Vinicius Aloia and Ananyo Bhattacharya
Commercial Space Project Group
Space exploration has contributed to the development of humankind since the early 1960s. With the development of efficient launch vehicles and cost-effective small satellite technology, the democratization of space has been facilitated by easing the access to space. More agencies are able to send their payloads in space at a rate which is economically feasible. Satellites are dual-use applications, serving both military and civilian purposes. They have a wide variety of applications, including but not limited to Earth observation, meteorological, scientific experimentation, navigation satellites, and communication services. There is a growing trend towards the privatization and commercialization of space activities, a phenomenon frequently referred to as New Space Economy. With clear democratization of space, more space agencies and most notably non-governmental entities are starting to provide services in space which have a commercial value. Indiscriminately, the population of artificial satellites launched by these new space actors will keep on increasing at much higher rates than the estimated previously.
A question might arise: What happens to the objects we launch into space? What happens to a spacecraft or satellite after their mission is over? A satellite, like any other machine, will stop working beyond its life, essentially becoming junk in space. Like all other space objects orbiting the planet, they will keep orbiting and adding up to the population of the mass that already orbits the planet.
Today, 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 circular 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 the space objects travel at the same altitude as they do in GSO, they travel in a circular path around the planet in the plane of the equator. This one special 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.
However, the low Earth orbit (LEO), ranging from the very edge of outer space up to approximately 2,000 km above the Earth’s surface, has certain advantages. Launching an object 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 in order to ensure the same coverage as offered by constellations in GEO/GSO, the number of satellites has to be much higher than constellations in GEO/GSO. That is because satellites in LEO have a small momentary field of view, 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 a very large satellite constellation, as known as “mega-constellations”. SpaceX’s Starlink and OneWeb large satellite constellations are two of the furthest developed projects in this field. Some of the other companies joining this venture are, i.a., Boeing, Samsung, and Telesat.
These constellations will be placed in LEO and Middle Earth Orbit (MEO) i.e. from 600 km to 1,500 km from the surface of Earth. The size of each of these constellations varies from about 200 up to 4,000 satellites. In November 2018, the Federal Communications Commission (FCC) approved SpaceX to launch about 7,500 broadband satellites. Large satellite constellations will be accompanied by mass-manufacturing of small satellites and an increase in the number of launches per year. In 2017, OneWeb satellites inaugurated its assembly line in Toulouse, which is a joint venture between OneWeb and Airbus Defence and Space.
Looking at the current debris population models, and present debris mitigation guidelines, the current scenario poses a serious risk to the sustainability of mega-constellations, as the current guidelines allow for a 10% failure rate, which is not acceptable under such space-traffic conditions in the LEO and the present orbital debris environment. It also a question of future sustainability of space missions. The term “space debris” is used to define any non-operational satellites, spacecraft, and parts thereof which remain in their orbits even after the end of their operational time.
There is a serious concern that the ever-increasing population of space objects and, consequently, space debris may lead to catastrophic collisions which may lead to a further increase in orbital debris, threatening future launches and space missions. In 1978, NASA scientist Don J. Kessler proposed the Kessler syndrome. The theory predicts that impacts will become more and more common and create tinier non-trackable 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.
Space debris clearly stands out to be a problem for the orbital environment. One may ask, however, how many objects are there and what one can expect when it comes to the term “space debris”.After nearly 60 years of space exploration, the Space Surveillance Network 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.
Interestingly, there is no official definition of the term “space debris”. 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 NewSpace.
There have been proposals for an Active Debris Removal (ADR) at the end of life cycle in order to clean the space junk generated by us. Space operators have started planning and working on the possibility of refuelling, repairing and even resurrecting satellites in outer space. This is called ‘on-orbit servicing’, which is another possibility to militate the accumulation and clogging 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). Space Traffic Management (STM) is considered a ‘concept to provide a framework for the safety, stability, and sustainability of space activities’. This concept has been defined 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 approach adopted, either political, legal, or technical, a solution must be found to ensure the sustainability of future space activities. The number of satellites launched into outer space is increasing significantly and the quantity of space objects orbiting the Earth, especially in low Earth orbit, is causing serious concerns for space agencies as it poses a key threat. Space and non-space faring nations need to come together reach a consensus on how to best address the issue of space debris and the sustainable use of outer space. Otherwise, after 60 years of space exploration, those who have not had the chance of reaching the stars might never be able to do so in many generations to come.