Developing a cross-sector approach for effective space debris remediation and removal

From Space Tech Conference (http://www.spacetechexpo.com)

The accumulation of artificial debris in orbit around Earth is one of the greatest potential challenges to the future exploitation of space. In the six decades since the Space Age began, low-Earth orbit (LEO) in particular has become alarmingly crowded, with an estimated half-million objects, ranging in size from paint flecks to spent rocket stages and defunct satellites – any of which can present a significant hazard to satellites and manned spacecraft.

“Today on orbit we have a huge asset for humankind – more than a thousand active satellites and two space stations, and we expect those numbers to significantly increase,” explains Paola Leoni of Geneva-based Leoni Corporate Advisors (LCA). “We conservatively estimate that replacing today’s active satellites would cost around US$200 billion, and that’s just the pure assets – in terms of disruption and potential lost revenues the costs are much higher.”

Given the scale of the problem, it’s little wonder that the major space agencies, satellite manufacturers and ambitious startups are all working on different ways to address the challenge. At the moment, says Leoni, the agencies are providing the driving force: “The European Space Agency ESA has a commitment to provide funding for missions for active debris removal to maintain the current level of pollution, but NASA policy, while financing technology demonstration in ADR [active debris removal], is more concerned with pushing policy aimed at prevention and mitigation – on-orbit servicing, for example, can help to minimize the creation of new orbital debris.”

So far, the idea of routinely repairing and refitting satellites in orbit remains largely hypothetical – but several organizations are working to make it a reality. Leading the way is NASA’s Satellite Servicing Capabilities Office (SSCO), based in Greenbelt, Maryland.

Systems Engineering Manager Bo Naasz takes up the story: “We’re building systems for autonomous capture and servicing to extend the life of satellites rather than dispose of them, but of course there’s a dual use, and the things we’re doing for servicing could possibly be a way of doing remediation for large debris objects. NASA has a mandate to study remediation techniques, and J C Liou (Chief Scientist at NASA’s Orbital Debris Program Office) has done studies that suggest the problem could be remediated if you could get five large objects a year out of orbit.”

Naasz and the SSCO team are working on a proof-of-concept servicing mission called Restore-L, scheduled for launch in late 2019. “Restore-L is developing technologies that could be interesting for active remediation, but that’s not what our mandate is, he says. “We have a notional client, Landsat 7, for design reference purposes. Because it wasn’t built to be serviced we call it legacy – it doesn’t have cooperative visual markers that can be used to track it, or a grapple feature, so Restore-L will autonomously rendezvous using various sensors and algorithms, and then capture and berth it with a robot arm using the launch vehicle interface. We’ll then use the robot arm to gain access to its fuel valve and replenish its hydrazine supply.”

Keeping satellites in operation for longer might seem a promising way of reducing orbital clutter, but Alberto Accogli, Case Manager at Leoni Corporate Advisors in Milan, Italy, suspects that on-orbit servicing may only be commercially viable for the largest and most expensive satellites in geostationary orbit. “The trend we are seeing now with major constellations seems rather to focus on a shorter lifetime,” he says. People are looking towards a lower manufacturing cost for the satellite to have a more commercially viable business model. Servicing could be a good solution for geostationary satellites, but if those are the final destination of the journey, the real problem is getting there – the LEO orbit is like a sort of highway to your workplace, and if the highway is clogged you’ll never get to work.”

Another important element of the solution, then, must be to ensure that LEO satellites leave as little debris behind as possible at the end of their active lives. That’s a priority for Max La Rosa of satellite manufacturer Thales Alenia Space in Arlington, Virginia. “Right now only 70% of satellites in service actually incorporate a post-service disposal technique,” he says. “And that’s not enough – there are studies that show we need at least 90% of new satellites to meet the guidelines set by the agencies, and in conjunction we should remove five large objects a year from LEO just to keep the situation stable. Thales has an obvious interest in taking part, and we’re trying to pursue a two-stranded approach: active debris removal and what we call ‘design for demise’.”

For Thales, active debris removal missions are a natural spin-off from the on-orbit servicing of satellites. “There are really appealing commercial opportunities in that field and we’re trying to develop robotic capabilities for a space dock that could extend the life of orbiting satellites through refuelling, fault diagnosis and maintenance,” says La Rosa. “As we develop capabilities for docking, flexible capture, navigation and attitude control, then as a spin-off we can try to extend the use of these space docks to address the problem of orbital debris.”

In terms of ‘design for demise’, La Rosa explains, most of the work is going on at Thales’ plant at Turin, Italy. “As a satellite manufacturer we’re sort of the primary source for increasing the problem, so we’re also called to be in the first line of helping to solve it.”

While friction with the upper atmosphere alone can often be relied on to cause orbital decay and re-entry of satellites in LEO, it’s still important to ensure the spacecraft burns up completely before reaching the ground. “We have two approaches to the problem,” explains La Rosa. “At system level, we’re implementing techniques so that once a satellite enters its inactive phase, we have an active or passive mechanism to open it up and expose its inner parts to thermal flux, making it easier for the components to burn up. At component level, meanwhile, the problem is that with current technology there are some parts that may not burn up completely. Ultimately the approach is to change the material or design to increase the likelihood of complete burning.”

A big question mark still hangs over who will ultimately foot the bill. “Anything that is a common asset of humanity, like outer space, or the Antarctic for example, is very difficult to handle,” says Leoni. “There’s a common interest, but nobody wants to pay.”

“We’ve been working with the Graduate Institute of International Study at Geneva to look at policy making,” she continues. “They’ve been looking at the Kyoto Protocol on Climate Change – that kind of management of what economists call ‘externalities of the commons’. Are there lessons we can learn from other situations and import into the space industry? We need to address the problem in a systemic way, looking at the governance, the funding and the business model.”

LCA’s Accogli agrees: “People are working at every level on removal and prevention techniques. There are several solutions that can be applied depending on the type of incentive or regulation you’re going to face, but that’s the focal point: the regulation and incentives are the only way you can define a roadmap for the private sector to address the issue.”

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