Proof that the Echelon system was still operating was found in US government documents in 1998 and 1999. US intelligence specialist Dr Jeff Richelson, of the National Security Archive, Washington DC, used the Freedom of Information Act to obtain a series of modern official US Navy and Air Force documents which confirmed the continued existence, scale and expansion of the Echelon system. The documents identified five sites as part of the system collecting information from communications satellites.

The first station to be confirmed as part of Echelon was Sugar Grove, in West Virginia. According to the station's history, an "Echelon training department" was established in 1990. When training was complete, the first task assigned to the station was "to maintain and operate an Echelon site".

According to these official documents, Sugar Grove's mission is "to direct satellite communications equipment [in support of] consumers of Comsat information ... this is achieved by providing a trained cadre of collection system operators, analysts and managers...".

In 1990, satellite photography showed that there were four antennae at Sugar Grove field station. In 1998, a ground visit by a TV crew revealed that this had expanded to nine. All were directed towards the satellites over the Atlantic Ocean, providing communications to and from the Americas as well as Europe and Africa.

The documents also identify four other intelligence bases that were part of the Echelon network by 1995. These were Yakima, Sabana Seca in Puerto Rico, Guam, and Misawa, Japan.

What we know

• In 1997, a judge slammed British Telecom for revealing detailed information about high bandwidth cables that were fitted at Menwith Hill, the UKUSA alliance monitoring base in Yorkshire. BT admitted it had fitted three digital optical fibre cables capable of carrying 100,000 telephone conversations simultaneously.

• Patent number 5,937,422 was applied for in 1997 by the US National Security Agency (NSA) and describes a technology as a 'method of automatically generating a topical description of text by receiving the text containing input words'. It employs machine transcription -- 'a technique for converting speech into text'.

• The Dictionary system: Echelon uses computers powerful enough to search through masses of traffic for keywords. In 1991, a former British GCHQ official spoke anonymously to Granada Television's 'World in Action' about the Dictionary system.

• A Canadian spy disclosed surveillance orders allegedly given during Margaret Thatcher's premiership to American television in February. Mike Frost, an ex-spy, told 60 Minutes that Thatcher had ordered surveillance on two cabinet colleagues using Echelon.

• In June, Lindis Percy, campaigner for the accountability of US bases in Britain, issued a challenge to the MoD over its role in the expansion of Menwith Hill. Percy argues that Washington may be in breach of a 28 year old disarmament treaty with Moscow if it builds an anti-nuclear shield to protect Menwith from attack. In 1997, the MoD confirmed it leases Menwith Hill to the Americans and that it was expanding to include the Space Based Infra-Red System (SBIRS). SBIRS tracks satellites by infra-red telescope detecting the heat emitted by any nuclear, chemical or biological missile.

• In November 1999, the BBC published an article that said the Australian government had confirmed the existence of Echelon. Bill Blick, inspector general of intelligence and security for Australia, told the BBC that the Australian Defence Signals Directorate (DSD) forms part of Echelon.

• The Electronic Privacy Information Centre (EPIC) recently obtained secret memos from the US government which outline protocols to NSA staff for reporting on intercepted intelligence. Former President Jimmy Carter is mentioned in the documents with references to his trip to Bosnia in 1994.