Even if we stop launching objects into space completely, we won’t prevent the orbital collision cascade from triggering in the 20-year timeframe, said Heiner Klinkrad, Head of ESA’s Space Debris Office.
Speaking during the Space Traffic Management Conference organised by the Royal Aeronautical Society in London on 2 July, Klinkrad said the world’s space stakeholders need to start acting promptly if they want to avoid increasing costs and putting their missions at risk as a result of the growing number of orbital collisions.
“We have to start removing 5 to 10 large intact objects from low Earth orbit per year to avoid Cosmos- Iridium type of collisions in the near future,” Klinkrad said, referring to the catastrophic 2009 collision when a dead Russian military Cosmos 2251 satellite knocked out operational American telecommunications Iridium 33. “According to our calculations, such a collision in the current environment can statistically occur every 5 years, but with time the average interval between collisions will decrease,” he said.
The Iridium-Cosmos collision that occurred at the altitude of 789 km above the Earth’s surface smashed both satellites to pieces, increasing the amount of known orbital debris objects considerably. This single event created almost 1,800 debris fragments larger than ten centimetres. “You have to realize that these objects travel in low Earth orbit at extreme velocities – 16 km per second, a 1cm in diameter fragment travelling at such velocity crashing into a satellite causes similar damage to a medium-sized car crashing at 50 km/h or to an exploding hand grenade,” Klinkrad explained.
These fragments, products of collisions, are of the greatest concern to the scientific community. When one large object is smashed into thousands of pieces, the frequency of further collisions increases. “These fragments are very dangerous, they result in the so called Kessler syndrome, which means that every collision leads to more collisions taking place. Eventually, it could make utilisation of space very difficult,” said Heiner Klinkrad.
The situation is worst in low Earth orbit where not only most of the Earth observation and surveillance satellites reside, but where also many telecommunication and navigation satellite constellations operate.
The only way to protect satellites against the Iridium-Cosmos type of collision is by performing avoidance manoeuvres. In the past years it has became a regular routine for satellite operators. "All ESA missions are planned with avoidance manoeuvres in mind, however, we always lose a lot of valuable time we could have used to acquire scientific data while avoiding space debris," said Klinkrad, who believes current mitigation measures, which include deorbiting objects for faster re-entry at the end of each mission, are not enough. Without active space debris removal the situation will aggravate in the next 20 years.
“The concepts for active space debris removal already exist, there are many of them, it depends on the will of the space community, whether we will manage to deploy them quickly enough,” he said.
According to the US Space Surveillance Network Catalogue, there are currently 23,000 known objects in Earth’s orbit larger than 10 cm. Only 6 per cent of them are active satellites, the rest is comprised of satellites that are no longer operational, spent rocket stages, fragments of collisions or objects that astronauts lost during missions. All the space debris currently in orbit weighs over 7,000 tonnes – a result of 55 years of space utilisation since the launch of Sputnik in 1957.