In 2007 China tested an anti-satellite missile against one of its decommissioned weather satellites 800km above the earth in an explosion, creating 100,000 new pieces of orbital debris in a single instant. In 2009 a commercial Iridium communications satellite and a defunct Russian satellite collided over Siberia creating over 2,000 of pieces of debris capable of being tracked and even more that we cannot yet see. In 2015 the ISS performed a Red Conjunction where the crew evacuated to the Soyuz escape craft while a piece of debris passed close to the station without enough warning for a debris avoidance maneuver.
Even higher in orbit, there are many more defunct spacecraft posing risks to geostationary satellites. Since Sputnik first blasted its way into space in 1957, thousands of satellites have been sent into orbit around the Earth. But what happens to these satellites once they are no longer used?
There are several disposal or graveyard orbits where satellite operators move satellites that have come to the end of their usable life. Depending on the orbit of the satellite and its remaining fuel, it may also be possible to send the satellite back to earth in a decaying orbit that will cause it to burn up during reentry.
Unfortunately, it is never quite that simple. Satellites will require fuel to reach their final destination orbits, which limits the operating life of the satellite. As a result, operators must launch more frequently fueling the increase of space debris.
Moreover, while the defunct satellites are parked in the disposal orbits, there is still a possibility of collision and the resulting creation of thousands of fragments that can be launched into operational orbits. This is problematic because satellites are travelling around the planet at speeds of up to 17,000 mph, so debris even in the millimeter range can cause significant damage to spacecraft.
Even more troubling is the theory that the creation of such debris could become self-sustaining as space gets more congested. The “Kessler Syndrome,” first proposed in 1978 by Donald Kessler, argues that each satellite collision or breakup in orbit increases the chances of future collisions, eventually causing a chain reaction which produces a debris belt around the planet.
Keenly aware of this threat, there have been multiple policy initiatives on both the national and international levels. In 2001, the US Government formalized a set of standard practices for satellite disposal and debris mitigation. The Federal Communications Commission (FCC) also requires satellite operators to submit debris mitigation strategies and end-of life plans for placing the satellite in disposal orbit as part of the license application process.
Internationally, the Inter-Agency Space Debris Coordination Committee (IADC) acts as a forum for sharing technical information related to mitigation of space debris. While not a regulatory body, IADC establishes consensus guidelines for debris mitigation.
While many companies have signed up for the standards established by these organizations, space collisions and the creation of space debris have not abated. With thousands of small satellites predicted to enter orbit over the next decade, concerns that Kessler’s theory will become a reality are leading discussions, given that suitcase sized satellites will already be difficult to track.
Concerns also revolve around the possibility of a substantial increase in collision avoidance maneuvers reducing the usable life of the satellites. In such a complex system, unintentional collisions also become more likely and may produce cascade effects as the more disposable small satellites are damaged by debris.
While scientists have come up with unique ways to destroy space debris, these efforts are hindered legally because there is no law of salvage similar to maritime law, rendering in any removal of another country’s debris illegal. Article VIII of the Outer Space Treaty states that all satellites, even non-functioning satellites, continue to belong to their country of origin and are not salvageable. Up until 2005 almost a third of satellites placed in geostationary orbit could not be moved the graveyard orbit, resulting in defunct satellites which cannot be removed except by their country of origin, and which are uncontrolled near the orbits of active satellites. Additionally, given the amount of space debris in orbit and the small size of many pieces, it becomes extraordinarily difficult to determine where the object originated without capturing it and performing detailed analysis.
Against this backdrop important questions arise. Should an international body, like the IADC or the UN, have authority to impose some kind of sanction on governments which do not enforce debris mitigation standards? Should international rules about removal of space debris be changed to allow anyone to salvage defunct spacecraft? Should the FCC be more proactive in mandating companies comply with the space debris standards? Does parking satellites in graveyard orbits create a junk belt, but only at a higher altitude?