Low Earth Orbit, an area of outer space around Earth that encloses all orbits below 2000 km, is the home of the International Space Station and of other thousands of satellites. Satellites don’t last forever. Eventually, they stop working. However, when this happens they do not magically disappear or fall back to earth. These objects remain in their orbit, moving at incredible speeds.

Matter in orbit travels at ridiculously high speeds (22,000km/h). If this matter were to travel in the same plane and direction indefinitely, it would be impossible for any matter to collide, like cars going straight on a highway at the same speed, never endeavoring to switch lanes or get off on an exit. But in space, uncontrolled objects do not follow a straight path. Instead, each piece of debris is subject to drift and decay. The variation in Earth’s gravitation field causes drift, or the gradual movement of an object to a different orbital plane. The friction of an object with Earth’s atmosphere causes decay, or the slow decrease in an object’s altitude.

Back in 2017, there was a lot of talk about how the Indian Space Research Organization (ISRO) set a world record by launching no fewer than 104 satellites from a single rocket! With this bold move, the ISRO smashed the previous record held by Russia, which launched 37 satellites in a single mission back in 2014. The logical question is, of course, what happens when there are just too many satellites in the orbit? Impacts and collisions.

The Kessler Syndrome:

The Kessler Syndrome is a theory proposed by NASA scientist Donald J. Kessler in 1978, used to describe a self-sustaining cascading collision of space debris in LEO. Kessler published a paper in 1978 called the “Collision Frequency of Artificial Satellites:  The Creation of a Debris Belt” which predicted that, by 2000, the density of space debris in Earth’s orbit would be so great that random collisions would be inevitable, and that the outcome of these random collisions would be more debris, and subsequently more collisions. At that point, any entering satellite would face unprecedented risks of headfirst bombardment.

Kessler’s paper was significant because it emphasized the imminent danger of small debris in orbit as well as the inevitably of additional debris produced from collisions with catalogued objects. The orbital-debris problem is a classic tragedy of the commons problem, but on a global scale.

Effects of the Kessler Syndrome:

The Kessler Syndrome is bad news because impacts between objects of sizable mass can cause significant damage to ‘useful’ objects that are present in LEO. Not only that, but the resulting debris cascade could also make it extremely difficult to launch satellites in the LEO in a way that they wouldn’t be hit by flying debris. Finally, the long-term viability of new satellites in the LEO would become decidedly low.

There’s no doubt about it, a cascading collision of satellites in orbit would definitely affect life on Earth, by disrupting global communication, limit globalization and undermine military intelligence. 

Magnitude of problem:

Earth’s orbit is getting increasingly crowded with an estimated 500,000 pieces of space debris up to 10 cm long, more than 21,000 pieces of debris longer than 10 cm, and more than 100 million pieces of space debris smaller than 1 cm, according to NASA. That’s a lot to keep track of, and orbital debris researchers around the globe are doing the best they can to model and measure potential collisions.

Indian ASAT test controversy:

India's ASAT test represents an escalation toward space warfare and also heightens the risk that humanity could lose access to crucial regions of the space around Earth. That's because destroying the satellite created debris that' was floating in space. Those pieces had the potential to collide with, damage, and possibly destroy other spacecraft. This is worrisome for a global society increasingly reliant on space-based infrastructure to make calls, get online, find the most efficient route home via GPS, and more. The ultimate fear was a space-access nightmare called a "Kessler syndrome" event.

Strategy to tackle space debris problem:

The first thing is to reduce or stop unnecessary harmful activities. Kessler suggested the best way to avoid the exponential growth of the collisions was to reduce the number of non-operational spacecraft left in orbit. The only effective long-term means of stabilizing the space debris environment at a safe level is through the removal of mass (five to ten large objects per year) from regions with high object densities and long orbital lifetimes.

Several methods have been proposed to take care of the thousands of fragments orbiting Earth, like lasers, tugs, drag enhancement devices, momentum exchange tethers, and more, and the 2010 National Space Policy of the United States directed NASA and the Department of Defense to pursue additional research efforts to remove debris. Unfortunately, the cost and complexity – not to mention legal concerns – have so far prevented the proposals from becoming reality.

International treaties, cost, and complexity have prevented any significant effort to remove debris. The Kessler Syndrome is a very real threat. Pollution is a problem that follows humans everywhere we go, even in space. We can only hope that action to mitigate the dangers of pollution in space will happen quickly enough to prevent disaster.