Why is space junk a problem?

There's lots of space junk flying around in Earth's orbit, but how is this affecting our current exploits in space? Tim Flohrer, a Space Debris Analyst from the European Space Agency, spoke to Chris Smith.

Tim - You have to distinguish two things. We are operating our spacecraft so it’s part of our daily business to deal with the space debris that is up there. Secondly, of course, we are planning technologies to bring back these large objects that you are talking about. So it’s something we care about more in the future if you like.

Chris - So there’s both the worrying about where it is, and then worrying about making sure it doesn’t hit your spacecraft? So let’s unpick that a bit then and tell us how do you track these objects? How are you keeping an eye on where the things are?

Tim - There’s something that is called a catalogue of all the elements. So you can imagine it’s like the precisions and velocities of these debris objects down to about ten centimetres or a bit smaller. That is available from sensors on the ground and in space and basically it comes from the U.S from sensors that the U.S. is running. So these are radar sensors and also telescopes. The radars cover the lower altitudes, the lower orbits and the optical sensors more the higher altitudes.

Chris - So you build up a profile of what’s up where, basically, so you know what’s where and how big it is, and how fast it’s moving, and where it’s going?

Tim - Exactly. And from that we can calculate the risk that it is to be at the same position at the same time, you name it a collision.

Chris - OK. Once you’ve tracked something, say you want to put a spacecraft in a certain position, or go from A to B, and you now there are some of these objects around. How do you make sure that your spacecraft doesn’t get hit by them?

Tim - As you said, we are predicting the positions of these debris objects and we know where our object is and, if the risk is too high, then we do something that we call “collision avoidance.” So we move away our spacecraft and make it out of the way of the debris object, and then move it back after the close approach has passed.

Chris - Is there a financial cost to this? I presume there must be if you have to move things around then you’re using fuel, you’re using time, you’re maybe moving things out of service? So is there an impact on people’s pockets through having to do this?

Tim - You’re absolutely right. Being the European Space Agency, we can’t do science in that timeframe where the satellite is not where it’s supposed to be. So, for us, it’s mainly losing the value of the time for acquiring the science data. But for commercial operators it means that they can’t do business during that short timeframe but it’s a short time that they can’t do their business.

Chris - With an eye on the future, are you future proofing or has anyone put in place a policy now so that when we send things up there, we’ve got an end of life idea what’s going to happen to it? How we either retrieve it or stop it breaking up to contribute to the problem and make the problem worse?

Tim - There are two things. One is we call it “mitigation of space debris” and this covers these aspects like passivate your spacecraft at end of life, so make sure it can’t explode or fragment. So remove the fuel, shortcut the batteries, and those things. The second thing is to move it into an orbital regime that’s not in a protected regime and also to limit the time in orbit. That is very important and has been moved into standards and into guidelines and, in some countries, even into law but this is an ongoing process. The standards are there, the guidelines are developing and the law and regulations widely has to come still.

Chris - But if the Chinese decide they’re going to blow up another satellite tomorrow, is there anything that can stop them?

Tim - Well, political pressure of course can stop this. But if they have the technology then it’s something they can do, but I’m pretty sure they won’t do that.

Chris - So they’ve learned their lesson is what you’re saying?

Tim - I think so. Because they are operating in the same orbit as all the others so also their satellites have to move away from the debris they created with this event in the past.

Chris - What about the things that we’re working on right now? Things like the International Space Station because that’s huge. Is there an end of life plan for that to retrieve that safely so it doesn’t contribute to the debris up there?

Tim - First of all we hope that the International Space Station is still there for a few more years, but actually we are looking into this already how to bring it down. But this is a few years to go still.