Six thousand satellites have been launched since Sputnik in 1957. They support many vital activities, including weather forecasting, global positioning systems, aircraft and ship communications, financial services, agriculture, forestry, fisheries, climate change science, search and rescue, and disaster relief. Humankind’s dependency on space will only increase due to rapidly changing technologies such as small satellites, reusable rockets and artificial intelligence, as well as the growing involvement of commercial actors. For a current snapshot of space traffic, see AstriaGraph.
Space debris is the legacy of 5,000 orbital-rocket (i.e. satellite) launches since 1957. There are roughly 100 million pieces of debris in orbit, with 500,000 of them being larger than one centimeter. Some pieces are dysfunctional satellites; others are discarded rocket stages; a few are tools lost by astronauts during space walks. Most are the result of satellite fragmentation due to on-board explosions or deliberate destruction. However, some anomalous fragmentation events are thought to result from collisions between satellites and debris — at relative speeds of up to 58,000 kilometers per hour. Of greatest concern, each fragmentation increases the effective collisional cross section of material, which increases the probability of another collision. At a certain point, the dominant debris-generating mechanism will be debris-debris and debris-satellite collisions, initiating runaway space debris. This process, called the ‘Kessler Syndrome’, threatens a global economy which increasingly relies on satellites, as well as humanity’s long-term access to space and other celestial bodies. Fortunately, space debris can be addressed through international cooperation and technological innovation. Space-faring countries are already cooperating on this issue: 20,000 pieces of space debris have been detected, tracked and catalogued using Earth-based radar and telescopes. This information is widely shared, since advance warning of collisions can provide time for endangered satellites to be moved to safer orbits using on-board thrusters. National space agencies are also researching ways to remove derelict satellites from orbit, and perhaps most important, militaries are refraining from testing anti-satellite weapons in ways that could create long-lasting space debris. But this is not enough, particularly with the greatly expanding use of space.
What low Earth orbit and geo-orbital slots are needed to accommodate increased space use while minimizing risk to Earth’s growing satellite population, and can these be regulated more effectively than the current International Telecommunications Union regime? Can recent guidelines on satellite design, ensuring the ability to de-orbit at the end of the equipment’s operational lifetime, be made binding under international law?