banking, stock underground can defeat the signal, and it continues to be a major force in the aviation
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navigation market as well as in stellar-inertial The NG Philosophy: The Hub or timing or both which cannot all include
and maritime navigation: NG products are anti-jam protection. As a result there can be
in use in ICBMs and on more than 60 naval The NG approach moves the burden of a multiplicity of self-contained GPS receivers
surface and subsurface platforms from a trusted APNT away from sole reliance on a single platform, leading to what Ebert
number of countries, including the USN’s on GPS to the complementary use of describes as “an integration and resilience
Los-Angeles-, Sea Wolf- and Virginia-class inertial devices augmented with additional nightmare that needs to be managed”.
submarines. alternative methods of navigation. INS
calculate direction moved over time, with a The NG solution is to harness as much of
With this background NG is well aware of varying degree of drift, and with the use of this sensor data as possible to contribute to
the challenge set by the need to provide high precision oscillators provide continuity an accurate and robust APNT solution which
APNT under all circumstances, a challenge of time. Their great advantage is that they will be trusted. The core of this philosophy is
accentuated by the needs of a broad user cannot be spoofed or jammed. a software-defined open architecture that
base which ranges from the submarine to can affordably integrate data from diverse
the dismounted soldier, with a wide range of On an individual platform there may be sensors, both GPS and non-GPS, in a single
missions, requirements and constraints. a number of sensors, each of which is hub for distribution throughout the platform.
a potential source of complementary
Dean Ebert, vice president, navigation and information to support navigation. For The sensor fusion framework functions at
positioning systems, Northrop Grumman, example, in addition to INS and celestial both the sensor measurement and signal
processing levels, providing access to the
different signals and enabling multiple
levels of checks on their validity. The raw
information from all the relevant sensors
on board the platform is available to the
hub, with each additional source of data
increasing resilience, adding accuracy and
improving the integrity of the solution.
The centralised framework for GNSS and
other RF PNT signal processing which
the hub provides also gives it the capacity
to extract the particular signals it needs
to provide APNT for a specific mission or
threat environment, thus offering flexibility
in creating the sensor measurements
for fusion as well as flexibility in the fusion
process itself.
A hub solution reduces vulnerability through
its use of a variety of information sources and
reduces cost as it utilises existing sensors.
The modular open systems architecture
allows rapid reconfiguration to allow
acceptance of different signals, with standard
interfaces developed for individual sensors
which can access a signal as early as possible
to reduce the amount of processing.
This common philosophy espoused by NG
has a wide range of applications which are
Top Two ships in company maintain Assured PNT with a satellite and each other as appropriate to diverse users, but to achieve
they approach a GPS denied area this it must be scalable and flexible and
Bottom Once in the GPS-denied zone they mutually maintain Assured PNT using realised in widely differing hardware.
alternative methods and provide this for a helicopter (Northrop Grumman)
Integrated Systems
emphasizes that the initial response to a systems, vision-aided navigation using EO/
GPS-challenged environment should be “to IR and LADAR imagery sensors is capable A good example of this approach is the
hang on to GPS for as long as possible”. of maintaining a position of near GPS quality USAF’s Embedded GPS/INS-Modernization
This may mean increasing the sensitivity both on the ground and in the air through (EGI-M) programme, for which NG was
of the GPS receiver and its antenna, a variety of techniques, including visual awarded a contract by the USAF to
improving its anti-jam capability or using odometry, simultaneous localisation and develop the technology in May 2017. The
other onboard sensors to check its integrity mapping (SLAM) and absolute positioning EGI-M will have a modular, open systems
as an anti-spoofing precaution. However, (map matching). architecture to support the rapid insertion
this approach can run into issues of size of new capabilities and adaptability based
and affordability so there needs to be an There can also be several systems each on specific platform requirements and it
alternative. with its own GPS to provide either position will incorporate the more robust military-
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LEFT A range of sensors can contribute
to the provision of Assured PNT,
with their data fused using an open
architecture, open interfaces and
SSensors
modular software (Northrop Grumman)
Integrating the data from existing sensors
in this fashion improves accuracy and
FFuture
assurance at little extra cost.
t
As a possible future example, an F-16
equipped with a Litening targeting pod,
the software framework architecture and
an APNT distribution sensor fusion hub
might utilise all the EO/IR capabilities of
the pod to reinforce the PNT solution from
Inertial the platform’s existing GPS/INS system,
& particularly under GPS-challenged conditions.
Freq. Ref SuPPortIng SolutIonS
The modernisation of GPS satellites
to broadcast M-code requires the
modernisation of GPS receivers which
are currently hard-wired for the legacy
signal. To meet this need NG has developed
the SERGEANT software defined GNSS
transceiver. This utilises COTS processors,
allowing rapid upgrades to take advantage
of technology developments and outpace
threats, and it has advanced anti-jam
capabilities. SERGEANT’s software design
now allows it not only to access M-code
but also any satellite navigation signal,
providing significantly increased resilience
and flexibility. It has a modular architecture
and can be integrated with other systems:
code (M-code) GPS signal, which has been inertial device, a chip-scale atomic clock it has already been successfully hosted in
developed in response to the increased GPS- (CSAC) and a GPS receiver, and it will also the proven NG LN-260 INS/GPS which is in
hostile environment. EGI-M is also designed have access to existing data, such as from service with the USAF.
for compatibility with current systems on a vehicle odometer. Other sensors which
legacy aircraft. are already installed on the platform, such The flexibility of the hub approach and its
as EO/IR devices, could also be integrated scalability for use on a range of platforms is
The same approach is being taken with the into the hub to reinforce the APNT solution. reinforced by improvements NG is making
US Army’s Mounted Assured PNT System
(MAPS) programme. This will provide APNT Northrop Grumman will leverage its
data to land vehicle platforms, distributing hub philosophy for the US Army MAPS
it from a fusion hub over the standard programme, which will provide a low-cost
VICTORY electronic vehicle architecture to solution for APNT utilising all the available
any warfighting function application that data on a vehicle platform such as this
requires it. It will use anti-jam antennas Stryker IFV (US Air Force/Justin Connaher)
to improve the anti-jam margin of existing
military GPS receivers and will detect and
report GNSS interference sources. By
integrating timing capabilities and a PNT
distribution hub it will replace the need for
multiple GPS receivers on a single platform.
MAPS will be deployed in large numbers so
the solution needs to be affordable. It must
therefore rely on a different balance of
inertial and other sensors to complement
the GPS data and maintain accuracy when
it is absent. While the MAPS sensor suite
is not finally decided it is likely to include an
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An F-16 with a Litening pod. In future the pod’s capabilities
could be used to reinforce the PNT solution via a sensor
fusion hub (US Air Force/Senior Airman Jorden Castalan)
to inertial systems. It is taking advantage This development is of particular value The NG LN-220 is a Stellar-Inertial system
of new technology to shrink size and cost to weapon systems, where the provision that is the latest in an evolutionary process
with the Precise Robust Inertial Guidance of APNT in a low size, weight and power that has seen systems shrink by 80% in
for Munitions Navigation-Grade Inertial (SWaP) form factor will make a significant size and weight and over 90% in power
Measurement Unit (PRIGM: NGIMU) contribution to weapons guidance in a GPS- consumption. It integrates proven NG
programme funded by the US Defense hostile environment. advanced inertial sensors with a star tracker
Advanced Research Projects Agency and video processor. The result is a device
(DARPA), for which it was selected in March There is also a new focus on stellar and which in a GPS-denied environment suffers
2016. celestial navigation as this can provide from a drift of less than 30m in an hour,
another non-interferable alternative to which can be corrected by the embedded
The resultant highly accurate GPS. Celestial navigation, which uses the GPS if the service becomes available.
microelectromechanical systems (MEMS)- known orbits of resident space objects
based IMU, designated the LR500, is (RSOs), provides an absolute position fix. “In developing these APNT solutions
only 5in3 in volume and weighs 0.35lbs, Stellar navigation, which uses the stars Northrop Grumman brings its world-
a 4000% improvement on some of its and is therefore not always available, gives class experience and innovative approach
predecessors, and it combines the best roll, pitch and drift. These can be combined to inertial instrument technologies and
features of current MEMS gyro technology. with an inertial system to lower the drift navigation systems. In particular, making
Coupled with NG’s proprietary dynamic rate: while an inertial system by itself drifts inertial navigation units smaller and
self-calibration (DSC) this gives a positional as much as 9 nautical miles in 12 hours, a lighter than ever before and introducing
drift rate near that of high end airborne combined solution drifts by far less. Such a software-defined open architecture-based
inertial navigation systems. A prototype at combination of these technologies, which systems will make a huge difference in GPS-
technical readiness level six will be available can be used when mission-relevant, provides denied and highly contested environments,”
in early 2019. more resilient APNT. said Ebert.
Northrop Grumman
Navigation and Maritime Systems
21240 Burbank Boulevard
Woodland Hills, CA 91367 USA
1-866-NGNAVSYS (646-2879)
www.northropgrumman.com
www.northropgrumman.com/a-pnt
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