http://news.bbc.co.uk/hi/english/sci/tech/newsid_1548000/1548860.stm US spy satellites have been given new instructions to concentrate their attention on Afghanistan and the search for Osama Bin Laden, and groups associated with him, sources have told BBC News Online. So-called Signal Intelligence (Sigint) satellites, designed to intercept radio and mobile phone traffic, have been "retasked", as have two spy satellites that take high-resolution images. The use of Sigint satellites marks a departure from normal procedure, as they are not usually used to gather intelligence about dissident groups in that region. BBC News Online also understands that US military sources have also made approaches to two commercial satellite operators, to use data from two private imaging satellites that will be launched in the next few weeks. Following conversations The so-called "retasking" of spy satellites is an unusual step that reflects the seriousness of the response to the hijack plane attacks on New York and Washington DC. Sigint satellites monitor electromagnetic signals and send them to sophisticated listening posts scattered over the globe where they are relayed to supercomputers in the US for analysis. In co-operation with the Echelon phone, fax and e-mail monitoring system that is also searching for evidence of subversive activity, the Sigint data are analysed using sophisticated programs that allow information to be extracted from the jumbled signals. It is thought that when conditions are favourable, individual mobile phone conversations can be followed. The main suspect identified by the US for last Tuesday's attacks, Osama Bin Laden, is said not to use mobile phones, for fear of being eavesdropped. But US military officials are clearly hoping that they may intercept some phone coverage, a task that should be helped by the small size and sparse communications infrastructure in Afghanistan - the country where Bin Laden is thought to reside. Imaging spy satellites are also returning high-resolution images back to the Pentagon. These images, able to detect individual people, will also be studied by computer to spot movements that could help analysts pinpoint Bin Laden. Private help Military officials are also considering using the capabilities of two private satellites that will be launched in the next few weeks. The first of these, Orbimage-4, is due to be put into orbit on 21 September from California. This is a private remote-sensing satellite with unique capabilities. It carries a camera that takes images in 200 spectral bands - designed to analyse surface composition. Military analysts are considering whether it could be used to see through camouflage, which is often used by those on the ground who do not want their activities exposed by spy satellites passing overhead. The other satellite, Quickbird, to be operated by Digitalglobe, is set for launch on 18 October. It will have the greatest resolution of any non-military satellite. Able to see detail smaller than a metre, Quickbird could be used when military spy satellites are not in the correct place.