Reaper has become an indispensable tool for the military
To a casual observer, Britain's most sophisticated unmanned aerial vehicle looks rather like a large white model aeroplane. But its sleek exterior hides the deadly capabilities beneath.
It is one of Britain's most crucial intelligence weapons, and is playing an increasingly vital role on the battlefield in Afghanistan.
These roving eyes in the sky are becoming an indispensable tool for the British military, able to detect snipers or insurgents planting the deadly roadside bombs that have become one of the biggest threats to forces on operations in Iraq and Afghanistan; as well as being one of the UK's main weapons in hunting down Taliban or Al Qaeda operatives.
Now, Britain's Reapers are also - on some missions - armed to shoot down their targets, rather than simply locate, identify and film them.
The RAF Reaper was only recently authorised to carry munitions, though what arms may be carried on each specific flight is mission-specific and will not be made public for reasons of operational security.
The Ministry of Defence says it "cannot comment on specific operations, but can confirm that an RAF Reaper used its weapons system. As with any other munitions, rules of engagement are strictly adhered to, ensuring that collateral damage is minimised in accordance with the laws of armed conflict".
I encountered Britain's first Reaper MQ-9 UAV in Afghanistan last December, shortly after its first operational flight there in October 2007.
The rapid acquisition of three Reapers for the RAF was deemed "a major milestone" by the UK's Chief of the Air Staff, Air Chief Marshal Sir Glenn Torpy.
The MoD's new Skynet system can handle real-time video feeds
He said the planes would "significantly enhance" the UK's surveillance and reconnaissance capability in Afghanistan.
An RAF pilot based in Afghanistan takes care of the take-off and landing, but the UAV itself is flown for most of its mission by RAF pilots operating Reaper remotely via satellite link from a distance of 7,000 miles (11,300km) away, from the US Air Force's Creech airbase in Nevada.
The pilot and an observer sit at computer screens, seeing what the plane sees through its cameras and sensors.
One computer screen shows navigational data, another what the plane is viewing, while a third screen provides operational data.
Some 44 RAF crew from RAF 39 Squadron also help fly the US's Predator surveillance aircraft from their base in the Nevada desert.
Reaper was initially known as Predator B, a larger turbo-prop powered version of the original Predator.
Reaper is not, however, a cheap option. It costs about £5m per plane, but the price of back-up services brings the total bill for three to some £50m - and earlier this year one of the UK's two current Reapers came down in the Afghan desert thanks to a technical fault.
It had to be destroyed to keep its secrets from the enemy. Another is due to be delivered in January, while a replacement for the lost plane is also on order.
The "eyeballs" - the rotating sensors strapped to the nose - offer extremely high-quality video feed, which can show clearly from 15,000ft (4,500m) what an insurgent is doing.
The video is streamed back in real-time to the controllers' screens at Creech. The ground control stations send their commands to Reaper via a fibre-optic link to a satellite relay station in Europe, which bounces them into space and back down to the aircraft.
The space link is handled by the UK's new high-bandwidth Skynet 5 satellites.
"Reaper matters because it can loiter above a potential target, for example the home of an insurgent commander, for hours on end, watching the pattern of life and ensuring that the target individual is in the building and - just as importantly - there aren't innocent people in there as well," says Andrew Brookes, aerospace analyst at the International Institute for Strategic Studies and a former RAF reconnaissance and bomber pilot.
"Both of these factors are crucial in the battle for hearts and minds," he says.
"In previous years, a separate strike asset had to be called in when the UAV reconnaissance feed proved conclusive, but that took time - and maybe the bad guy got away.
"Now, the same Reaper that validates can also strike and then send back battle damage video feed, which again is crucial in the modern media age."
However, he also strikes a note of caution.
"Reaper could not operate if the Taliban or al Qaeda had any sort of air defence capability. Reaper is today's answer to today's conflict - but it might well not be the answer in a future operation."
But the RAF is keen to operate more Reapers within the current conflict.
Last year, it requested 10 Reapers, made by General Atomics, which could cost up to £250m with their associated equipment.
However, it is believed the request has been turned down in the current MoD planning round, though the RAF is sure to continue asking to enlarge its fleet.
An RAF Nimrod similar to the one lost in Afghanistan
The unmanned vehicles may be costly, but they are far less costly in terms of lives if shot down or lost.
Britain suffered one of its worst ever losses of life in September 2006, when a Nimrod reconnaissance aircraft exploded in mid-air over Kandahar in Afghanistan, killing all 14 servicemen on board.
A coroner recently ruled that the current Nimrod fleet was unsafe, something the MOD disputes. However, its replacement - the Nimrod MRA4 - will not be ready for several years, perhaps offering an ever-more vital role for UAVs.
Thanks to their light weight and big wings, the Reapers burn relatively little fuel compared with many other types of reconnaissance planes; and that allows them to take up long-duration station over targets.
In addition to its current "hunter-killer" role, Reapers operated by the US Air Force are likely to be equipped as signals intelligence aircraft - capable of detecting mobile telephone signals, as well as signals emitted by surface-to-air missile batteries, which would bring Reaper's intelligence capabilities a little closer to those of the Nimrod.
The US Air Force's Reapers are typically armed with four Lockheed Martin AGM-114 Hellfire air-to-surface missiles, plus two Raytheon 500lb (226kg) Paveway II-class laser-guided bombs.
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