20/02/2014 11:40 GMT | Updated 06/08/2014 10:59 BST

How Worried Should We Be That Our Best Asteroid-Spotting Telescopes Are 50% Useless?

Today in terrifying news about our total inability to spot incoming asteroids, we have a reality check for you.

For while the existence of reassuring-sounding programs like Nasa's Near Earth Object Program, ESA's CEO Coordinating Centre and the Space Weather Coordination Centre, we really have no idea what we're doing when it comes to preventing a devastating asteroid impact.

As evidence of that fact we present two events. The first took place almost exactly a year ago, when a massive asteroid exploded over Russia and injured 1,500 people with absolutely no warning at all. The other occurred on Monday, when an asteroid precisely tracked and monitored by Nasa totally failed to show up, because we lost it.

Now we read in New Scientist new and harrowing details about how our current asteroid defence systems are improving, well-meaning and yet still totally pathetic.

The magazine reports that according to a new study, two "next generation" asteroid warning systems set to come online in 2015 would miss more than half of the asteroid equivalent in size to that which tore apart Chelyabinsk.

Amazing Meteor Strikes

They include the ATLAS telescope array in Hawaii which from late 2015 will start to look for asteroids similar in size to the Russian meteor and should be able to give us up to two days warning - except for the fact that it doesn't work during the day. Which means it actually only works for roughly a third of the sky.

Similarly, a planned global array planned by ESA would give twice as much warning - but again, only for a third of the sky.

Trouble is, there's no way around this unless you build a telescope in space. It's just that no such telescope is being planned by anyone. The $1 billion cost of such a telescope might seem high - especially since a Chelyabinsk-size rock generally only falls once per century. But with the US Congress already committed to finding 90% of asteroids near Earth and larger than 140 metres by 2020 (currently we know of about 25% of these), something will have to be done.

Other plans are in the works - New Scientist has a good summary of these. But for now there's really nothing to do except believe in the law of averages, wear a protective helmet, and pray.