Webinar Round-up: Pursuing Urgent Consensus on Space Situational Awareness and Debris Mitigation
During the first week of December 2020, professionals from ESA, Alden Legal, Astroscale, OKAPI:Orbits and the Secure World Foundation came together on Space Tech Expo Europe’s webinar to discuss developments regarding space situational awareness and space debris mitigation.
The panel received so many great audience questions but did not have enough time to answer them all. We followed up with the panel, who answered some of the remaining burning questions on this pressing issue.
What are the most dangerous debris in space?
Jonas Radtke, CEO at OKAPI:Orbits: This depends a bit on the definition of ‘dangerous’ – there are two views on the topic. Looking at a single space mission that is capable of doing collision avoidance, the highest risk comes from objects between circa 1 cm and 10 cm in low-Earth orbit (LEO). By a rough rule of thumb, these have a sufficient kinetic energy to immediately end the mission yet are too small to be continuously tracked.
In terms of ‘risk on the environment’, risk can be defined by the probability of the breakup of an object (by collision and explosion) and the impact such fragmentation would have on the environment. Different formulations exist for this, but generally this equation is governed by the region in orbit where the object is located (the denser, the more critical), its mass (the larger, the more critical) and remaining orbital lifetime (the longer, the more critical). There are several studies that provide a ranking of space objects in regard to their criticality, and usually you find objects such as old soviet rocket stages and Envisat on the top of these lists. For more details, please find links below to interesting papers Jonas has shared with us:
- Deriving a priority list based on the environmental criticality (tu-braunschweig.de)
- Ranking in-orbit fragmentations and space objects | Proceedings of the International Astronomical Union | Cambridge Core
- Application of a debris index for global evaluation of mitigation strategies - ScienceDirect
Harriet Brettle, Head of Business Analysis at Astroscale: Darren McKnight has recently published a paper at the IAC Cyber Space event that brought together 11 teams that analysed, using their own methods, the riskiest objects in LEO. The consolidated list of the top 50 riskiest objects largely includes soviet upper stages, other upper stages and some large failed satellites. More info can be found in this article.
Victoria Samson, Washington Office Director at the Secure World Foundation: One complicating factor is that most of the mass of debris on orbit is of Soviet/Russian origin, which lends itself to concerns about cooperation between political competitors on a technology that could have counterspace implications.
How is liability split between launching state, registration state, owner, operator?
Joanne Wheeler MBE, Managing Partner at Alden Legal: Article VI of the Outer Space Treaty 1967 states that States bear international responsibility for national activities in outer space, including activities of non-governmental entities, and requires States to exercise authorisation and continuing supervision over these activities. Article VII, concerning liability, mentions that each State that ‘launches or procures the launching of an object into outer space… and each State Party from whose territory or facility an object is launched’ (the launching State) is internationally liable for damage done by that object. Article VIII adds that States, on whose registry a space object is registered, must ‘retain jurisdiction and control’ over the object.
This international liability of launching States is clarified by the Liability Convention 1972, under which launching States are absolutely liable to compensate for damage caused by their space objects ‘on the surface of the earth or to aircraft in flight’ (Article II) and bear liability for damage caused in outer space where they are at fault (Article III). Additionally, where there are two launching States both shall be jointly and severally liable to the third state (Article VI), meaning that the third state can sue either for the full amount.
In practice, states flow this liability down to non-governmental parties through legislation and in licence conditions. In the UK, a licence must be acquired by whoever has ‘direct and effective’ operational control over the space object, as opposed to ownership of it. Under English law, licensees must indemnify the Government against claims up to the capped amount specified in their licence, and must, in general, take out third-party liability insurance (up to €60 million for standard missions) against liabilities arising from the licensed activity.
What is the role and, more importantly, the future of satellite laser ranging in the space situations awareness (SSA) infrastructure?
Brettle: At the moment satellite ranging provides an excellent capability to provide high-fidelity positional and velocity information for a specific object. This is both essential for validating new remote sensing systems and networks, as well as providing accurate observations for complex, bespoke manoeuvres, especially for Rendezvous and Proximity Operations (RPO) such as in-orbit servicing (IOS), active debris removal (ADR), end-of-life (EOL) and Inspection missions. Should the use of retroreflectors become more commonplace on spacecraft, SSA would benefit from having reliable, objective ground-truth state-vectors with which to compute orbital element sets and enhance conjunction assessment and collision avoidance abilities.
Radtke: From my personal point of view, debris satellite laser ranging (SLR) can play a very important role of filling the gap of high precision on-demand observations for critical events in LEO. Currently, most LEO data comes from surveillance radar measurements. In critical events affecting active satellites, usually more precise data on the active satellite is available, but none for the incoming debris object (which due to its characteristics more often has larger orbit uncertainties). Being able to increase the precision of the debris object, would help reducing performing avoidance manoeuvres for false positives.
When will a commercial debris mitigation company get its first non-government contract for removal of space debris?
Brettle: Astroscale is developing commercial end-of-life services that will be available for debris removal in the early/mid 2020s. We are working closely with satellite operators to demonstrate the value of end-of-life services in order to reduce collision risk and protect operational service, mitigate the risk of extended satellite lifetimes, or provide satellite operators with a responsible way to deploy into higher orbits.
Wheeler: I am aware of Government funding agencies just recently beginning to refuse funding or withdraw funding where sustainable use of space, including managing debris (defunct/failed satellites), cannot be evidenced by companies. I am also increasingly aware of investors being aware of sustainability issues (SSA and STM). Both aspects I believe will, albeit slowly, lead to commercial debris removal demands.
What are current policies on sharing of debris/satellite tracking information? What would be the obstacles to aggregating this information?
Brettle: There are no laws on rules compelling the sharing of data. There are, however, a number of guidelines, standards and groups which have attempted to improve the dissemination of object data. The UN COPUOS Long Term Sustainability guidelines are a recent example of the development of successful international consensus on a range of space safety topics, including safety of space operations, particularly sharing contact information, information on space objects and activities, sharing orbital data and observations, and joint analysis of conjunction events. Commercial groups too, such as CONFERS and The Space Data Association, which is an association of satellite operators who share operational data on spacecraft to enhance space safety, are also good examples of agreeing protocols and processes to exchange information. One of the largest obstacles is the distributed nature of SST across the globe, not so much in capability but in where the data should be held and how it should be maintained, verified and accessed for a truly global system. This is very much the problem the current issue of Space Traffic Management faces, and one that some organisations, including for example the US Dept of Commerce through their Open Architecture Data Repository are now trying to address.
Wheeler: I agree with the above answer. There needs to be further international confidence building measures to encourage the sharing of data and commercial companies need to be incentivised to share what they collate and track. Such incentives, guidelines and requirements can be encouraged, using several regulatory, licensing and policy tools, through national policy and institutional programme measures.
Almost all commercial satellite operators are using ground stations to command and control their satellites. Such a means of communication is hardly real-time. Do you think a more real time inter-satellite communication link will contribute to collision prediction and avoidance?
Brettle: Certainly the use of direct communication could indeed enhance space-safety, however, it is unclear whether inter-satellite links on their own (i.e. without ground interaction) would necessarily enhance space safety, or at least provide the most efficient route (in terms of fuel usage, for example) to ensure it. Screening analysis is done many hours in advance, taking into account the entire orbital environment, often more than once (i.e. to rescreen against new conjunction events) and therefore requires information flow from up-to-date catalogue data. In addition, spacecraft-to-spacecraft collision avoidance makes up only a tiny number of daily conjunctions, many between inert debris etc.
Capturing debris at LEO/MEO altitudes requires velocity and altitude changes. How do you propose to capture at these LEO/MEO altitudes? How much fuel will be needed to clear LEO/MEO to be economical? Who will pay for this collection?
Brettle: RPO in space are complex and advanced GNC (guidance, navigation and control) and propulsive capabilities are needed in order to undertake this. Astroscale's ELSA-d demonstration mission is launching in March 2021 and is a demonstration mission to mature such RPO capabilities. It will demonstrate the first semi-autonomous capture of a non-responsive, tumbling client. Beyond ELSA-d, Astroscale is developing commercial end-of-life services for satellites in LEO. Some further information about Astroscale's services can be found here.
In regards to who pays for debris removal services, I would look to the split of responsibility for clean-up that we see in other sectors whereby legacy waste is considered as an environmental challenge for which governments play an important role, and future debris is the responsibility of operators. We are at a unique time for the next generation of satellite operators, including many large constellations, that need to be incorporating provisions for end of life (and debris mitigation) into their satellite design. Future satellite operators must take responsibility. The technology is there to be prepared for future debris removal, service providers such as Astroscale are willing to provide end of life services, and we have a growing demand and expectation from the space community and beyond to act responsibly in space.
What are your thoughts on a space debris yard where the debris can be used for future in-space manufacturing?
Radtke: I can add two cents on that. In studies modelling long-term activities of the space debris environment, we did analyses for megaconstellations, including the possibility of disposing constellation satellites to so-called graveyard orbits above 2,000 km, thus including a debris yard for LEO objects in that altitude, with an altitude dispersion of circa 50 km. We found that after a certain time (depending on the number of objects deorbited there), a dynamic between the disposed objects develops that leads to a collisional cascade between them, creating almost a shell of fragments very slowly moving downwards towards LEO. Considering now, that the recyclability of current spacecraft is rather low and you would have to employ very sophisticated processes in orbit, which in part even do not work on-ground, I am very much against the deliberate creation of a debris yard, currently. I see this situation a bit different for geostationary orbit (GEO), where we ‘naturally’ already create a debris yard. So, instead of creating one, I think it makes sense looking into what materials from that yard can be used for future missions, and how this can be done technically (I know there are already concepts for re-using antennas of old GEO satellites). Once the tech and use cases have been proven in GEO, maybe it could be useful for LEO as well.
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