Orbital Debris

Artist's Representation of Earth's Satellite Population (European Space Agency)
Illustration: Brandon Celi

Ten thousand satellites have been launched since Sputnik in 1957. They support many vital activities, including weather forecasting, global positioning systems, communications, financial services, agriculture, forestry, fisheries, climate change science, search and rescue, and disaster relief. Our dependency on space is only increasing, and new technologies such as small satellites, reusable rockets and artificial intelligence, as well as the growing involvement of commercial actors, are reducing the cost of developing and launching satellites. The number of objects launched into Earth orbits is rapidly increasing every year as a result. For a current snapshot of space traffic, see AstriaGraph. Frequently updated statistics concerning the increase of space objects over time are available at ESA Space Environment Statistics and CelesTrak.

Space debris is the legacy of 6,020 orbital-rocket (i.e. satellite) launches since 1957. There are roughly 128 million pieces of debris in orbit, with 900,000 of them being larger than one centimeter. Some pieces are dysfunctional satellites; others are discarded rocket stages. Most are the result of satellite fragmentation due to accidental on-board explosions. Deliberate destruction has also occurred. 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 per time. At a certain point, the dominant debris-generating mechanism will be debris-debris and debris-satellite collisions, initiating runaway orbital 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. Concern of this process is only elevated as the number of satellites and objects in space increases rapidly over the next decade.

Fortunately, orbital debris can be addressed through international cooperation and technological innovation. Space-faring countries are already cooperating on this issue: over 28,000 pieces of orbital 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 kinetic anti-satellite weapons in ways that could create long-lasting orbital debris. But this is not enough, particularly with the greatly expanding use of space. Overall, we need to have a major shift in our concept of space – an environment that is worth preserving.

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? How can space traffic management norms for operating in space be better developed and diffused globally? 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? Will the high frequency of space objects re-entering Earth’s atmosphere pose safety and environmental risks on Earth?

In January of 2020, The Outer Space Institute held an international, transdisciplinary workshop that addressed many questions concerning the issues of orbital debris. The consensus “Salt Spring Recommendations” reached by the participants encourage sustainable on-orbit operations, and comprehensive governance and licensing regimes that reflect developments in the ‘NewSpace’ era. The Recommendations serve as an instrument to guide national and international policy makers to adopt solutions that encourage the long-term sustainability of space.