Space might seem an empty, vast expanse, but satellites in Earth's orbit face the constant risk of collision - with other satellites and rockets, dead or alive, or with fragments of their debris.

It is now routine for operators of spacecraft in busy highways to divert their mission out of harms way. In fact at ESA, each mission flown performs on average two 'collision avoidance manoeuvres' per year.

In this podcast, episode 3 in the ESA-UN space debris series, Benjamin Bastida Virgili and Hazuki Mori discuss the cost of these manoeuvres and what can be done.

While you listen, check out the corresponding ESA-UN infographic that illustrates this topic.