The base, which plays a key role in the global network of the National Security Agency (NSA), GCHQ's American partner, now includes 33 radomes – commonly called "golf balls" after the white sheeting protecting the satellite receiving and transmission stations – and is undergoing a big construction programme.
The study describes the programme, called Project Phoenix, as "one of the largest and most sophisticated high technology programmes carried out anywhere in the UK over the last 10 years". Work on it has been reserved for US-based arms corporations including Lockheed Martin and Northrop Grumman, and their personnel with high-level security clearance, it notes.
Though the base is officially called RAF Menwith Hill, most of the staff there are US employees of the NSA. The total number of people working there is due to increase from 1,800 last year (of whom 400 were British) to 2,500 in 2015.
The costs to Britain of servicing Menwith Hill, like other American bases in Britain, are confidential under cost-sharing arrangements between the UK and the US. The total cost of the equipment at the base, and running it, is classified.
However, official figures released in the US show that this year the NSA is spending $68m (£43m) just on a generator plant to provide power for new supercomputers at the base.
Computers at the base are capable of carrying out 2m intercepts an hour, according to the Federation of American Scientists, an independent US body.
The report on the base was commissioned by the Yorkshire Campaign for Nuclear Disaarmament (CND) and funded by the Joseph Rowntree Charitable Trust. It said the base was being expanded "to provide qualitatively new capabilities for intelligence-led warfare".
Menwith Hill will combine its traditional role of eavesdropping on communications and missile tests to "co-ordinate real-time military operations such as covert warfare, using a variety of intelligence sources".
Satellite communications and imagery and supercomputers at the base "can provide real-time surveillance to support US military operations", according to the new study. It said Menwith Hill would be "fully operational as an upgraded, active intelligence hub by 2015".
Steve Schofield, the study's author, said: "It is no longer possible to think of Menwith Hill as simply carrying out traditional military, diplomatic and commercial electronic spying for the United States, but rather to recognise its role as an active provider of integrated intelligence to support new forms of warfare."
He added: "This paradigm shift towards permanent surveillance from space and real-time military interventions anywhere in the world through remotely-controlled weapons raises profound questions about the western way of war but questions that are, as yet, barely being addressed."
The RAF describes Menwith Hill's primary mission as providing "intelligence support for UK, US and allied interests". Satellite communications also provide data for the US missile defence system, the RAF says.
It would be "inappropriate to go into any detail about operations carried out at RAF Menwith Hill in support of national security", it says.
"Public and parliamentary scrutiny of RAF Menwith Hill is provided through
clear lines of ministerial responsibility and by the intelligence and security