The French Senate recently released a report shedding light on the escalating issue of satellite pollution and space debris.
Written by Jean-Luc Fugit, MP and Ludovic Haye, Senator, the analysis illustrates the growing awareness about this issue. The report points out that the last few years have seen an increase in the number of launches, particularly into low-Earth orbit, bringing the problem of space debris into sharper focus. The report states that in 2003, just 540 satellites were in service in outer space, rising to 900 in 2013 and currently standing at 8 700.
This proliferation of satellites, and in particular the ever-increasing number of constellations, multiplies the risk of collision. This risk is compounded by the explosive satellite destruction tests carried out by certain countries, including China and Russia, which create thousands of new pieces of space debris. Scientists fear a chain reaction scenario, where collisions ensue and create more and more debris in a vicious cycle. This hypothesis was devised by NASA scientist Donald J Kessler and is now known as Kessler syndrome. So far, it hasn’t happened.
In addition to the risk of collision, space pollution also causes other problems, such as the disruption of astronomical observation. For optical astronomy, which relies on the use of ultraviolet to infrared rays, the main problem lies in the reflection of sunlight by satellites. This causes visible bands on images, damages sensors and leads to interpretation errors. In radio astronomy, intentional or accidental radio emissions from satellites interfere with signal quality. Some companies have taken action, such as Starlink, which has chosen a less reflective paint on its satellite constellations and strives to switch off its satellites when they are over the main observatory radio telescopes.
Several bodies monitor debris, such as the European Union’s Space Situational Awareness programme. However, the largest registry is Space Track, maintained by the US military. It has been partly public since the 2009 collision between Kosmos 2251 and Iridium 33, and tracks more than 28 000 objects over 10 cm in size. Moreover, objects in low orbit eventually fall back to Earth due to the deceleration induced by the atmosphere, and between 10% and 40% of their mass survives re-entry. Even if the risk of collision with an individual is low, it does exist, as the proliferation of constellations increases the chance of collision with a human. This only adds to the environmental consequences of atmosphere re-entry, with most satellites ending up in the Pacific Ocean.
The report shows that space debris comes from a variety of sources:
– Decommissioned spacecraft, such as satellites that are no longer operational. These satellites have an average lifespan of around 15 years, mainly due to exposure to radiation in space.
– Unused stages of the rockets used to launch satellites into orbit.
– Objects abandoned in space during missions, such as debris jettisoned by space shuttles, small fragments resulting from collisions, explosions or degradation of active satellites, as well as larger debris.
According to their size, and thus their destruction capacity, these debris are under various levels of scrutiny. Debris larger than 10 cm are monitored in low earth orbit and geostationary orbit, while debris between 1 and 10 cm, sometimes referred to as “lethal debris”, are large enough to cause significant damage but too small to be monitored. Debris smaller than 1 cm are generally too small to destroy a satellite. The report suggests several solutions to take care of this problem. For example, Kevlar shields or metal foam in front of fragile satellite parts. Or using artificial intelligence to calculate trajectories and avoid collisions.
But the most efficient policies are those directly involving human decisions, such as improving tracking data, banning satellite destruction tests, removing the most dangerous debris and only allowing launch for sustainable end-of-mission solutions.
Written by ADIT – The Bulletin and republished with permission.
