When first discovered in 2004, initial orbital calculations for asteroid 99942 Apophis put Earth in a collision “danger zone” during its 2029 and 2036 passes.

Apophis is a clump of rocks about 350 metres across. That is about the size of a modern luxury cruise liner, or one of America’s enormous nuclear-powered aircraft carriers.

If it struck land, it could destroy an area the size of a country. A sea impact would unleash devastating tsunamis.

But additional observations and radar ranging have since considerably refined its orbital projections.

We now know that, on April 13, 2029, it will miss Earth by 32,000 kilometres.

And the math is good enough to rule out any risk for a further 100 years.

But the geostationary satellites power the GPS on your mobile phone are at 35,800km. And the Moon is 384,400km distant.

So, cosmically speaking, Apophis is still going to be a very close call.

Which is why the European Space Agency (ESA) wants to take a good look as it catapults by.