To illustrate Tuesday's successful airstrikes in Syria, the Pentagon released a number of before/after pictures highlighting the effects of US bombings. One slide showed a command and control centre in the Islamic stronghold of Raqqah, intact in the first picture, and partially destroyed in the next. The damage was done by GPS-guided bombs dropped from an F-22 stealth fighter - its first-ever combat mission - and other assets like the B-1B strategic bomber.

So we know what dropped the bombs, but what took the pictures?

On closer inspection, the Pentagon's before/after photos have been taken from a high-altitude aerial platform circling the target buildings. With the F-22 and other coalition aircraft lacking reconnaissance capabilities, it's safe to say the photographs were taken by an advanced Intelligence, Reconnaissance and Surveillance (ISR) aircraft. When asked by airforce-technology which ISR platforms were used, Air Force officials and US Central Command (CENTCOM) would not comment.

Due to its classified nature, the US military will not reveal the details of where ISR flights were carried out or what asset was used.

By examining open-source information, it's likely the US deployed one of its biggest and most advanced spy drones; the RQ-4 Global Hawk. The huge 14.5m-long unmanned aircraft, which can fly at 60,000ft and stay aloft for around 32 hours, is packed with advanced electronic sensors and systems for top secret surveillance missions. It can give military commanders "near real-time" ISR data over large geographic areas, according to its manufacturer Northrop Grumman.

The realities of autonomy in unmanned air systems today Despite significant technological leaps, the development of truly autonomous systems is still in its early days.

Flying at 60,000ft over Syria, it would provide vital situational awareness for commanders overseeing the airstrikes and allow them to assess tactical information instantly via satellite data-links.

Global Hawk was used in May as part of international efforts to locate hundreds of schoolgirls kidnapped in Nigeria by militant group Boko Haram. It also mapped the devastation caused by the Haiti earthquake in 2010 for military units working on the ground. The aerial pictures of crumbling buildings in Haiti, snapped by the Global Hawk, look almost identical to the pictures released by the Pentagon on Tuesday.

It has also flown in Iraq, Afghanistan and Libya and is configured to carry what's known as an Enhanced Integrated Sensor Suite (EISS) and an Airborne Signals Intelligence Payload (ASIP). The EISS includes an all-weather synthetic aperture radar/moving target indicator (SAR/MTI), high-resolution digital camera and third-generation infrared sensors.

These advanced sensors mean commanders can distinguish, in real-time, different vehicles, buildings and people, even in adverse weather conditions like fog or cloud cover. The ASIP payload will also allow commanders to listen in on enemy communications, although many details about this capability are classified.

Sucking up vital intelligence on Islamic State

With this advanced technology, Global Hawks could have been flying over Syria well before this week's airstrikes to gather intelligence on potential targets, sucking up vital intelligence data from various Islamic State hotspots like Raqqah.

Global Hawk is also capable of being used as a Battlefield Airborne Communications Node (BACN), a platform which 'fuses' different data links used by stealth and non-stealth aircraft into a common "language" which allows for greater interoperability. This is particularly important with the F-22, which cannot communicate with non-stealth aircraft without BACN capabilities.

If the Global Hawk was utilised, it would have been from a detachment currently based at the Al Dhafra Air Base in the United Arab Emirates, home of the US Air Force's secretive 380th Air Expeditionary Wing. The wing's mission, according to its website, is to conduct operations using high-altitude ISR assets like the Global Hawk and U-2 spy plane. The 308th Expeditionary Operations Group "includes four diverse squadrons responsible for executing the US Central Command's daily air tasking order with high altitude all-weather ISR, airborne command and control and air refueling missions."

"So we know what dropped the bombs, but what took the pictures?"

Satellite images of Al Dhafra show several E-3 Airborne Warning and Control System (AWACS) aircraft and KC-10 aerial refuelling tankers visible on the tarmac but other aircraft like the Global Hawk are not visible, owing to their sensitive roles.

The F-22s involved in Tuesday's airstrikes are also thought to be stationed at the UAE base.

The RQ-4s have become so capable that the US Air Force plans to replace its remaining U-2 spy planes, relics from the Cold War, with the unmanned aircraft. The Global Hawk concept was dreamt up back in 1995, and several prototype aircraft have been deployed on operations since 2001. But it is only over the last few years, and the introduction of the advanced Block 30 variant, that the US Air Force has given the aircraft a greater role in high-altitude ISR missions.

It's a significant turnaround for the Global Hawk, which was due for the chop only a few years ago. In 2012, the US Air Force said it would retire the drones in favour of the U-2 citing cost issues and capability concerns. But that decision was reversed, owing to the fact that RQ-4 costs have dropped, and the Air Force will instead begin retiring the 33-strong U-2 fleet in 2015, while at the same time bolstering the Global Hawk inventory.

So while this week's Syria airstrikes were a baptism of fire for the F-22, was it also the first true test for the US Air Force's premier high-altitude spy drone?

Follow Grant Turnbull on Google+