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satellite explosion illustration
Both technical and non-technical solutions are needed to avoid an orbital debris catastrophe in the coming decades. (credit: ESA)

Overcoming non-technical challenges to cleaning up orbital debris


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Orbital debris is any human-made and uncontrollable litter left in Earth orbit. It includes inactive satellites, rocket stages, and fragments created by collisions, explosions, and even normal operations. There are more than 21,000 Earth-orbiting debris objects larger than a softball (10 centimeters) and more than 500,000 shrapnel fragments between 1 and 10 centimeters. The amount of shrapnel smaller than 1 centimeter exceeds 100 million (NASA 2013). With relative impact velocities higher than 35,400 kilometers per hour (Olliges 2015), even debris as small as half a centimeter across can take out a spacecraft (Liou 2014). The number of debris objects larger than one centimeter will reach around one million in year 2020 (European Commission 2013).

Future large structures in Earth orbit, such as commercial space stations, hotels, solar power satellites, and settlements will also be vulnerable to orbital debris that will continue to grow from future collisions, even if we put no new spacecraft into Earth orbit.

The deliberate destruction in 2007 of the Chinese Fengyun satellite with an antisatellite weapon and the catastrophic 2009 collision between a defunct Russian Cosmos satellite and an operating Iridium satellite account for nearly as many fragments currently tracked as all previous fragmentation events combined (NASA 2015). Largely because of the debris caused by these two events, NASA, analyzing data from six space agencies, estimates that there will be another catastrophic collision every five to nine years (Liou 2014). We may have already reached a “tipping point” whereby orbital debris in congested low Earth orbit (LEO) altitude bands is already colliding in a runaway debris-generation scenario, often called the Kessler Syndrome (McKnight & Kessler 2012).

Orbital debris is an ever-growing hazard to the International Space Station (NASA Orbital Debris Quarterly News 2015) and the approximately 1,300 operating satellites, which represent only about 6 percent of the 21,000 tracked objects in orbit (Baiocchi & Welser 2015). Those satellites include ones that provide communications, collect weather data, serve national defense needs, and more. Although it is difficult to determine what percentage of satellite failures are due to orbital debris as opposed to other causes, such as meteoroid impacts, annual economic losses in the satellite industry have been growing, and the increasing amount of orbital debris is undoubtedly a factor. In fact, claims paid out by insurance companies for on-orbit spacecraft failures just in 2013 reached $800 million (OECD Publishing 2014).

Future large structures in Earth orbit, such as commercial space stations, hotels, solar power satellites, and settlements will also be vulnerable to orbital debris that will continue to grow from future collisions, even if we put no new spacecraft into Earth orbit (Moskowitz 2011; Liou 2010 & 2014). Yet, space companies are planning thousands of new satellites for the near future (Davis 2015).

There are both non-technical and technical challenges to cleaning up orbital debris. Because the greatest debris threats lie in LEO (160–2000 kilometers, with a particular concern at 750–1000 kilometers) and GEO (35,786 kilometers), this essay focuses mostly on those altitudes. However, some of the technologies and policies we recommend will apply to dealing with orbital debris at other altitudes as well.

Non-technical challenges consist of adverse economic factors, policy and legal barriers, and international/geopolitical sensitivities. These non-technical challenges overlap with each other and complicate technical challenges, which include inadequate space situational awareness (SSA)—including debris detection, tracking, and conjunction predictions—and a lack of available technology for removing or using orbital debris.

The essay only deals with overcoming the non-technical challenges listed above.

Mitigation (alone) will not stop the threat from growing

Mitigation refers to any policy, activity, or technology that seeks to prevent orbital debris from being created or seeks to prevent debris from knocking a spacecraft out of service. Examples of debris mitigation include lowering a spacecraft at its end of life (EOL) to force the satellite to deorbit naturally within 25 years (the “25-year guideline”), raising the orbit of a GEO spacecraft at its EOL to a graveyard orbit (Liou 2011), or shielding a spacecraft so that it will not be damaged by debris

Mitigation is important to help slow the growth of orbital debris. However, the space community is planning thousands of new launches within several years (Davis 2015), and even without new launches and with 90-percent compliance with the 25-year deorbiting-after-use guideline, orbital debris will continue to grow in quantity and threat for at least the next 200 years because of future collisions (Liou 2014; Liou 2011).

Remediation refers to active debris removal (ADR) or the active rehabilitation (ADRe) of defunct spacecraft to produce operational ones. ADR means to remove objects from orbit using measures beyond mitigation (Liou 2015). ADRe means taking actions to rehabilitate spacecraft by either refueling, repair, or reuse of parts. Reuse could be accomplished by attaching functioning units to spacecraft in a process called “cellularization” (Barnhart 2014). Remediation also includes the possibility of recycling a defunct spacecraft or its parts for use as feedstock metal for on-orbit fabrication (Anzaldua 2014).

The altitudes with the largest number of objects pose the greatest current risk or threat to satellites. However, the altitudes with the highest overall mass represent the greatest future threat, because the more mass involved in collisions, the more destructive will be the debris (McKnight & Kessler 2012). Based on these criteria, and accounting only for trackable objects in LEO, orbits around 780 kilometers are currently the most hazardous, and orbits around 780, 840, and 920–1,000 kilometers pose the greatest future threat or risk in LEO (McKnight & Kessler 2012). The good news is that NASA estimates that the LEO environment can be stabilized during the next 200 years with an ADR rate of five large objects per year, carefully selected on the basis of mass and collision probability (Liou, “Controlling…” 2010).

The space community must therefore face the hard reality that, as soon as possible, it must carry out not only orbital debris mitigation, but also orbital debris remediation of objects 0.5 centimeters and larger.

Unfortunately, in terms of future debris creation, only around 40 percent of the about 6,000 tons of material in Earth orbit is in LEO. The rest is in higher orbits (Liou, “A parametric…” 2010): half in and near GEO, and most of the rest between LEO and GEO. Worse yet, the most dangerous debris, at least in LEO, consists of shrapnel smaller than 10 centimeters currently too small to detect and track. Shrapnel between 1 and 10 centimeters number around 600,000 objects (European Commission 2013), and there are over a million objects as small as 0.5 centimeters that can put a spacecraft out of commission (Liou 2014).

The space community must therefore face the hard reality that, as soon as possible, it must carry out not only orbital debris mitigation, but also orbital debris remediation of objects 0.5 centimeters and larger (Liou 2014). A great improvement in international SSA will also be necessary for effective remediation of objects smaller than 10 centimeters.

Mitigation of space debris in the future: FAA’s role

We recommend that the Federal Aviation Administration (FAA) require (for the licensing of companies launching to LEO) clear demonstration that they will:

  1. use the shortest-life and least-crowded orbit compatible with the mission;
  2. include cost-effective spacecraft shielding against small impactors;
  3. safely deorbit or re-use dead spacecraft within two years post-mission; and
  4. obtain insurance (government launches, self-insure) against launch failure, liability, and safe de-orbit or re-use failure.

The FAA, as the US entity currently responsible for issuing launch licenses based on its judgement of adequate liability insurance and safety characteristics, is the logical agency to judge the adequacy of deorbit plans and insurance policies. The FAA would be able to coordinate internationally with analogous institutions in other countries through a national Space Traffic Management entity we discuss below.

At this time, services to deorbit spacecraft that lack functioning automated deorbiting mechanisms are not commercially available, so pricing such insurance would currently be difficult. For this reason, we also recommend that public and private spending be greatly expanded to develop cost-effective deorbit and reuse technology. Such insurance would be fundamentally similar to purchasing insurance against launch vehicle failure. However, rather than simply paying out damages, the insurance companies would undertake actively to dispose of, rehabilitate, or recycle the orbital debris through commercial contractors, as described below. While the purchase of de-orbit insurance is in part of a mitigation strategy, details of subsequent debris cleanup will be covered below.

An existing policy complicates implementation of the above mitigation system. Under the US government’s Orbital Debris Mitigation Standard Practices (US Government 2015), satellite companies are not required to deorbit or otherwise move their satellites to higher-altitude graveyard orbits until 25 years have passed after the end of the satellite’s mission. This policy, being adopted internationally, amounts to 25 years “free parking” post-mission. While an improvement over the previous situation with no deadline to deorbit satellites, such free parking for any object that cannot actively avoid all dangerous conjunctions still endangers operating satellites and other operating spacecraft. Therefore, we recommend that the international space community phase out 25-year post-mission free orbital parking by periodically shortening the allowed post-mission periods, while grandfathering in all spacecraft launched and operated in compliance with regulations then in force.

Orbital debris cleanup would be facilitated if insurance companies offered lower premiums to companies utilizing reusable boosters, automatic deorbiting mechanisms, locator beacons, or other technologies enabling either orbital debris mitigation or remediation. For these reasons, we recommend that insurance companies participate in any national or international agreements dealing with orbital debris mitigation or remediation.

Remediation of existing debris in LEO

The ISS offers us an ongoing way to engage the international community and overcome geopolitical rivalries. However, some partners, particularly Russia, many no longer participate in ISS activities after 2024. This future loss of cooperative engagement will be particularly unfortunate given that Russia and the United States have been the major producers of empty upper stages, the major source of future debris in LEO (Pearson 2012; Carroll…speaking 2014).

We recommend that the US openly and transparently begin removing, through public-private space agreements, old US rocket bodies and dead satellites from LEO, which accounts for just over half of the non-Russian mass in LEO. This removal will set an example, while testing the requisite technology.

Launching governments, through their classification of technological secrets and their dual-use technology transfer rules, have shown themselves to be very sensitive about the attributes and capabilities of their satellites, especially military ones. Therefore, to induce international cooperation to remove, repurpose, recycle, or rehabilitate large debris objects, it is best to start with these much less sensitive, but still dangerous, upper stages, which make up about half of the LEO debris mass. Capturing aluminum tanks would also be a lot less complicated than grabbing or manipulating satellites with solar arrays or antennas. In addition, on-orbit recycling may be more practical with such tanks than with most other materials or objects.

We recommend that the US openly and transparently begin removing, through public-private space agreements, old US rocket bodies and dead satellites from LEO, which accounts for just over half of the non-Russian mass in LEO. This removal will set an example, while testing the requisite technology. The use of public-private partnerships, similar to those used by NASA’s Commercial Orbital Transportation Services (COTS) program, could offer a significant reduction in costs compared to conventional government-led programs.

However, about 900 of the 1,100 tons of rocket bodies in LEO is Russian, and removing only Russian rocket bodies from LEO could reduce shrapnel creation by nearly 62 percent (Pearson 2012). This exceeds the 48-percent reduction that would occur if all non-Russian mass were removed from LEO.

debris chart
LEO mass ownership, shown as mass (in tons) versus altitude (in kilometers). (Carroll 2015)

As the US government, in coordination with US companies, takes steps to clean up its own debris, the US should approach Russia for bilateral collaboration. A good start would be for talks between Russia and the US on the range of space operations and safety considerations, including SSA, respective catalogs of space objects, national research and regulations for debris mitigation, conjunction analysis, and more. Ideally, these talks would lead to US-Russia bilateral orbital debris agreements, which would cover more than 85 percent of the mass in LEO.

Although US-Russian relations have fallen to their lowest levels since the end of the Cold War, there is a shared interest in and responsibility for ensuring that the space environment is safe and sustainable. Throughout such talks, the goal should be to demonstrate to Russia that it is in its own best interest to address the threat of orbital debris, regardless of what the US and other countries do. What can we therefore say to the Russians along these lines?

First, under the 1972 Space Object Liability Convention, all space objects, large and small, carry with them strict launching state(s) liability for reentry damage and “if at fault” on-orbit damage (although “if at fault” is undefined). Second, cleaning up the debris represents enormous potential value in terms of already emplaced debris objects for repurposing and recycling. Third, if Russia collaborated with the US to remediate orbital debris, it would have a chance to advance its own space technology and industries, while keeping an eye on the advancement of space technology, including laser technology, of other countries. Fourth, cooperation with the US would offer a way to lower geopolitical tensions.

There is nothing for the US and other countries to lose and much to gain by reaching out to Russia to clean up orbital debris. The same goes for reaching out to China, which has recently signed agreements with Russia regarding cooperation in space (Song 2015). Although the 2011 Wolf amendment effectively bars NASA from engaging in bilateral space agreements with China, there is growing debate over whether that legislation is counterproductive and should therefore be overturned (David 2015). For dealing with either country, provisions of the International Traffic in Arms Regulations (ITAR) may also need also to be addressed.

Continuing to exclude China from civil space cooperation will not prevent it from developing its own capabilities (Weeden 2015). Space weather, scientific research, exploration, disaster response, and global environmental monitoring are areas where the US and China could collaborate with each other and other interested countries in a way that would lower tensions while achieving positive gains (Weeden 2015).

We recommend that the White House create by executive order a new national entity called the Space Traffic Management Executive Committee (STM ExCom) to carry out space debris cleanup in collaboration with analogous entities in spacefaring countries worldwide.

No country alone can affordably clean up enough debris to remove the threat of catastrophic collisions, and both Russia and China are key players in cleaning up orbital debris. We therefore recommend that the United States actively seek to include both countries in its international, public-private efforts to clean up orbital debris. To facilitate cooperation with China, we also recommend that the US Congress repeal the 2011 Wolf amendment, which bars the use of federal funds by NASA to conduct bilateral science exchanges with China. Instead, Congress might consider the option of limiting science exchanges to areas of overwhelming common interest, such as orbital debris, planetary defense, and space weather.

Facilitating remediation of current and future orbital debris

The worldwide space community, and the public it serves, needs national and international entities to cooperatively generate policies and guidelines for orbital debris cleanup. From the standpoint of international law, existing and future operating spacecraft and debris are the responsibility of each spacefaring government (Treaty 1967). Therefore, to honor this responsibility in matters of remediating existing or future debris, we recommend that the White House create by executive order a new national entity called the Space Traffic Management Executive Committee (STM ExCom) to carry out space debris cleanup in collaboration with analogous entities in spacefaring countries worldwide.

STM ExCom could be established in full compliance with existing international treaties and law. Under Article VI of the Outer Space Treaty (OST), the US government has agreed to authorize and continuously supervise the space activities of both its governmental agencies and its non-governmental entities (Treaty on Principles…, Art. VI 1967). Ideally, the STM ExCom and its connected offices would:

  1. be established quickly through executive action;
  2. function within the Executive Branch of the US government (USG);
  3. have input from relevant USG agencies and private experts connected to space;
  4. be flexible and nimble so as to be able to react quickly to changing circumstances;
  5. have permanent staff provided by connected agencies, yet have the ability to form ad hoc committees to plan and solve particular problems; and
  6. be able to interact cooperatively and transparently with national and international entities and persons, both public and private.

As it turns out, a national entity already exists that fulfills the above conditions and could serve as a model for a separate orbital debris management entity. The National Executive Committee for Space-Based Positioning, Navigation, and Timing (PNT ExCom) was created by executive action in 2004 and serves under the White House. It deals nationally and internationally with planning and problems arising from the GPS and space-based PNT. The STM ExCom would therefore be structured and staffed similarly, but with important variations, to the PNT ExCom:

org chart

The organizational chart above is only notional, and we expect it to be later refined. Although the STM ExCom would be the overall supervisory body, the STM Coordination Office would organize the actors, coordinate the action, carry out everyday work, and house permanent staff provided by the relevant federal agencies.

Note that we are also proposing an International Working Group connected to the STM Coordination Office. The International Working Group, chaired by the State Department, would be the body coordinating with the International Telecommunication Union (ITU), UN Office for Outer Space Affairs (UNOOSA), spacefaring countries, and international space entities, such as the Space Data Association.

We recommend that the space entities responsible for any spacecraft already in orbit be grandfathered under the policies in existence at the time of their launch, so that they are not penalized by any new anti-debris policy, which the STM ExCom develops in coordination with international entities.

page 2: economic aspects affecting remediation >>