As the amount of space debris orbiting the Earth continues to increase, issues pertaining to sustainable space usage are rising on both international and national agendas worldwide. Amongst the latest actions aimed towards bolstering space sustainability efforts was the US military’s 3 November 2009 announcement about upgrading their space debris surveillance program. According to Reuters, General Kevin Chilton of US Strategic Command said the US military was now tracking 800 maneuverable satellites for possible collisions, and expected to add 500 more non-maneuvering satellites to their tracking systems by early 2010.

Satellite tracking has become an essential part of space sustainability efforts, especially following a major collision in the Earth’s orbit earlier this year. This collision contributed immensely to the reported million or more – as estimated by The Center for Orbital and Reentry Debris Studies (CORDS) – man-made space debris or debris fragments in orbit. The unprecedented collision took place on 10 February 2009 between a US commercial satellite and a defunct Russian military satellite traveling at thousands of kilometers per hour, and produced a cloud of debris that has just started being incorporated into tracking systems.

This collision is not only incident that contributes to space debris in the Earth’s orbit. On 11 January 2007, the Chinese military used a ground-based missile to destroy one of its deteriorating weather satellites. The United States’ National Aeronautics and Space Administration (NASA) estimated that the explosion produced over 1500 large pieces of space debris and a 2000 mile-long cloud of smaller space debris and debris fragments. About a month later, a Russian rocket body exploded on 19 February 2007, adding over 1000 pieces of space junk to the Earth’s orbit. These incidents, along with other smaller explosions, have contributed greatly to rising space debris rates in the Earth’s orbit.

The importance of space to life on Earth

Space has become crucial to a wide range of activities on Earth. Satellites orbiting the Earth are necessary for worldwide telecommunications, military intelligence, digital navigation, cellular phones, television, and monitoring weather. Space technology is also a part of environmental sustainability efforts on Earth. Environmental initiatives, like the United Nations Collaborative Programme on Reducing Emissions from Deforestation and Forest Degradation (UN-REDD), often rely on satellite surveillance systems to conduct research on current environmental degradation and climate patterns. With accurate research, additional and effective steps can be taken to improve environmental sustainability. An example of this is the 2002-launched Envisat, a sophisticated Earth-observation spacecraft that provides scientists with data on oceanic temperatures, wind and wave speeds, ice-sheet thickness measurements in Antarctica, and rates of deforestation.

Debris hazards in space

Since the 1957 Soviet launch of Sputnik, the first artificial satellite in space, the amount of objects in the Earth’s orbit has continued to increase drastically. According to the Secure World Foundation (SWF), currently over 90 per cent of objects orbiting the Earth consists of useless materials.

With rising space debris rates, the amount of potential collisions is thought to increase as well. Mr Hugh Lewis, a lecturer of Aerospace Engineering at the University of Southampton, announced at the Council of European Aerospace Societies’ (CEAS) November 2009 European Air and Space Conference that the number of space debris has risen by 40 per cent in the past four years. He estimates that the number of close encounters between objects in orbit will rise by 50 per cent in the next decade, and could quadruple by 2059. The correlation between rising amounts of space debris and rising close encounters connotes a vicious cycle that poses great risks to space sustainability efforts. The rising amount of debris challenges the competence of existing tracking systems, threatening preventative measure towards potential collisions that have resulted from rising close encounters. Thus, this could lead to rising collision rates, and increasing collisions would produce more space debris polluting the Earth’s orbit.

Threats of rising collision rates aside, Mr Lewis also warns that rising close encounter rates will lead to an increase in the number and the cost of necessary steps to avoid them. According to Reuters, he estimates that future satellite operators will have to make five times as many collision avoidance moves in 2059 as they will in 2019, and each of these moves will take time, skill, and money. Dr Heiner Klinkrad, head of the European Space Agency’s (ESA) Space Debris Office, shared this perspective on rising tracking costs. But Dr Klinkard also believes that while rising tracking costs will be a challenge, they are a surmountable challenge. According to space.com, Dr Klinkrad said, “… space debris remediation will be a technically demanding and expensive undertaking, but such costs must be viewed in relation to the value of space assets.

Another threat posed by rising space debris rates involves damage to satellites, space stations, and other serviceable entities in the Earth’s orbit. According to CORDS Director William Ailor, the rise in space debris rates has also led to an unfortunate rise in untracked objects, specifically those that are greater than one centimeter in size. Currently, CORDS believes that untracked objects greater than one centimeter range anywhere from between 200,000 to 600,000. These include waste from solid rocket motors, liquid metal droplets from nuclear reactors, and items like lens covers which are shed during operations. During a session called Green Space: Addressing Space Debris — End of Life Operations at the American Institute of Aeronautics and Astronautics’ (AIAA) Space 2009 Conference and Exposition, Dr Ailor said: “These objects, most of which flitter through low-Earth orbit, are of a size that could take out a satellite, or could reduce the performance of orbiting assets.” His fears seem to have been demonstrated earlier this year, when an evacuation of the International Space Station was ordered on 12 March 2009, after a piece of debris – which according to BBCmeasured about 1 cm in size – passed perilously closely to the station.

Debris mitigation

An important strategy that could enable success for space sustainability efforts involves controlling the growing rate of debris. At the moment, debris mitigation seems to be the most-explored sustainability solution by space agencies worldwide, and involves limiting the amount of debris generated by three key phases of space operations: the launch, the on-orbit, and the re-entry. In 1993, several major space agencies – including the ESA and NASA – formed the Interagency Space Debris Coordination Committee (IADC), which began developing a set of debris mitigation guidelines that became the groundwork for UN space sustainability-related legislation.

In June 2007, the UN Scientific and Technical Subcommittee (STSC) of the UN Committee on the Peaceful Uses of Outer Space (COPUOS) adopted their own set of space debris mitigation guidelines, which were based upon what had been developed by the IADC. According to the UN Information Service, these guidelines outlined debris mitigation measures for the planning, design, manufacture, and operational phases of spacecraft and launch vehicles: “The guidelines call for limiting the long-term presence of spacecraft in low-Earth orbit (LEO), up to some 1,600 kilometers above the Earth’s surface, after the end of their mission. The guidelines call for the removal of such spacecraft from orbit or for their disposal in other orbits that avoid their long-term presence in the LEO region, where the majority of satellites are placed and where they are in greatest danger of collision.” In January 2008, the UN General Assembly adopted a resolution based upon these guidelines, outlining how the international community must cooperate in the peaceful uses of outer space.

Space traffic management and space situational awareness

While debris mitigation is undoubtedly an important sustainability strategy to pursue, it
fails to address the problem of the existing mass of debris orbiting the Earth. Thus, the management of space traffic is another notable sustainability strategy that could assist current efforts . According to SatMagazine, an online satellite news publication, even without additional satellites placed into orbit, the existing population of orbital debris is likely to increase through collisions between each other; this was demonstrated earlier this year with the collision between US and Russian spacecraft. The development of methods that actively remove debris would require a lot of research and money, but if developed correctly they could make great contributions to sustaining space usage. Moreover, research and analysis should be conducted on how the effects of existing debris on existing spacecraft and satellite services can be minimised.

Presently, the major space traffic management initiatives are administered by the United States. In a paper called Achieving a Sustainable Space Environment by SWF President and co-founder Cynda Collins Arsenault and SWF Director Ray Williamson, it is described how the United States has developed and how they manage these initiatives. The US Air Force currently maintains ground-based optical and radar observatories that keep track of approximately18,000 working satellites and larger debris. Commercial entities and non-US national agencies can request and receive guidance from the US Air Force in planning needed for spacecraft maneuvers, and many other countries often depend on them for critical information.

A relatively new but important space traffic management initiative is also being developed by theESA, and was officially launched in 2008. The Space Situational Awareness (SSA) Preparatory Programme aims to “sustainably and safely operate Europe’s critical space infrastructure.” Mr Nicholas Bobrinksy, the current head of ESA’s Ground Stations Systems Division, says the SSAprogramme will operate in two specific areas: “The first is surveillance of objects orbiting Earth in various orbits – to be achieved by detecting, tracking, and imaging these objects. The second is space weather – addressing primarily the effects of solar activity on satellites and ground infrastructure such as power grids and communication networks.” Mr Bobrinsky also called the SSAprogramme essential to Europe’s role in international efforts for the peaceful uses of outer space.

Debris removal

A third option that can contribute to space sustainability efforts is debris removal. Even with debris mitigation and space traffic management, the debris that exists in orbit will likely remain there for thousands of years and continue to travel at incredibly rapid speeds. Space debris removal was a prominent topic at the 60th International Astronautical Congress in Daejon, Republic of Korea. According to spacemart.com, there was consensus at the conference that unless steps are taken to remove at least a portion of existing debris objects, the space environment surrounding the Earth will continue deteriorating; this could lead to a loss of access to parts of the near-Earth space region.

In a report released by SWF and L’Institut français des relations internationales entitled Towards Greater Security in Outer Space: Some Recommendations, it was stressed that research should be increased on methods of de-orbiting critical pieces of debris safely and effectively, and research should also be conducted on the legal and political issues pertaining to the removal of debris from orbit to provide the legal and policy bases for such activities. The report also called on non-governmental organisations to contribute to improving civil society’s understanding of outer space matters.

However, technology for debris removal must be cost-effective, as it is a method that must work alongside the already expensive debris mitigation and space traffic management efforts. According to the Small Business Innovation Research programme (SBIR), a component of the US Department of Defense, debris removal efforts should focus on targeting higher risk objects. These objects include rocket upper stages and other orbiting items, which can explode shortly after they become inactive.SBIR believes such explosions result in clouds of smaller orbital debris, and thus also sees targeting higher-risk objects as a preventative measure towards interrupting growing smaller debris rates.