Modern fighters bristle with data, but attempts to share it have so far been hampered by bandwidth restrictions. Are things about to change?
Airborne “nodes” in charts depicting network-centric warfare concepts have looked more ruse than reality to date, with any connections suffering from 1980s-era bandwidth limitations and lack of modern network processing power.
Allowing aircraft at the forward edge of the battlespace – particularly strike fighters – to share information at the same speeds as any office’s local area network remains a high priority and change is rapidly approaching.
In the next year, a long-term plan to develop a family of software-defined radios using an internet protocol (IP)-based wideband network waveform will enter the final development phase. The first attempts to produce even wider bandwidth channels will also be undertaken. Meanwhile, military and industry officials will explore maximising the potential of datalinks already on board aircraft. The efforts are fuelled by a new realisation of the potential for allowing tactical aircraft with advanced sensors to share their data with others on a wideband network.
A new breed of fighter aircraft coming into service with the US military this year will boast a sensor payload that may rival those of spy aircraft, yet lack the means to share that raw intelligence data with anyone besides the pilot.
An ambitious plan to create a wideband, IP-based airborne network – called the Airborne and Maritime/Fixed Joint Tactical Radio System (AMF JTRS) – is due to enter a new phase of development later this year. However, this is now thought by some to offer only a partial solution.
Although AMF JTRS promises to increase network capacity dramatically over current standards, the volumes of sensor data being collected by fighter aircraft in the future may demand even higher bandwidth capacity, according to some industry sources.
Meanwhile, alternative – and perhaps complementary – wideband networking methods are starting to be pursued, with the focus on achieving data transmission rates at least dozens of times faster than promised by the AMF JTRS high-bandwith waveform, which is now known as the Tactical Targeting Network Technology (TTNT), developed by Rockwell Collins. TTNT is transitioning from a three-year demonstration by the Defense Advanced Research Projects Agency (DARPA). It is being designed to produce a total network throughput of 10Mb/s for 200 active users within a range of 185km (100nm).
Waveform goal
The ultimate goal of TTNT is to produce an airborne networking waveform to be used by the AMF JTRS terminals. Operationally, TTNT will primarily be used to co-ordinate airborne strike packages. A Collins-produced video, for example, shows a scenario in which a Northrop Grumman RQ-4A Global Hawk unmanned air vehicle uses TTNT to pass sensor data to a Boeing E-3 Airborne Warning and Control System. The AWACS then passes the UAV imagery to a formation of TTNT-equipped Lockheed Martin/Boeing F-22As.
Two months ago, the US Air Force decided to integrate TTNT on F-22As by around 2010, withdrawing a plan to install a low-speed Link 16 transmit capability by 2008. That change highlights TTNT’s capabilities as an air-to-air transmission system, but perhaps underlines its ability to contribute to air-to-ground communications demands. The DARPA demonstration proved that TTNT can pass useful data to ground nodes, but pending advances in sensor technology may create a requirement for much higher data rates.
Although TTNT provides total network throughput of 10Mb/s, the next generation of dual-mode active electronically scanned array (AESA) radars will be able to collect data at much faster speeds. A dual-mode AESA upgrade planned for the F-22A, for example, is expected to generate data at a rate of more than 80Mb/s.
There are several technical options being pursued, including a concept to modify on-board AESA radars to transmit data in the X-band frequency, which is capable of providing transmission rates up to 1 gigabyte a second. Another option known to be under study is creating a military version of a high-bandwidth datalink that appears to be similar to the commercial technology offered by Connexion by Boeing, which provides bandwidths at around the 300Mb/s level.
For the AESA transmitter capability, an industry consortium called DirecNet, led by Cubic Defense Applications, has been tapped by US defence officials to begin a series of demonstrations. The goal is to prove the viability of converting an AESA into a data transmitter. Unlike TTNT’s omni-directional signal, the AESA beam would have to be directionally steered to a precision receiver antenna.
At the same time, the lower data transmission capabilities available under the AMF JTRS programme are being pressured by immediate demands for already operational technologies that can be adapted for military purposes in combat areas, such as Afghanistan and Iraq.
A requirement for data modems that can transmit airborne video imagery captured by unmanned aircraft or fighters equipped with advanced targeting pods to small ground units has led to a demand for the family of L-3 Communications Rover terminals. In two years, L-3 has released two upgraded versions and a fourth improved design has already been developed.
Such simple datalinks that can transmit video footage from current advanced targeting pods, which are already in wide use, may become a threat to the demand for more expensive and complicated systems such as AMF JTRS.
Real-time contact
The Rover terminals have filled a capability need created by the recent deployment of advanced targeting pods on fighters. With the pods now linked to ground troops, there is new demand for the tactical intelligence they provide, not only from the pilot, but also to small units on the ground that may be in contact with or searching for enemy forces.
Meanwhile, the dual-mode Raytheon APG-79 AESA is due to enter service next year with the US Navy’s Boeing F/A-18E/F Block 2 Super Hornet. The Northrop APG-77 radar is being upgraded in a few years with a dual-mode feature for the F-22A.
Both radars are able to sweep for emissions in the air and on the ground. Such a system offers the pilot an instantaneous and integrated view of air targets and ground emitters, such as integrated air defence radars and command and control sites. Although such systems are designed to aid the pilot, each provides a voluminous amount of tactical intelligence that may of use to friendly troops in their general proximity.
The combination of targeting pods and advanced radars would offer a potential new source of real-time raw intelligence for the ground forces, essentially transforming the air force’s and navy’s premier strike fighters into non-traditional spy aircraft. Exchanging such video footage and precise identification and location of friendly and enemy positions also holds the promise of revolutionising the concept of close air-support missions.
For example, US Air Force Boeing F-15Es are their quintessential attack aircraft, but one of its most useful payloads in Iraqi battles has been a forward-looking infrared pod and a modem.
The US military’s dream of turning the sky into an IP-based, high-speed local area network with AMF JTRS for fighters is many years away, but F-15s equipped with the Lockheed Sniper XR targeting pod are already providing imagery directly to ground troops conducting raids and alerting ground troops to potential sites of improvised explosive devices (IED).
Similarly, the same capability has been available on the US Navy’s F/A-18E/F Block 1 Super Hornets since late 2002. Next year, the Block 2 aircraft will allow the pilot to use the AESA radar to cue the ATFLIR targeting pod to scrutinise specific points of interest with the electro-optical sensor and targeting laser, which could become a useful source of intelligence for other platforms and even ground units.
Dramatic upgrade
The ATFLIR pod is poised to become a critical test of the USN’s ability to maximise the connectivity potential of current platforms. The USN has contracted Raytheon to upgrade the ATFLIR’s C-band datalink to Ku-band, essentially converting the pod from a data transmission rate of 455Kb/s to up to 10.7Mb/s, says Raytheon business development manager Dave Goold. The USN’s initial plan is to make this connectivity available to improve air-to-ground communications, particularly through the Rover datalink. Goold says the upgrade will dramatically improve the quality of the video transmissions.
However, the new Ku-band transmitter may eventually offer capabilities to improve air-to-air data communications, says Goold. The first step in the USN’s plan is to use the Ku-band to port the ATFLIR imagery to the Super Hornet’s current on-board datalink – the Link-16 multifunction information distribution system.
STEPHEN TRIMBLE / WASHINGTON DC
Source: Flight International
