The mega-constellation projects, like the ones of SpaceX, Amazon, Facebook, and many others, some of which are being put in service now, offer us some advantages. However, they could also be harmful to us. As I explained in the previous article, mega-constellations will suppose a big problem for the progress of astrophysics. But another of the problems of mega-constellations is that they could also threaten the own human species.
Normally they present us the solar system like an ensemble of planets and moons which orbit around the Sun. But the reality is much more different. In the solar system, there are millions and millions of bodies orbiting, the named asteroids and comets. All of them have their orbits, which are mostly situated in certain zones of the solar system. However, sometimes, due to planetary disturbances, some of these orbits change and cross with the one of our planet.
All these asteroids and comets that, alarmingly, approach the Earth, are the named NEOs (Near Earth Object). Obviously, it is important to have them well located, as an impact of these would cause devastating effects.
Dangers of the asteroids
The dangerous a meteorite depends on many factors: of its composition, its shape, of how it inserts in the atmosphere, but, fundamentally, of its size.
- The impact of an asteroid of 10 kilometres in diameter would be devastating and would end with the human species. In fact, the dinosaur’s extinction was due, in big part, to the impact of a meteorite of 10 kilometres in diameter. Luckily, of this size, there are very few asteroids and they are well located.
- Nevertheless, one-kilometre diameter asteroids don’t fall short either. An impact of these would release an energy equivalent to thousands of atomic bombs, which would put our civilization at risk with a lot of undesirable climate effects, such as nuclear winter, acid rains and massive earthquakes. It is thought that an impact of this type could represent a possibility for the extinction of the human species. It is estimated that there are about 1 000 asteroids of 1 kilometre in diameter.
- Next, we find the asteroids of 500 metres in diameter. After impacting against the earth they create kilometres-long craters, and in the oceans, they give rise to enormous tsunamis. It is also theorised that they could eject sufficient water into the atmosphere to cause a series of chemical reactions that would cause the disappearance of the ozone layer. This would provoke millions of deaths. It is estimated that there are about 3 500 asteroids of this size.
Despite the devastating effects that these asteroids can provoke, in 2007, and thanks to NASA’s Spaceguard Survey, we had only localised the 90% of the asteroids which are bigger than 1 kilometre. Fortunately, the United States congress refinanced the project, and now the bigger asteroids of 140 metres are being identified, a mission in which participates the Vera C. Rubin observatory, between others.
As we see, work is being done in the detection of the most critical asteroid, but it isn’t enough. In 2003, NASA considered as inoffensive the asteroids less than 40 metres in diameter. Despite this, many scientists doubted this number. Indeed, in 2013, an enormous fireball appeared in the Russian city of Chelyabinsk. It provoked damages in the houses, it caused the hospitalisation of some people, it covered the city with a cloud of dark smoke, it moved telephony antennas, and it provoked rock avalanches.
This enormous fireball was a meteorite of only about 20 metres in diameter. It didn’t cause the extinction of any species, but it provoked an emergency situation. In addition, it is thought that it could have been worse. If instead of having entered the atmosphere so horizontally, it would have done it vertically, the explosion of the meteorite, equivalent to 400 000 tons of dynamite, would have been produced nearer to the surface, causing a major crisis.
The worse of it is that anybody saw it come. NEOs are so small bodies and with orbits that go out a lot of the norm, that only once they are very near to the Earth start to be detectable. The problem is that, once detected, they are very near the Earth and it would be difficult to prepare a mission to deviate them.
To prevent this we would need a complete infrastructure dedicated to the exhaustive search of these bodies. If we had a telescope system capable of detecting in advance the possible impacts, we could consider sending a mission to deviate them or prepare a mitigation plan, evacuating the risk zones or preparing the inhabitants for the shock wave.
The problems of detecting asteroids with mega-constellations
NASA and ESA are already working on these alarms, but mega-constellations will suppose some problems for the detection of possible asteroid impacts.
Many of the measures for asteroid detection are made in the twilight or the dawn. This is due to that many of the orbits of the asteroids in the interior zone of the solar system, are so close to the Sun that they are only visible in these time-lapses. Before these moments of the day, the sunlight makes them impossible to be detected, and after they are behind the horizon. Here mega-constellations give us problems as the twilight and the dawn are the moments in which mega-constellations are the most visible in the sky.
If the task of detecting asteroids is yet complex, it is made even more difficult if we fill up the sky with annoying light trails, as there are possibilities for the tracking systems to have errors. Even if afterwards the images could be processed, as we’ve seen, with NEOs there is no time to lose.
To be capable of detecting previously the potentially dangerous asteroids we need telescopes with big vision fields. As more portion of the sky, they analyse in a single photo, there are more possibilities to find one of them. The complication is that once deployed the mega-constellations, these images would be compromised. The processing of the images would be complicated and the process would be slow down.
However, it is true that we won’t become completely blind to the sky. There is a big quantity of smaller telescopes, either professionals or amateurs, that devote big parts of their nights to search NEOs.
As I explained in the previous article, mega-constellations will provoke a big delay in the advancement of astronomy. This will not only difficult the detection of an approaching NEO, but also their scientific study. As more knowledge we will have about them, we will know more about the consequences of an impact, or we will be in better conditions to send a mission to deviate its trajectory. Mega-constellations will result in some problems at the moment of detecting and studying many celestial bodies.
Moreover, as I will explain in the following articles, mega-constellations won’t only suppose an obstacle for astronomy, but satellites could also be damaged between them, and, even worse, difficult the fact of putting more of them in orbit. This is due to the problem of space junk.