Space Debris: Small But Growing Problem
An anti-satellite missile test conducted by China in January brought widespread attention to a threat that many in the satellite industry have been keeping tabs on for years — space debris. More than 12,000 objects larger than 10 centimeters across are known to exist in Earth orbit, and satellite operators have as much, if not more, to fear from these small pieces of debris already in orbit than from missiles. The amount of debris will continue to grow as long as there are launches of satellites and other spacecraft, but companies can help minimize the problem.
Orbital debris, or space junk, is any man-made object in orbit around Earth that no longer serves a useful purpose. The largest pieces, those tracked by the U.S. Space Surveillance Network, now number 12,351, with 9,250 pieces categorized as rocket bodies and debris, and the other 3,101 pieces listed at payloads, according to NASA’s Orbital Debris Program Office based at Johnson Space Center, which keeps an “Orbital Box Score” each quarter. But even more exists, as the estimated population of particles between 1 and 10 centimeters in diameter is greater than 100,000, and the number of particles smaller than 1 centimeter probably exceeds tens of millions, according to NASA.
The debris, created by a half-century of space exploration, includes exploded boosters, burned out rocket motors, radioactive coolant, paint flakes, an astronaut’s camera, a toothbrush and even an old Russian spacesuit tossed overboard from the International Space Station, according to Bethesda, Md.-based Futron Corp. Because of their high orbital velocities, collisions with even small pieces of debris can involve considerable energy, and therefore pose a significant danger to spacecraft and astronauts. Data released by NASA in January 2006 indicates that orbital debris continues to be a growing problem for government and commercial satellite operators and manufacturers. From 2000 through 2005, the number of on-orbit objects larger than a bowling ball has increased by nearly 10 percent, with the United States and Russia each contributing approximately 40 percent of the total debris, according to “Orbital Debris Mitigation: Regulatory Challenges and Market Opportunities,” released by Futron in March 2006.
“With the increase in orbital debris that has been occurring, not just because of the as Chinese test but because of multiple events recently, there is an increased concern for LEO and GEO operators in terms of just having safe operations and what they can do to help the problem so they are not causing the problem as well” says Chad Frappier, space industry analyst for Futron.
While China’s anti-satellite system test created a bit more debris in orbit by reducing China’s Feng Yun 1C polar-orbiting weather satellite to a cloud of debris, it is everyday space operations that contribute the vast majority of the space junk in orbit. “The response to the Chinese test was probably overdone,” says Marco Caceres, senior analyst and director of space studies for Teal Group of Fairfax, Va. “Debris is going into space all the time. Satellites are maneuvered down and burn up in the atmosphere and spread into tiny pieces.
Often where there is a launch, the upper stage of the rocket eventually drops off before placing satellite into orbit. Much of that will burn in the atmosphere, but some will stay in orbit. … The Chinese test was not anything particularly alarming in itself,” he says. “The issue of space debris is alarming, particularly for commercial operators and especially at low-Earth orbit, where a lot of that debris will end up. There is still a chance to be hit, even though it’s a huge area. This has to be addressed as we put up more satellites.”
NASA identified five satellite breakups in the first two months of 2007 but no significant incidents since. In the third quarter, only a pair of minor satellites fragmentations were recorded by the Space Surveillance Network. For example, in July, the second stage of a Japanese H-2A rocket body that was launched in September 2006 experienced a second debris generation event, producing an estimated 15 pieces of new debris, although all but one of nine fragments officially cataloged reentered the atmosphere by the end of August, according to the October issue NASA’s Orbital Debris Quarterly News.
“Luckily, there hasn’t been the boom that we thought would happen in the 1990s,” says Caceres. “It’s a good thing that the Teledesics of the world never happened. The industry discovered it is cheaper and more efficient to provide services using big satellites at GEO rather than a lot of satellites at low-Earth orbit. If the Iridiums and Globalstars had shown a great plan to build satellites cheaply and provide service cheaply, then we would have had people swarming to these systems, and then there would be money to build even larger constellations.”
But there will be more satellites placed in orbit, particularly as the LEO constellations that are operating come up for replacement in the next few years, says Caceres. “Those old satellites will come to the end of their lifetime and either by themselves fall into the atmosphere and be burned up, or maneuvered carefully and then burn up. But there is a gradual, growing concern that if we don’t do something radically different then we’ll see exponential growth in debris. It won’t be a huge spike, but it may be that at some point in the next five to 10 years we will see noticeable growth in space debris.”
While the possibility of large numbers of LEO constellations contributing to space debris seems to have been avoided, the next generation of small satellites could be the next big contributor to the amount of debris, says Caceres. “There is still a possibility that there will be an explosion of nanosatellites, picosatellites and other tiny satellites launched by universities and research institutions”, he says. “We could then see literally hundreds or even thousands of those being launches, particularly when you have lots of launch vehicles that could launch them for next to nothing. The only thing keeping them from doing that today is that they are too expensive to launch. The day we see reusable launch vehicles being offered and launch prices at $10,000 per satellite, then every community college in the world with a science department will build minisatellites and launch them. You may have hundreds of satellites launched on one mission. That sounds pretty scary from an orbital debris standpoint.”
Governments around the globe are taking a more active interest in helping control the problem, says Frappier. At the end of 2005, the U.S. Federal Communications Commission increased its reporting requirements for an orbital debris mitigation plan, including post-mission disposal. “This is something all of the operators have to pay attention to a greater extent. For LEO, it looks at how you take care of your spacecraft within the 25 years that’s mandated — how quickly you de-orbit, ensuring there isn’t any onboard propulsion that would increase the likelihood of an explosion once you stop your operation. If the satellite dies, you have to make sure that before you lose control you can implement any end of life plan that you have so that the satellite is going to create as little debris as possible. For GEO it’s basically putting it in a junk orbit, or raising the orbit so it’s out of the way and isn’t crowding the increasingly closely located satellites in the GEO positions,” he says.
Other government agencies — NASA, the U.S. Department of Defense, the U.S. Federal Aviation Administration and the U.S. National Oceanic and Atmospheric Administration — also look at orbital debris issues in the licensing process for spacecraft and upper stages under their control. Russia, Japan, France, and the European Space Agency all have issued orbital debris mitigation guidelines, and space agencies around the globe formed the Inter-Agency Space Debris Coordination Committee to address the issue as well. Governments also have called on manufacturers and operators to address the issues, and many firms voluntarily adhere to measures designed to limit the growth of orbital debris, NASA says.
“I would say there is likely a small cost involved in this but definitely wouldn’t say it’s significant,” says Frappier. “Margins are always built in with whatever you are developing. There are methods for preparing your spacecraft for the end of life that would not be cost intensive. … I would guess that most operators place the satellites up have a general concept of the debris issue. Whether they are fully committed to solving the debris problem is questionable, but there is some concern out there. … Implementing the guidelines and doing something about the new stuff we put up will definitely help but it won’t solve the problem. There’s already enough debris up there where the chance of collision between different items can cause as much of a threat as any new items being launched.”
Along with commercial operations, NASA is concerned about debris and its potential impact on the International Space Station and the space shuttle. NASA Administrator Michael Griffin told the U.S. Senate Commerce, Science and Transportation Committee space subcommittee in March that the Chinese test temporarily doubled that probability that the station might be seriously damaged or destroyed by debris before receding. The growth of the space tourism market will put even more humans in space. “It’s one thing when debris hits a satellite and disables it, but it’s another when it hits a space station with humans, particularly in an area that will be increasingly populated with humans when you look at space tourism,” says Caceres. “The problem is not decreasing. The questions is whether it will increase fast or slow and the question is what is at stake — expensive satellites or human beings.”