Intelligence from Australia's Pine Gap base is being used on US battlefields, leaked documents from the US National Security Agency have revealed for the first time.

The documents reveal that the base outside Alice Springs, officially titled Joint Defence Facility Pine Gap, provides detailed geolocation intelligence to the US military that can be used to locate targets, including for special forces and drone strikes.

The use of lethal unmanned drones by the US military has been blamed for hundreds of civilian deaths across countries like Pakistan, Afghanistan Syria, Yemen and Somalia.

The documents, which Background Briefing is publishing for the first time, come from the massive archive of classified documents leaked by NSA whistleblower Edward Snowden.

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One document, titled "NSA Intelligence Relationship with Australia" is marked "top secret", and demonstrates that the role of Pine Gap, referred to by its NSA codeword RAINFALL, has become more military-focused over time.

It says: "Joint Defence Facility at Pine Gap (RAINFALL) [is] a site which plays a significant role in supporting both intelligence activities and military operations."

Another document reads: "One of RAINFALL's primary mission areas is the detection and geolocation of Communications Intelligence, Electronic Intelligence and Foreign Instrumentation signals."

Finding targets for America's military strikes

Locating the source of signals is crucial for targeting military action, including the lethal unmanned drone strikes.

Richard Tanter, a professor at the University of Melbourne's school of political and social studies and the co-author of a recent Nautilus Institute report on Pine Gap, says the documents confirm the facility's military role.

"Those documents provide authoritative confirmation that Pine Gap is involved, for example, in the geolocation of cell phones used by people throughout the world, from the Pacific to the edge of Africa," he said.

"It shows us that Pine Gap knows the geolocations, it derives the phone numbers, it often derives the content of any communications, it provides the ability for the American military to identify and place in real time the location of targets of interest."

Another secret NSA document, a "site profile" of Pine Gap, explains that the facility's role is not only to collect signals, but to analyse them.

"RAINFALL detects, collects, records, processes, analyses and reports on PROFORMA signals collected from tasked target entities," the profile says.

These PROFORMA signals are the communications data of radar and weapon systems such as surface-to-air missiles, anti-aircraft artillery and fighter aircraft — vital tactical information that is provided in near real-time to US forces on the battlefield.

Senior veteran speaks about facility's role

David Rosenberg, a 23-year veteran of the NSA who worked inside Pine Gap as team leader of weapon signals analysis for 18 years until 2008, confirms the base's geolocation capability.

"We're talking about the ability of satellites to geolocate particular electronic transmissions," he says.

"The tasking we get at Pine Gap, is [to] look for this particular signal coming out of this particular location. If you find it, report it, and if you find anything else of interest, report that as well.

David Rosenberg believes intelligence from Pine Gap helps minimise civilian casualties. ( ABC RN: Teresa Tan )

"That is the kind of tasking we are looking for. It would be up to the recipients who get this kind of intelligence to make these types of decisions to say, 'Is that relevant? Is that what we are looking for? Are these the people we are targeting?'"

But Mr Rosenberg says preventing civilian casualties is a high priority.

"One thing I can certainly tell you the governments of Australia, and the United States would of course want to minimise all civilian casualties," he says.

"Pine Gap does help to provide limitation of civilian casualties by providing accurate intelligence."

Could Australian personnel be charged with war crimes?

Not everyone is sure things are that clear cut.

Emily Howie, the director of advocacy and research at the Human Rights Law Centre, believes Pine Gap's potential role in drone strikes may leave Australians open to prosecution.

"The legal problem that's created by drone strikes is that there may very well be violations of the laws of armed conflict, or war crimes as it's called colloquially, and that Australia may be involved in those potential war crimes through the facility at Pine Gap," she says.

"Australia, in so far as it is locating suspects that the US targets, is assisting the US. So it could be liable for any crimes committed by the US, in terms of aiding and assisting in that.

"The question then is: is the killing that's done by the United States a war crime or not?"

Intelligence from Pine Gap is used in near-real time by US forces on the battlefield. ( US Air Force: Master Sgt Kevin J Gruenwald )

Ms Howie argues there is an urgent need for greater public knowledge and debate about the Pine Gap base.

"What we have here are credible and really serious allegations made against the personnel at Pine Gap that they could be involved in assisting international crimes — war crimes — and we have absolutely zero transparency around what's happened," she says.

However, Peter Jennings, the executive director of the Australian Strategic Policy Institute, an independent thinktank in Canberra funded largely by the Department of Defence, says Pine Gap's role is a natural part of Australia's alliance with the US.

"If you accept that the USA and Australia, we're fighting in necessary conflicts in the Middle East, then it's appropriate that our intelligence facilities support those conflicts," he says.

"It reflects a reality that both Australia and the United States and a significant number of other countries besides, are engaged in military operations against a fairly entrenched enemy in the form of extremists or terrorists that are operating in a number of countries in the Middle East. So I think it's perfectly reasonable that we should be using our intelligence resources to support our military operations in in those countries."

According to Cian Westmoreland, who worked for four years as a US Air Force signals relay technician for lethal drones in Afghanistan, it's difficult to say who is responsible for any one piece of targeting information.

"All of this information that's getting sucked up is being used to basically develop targets and find out where the next strike is going to be," he says.

"You have different countries doing different things all working together. You have stations in Great Britain and the Australians would be working with the Americans and the British.

"It's collaborative, and it's really hard to say 'the Australians are responsible for this' or 'the British are responsible for that'.

"Everybody is working together and if the Australians were involved in one piece that happened to be used in a strike, they're essentially complicit with whatever the end result is."

This report was prepared in collaboration with The Intercept, a US investigative news website. The leaked NSA documents are available on the Background Briefing website.