Satellites in orbit in many ways impact our modern lives, they are used in many areas and disciplines, including space science, Earth observation, meteorology, climate research, telecommunication, navigation and human space exploration. They offer a unique perspective, a resource for collecting scientific data, commercial opportunities and various essential applications and services, which lead to unrivalled possibilities for research and exploitation.
Space debris, also called space junk, is artificial material that is orbiting Earth, these are man made but not active, not functional and useful. The debris could be as large as a discarded rocket stage or as small as a microscopic chip of paint. Much of the debris is in low Earth orbit, within 2,000 km of Earth’s surface, though some debris can be found in geostationary orbit 35,786 km above the Equator. As of 2021, a Space agency Surveillance Network was tracking more than 15,000 pieces of space debris larger than 10 cm across. It is estimated that there are about 200,000 pieces between 1 and 10 cm across and that there could be millions of pieces smaller than 1 cm. How long a piece of space debris takes to fall back to Earth depends on its altitude. Objects below 600 km orbit several years before reentering Earth’s atmosphere. Objects above 1,000 km will orbit for centuries.
Every satellite that goes into orbit has the potential of becoming space debris. With the launch of more satellites from companies such as Elon Musk’s Starlink and OneWeb satellite constellation, near Earth space will likely see more space debris.
In more than 60 years of space activities, more than 6050 launches have resulted in some 56450 tracked objects in orbit, of which about 28160 remain in space and are regularly tracked by a Space Surveillance Network and maintained in their catalogue, which covers objects larger than about 5-10 cm in low-Earth orbit (LEO) and 30 cm to 1 m at geostationary (GEO) altitudes. Only a small fraction – about 4000 – are intact, operational satellites today.
All the space hardware orbitting the earth put together has a total mass of more than 9300 tonnes.
Menaces from Debris
Because of the high speeds at which debris orbit Earth, a collision with even a small piece of space debris can damage a spacecraft. For example, space shuttle windows often had to be replaced because of damage from collisions with debris smaller than 1 mm. Space shuttles are made to fly tail-forward to protect the forward crew compartment from debris menace.
The amount of debris in space threatens both crewed and uncrewed spaceflight. The risk of a catastrophic collision of a space shuttle with a piece of space debris was 1 in 300. Astronauts perform a debris avoidance maneuver in which the space station orbit is raised to avoid collision.
International Space Station, orbits the Earth 15 to 16 times a day, Debris, near the space station increases the risk of collision, if the build-up of space debris continues, some regions of space might become unusable.
As of 2021, a Space agency Surveillance Network was tracking more than 15,000 pieces of space debris larger than 10 cm across. It is estimated that there are about 200,000 pieces between 1 and 10 cm across and that there could be millions of pieces smaller than 1 cm. How long a piece of space debris takes to fall back to Earth depends on its altitude.
The very first noticed collision between an operational satellite and debris happened on July 24, 1996, wherein a piece of space debris, a fragment from the upper stage of a European Ariane rocket collided with Cerise, a French microsatellite. Cerise was damaged but continued to function. The first fatal collision that destroyed an operational satellite happened on February 10, 2009, when Iridium 33, a communications satellite owned by Motorola company, collided with Cosmos 2251, an inactive Russian military communications satellite, about 760 km above northern Siberia, shattering both satellites.
Chinese have to prove their presence in space too, the worst space-debris event happened on January 11, 2007, when the Chinese military destroyed the Fengyun-1C weather satellite in a test of an anti-satellite system. This created more than 3,000 fragments of debris, which is more than 20 percent of all space debris. Within two years those fragments had spread out from Fengyun-1C’s original orbit to form a cloud of debris that completely encircled Earth that would be in the space for decades. On January 22, 2013, the Russian laser-ranging satellite BLITS (Ball Lens in the Space) experienced a sudden change in its orbit and its spin, scientists have to abandon the mission. The culprit was believed to have been a collision with a piece of Chinese Fengyun-1C debris. Fragments from Fengyun-1C, Iridium 33, and Cosmos 2251 account for about one-half of all debris below 1,000 km.
Debris in orbits below 600 kilometres will fall back to Earth within several years, but debris above 1,000 kilometres will continue circling the Earth for a century or more.
Space debris increases the cost for satellite operators, Satellite operators in the geostationary orbit have estimated protective and mitigation measures account for about 5-10% of mission costs and for lower-Earth orbits the cost is higher, according to a recent study.
Increasing debris in space could lead to a disastrous situation, wherein a collision will destroy space object which will in turn increase debris density and in turn destroy more space objects and finally leading to a chain reaction situation. Space agencies have begun taking steps to mitigate the problem, such as burning up all the fuel in a rocket stage so it does not explode later or saving enough fuel to deorbit a satellite at the end of its mission. Some agencies are trying to develop methods to capture debris with a net and even methods to slow down aged satellite so that it could reenter the atmosphere.
The scourge of space junk threatens the future. In 1978, an astrophysicist outlined a theory of what would happen if space traffic continues to grow and collisions occur. The debris created by those collisions would skitter off into the paths of other satellites, creating yet more debris. Over time, he argued, a chain reaction of cascading collisions could one day make low Earth orbit hard to access and even prevent manned spaceflight from leaving Earth, a phenomenon since labelled the “space debris syndrome”.
A cluster of startups has emerged to help navigate this new reality, and perhaps begin the process of cleaning up low Earth orbit. But some experts believe the chain reaction has already begun.
Even if we stop launching new satellites, modelling shows that the number of space objects will still grow because collisions are happening and producing fragments at a higher rate than those that decay.
It’s not just satellites at risk, space debris is threatening new missions, even human missions. One can imagine on a spacewalk if some of debris hit an astronaut’s. suit, it would punch a hole in it resulting in fatal end.