The growing issue of space debris now threatens future satellites and spacecraft. BILL READ examines recent international progress in addressing this challenge.
[caption id="attachment_8355" align="alignnone" width="403"] Artist’s concept showing how a defunct satellite could be grappled for a controlled reentry into Earth’s atmosphere, where it would burn up and be destroyed harmlessly. (ESA)[/caption]
It has been estimated that there are currently over 1m pieces of space debris currently in orbit around the Earth, of which over 16,000 are larger than 10cm across. These include payloads, rocket bodies, mission-related debris, breakup debris and anomalous debris from the deterioration of satellites – all of which could cause catastrophic damage should they collide with an operational satellite or spacecraft. The most densely populated region in LEO is around 800-1,000km altitude at high inclinations and the amount of debris is constantly growing. Studies by NASA and the European Space Agency (ESA) estimate that there are currently around 3,300 intact objects in low Earth orbit (LEO) which are being supplemented with an average of 72 new objects being added per year.
One of the biggest problems currently facing researchers trying to deal with the space debris problem is that no one knows how much debris is out there. A recent paper published in the June 2013 edition of The Aeronautical Journal (D Dean on Creating a space debris catalogue for an orbital band with suitable candidates for active removal) has proposed the creation of a catalogue of existing space debris so that those pieces that pose the biggest threats can be identified
Because orbiting satellites have become such an integral part of the 21st Century economy, supporting communications, weather, navigation and Earth-monitoring systems. The cost of losing one or more to debris damage would be immense. ESA has calculated that to replace approximately 1,000 active satellites in orbit today would cost around €100bn, a figure which does not include the cost to the global economy of losing the services they provide.
[caption id="attachment_8356" align="alignnone" width="403"]
Active Debris Removal requires navigating in the close vicinity of the target. This might be achieved by Lidar.(ESA)[/caption]
The removal of space debris has become an environmental problem of global dimensions. In April, findings from the Sixth International European Conference on Space Debris
were released during a concluding press briefing at ESA’s European Space Operations Centre in Darmstadt, Germany. The conference agreed that future space missions should be sustainable and must include provision for safe disposal when they are completed. “There is a wide and strong expert consensus on the pressing need to act now to begin debris removal activities,” said Heiner Klinkrad, Head of ESA’s Space Debris Office. The Agency has launched the Clean Space initiative which look at maturing technology to approach, capture and deorbit targets. NASA and ESA believe that the risk of collisions can be significantly reduced by removing ten of the largest objects from LEO per year.
Research and development on pilot ‘space debris cleaning’ missions is already under way. At a press conference at the Paris Air Show in June, EADS Astrium Space
CEO Alain Charmeau explained that autonomous technology developed for the unmanned ATV cargo transporter used for carrying supplies to the International Space Station could be adapted for an unmanned spacecraft designed to locate and capture space debris. In April Astrium was awarded a contract
by the French space agency CNES as part of the Orbital Transfer Vehicle (OTV) programme, which will focus on the removal of large pieces of space debris between now and 2020. Astrium is to work first on a OTV-DEMO/X technological demonstrator, followed by a system demonstrator known as OTV-DEMO/Y
in which a satellite is fitted with a manipulator system which could enable it to rendezvous and capture out of control spacecraft which could either be repaired and de-orbited. Other partners in the OTV programme are Surrey Satellite Technology
, Ecole Polytechnique Fédérale de
Lausanne in Switzerland, Bertin Technologies
in France and US company Oceaneering Space Systems
. CNES has a number of other innovative proposals for space debris removal, including space debris collection satellites fitted with 30-50km tethers
which could lower captured debris down towards the Earth.
There are also legal issues to be tackled concerning the ownership of space debris objects and reaching agreements with the owners of debris object to permit them to be removed. In addition, when a removal spacecraft attaches itself to an inoperative body for deorbiting, the legal responsibility becomes shared. There have also been proposals for the creation of an ‘ICAO of space’ to regulate and manage commercial space activities.
The RAeS is holding a conference on Tuesday 2 July on Space Traffic Control – Is the Space Debris Problem Solvable?
which will include speakers from both the civil and military space sectors, government bodies, space lawyers and financiers.