For all of you who have seen Gravity, you saw the potential dangers of space debris. Despite the movie being pure fiction, a scenario like that playing out in real life is not a very far stretch to imagine.
Let’s go over some basic definitions provided by The Inter-Agency Space Debris Coordination Committee (IADC). Space debris, also known as orbital debris, are all man-made objects, including fragments and elements thereof, in Earth orbit or re-entering the atmosphere, that are non-functional. Space debris mitigation consists of all efforts to reduce the generation of space debris through measures associated with the design, manufacture, operation, and disposal phases of a space mission.
The Inter-Agency Space Debris Coordination Committee (IADC), an international forum of space agencies, was founded in 1993. The main goals of IADC are to exchange information on space debris research activities between member space agencies, to facilitate opportunities for cooperation in space debris research, to review the progress of ongoing cooperative activities, and to identify debris mitigation options.
What you probably did not know is that there are two protected zones that IADC is monitoring at the moment and that were adopted by the United Nations: Region A, or low Earth orbit (LEO) which spans from the lowest maintainable orbital altitude to a height of 2,000km, and Region B, or geosynchronous orbit (GEO) which spans from in altitude by +/- 200 km of the geosynchronous altitude (35,786 km) and in inclination by +/- 15 degrees (source).
The “junk” in these two regions can be classified in to three main groups.
1. Objects larger than ~10 cm in LEO and larger than ~1 m in GEO (tracked by space surveillance systems and include intact spacecraft, launch vehicle stages, mission related debris, etc.)
2. Objects between 2 mm and 10 cm in LEO and between 10 cm and 1 m in GEO (monitored from the ground facilities and consist of mission-related or fragmentation debris)
3. Objects smaller than 2 mm in LEO (presence of these inferred by the examination of space vehicle surfaces once they return to Earth)
Regardless of its size, space debris, due to it’s high speed, represents a great threat to all of the objects in Earth’s orbit. It is estimated that there are approximately 370,000 pieces of space junk floating in Earth's orbit, travelling at speeds of up to 18,000 miles per hour. Space debris can come into existence in several ways: through accidental events in which objects either explode or collide, creating thousands of pieces of junk that could damage to valuable objects. One event of this kind occurred in 2007, when a Russian satellite exploded over South Australia. In 2007, China intentionally took down one of its weather satellites by shooting at it. This move resulted in creating a 900-piece cloud of debris. The most famous collision happened on February 10th, 2009, when the privately-owned Iridium 33 and russian military satellite Cosmos 2251 collided, creating 2000-piece cloud of debris. Other debris consists of the post-mission-related debris, or even whole spacecrafts that are out of function.
On April 3rd, the International Space Station, for the second time in three weeks, had to dodge space debris which came as close as 300 meters (around 1000 feet) to the station. To escape Gravity-style catastrophe, the astronauts fired 53 thrusters to raise the station more than 800 meters (Approx. 2500 feet).
Based on the previously read facts, it is safe to say that space debris mitigation is the next step in fighting the issue of space debris.
In February 2007, the Scientific and Technical Subcommittee (STSC) of the United Nations' Committee on the Peaceful Uses of Outer Space (COPUOS) completed a work plan with the adoption of a consensus set of space debris mitigation guidelines. The guidelines were accepted by the COPUOS in June 2007 and endorsed by the United Nations in January 2008.
There were 7 main guidelines to follow according to Space Debris Mitigation Guidelines of the Committee on the Peaceful Uses of Outer Space:
1. Limit the debris released during normal missions
2. Minimize the potential for break-up during operational phases
3. Limit the probability of accidental collision
4. Avoid intentional destruction and other harmful activities
5. Minimize potential for post mission breakups resulting from stored energy
6. Limit the long term presence of spacecraft and launch vehicle orbital stages in the low-Earth orbit region after the end of their mission7. Limit the long-term interference of spacecraft and launch vehicle orbital stages with geosynchronous Earth orbit GEO region after the end of their mission.