Monday’s announcement by Prime Minister David Cameron that the RAF’s Raytheon Sentinel R1 fleet will be extended in service until at least 2018 has breathed new life into the program, and sparked real interest in further development.

One of the key features that could be added is a greater maritime capability. While the RAF is quick to stress that a maritime-capable Sentinel is not a maritime patroller, it could be used as a gap-filler in certain scenarios, and has considerable applications in littoral operations, such as amphibious landings or humanitarian missions.

An embryonic maritime capability for the Sentinel radar first came to the fore during Operation Ellamy in 2011. RAF Sentinels working along the Libyan coast noted that the moving target indicator mode of the dual-mode radar could track vessels entering and leaving Libyan harbors, resulting in intelligence that was swiftly acted upon.

Now the question of adding further maritime modes to the system is on the table for inclusion in an updated Sentinel. Raytheon has developed technologies across its sensor range that could be applied to the Sentinel’s Astor radar, and maritime modes could be adapted from those developed for the APY-10 radar that is operational in the Boeing P-8 Poseidon.

Canoe Sensor

Other new functions that the Sentinel could gain include a signals intelligence-gathering capability and a standoff electro-optical/infrared sensor. Changes to the way the aircraft communicates via satellite have made some original communications systems redundant, with the result that enough SWAP (size, weight and power) capacity could be freed up in the canoe fairing to install a system in the class of the UTAS DB-110 or Raytheon’s sensor for the Global Hawk. The Global Express business jet platform, upon which the Sentinel is based, can easily accommodate any rapid changes in altitude that the different sensors might require, unlike an airliner-type platform.

Adding a long-range EO/IR system would not only allow the Sentinel to provide high-quality imagery to complement that from the synthetic aperture mode of the radar, but also give it a visual positive identification capability, something that is not possible under UK rules of engagement when using radar imagery alone.

With a number of options available and funds now becoming available, the RAF is now in a position to prioritize which capabilities and upgrades it adopts, and in which order. This process should take about six to seven months.

One element that is currently under development by Raytheon is the Overseer enhanced airborne mission management system, which would facilitate the integration of these additional capabilities, as well as providing an improved and “de-cluttered” human-machine interface. One of the five aircraft will be assigned as a testbed for new systems when they are added.

In the meantime, the RAF Sentinel fleet has been undertaking some important missions away from the principal operational theater in Afghanistan (Operation Herrick). In Operation Newcombe the Sentinel flew 58 missions in support of French forces during the Mali intervention, while an aircraft was deployed on Operation Turus in the hunt for the Nigerian schoolgirls kidnapped by Boko Haram. Closer to home, the Sentinel mapped flooded areas of southern England during Operation Pitchpole.