Space exploration has contributed to the development of humankind, most prominently since the early 1960s. The development of efficient launch vehicles and cost-effective small satellite technology made sending payloads into space economically feasible for more space agencies and private companies. Even developing countries, many of which lack in infrastructure or financial backing to support a standalone space program, now have the opportunity to develop and fly payloads for an extended duration.
Commercialization of Space
There is a growing trend towards the privatization and commercialization of space activities—the New Space—which has revolutionized space development, contrary to the approach followed in the mainstream aerospace industry. The democratization of space has been increasingly facilitated by easing the access to space through services which have commercial value. Indiscriminately, the population of artificial satellites launched by New Space actors will keep on increasing at much higher rates than estimated previously.
Satellites have a wide variety of applications, including but not limited to Earth observation, meteorology, scientific investigation, navigation purposes, and communication services. Due to their intrinsic characteristics, satellites are dual-use applications, serving both military and civilian purposes.
Telecommunication satellites are launched and placed into geosynchronous (GSO) and geostationary (GEO) orbits, to ensure global and real-time coverage. In GSO, satellites travel in a path around the Earth at an altitude of c. 35,786 km, at any inclination, in an orbit which synchronizes with the rotation of the Earth. In GEO, although space objects travel at a similar altitude as they do in GSO, they travel in a circular path around the planet in the plane of the equator. This one characteristic makes it unique from GSO. By placing a satellite in this position, it appears from any given point on Earth to be stationary, which is perfect for communication purposes. A constellation of just three equidistant communication satellites in the same orbit is enough to ensure full coverage of the Earth.
In their turn, low Earth orbits (LEO), ranging from the very edge of space, between 80 and 120 km above the Earth’s surface, up to approximately 2,000 km, have certain advantages. Launching an object, for instance a satellite, into LEO is much more cost-effective, since the energy required for placing a constellation there is substantially smaller than placing an object in GSO. The main issue, however, is that, to ensure the same coverage as offered by communication satellites in GEO/GSO, the number of satellites has to be much higher. That is because satellites in LEO have a small momentary field of view and are only able to observe and communicate with a fraction of the Earth at a time. Therefore, the present infrastructure demands for an upsurge in the number of satellites within a constellation or the launch of a very large satellite constellations, also known as mega-constellations. Two of the furthest developed large satellite constellation projects to date are SpaceX’s Starlink and OneWeb, a joint venture between OneWeb and Airbus Defence and Space.
These mega-constellations will be place in LEO and middle Earth orbit (MEO), i.e., ranging from 600 to 1,500 km from the Earth’s surface. The size of each of these planned constellations varies from about 200 up to 4,000 satellites and more. In November 2018, for instance, the Federal Communications Commission (FCC) approved SpaceX to launch about 7,000 broadband satellites. Although addressing the lack of basic internet coverage in some world regions, these mega projects may disrupt the sustainability of the space environment. Also, large satellite constellations will be accompanied by mass manufacturing of small satellites—thanks to standardization and commercialization of their production taking advantage of commercial off-the-shelf components—and an increase in the number of satellites launched per year.
The term “space debris”, although not legally defined, is used to refer to any non-operational satellites, spacecraft, and parts thereof which remain in their orbits even after the end of their operational time. These defunct satellites and parts thereof clearly stand out to be a problem for the orbital environment. After nearly 60 years of space exploration, the Space Surveillance Network, a critical part of the United States Space Command’s mission that involves detecting, tracking, cataloguing and identifying man-made objects orbiting Earth, is tracking more than 750,000 pieces of debris. In earlier days of space exploration, the upper stages of launch vehicles were prone to explosions and leakage of metals. Coolants from Soviet nuclear reactors (i.e. sodium and potassium) were ejected after the end of their life cycle. Due to low sublimation rates, they still exist in form of spherical droplets about 100,000 in number, each greater than 5 mm in size.
However, looking at current debris population models, the current scenario poses a serious risk to the sustainability of outer space. There is a serious concern that the ever-increasing population of space objects and, consequently, space debris, may lead to catastrophic collisions, leading to a further increase in orbital debris, threatening future launches and space missions. In 1978, NASA scientist Don J. Kessler proposed a theory commonly called Kessler Syndrome predicting that impacts will become more and more common and create tinier non-traceable bits of debris to clog up space around the Earth. The collisions can be classified as negligible non-catastrophic, non-catastrophic, and catastrophic collisions, depending upon the scale of debris produced and their effects in short term and long term durations. An example of catastrophic collision is the 2009 collision between US Iridium-33 satellite and the Russian satellite Cosmos 2251. It resulted in an estimated 1,500 traceable objects and other small untraceable debris.
As the number of artificial objects in orbit continues to increase and, with it, a key threat to space sustainability, the question of what happens to objects launched into space after the duration of their mission remains. A satellite, like any other machine, will eventually stop working, rendered useless, essentially becoming junk in orbit around the Earth. Like all other space objects orbiting the planet, they will keep on rotating and adding up to the population of mass until the atmospheric drag slows their orbital speed enough so they burn up in the atmosphere upon re-entry. This process could take from a couple of years to even billions of years, depending on the orbital plane and altitude of the satellite.
Debris Mitigation Strategies and Space Situational Awareness (SSA)
In response, space agencies have identified a set of mitigation guidelines aimed at enabling space users to reduce the generation of space debris, for example, by limiting the orbital lifetime of their spacecraft and launcher stages after the end of their mission. The debris mitigation guidelines, for instance, allow for a 10% failure rate and a maximum orbital lifetime of 25 years, which is no longer acceptable under such space traffic conditions in the LEO region, and the present orbital debris environment. The Inter-Agency Space Debris Coordination Committee (IADC), consisting of 13 space agencies from all over the world, has laid down guidelines for space debris mitigation. These guidelines, which became the basis for the space debris mitigation guidelines developed and adopted by UNCOPUOS in 2009, establish a series of measures and good practices aimed at reducing the risk of creation of debris. These guidelines, however, are voluntary in nature and not legally binding under international law. Consequently, no binding international norms regulating space debris exist today, which is a problem. Moreover, it has become apparent that these mitigation guidelines are not comprehensive enough and the current legal and regulatory framework does not adequately respond to the new challenges presented by New Space.
Furthermore, several states have included in their national space legislation provision on space debris mitigation and prevention. These provisions are compulsory for the actors and compliance with them is a frequent condition for the authorization of space activities in accordance with Article VI of the Outer Space Treaty. The insertion of non-legally binding instruments in national space laws transforms them into rules that are enforceable, at least on a national scale. Since the guidelines may contain slightly different standards and requirements, the use of the wording “internationally recognized standards and guidelines” in national space laws, a common state practice, may not comply with the domestic legislative requirements of being clear, specific, and unequivocal.
There have been proposals for Active Debris Removal (ADR) at the end of life cycle to clean the space junk generated by space missions. Space users have started planning and working on the possibility of refueling, repairing, and even resurrecting satellites in outer space—the so called on-orbit servicing—which is another possibility to mitigate the accumulation of orbital debris. A new and broader approach was provided with the concept of Space Traffic Management (STM) in combination with Space Situational Awareness (SSA). STM is considered a concept to provide a framework for the safety, stability, and sustainability of space activities. This concept has been defined by Contant-Jorgenson, Lala and Schrogl in Cosmic Study on Space Traffic Management as “the set of technical and regulatory provisions for promoting safe access into outer space, operations in outer space and return from outer space to Earth free from physical and radio-frequency interference”.
Regardless of the political, legal, or technical nature of the adopted approach, a solution must be found to ensure the sustainability of future space activities. The number of satellites launched into outer space is increasing exponentially and the quantity of space objects orbiting the Earth, especially in LEO, poses a key threat for space agencies and private companies. Space and non-space faring nations need to come together to reach a consensus on how to best address the issue of space debris to guarantee the sustainable use of outer space. Otherwise, after 60 years of space exploration, states who have not had the chance of reaching the stars might never be able to do so in many generations to come.
Posted by Ananyo Bhattacharya and Vinicius Aloia