14.06.19 – ClearSpace, a Swiss start-up**, spin-off of the EPFL Space Center (eSpace), wants to clean up nearby Space (Low Earth Orbit), which is starting to be seriously cluttered with old, broken satellites and debris of all kinds. It’s a real challenge but ClearSpace could take it up. It is also a business and it has an important niche to develop. We wish them a brilliant success!
On May 23rd, 2019, SpaceX launched 60 satellites, 227 kg each, which should be put in orbits at an altitude of about 550 km (the International Space Station turns around the Earth at an altitude between 350 and 400 km). The launch was part of the “Starlink” program, which goal is to provide Internet access anywhere around the world. Many more such launches are planned because Elon Musk wants to put up a constellation of 12,000 satellites, positioned between 500 and 1325 km on the one hand and between 346 and 335 km on the other hand, in order to “cover” the entire globe! Low Earth Orbit (“LEO”) was chosen rather than Geostationary Orbit (36,000 km altitude) in order to minimize the lag-time between any request and response (on account of the speed of light!) and it is this choice that constrains the high number of satellites (being closer to the ground, the coverage of Starlink satellites will be narrower).12,000 is really a lot and it’s way too much! There are two problems resulting from the number: these satellites can create troublesome parasitic effects for sky observation from the terrestrial telescopes and this, not only in terms of visible light but also in terms of radio waves (satellites not only reflect but they also emit); they are also potential sources of collisions and therefore of a multitude of future debris that will disappear all the more slowly than their altitude is higher. Below 600 km, the orbits are called “self-cleaning” because the objects that run through them are slowed down by an increasingly dense atmosphere and burn up relatively quickly (albeit up to 25 years on the highest orbits!). Those that evolve above this altitude, potentially constitute a real nuisance (which can degenerate into a Kessler syndrome by successive impacts). They will descent to be consumed in the atmosphere within a reasonable time only if they have a propulsion system that can slow them down and propellant to feed the system or if “somebody” will go and fetch them!
Elon Musk is aware of the problem but answers “that the chances of collisions happening in space will be small. The space junk thing – we do not want to trivialize it or take it seriously, because we certainly do not take it seriously – but it’s not crowded up there. It’s extremely sparse”. It is true that SpaceX had to report to the Federal Communications Commission that they took measures deemed necessary to avoid collisions and debris production. But an acknowledged ESA expert (Stijn Lemmens, Senior Debris Mitigation Analyst) publicly expressed his doubts about the likelihood of these measures being sufficient. With regard to light pollution, Elon Musk suggests practicing astronomy in Space rather than on the surface of the Earth. This is a little offhand!
Moreover, SpaceX is not the only company that plans to launch objects in LEO above 600 km. To the Starlink satellites will be added those of OneWeb, Telesat, Amazon and others (as we say, “sky is the limit”!). Today it is estimated that 1540 satellites are operational, of which 1300 in LEO between 600 and 1100 km. This number will quadruple in the coming years. Apart from this, there are about 23,500 objects more than 10 cm long in orbit (including 3,000 non-operational satellites), resulting of a story that began in 1957 with Sputnik (there have been since then more than 5,250 launches and more than 500 explosions, collisions or destructions in orbit). 18,000 of them have been catalogued by the Space Surveillance Network of the US Air Force (SSN). 75% are located on LEO and they are the most dangerous because they occupy the most crowded area of Space and the smallest one (the surface of the Earth spans 510 million km2, the surface of a sphere of same center but of a radius extended 600 km above ground: 610 million km2, the sphere of the geostationary orbit: 22,490 million km2). To appreciate these figures, we must understand that a satellite is not only a point in the sky. It is primarily a mass traveling on a trajectory at about 8 km/s (more precisely, the speed that allows it to stay in LEO). To worsen the situation, any collision results in the dispersion of objects in several directions (function of angle of impact, relative speeds and structure of the satellites, cf Kessler’s syndrome above). And some people seem to enjoy this degradation as evidenced of the destruction of satellites by missiles from the ground. The USSR and the United States did it in the past (they have officially renounced to do it today) and China or India did it just recently (without neither excuse nor remorse!).
It is obviously inconceivable to forbid anyone to launch satellites, the ban would not be respected since humanity needs the services they provide and since there is no World government that could impose such a ban. On the other hand, it is in the common interest of all of us, not to keep polluting Space as we started doing since a few decades ago when we were not aware of the real danger to stifle our civilization under our own debris or waste. What is valid on the surface of the Earth is obviously valid in our nearby space.
Satellite manufacturers can include, before launch, devices that would allow braking, deorbiting and therefore destruction in the upper atmosphere when they so decide. But what about those who did not do it and others who do nothing or who wanted to do it and did not succeed? The electronics of a satellite is fragile in a radiative environment, in addition to the risk of collisions… Even if a satellite has a whole system to bring it back to Earth, there can be failures and therefore a risk that despite good will, such a return would be impossible.
This is where ClearSpace provides an essential and realistic solution. ClearSpace was created from the CleanSpace One project initiated by Muriel Richard of the EPFL Space Center (eSpace) in 2012. The first step (planned for 2024) is to launch an experimental satellite “CleanSpace One”, to go and fetch the SwissCube nano satellite (launched by same EPFL Space Center in 2009) and, on the basis of this experience, to commercialize a fetching/deorbiting satellite service that would be adapted to the different types of debris to be de-orbited.
The CleanSpace One project was designed in collaboration with the University of Bern, HES-SO and NTB. The satellite will be equipped with an “uncooperative” rendezvous system (the intended target does not participate in the maneuver and its rotation may be erratic) and a capture system. For the former, it was necessary to adapt/develop new technologies to detect a target and to get to it; for the latter, technologies required to grasp the object (deployment of a cone-shaped net hold by carbon tubes), stabilize the couple of both the satellite and its target, deorbit it and send it to low Earth atmosphere layers. The choice of propulsion is important. Electricity is considered; will this mode make the deorbiting satellite nimble enough?
As mentioned above, the first de-orbiting will involve a small satellite. The SwissCube is by definition a cubesat, a cube of 10 cm side with antennas in addition. The ambitions of ClearSpace are obviously not to satisfy itself with this format but to apprehend targets up to 300 kg and that covers a significant percentage of the cases to be treated. Most of the technologies developed today will be used for the future and will allow to better assess the needs and actual possibilities.
There is definitely a lot of work to do. Will this work be lucrative enough for a company like ClearSpace to make money and thrive ? Obviously companies from which inactive satellites or their debris proceed, are not going to rush to pay for de-orbiting if they have not planned for it or if their de-orbiting system did not work. However, there are several ways to force them to behave, beyond asking them to do so politely. Indeed almost all satellites are known since their number is not yet so extraordinarily high and since the history of launches in space is not so old. The SSN registry is a good basis to start the process. International relations can then be relied upon to request de-orbiting, including those around the United Nations Office for Outer Space Affairs, which would normally cooperate fully for implementing the “Space Debris Mitigation Guidelines of the Committee on the Peaceful Uses of Outer Space” adopted in 2007 by member countries. Beyond that, there is “name-bashing” (or the fear of it) because public opinion today has a formidable power. There are reasons to hope, but above all it is necessary that a de-orbiting service exists. ClearSpace having developed an efficient and complex technology will have a decisive lead over its competitors. As for the price, it will be as always when it comes to a bid formulated on the world market, the result of supply and demand. Supply even if not at the beginning, will become competitive soon. It will also be necessary to get quickly a good market share and to satisfy customers by an efficient service.
So, is the situation serious? Not yet but it is likely to become so, soon, in case the satellite manufacturers do not take the necessary steps and if ClearSpace and its competitors fail to market their services. Already the Starlink project is expected to cause significant deterioration. In the long run, astronomical observations are likely to suffer from these parasites, especially as their focus tends to become more and more precise, as the observed events often require a long time of exposure for appropriate data collection and as the pooling of resources from observatories all over the world (VLBI) will demand a clearer sky simultaneously all over the world (in the visible area but also in the field of radio waves). The Public must therefore insist not only to get a night less polluted by domestic and industrial lights (which is also in the interest of saving our energy resources) but also to get a clean and clear space. Good habits must be taken now so that all new satellites launched above 600 km altitude (above the self-cleaning-orbits) are equipped with a deorbiting device and so that the projects as polluting for the visibility of terrestrial observatories as that of the Starlink project, be not repeated. When it comes to the use of a common good (near Space), people must show some discipline. If they do not do it spontaneously, an “authority” will end up imposing it (perhaps through companies like ClearSpace?). We have to make it clear to Elon Musk, so that he himself would be giving the example. We do not want to be cut off from our sky and from our window to near and far Space on account of our own misdemeanors; he should not want it either!
Title picture: CleanSpace One about to capture SwissCube in its net. © EPFL, J.Caillet.
The original article can be found in Le Temps
* the human population, conscious, educated and communicating, on the surface of the planet
** founded by Luc Piguet, Muriel Richard-Noca and Catherine Johnson.
NB: this article has been reviewed by Luc Piguet and Jean-Paul Kneib (director of the EPFL Space Center eSpace).