What goes up must go down. When it comes to satellites, this dictum has become a statutory requirement. Otherwise, key low orbits may well become unusable as they fill with debris. In March, European satellite manufacturers will come together to discuss redesigning low-orbit missions to meet anti-debris regulations.

Prompted by ESA's Clean Space initiative, devoted to safeguarding the terrestrial and space environments, they will consider new technologies devoted to cutting down on derelict satellites being abandoned, reducing the risk of orbital collisions from increasing debris while also reducing the threat posed by reentering satellites.

"This workshop is an essential step for involving the whole European space sector in shaping the way forward for low-orbiting satellites," explained ESA organiser Jessica Delaval.

"Companies will have the opportunity to put forward their own technologies for debris mitigation."

There are more than 12 000 trackable items of space debris larger than 10 cm orbiting Earth, including derelict satellites, spent upper stages and fragments of old missions - all presenting a clear and present danger to current missions.

The number of smaller, untraceable objects is in the millions: hundreds of thousands of 1-10 cm pieces and literally millions of smaller particles. At orbital speeds, a 1 cm nut can strike with the force of a hand grenade.

Today, international regulations state that minimal debris should be left to propagate within heavily trafficked orbits, especially the low orbits favoured by Earth-observing missions and some classes of communication satellite, not to mention manned spacecraft and the International Space Station.

For these orbits, extending up to about 2000 km above Earth, the requirement is that satellites are removed within 25 years of ending their lives. Either they should end up at an altitude where atmospheric drag gradually induces reentry, or alternatively be despatched up to quieter 'graveyard orbits'.

So mitigation methods are having to be built into new low-orbit missions, with important implications for their design - not least because any mass added to the platform means less is left for the payload, the part of the satellite that actually achieves the mission goal.

That means smaller satellites find it more difficult to meet mitigation requirements.

The workshop at ESA's ESTEC technical centre on 17-18 March will promote a common approach to debris mitigation, summarising the current state-of-the-art for both passive and active deorbiting approaches, as well as detailing ESA's new CleanSat programme - seeking to adopt debris mitigation techniques within common platform building blocks.