The use of satellites in orbit goes beyond space science and exploration, Earth observation, it is used for many areas, from climate and meteorology to navigation, telecommunication, and broadcasting. It is a unique resource in scientific data, and a tremendous commercial opportunity, providing not just economic benefits but also gain to our daily life.   
 

Therefore, space became attractive for research and exploitation, what increased space activities resulting in a dangerous problem we still don’t have an answer for the space debris; in other words, space trash. The exponential increase of space debris is an alarming threat to orbital regions with vital economical and scientifical usages.  

What is debris, and how it is generated? 

With new opportunities come new investments and the number of space activities rapidly increased. In almost 60 years, more than 5250 launches resulted in 42000 tracked objects by US Space Surveillance Network. SSN can track objects about 5 to 10 cm or larger in low-Earth orbit (LEO), and objects from 30 cm to 1 m at geostationary (GEO) altitudes. From this, only 1200 are functional spacecraft, and 23 000 objects in orbit objects are remains or space debris.  
 

Of those 23,000 trackable objects, 7,500 are very small and can only be tracked by a minimal number of sensors. The loss of those sensors would compromise the ability to provide safety for spaceflights. It is estimated that there are more than 150 million objects smaller than one cm that can’t be tracked.  

A large part of those remains are fragments from approximately 290 breakups, collisions, and explosions. One fragment with the size of a marble ball is enough to destroy a spacecraft. The main reason for in-orbit explosions is related to residual fuel or other remaining energy sources that remain in the satellite or rocket after it has been discarded in orbit. Besides the accidental collision and breakups, the anti-satellite interceptions by surface-launched missiles have been a significant contributor, creating 25% more debris, according to ESA.   

What is Kessler Syndrome? 

Satellites launched into LEO are exposed to aerodynamic forces from the upper reach of Earth atmosphere, after a specific time, it can be weeks or centuries, the satellite decelerates enough to reenter the atmosphere. Air drag becomes less effective above 800 km, and objects can stay in orbit for many decades. If the spacecraft doesn’t de-orbit or move into graveyard orbits, the risk of a cascade of collisions caused by space debris, generating more debris, called Kessler Syndrome increases. Those collisions are already happening, and NASA predicts a 100% likelihood of it happening again. Even if in an ideal scenario without further launches, debris releases, or explosions, ESA and NASA say that the number of debris objects would continue to grow by those collisions. It must be avoided not only by mitigation but also by remediation measures.  

What are the mitigation and remediation measures? 

To avoid the collisions, we need an accurate space traffic management solution and a de-orbiting plan. There a considerable amount of satellites, including CubeSats in LEO, without taking the necessary debris mitigation measures. And the number of satellites will increase significantly with the launch of constellations planned by SpaceX Starlink, OneWeb, and Amazon.  
 

De-orbiting measures should not be considered just for the satellites already in orbit but also for the ones yet to be launched. International guidelines say that the satellites should de-orbit within 25 years of their missions. In LEO, they should reenter Earth’s atmosphere and safely burn by gravity actions; in GEO, they should move up into graveyard orbits.  

Although even if the 25 years rule were respected, the massive objects in LEO reached a critical level, and mitigation isn’t enough. It is necessary for an active removal plan. According to ESA, it might be necessary to remove five to ten large objects per year to control the debris population. Even though we might don’t have a solution ready to be implemented, innovative ideas are beginning to have success, including ideas using an electrodynamics tether designed to generate electricity to slow down the object allowing it to return to Earth. The International Space Station (ISS) also is experimenting with removing debris through a harpoon net and dragging it down. ESA is also focusing on tackling down the debris problem with the eDeorbit mission that has the goal of bringing a large ESA object to a controlled Earth’s atmosphere reentry.  

Even though the European Cooperation on Space Standardization (ECSS) adopted the ISO­24113 in the space sustainability branch, the mitigation guidelines are only recommendations and not requirements. A lot has been discussed about debris, and it is still a grey area. ESA just had its Ministerial Council Space19+, and one of the subjected discussed was Safety and Security in Space; you can find out on its website. Also, next week, the First International Orbital Debris Conference will happen. 

What are your thoughts on this matter? Share with us. 

Update 09/12/2019: ESA just released the information about ClearSpace-1, planned for launch in 2025, will be the first mission to remove debris from orbit.



This article was inspired in contents from http://www.esa.int/ and http://satellitetoday.com/ 

And written by Juliane Verissímo - Marketing Department of VisionSpace