[Via Satellite 06-22-2015] While recycling and sustainability efforts have taken hold on the earth’s surface, few of us stop to think about the pollution taking place outside of our atmosphere. With nearly 60 years of satellite launches behind us, left over debris is piling up in orbit faster than we would like to think and posing real and current dangers to operating satellites from every county and in every orbit.
“Scientific studies have shown that there’s a total of around 500,000 pieces of space debris in orbit that is between 1 and 10 cm in size, but too small to track regularly,” Brian Weeden, technical advisor at the Secure World Foundation told Via Satellite. “You can make the case that all of the human-generated space debris was created by satellites, because it’s all there as a result of launching and operating satellites.”
Weeden estimates that global organizations are tracking 22,000 human-generated objects in orbit around the Earth larger than 10 cm (roughly 4 inches), of which only about 1,500 are functional satellites. The rest of these remains represent dead satellites, spent rocket stages and other fragments, each of which could strike an operational satellite with the force of a hand grenade.
“Space debris bigger than several centimeters can completely destroy a satellite if they collide,” said Weeden. “Space debris between one and several centimeters can severely damage a satellite, perhaps rendering it inoperative or taking out key systems.”
While space platforms such as the International Space Station (ISS) are usually armored to protect against smaller pieces of space debris, and the larger satellites have the ability to maneuver around sizeable pieces of debris, it is possible that soon the area surrounding Earth could become so polluted that collision scenarios could be unavoidable. Because of this, the European Space Agency (ESA) alongside several other organizations and industry partners are stepping up efforts to cut down space debris through modernizing satellite design and fielding efforts to remove current debris from the most congested regions of space. These highly polluted areas mainly include Low Earth Orbit (LEO) or those regions up to 2,000 km, which are widely used for Earth observation and some telecom satellites.
“The number of collision avoidance maneuvers per satellite are dramatically increasing according to satellite operators,” said Luisa Innocenti, who heads up ESA’s CleanSpace initiative, which aims to limit and remove debris from orbit. In 2009 the Iridium 33 and Kosmos 2251 satellite collision created a significant amount of debris. Both Innocenti and Weedon see the possibility on the horizon of another large piece of space debris, such as a several-ton rocket stage, colliding with separate piece of debris to create an ever-growing cloud of harmful fragments. This is a reaction named the Kessler Syndrome and originally proposed by NASA scientist Donald J. Kessler in 1978.
“Some of the experts are saying that if we don’t start to remove large debris in very polluted orbits we will not be able to limit this chain reaction effect. The debris currently in orbit, particularly in the most polluted areas of orbit, will most likely stay there for 200 years. There is a high chance it will get hit by another piece of debris and create a cloud,” Innocenti said, noting that eventually even traditional maneuvers or armoring will not be able to limit the effects of a chain reaction that a large collision could trigger.
While international regulators have established more solid regulations regarding space debris in recent days, Weeden noted that voluntary guidelines and standards do exist. In 2007, the Inter-Agency Space Debris Coordination Committee (IADC) published a set of technical guidelines set to minimize the creation of new space debris, including the important standard that set the timeline for satellites to return to the atmosphere after reaching end-of-life at 25 years. But even with the United Nations endorsing these guidelines and several countries making debris mitigation laws mandatory over the last few years, Innocenti believes these recommendations still are not doing enough. Industry, she claimed, has been brushing off the guidelines and governments have excessively granted waivers to bypass them.
ESA is working with large system integrators, such as European primes Airbus and Thales Alenia Space — as well as small companies who may have innovative ideas — in the area in order to validate viable solutions, “so that in the evolution of their platforms they take this into consideration, not only the market perspective but also the end of life for the satellite,” she said. It is particularly important for ESA to work with industry on this, according to Innocenti, because she sees a tendency of industry to not want to apply the previous guidelines surrounding sustainable satellite designs that can result in higher costs, potentially dulling their competitive edge.
ESA aims to change that and is looking to attack the problem in two ways: mitigation and remediation.
“Mitigation is planning to stop pollution in the future, remediation is cleaning what we have already left up there,” said Innocenti.
Mitigation looks to work alongside industry to design and develop new satellites in a way that will return them to the atmosphere according to the IADC standard within 25 years of their end of mission. The ESA has recently put out a call for ideas regarding this initiative, known as their CleanSat technology program, which aims to tackle the following issues: propulsion for deorbiting or reorbiting; a “design for demise” approach to ensure satellites will definitely burn up in the atmosphere without the need for targeted reentry: drag augmentation devices such as sails: and propulsion and power passivation to remove leftover propellant and power down batteries to avoid explosions.
The agency also held a CleanSat workshop in March that worked to introduce and communicate new ideas surrounding the initiative at which deorbit sails were posed as a possible solution for satellites that lack propulsion. “[The sails] work to increase the friction so the orbit decreases. You increase the surface and create the friction that will drive it back within 25 years,” said Innocenti, noting that these could be particularly useful for small satellites.
ESA is also pursuing remediation efforts, which are equally if not more important.
“You can go up there, catch the debris with a net, robotic arm or a harpoon and then you have to drag it back into the atmosphere so that it either burns up in the atmosphere or falls into the ocean. This is what we are doing with the deorbit missions,” Innocenti explained. It’s still relatively early days for the mission, although the ESA has some ideas on paper and has been fielding some technology demonstrations for a net to catch the debris and has flown a series of parabolic nets to field how a net might work in microgravity. The agency is also working on a robotic arm to aid in remediation.
“We are also developing on some sensors because the problem is also that you launch a “chaser” that observes the target, the debris. The observations you use on the ground are not accurate enough to grab the satellite. You know where it is but you might not know exactly how it orbits or the state of the surface satellite after tens of years in space. So you need to develop some image processing before you grab it,” said Innocenti.
Ultimately, with the possibility of an incident ever closer, the ESA would like to see everyone in the satellite industry begin applying guidelines and regulations to not only stop future space debris, but also begin cleaning orbits.
“If we want to continue to launch we have to start managing what happens to the satellite at the end of life,” Innocenti said. “People will have to apply the regulations; it will be a disaster if they don’t.”
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