The US and China have been involved in a war of words over spy balloons since US jets shot down what the Americans call a “high altitude balloon”, off the South Carolina of the US on February 4.
US defence officials say the balloon, which was 60m in diameter and flew far above commercial aviation at altitudes up to 24km, carried a range of surveillance equipment that is currently being analysed after being recovered from the ocean.
China now claims that the US has an active “spy balloon” over its airspace.
Experts say surveillance balloons are a cheap alternative to spy satellites. They can take images from closer to the ground, require no special fuel and are able to intercept enemy communications. However, the big drawback is that they are hard to control.
The balloon shot down on February 4 sparked fears of a wider balloon-based espionage programme over North America. US F-22 stealth fighter jets shot down three more airborne objects on February 10, 11 and 12 that now appear to have been launched by "commercial or research entities", according to a US government statement.
Spy balloons near Iran
Stray balloons have caused alarm before, including what the Americans call aerostats — small airships or balloons tethered to the ground and fitted with cameras to give the US military a wide field of observation.
Fitted with a high-tech camera, these were used to track approaching threats in Afghanistan and Iraq, identifying them long before they could launch attacks.
There have been at least three incidents of US aerostats coming loose and drifting towards Iran, according to the trove of leaked military and diplomatic cables related to the war on terrorism and US foreign relations that was published by WikiLeaks in 2010.
No information is given on the outcome of these incidents, which are described under the category "equipment failure", but Iran has a long history of reverse engineering captured US equipment.
This might explain a purported UFO sighting by US forces during the 2016-2017 Battle of Mosul that ousted ISIS from its last stronghold in Iraq.
In April 2016, the Pentagon's Unidentified Aerial Phenomena Task Force, set up by the US Department of Defence to investigate UFO sightings, released an image taken by a reconnaissance drone showing a shining orb drifting across the northern Iraqi city.
US investigative journalist Jeremy Corbell called it the “Mosul Orb” and says it is the first instance of a UFO being seen over an active conflict zone.
While the image appears mystifying, the orb in question is not dissimilar to the Winch Aerostat Small Platform, a spherical surveillance balloon used by the US military — and possibly the Iraqi army — at the time.
