The item was picked up almost immediately by the BBC News web site and turned into an even bigger story. The thing was...... it simply was not true.

The uncredited author had noticed the similarity between apogee, perigee and orbital inclination of the two craft and jumped to the conclusion that they were in the same orbit. The spaceplane must, by definition, be checking out Tiangong 1. Had the idea been run past anyone with a knowledge of orbital mechanics and the full orbital parameters of the two vehicles, the story would never have seen the light of day.

Spaceflight did not question how the US could have launched the X-37B in 2011 March with full knowledge of exactly when, and into what orbit, Tiangong 1 was to be injected six months later. There is a secondary question of how the USAF could have known in advance that Tiangong 1 would fly at a subtly different inclination from its Shenzhou predecessors.

The whole assumption was flawed. because, although the heights and inclination were similar, the two orbits were hugely different. It relates to their relative orientation in space - they actually cross each other at quite a large angle. Spaceflight had simply assumed that the orbits were 'nested' within each other - rather like the rings of Saturn. The article describes a 0°.1 change in orbital inclination by the X-37B as being sufficient to make them co-planar. This can only be true if the two orbits had a second parameter in common, namely the Right ascension of the Ascending Node (RAAN). In reality, the two RAANs are 100° apart so the two orbits intersect each other at an angle of 62°.

The diagram shows the ground tracks of both vehicles around the middle of the day 2011 January 5. Positions are as they were at 11:53 UTC. Tiangong 1 was above the mid-Pacific, in darkness near midnight local time, heading south-east towards the tip of South America. It crossed the X-37B orbit on the way. The only thing was, 55 minutes had elapsed since the X-37B was there - equivalent to about half a circuit of the Earth. At the same time, the X-37B was approaching Gibraltar on a north-easterly heading that took it across the Middle East at around noon local time.

The relative locations of the orbits were largely unchanged since Tiangong 1 entered space. Any 'spying' could only be done if the two vehicles got to the intersection point at the same time. That would have happened naturally at intervals because of the orbital periods being slightly different, but at a relative speed of 15,000 kilometres per hour and the 62° closing angle, there would not be much time for the X-37B to train its sensors.

Unfortunately, the story is clearly nonsense