By David Shukman

Science and environment correspondent, BBC News

A portable radar device is designed to make measurements of ice thickness

After enduring ferocious weather, it has emerged that British explorers studying the Arctic are struggling with a series of technical problems. A portable radar device, known as Sprite, designed to make millions of measurements of the ice thickness, has been dogged by breakdowns and uncertainties. Another instrument, SeaCat, meant to measure the temperature and salinity of the water beneath the sea-ice, has malfunctioned as well. The expedition's organisers insist that other research - such as regular drilling through the ice - has meanwhile been carried out successfully. The radar system is dragged behind the sledge of expedition leader Pen Hadow and is meant to gather data about the ice for transmission via satellite to researchers. But when the expedition, the Catlin Arctic Survey, set off in late February, it encountered an unexpected wind chill as low as minus 70 degrees Celsius, and the technology failed. Cable break I understand that on the fifth day in these conditions, one of the radar system's cables simply snapped. On the ninth day it became clear that this had led to all the cables breaking. So with the team's early progress anyway hampered by the weather, the Sprite only gathered data over a total period of seven hours of trekking in the expedition's first 18 days. A resupply flight, which landed last month, collected the device for repairs back in the UK, and that work is now complete. But support staff are still having trouble accessing the ice data stored inside it. The same resupply flight also delivered a replacement radar to the expedition but it's not yet known how well it has functioned over the past few weeks or if its data can be retrieved. Another resupply flight on Wednesday brought the team the original Sprite device, now repaired, together with the communications system. Expedition organisers are now hoping that at last, after nearly 40 days on the ice, the radar data can be gathered and transmitted as planned. Assuming they can retrieve any data collected earlier, they hope to have lost only 13 days' worth of measurements in all - the period the original Sprite unit was out of action. Resupply flight The broken SeaCat device was extracted on the first resupply flight and a replacement is due to be delivered in a fortnight's time. Simon Harris-Ward, director of operations for the Catlin Arctic Survey, told the BBC: "Given the very extreme conditions they are operating in during the Arctic winter we were always going to face potential difficulties with the array of advanced technology despite our robust testing programme. "We have been cautious about making any statement about Sprite simply because of a combination of factors. First, an uncertainty about the exact nature of the problem and second, the inevitable delays in assessing data which had to be extracted on our re-supply flights before it could be analysed." "Most of the Catlin Arctic Survey science programme does not require data from Sprite and the Ice Team has been continuing to collect valuable data in its wider science programme, including measurements of the floating ice's thickness. So we remain confident in our ability to deliver data to our scientific partners." The expedition's other research tasks include drilling through the ice by hand, on average four times a day. With 102 holes drilled so far, hundreds of measurements have been made of ice thickness and snow cover over the 243km covered to date. The drillings have revealed a typical ice thickness of between 1.5-2m which is far thinner than a previous generation of explorers encountered. All this data - and any that can be gleaned from the radar system - will be sent to Arctic specialists at the US Navy Postgraduate School in Monterey, California, US, to help assess the likely fate of the sea-ice.



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