Secret mission accomplished: America's mysterious space plane to land after a YEAR in orbit - and no one knows what it did up there

• The X-37B has been circling the Earth at 17,000mph and was due to land in California in December
• Mission of highly classified robotic plane extended for unknown reasons
• Will now land in mid- to late-June
  

By Rob Waugh
Updated: 10:12 EDT, 4 June 2012

The U.S Air Force’s highly secret unmanned space plane will land in June - ending a year-long mission in orbit.

The experimental Boeing X37-B has been circling Earth at 17,000 miles per hour and was due to land in California in December. It is now expected  to land in mid to late June.

At launch, the space plane was accompanied by staff in biohazard suits, leading to speculation that there were radioactive components on board.

Mystery tour: The mission of the X-37B space plane was extended after it spent nine months orbiting the Earth

The men and women of Team Vandenberg are ready to execute safe landing operations anytime and at a moment's notice,' said Colonel Nina Armagno of the U.S. Air Force's Space Wing.

The plane resembles a mini space shuttle and is the second to fly in space.

It was meant to land in March, but the mission of the X-37B orbital test vehicle was extended – for unknown reasons.

The first one landed last December at Vandenberg Air Force Base in California after more than seven months in orbit.

The 29-foot, solar-powered craft had an original mission of 270 days. 

The Air Force said the second mission was to further test the technology but the ultimate purpose has largely remained a mystery.

The vehicle's systems program director, Lieutenant-colonel Tom McIntyre, told the Los Angeles Times in December: 'We initially planned for a nine-month mission. Keeping the X-37 in orbit will provide us with additional experimentation opportunities and allow us to extract the maximum value out of the mission.'

Questions: The unmanned space plane is the second of its kind to be sent up by the U.S. Air Force - but its purpose has never fully been explained

Finishing touches: Scientists in protective suits inspect the solar-powered craft prior to its mission

However, many sceptics think that the vehicle's mission is defence or spy-related.

There are rumours circulating that the craft has been kept in space to spy on the new Chinese space station, Tiangong.

However, analysts have pointed out that surveillance would be tricky, since the spacecraft would rush past each other at thousands of metres per second.

Keeping watch: An artist's rendition of the X-37B shuttle orbiting the Earth

And Brian Weeden, from the Secure World Foundation, pointed out to the BBC: ‘If the U.S. really wanted to observe Tiangong, it has enough assets to do that without using X-37B.’

Last May, amateur astronomers were able to detect the orbital pattern of the first X-37B which included flyovers of North Korea, Iraq, Iran, Pakistan and Afghanistan, heightening the suspicion that the vehicle was being used for surveillance.

Other industry analysts have speculated that the Air Force is just making use of the X-37B’s amazing fuel efficiency and keeping it in space for as long as possible to show off its credentials and protect it from budget cuts.

Enlarge  

This undated image released by the U.S. Air Force shows the X-37B spacecraft. Its mission and cost are shrouded in secrecy

Lift off: The X-37B sits on top of an Atlas V rocket as it's launched at Cape Canaveral Air Force Station in Florida in 2010

Ready for launch: The X-37B rocket in Florida before it blasted off into space

Mystery: Scientists work on a prototype for the rocket prior to its launch

After all, under budget cuts for 2013 to 2017 proposed by the Obama administration, the office that developed the X-37 will be shut down.

According to X-37B manufacturer Boeing, the space plane operates in low-earth orbit, between 110 and 500 miles above earth. By comparison, the International Space Station orbits at about 220 miles.

The current flight launched from Cape Canaveral, Florida, in March. 

Enlarge  

This computer image shows the space plane re-entering Earth. Although it resembles a small space shuttle it is not designed to carry humans. It's wingspan is a mere 4.5m with a length of 8.9m. It is powered by batteries and solar cells