The U.S. Defense Department is preparing to test a next-generation Global Positioning
System handheld receiver that will be lighter and easier to operate than current
devices, officials said.
The new system, known as the Defense Advanced GPS Receiver (DAGR), will replace
the so-called Precision Lightweight GPS Receiver (PLGR).
The two companies competing in the DAGR program are Raytheon Space and Airborne
Systems, in El Segundo, Calif., and Rockwell Collins, of Cedar Rapids, Iowa.
These firms received contracts valued at $357.1 million and $361.1 million,
respectively.
Each contractor will supply the GPS Joint Program office with 250 test units
by May 2003. The JPO will oversee the selection process in the fall of 2003.
Operational testing and low-rate production could begin sometime in late 2004.
The next phase of the program could be worth between $300 million and $400 million.
“Simply put, DAGR will reduce the logistical burden on the war fighter,
enabling greater tactical situational awareness in less time, using less equipment,”
said Air Force Maj. Keith Hirschman, project officer for the DAGR program. “Not
only will DAGR provide the soldier with ready-to-use data in one-sixth the time
of PLGR, but it will do it with less than half the battery consumption, in a
package less than half the weight and only two-thirds the footprint.”
PLGR technology has for a decade now enabled soldiers to use coordinated position,
velocity and timing data in continuously mobile, unfriendly environments. The
performance of the PLGR depends on a single frequency (L1) for reception and
switchover from commercial to encrypted GPS signal.
DAGR technology proposes to eliminate this reliance on one frequency by adding
a second frequency (L2), enabling soldiers to obtain position information with
greater accuracy, in less time, said officials.
“In essence, DAGR has twice PLGR’s capability of receiving clear
satellite signal transmissions,” said Mike Fleenor, business director
for land navigation at the Raytheon Company. “Attempts at jamming or spoofing
signals, where successful against PLGR, are less likely to be effective using
dual-frequency DAGR, since the bandwidth of each frequency will be available
for signal acquisition.”
To prevent unauthorized users from logging on a U.S. receiver, the GPS Joint
Program Office implemented a security technique built around a dual-key architecture
for controlling access to military encrypted P(Y) code. Color-coded, red or
black, cryptographic keys represent the basic authorization levels for operating
in classified P(Y) code.
The addition of a now-mandatory GPS security device called the Selective Availability
Anti-Spoofing Module (SAASM) into DAGR will offer the user the guarantee that,
in the event of enemy capture, the receiver’s encrypted architecture will
be fully resistant to any attempts at reverse-engineering its components.
At the crux of military GPS security is the reliance on Precise Positioning
Service-Security Module (PPS-SM) data storage and processing. Supporting a network
of digitally-based receivers, PPS-SM and an Auxiliary Output Chip (AOC) produce
the GPS encrypted P(Y) code, a signal requiring tight restrictions on user access
in maintaining classified data security.
As a result, a complex system of red-key (classified) and black-key (unclassified)
authorization codes often became a logistical burden during combat operations.
“The distribution of cryptographic classified red keys to hundreds of
thousands of users worldwide is a logistical nightmare,” said Hirschman.
“With the arrival of SAASM-based receivers like DAGR, protecting classified
GPS data will no longer be an external manual process, but an internal automated
one, based on the tamper-proof construction of the units themselves.
“With PLGR, access to P(Y) code is limited, meaning certain users are
cleared for classified red key access and certain are not,” Hirschman
said. “The introduction of DAGR with the SAASM chip will eliminate the
need for strict key controls to the P(Y) code since SAASM will simply not function
in the attempt of unauthorized use. This increased security will effectively
decrease user authorization standards, allowing for a system based solely on
unclassified black keys, enabling more soldiers in critical areas of the battlefield
to have needed access to the P(Y) code.”
So far, he said, the “challenge in GPS technology development has been
the creation of secure, yet open architecture systems capable of being both
backward compatible with existing hardware and software, as well as forward
compatible with future command and control networks.”
Increased Bandwidth
Aside from the added functionality of dual frequency, DAGR’s increased
bandwidth availability enables the receiver to process GPS position-location
data more rapidly and precisely than PLGR. That helps expedite the transfer
from rapid-pulse commercial-grade C/A code to slow-pulse P(Y) code. “Satellite
signal acquisition and re-acquisition is achieved by the precise timing needed
to go from C/A to P(Y) code,” said Fleenor. “DAGR’s dual-frequency
coordination gives the user greater signal clarity for faster initial, post-standby,
and post-power down signal acquisition.”
The susceptibility of P(Y) code to enemy jamming and spoofing techniques has
driven the development of GPS receivers that are able to switch from commercial
to encrypted code with greater efficiency. “Signal loss or switch-out
due to jamming or spoofing prior to desired code acquisition can be deadly to
the war fighter who is depending on timely position-location information,”
said Hirschman. “If the data is not received when it is needed, it does
the soldier no good.”
At the heart of DAGR’s ability to acquire and process GPS signals faster
than PLGR is an increased number of data correlators. Representing individual
translators from C/A to P(Y) code, the correlators attempt to recognize the
signal patterns in each code variation, so that a bridge can be made from one
code to the other. Faster code correlation means faster data acquisition.
With as many as 9,000 correlators built into it, DAGR will have 45 times the
correlation capability of PLGR, which has approximately 20 correlators. This
capability, made possible by DAGR’s dual frequency operation, will also
protect against signal interference, the contractors said.
“Resistance to signal jamming depends largely on the ability to recognize
signal traits through the interference,” said Fleenor. “As a jamming
source gets louder, it becomes more difficult to achieve signal-to-signal correlation.
The more correlators available to listen for the desired signal, the better
chance that one will recognize the coded signal and link it to another.”
Spoofing or swapping out of GPS signals with a false or manufactured signal
is common and is also more easily overcome by DAGR’s dual frequency reception.
“With DAGR, there is a greater likelihood that initial GPS signal correlation
will occur before any spoofing attempt can be effective,” Fleenor noted.
As a purely text-based receiver, PLGR displays GPS coordinate data that must
be plotted on a map, to be useful to the soldier in the field. In many cases,
this procedure must be performed at night, when a light source is necessary
to see the map.
“Though it may seem harmless, breaking out a map, compass and flashlight
to plot coordinates when a soldier needs timely data to react to changing battlefield
conditions can be quite detrimental to the soldier, let alone mission success,”
stressed Hirschman.
To help solve the problem of multi-tasking in order to obtain timely position
information, DAGR offers a lighted text- and image-based display.
Using software pre-programmed to show the general layout of a combat zone,
DAGR provides an integrated text/map interface using icons to designate user
position as well as other mobile or static objects.
A keypad and pop-up windows offer various options with regard to waypoint classification.
“In the time it takes to deploy an accompanying map, compass or flashlight,
the soldier will now be able to see his position on the battlefield relative
to other objects, using only his receiver, and promptly decide what course of
action to take,” said Hirschman.
The DAGR would make it much easier for soldiers to navigate in unknown terrain,
he added. The receiver’s display presents the soldier with a pre-mapped
visual of the operational zone. Continual one-second updates to the visual display
map enable the soldier to stay on the move, using a laser rangefinder and other
devices to input data directly into DAGR.
“Once an object is located, its coordinates are plotted by manual or
electronic inputs to the DAGR receiver,” said Fleenor. “Within one
minute, an icon representing the object will pop up on the display screen showing
the coordinates to its position. With PLGR, it can take as many as six minutes
to get a fix on an object, and this does not include the time it takes the soldier
to plot the received coordinates on a corresponding map.”
DAGR will process data much more quickly than PLGR, officials said. Operating
on one-second pulse intervals, DAGR, having achieved an initial fix, will reflect
changes, in real-time, to the position or direction of a given object.
Depending on the initial clarity of DAGR’s dual frequency reception,
both P(Y) code and waypoint reacquisition is achieved more quickly than initial
lock-on because DAGR correlators will store the initial fix data, making reacquisition
of a signal or waypoint simply a matter of re-matching recognized data.
Plotting Coordinates
Tracking mobile objects will be easier with DAGR, contractors claim. Unlike
acquiring fixes on static objects, obtaining and re-obtaining information on
moving ones involves regular surveillance.
Using PLGR, a soldier must continually re-plot new coordinates on a separate
map based on changing target course and velocity. With DAGR, initial-fix data
is automatically updated on the visual display map for targets with constant
speed and direction and with inputs for targets with changing speed and direction.
“DAGR does in one step what PLGR does in two,” said Steve Jones,
marketing manager for land navigation systems at Rockwell Collins. “The
act of plotting new coordinates can now be accomplished by the receiver itself,
reducing the total time-to-fix.”
DAGR also addresses the need for data sharing during operations. In situations
where a common picture of the battle-space is required for objective coordination,
soldiers can link PLGR with DAGR or DAGR with DAGR to update information where
necessary. Using PLGR, data is transferred textually and then must be plotted
by hand. DAGR will allow the instant transfer of visual displays with waypoints
already designated.
“This will eliminate the time it takes for one soldier to re-plot objects
that are already plotted on another soldier’s map,” Jones said.
One key difference between PLGR and DAGR is the latter’s ability to alert
a soldier to danger zones not depicted on an operational map. As a function
of DAGR’s visual display, threats such as the presence of enemy units
or terrain irregularities are designated by icons that differentiate them from
friendly or neutral waypoints.
“By not having to go from receiver to map and back to receiver again,
as is the case with PLGR, DAGR users can keep their eyes on the receiver to
show them objects and areas to be aware of,” Jones noted.
“Assuming these obstacles have a static location or constant course,
DAGR will continue to update their positions by the second. If the objects are
moving with continually changing courses and speeds, inputs from the user, either
visually or electronically, will result in updated positioning on the DAGR display.”
Program officials also predict that DAGR will help synchronize battlefield
communications systems, such as the single-channel ground and airborne radio
system and the joint tactical radio system. Using its dual frequency capability,
DAGR would establish optimal radio frequencies for soldier-to-soldier voice
transmissions.
“In situations where standard frequency hopping is being used, the synchronization
of GPS equipment to a particular radio network requires precise timing,”
said Jones. “With DAGR’s dual frequency operation, faster GPS signal
lock-on will in turn enable faster radio connectivity, giving soldiers quicker
access to the data they to need for performing their mission.”
As far as the development of DAGR goes, both contractors said that there is
a big push by the Defense Department to incorporate as much commercial technology
as possible.
“Providing user-friendly functionality within technologically advanced
packaging to the war fighter continues to be a top priority,” Hirschman
said. “DAGR’s visual display, ability to acquire a quick position
fix, and easy-to-manage platform are perhaps the aspects best demonstrative
of this trend toward the commercial.”
An example of a commercial-like capability is the integration of satellite
photography and the receiver’s visual display. DAGR software will enable
users to geo-reference a satellite image to specific GPS coordinates on the
display map.
“By downloading satellite views of a battle-space taken prior to a mission
into DAGR, a soldier can carry an accurate picture of the operational theater
and continually update that picture with inputs accordingly,” said Fleenor.
“In situations where a soldier is not line-of-sight to a moving object,
but has communication on an approximate location, speed and direction of that
object, DAGR’s visual display software will return instant position data,
once the waypoint has been entered.”
Efforts by the U.S. Army to digitize battlefield systems and improve interoperability
also have shaped the DAGR program. “Where PLGR has provided positioning
and timing functionality as part of larger integrated systems, DAGR will now
extend that functionality to a greater number of systems, maintaining backward
compatibility while simultaneously raising the standard of GPS receiver operation,”
Hirschman said. “DAGR’s presence should aid in transforming the
very manner in which operational commanders view the challenges in maintaining
control of mission situational awareness.”
Initial fielding of DAGR is slated for fall 2004. So far, only the U.S. Army
and U.S. Air Force have signed up for the new receiver. The Navy and Marine
Corps have expressed interest in integrating DAGR technology into their existing
GPS-capable platforms.
The JPO currently is conducting an international cooperative test with several
allied nations, including Norway, Germany, France, Australia and the United
Kingdom, which have expressed interest in purchasing the receiver for their
military forces.