The recently concluded 65th International Astronautical Congress in Toronto brought troubling news that a significant percentage of satellite and rocket operators still are not complying with voluntary space debris mitigation guidelines, and that the growing popularity of cubesats and nanosats is compounding the problem.
According to a study by the French space agency, CNES, some 40 percent of satellites and rocket bodies launched from 2000 through 2012 were left in orbits that will not ensure their atmospheric re-entry within 25 years as specified by guidelines first adopted in 2002 by the Inter-Agency Space Debris Coordination Committee (IADC), which is made up of the world’s leading spacefaring nations.
“There’s no clear trend toward improvement over the years,” CNES’s Juan Carlos Dolado Perez said in presenting the results of the study at the conference. In other words, the findings were not skewed by data from the early years, before practice would have had time to catch up with the newly adopted guidelines.
A new and fast-growing contributor to hazardous clutter, particularly in low Earth orbit, is cubesats — often measuring 10 centimeters on a side and weighing just a few kilograms — that are literally being launched by the dozen these days. Fueled by advances in microelectronics and in many cases by Silicon Valley venture capital, the cubesat revolution is dramatically expanding applications for space systems while toppling the long-associated cost barriers.
It is clear from the CNES study that everyone needs to do a better job of preserving the space environment. A recent example of just how bad it is already is Europe’s Sentinel 1A environment-monitoring satellite, which, after being left in a lower than expected orbit, had to make eight collision avoidance maneuvers during its climb to its operating orbit.
The cubesat sector deserves special attention, however, both because it is relatively new and thus not as attuned to the problem as longtime players, and because it is populating low Earth orbit at a dizzying rate. According to another study presented at the conference, some 150 cubesats will be deployed during 2014 when all is said and done, a 63 percent increase over 2013, which saw a threefold increase over 2012.
Moreover, the number of conjunctions — or relatively close orbital passes — involving cubesats is growing rapidly. In 2007, cubesats accounted for just 1 percent of the total; for the first nine months of 2014, that percentage was up to 5.
Most cubesats, including those deployed from the international space station, are placed into orbits with an altitude of 500 kilometers or less, making it likely that they will re-enter within 25 years. But a significant portion — including a third of the roughly 160 cubesats launched from 2003 to 2013 — operate in higher orbits that make it impossible for them to meet the 25-year guideline. Cubesats typically do not have onboard propulsion, meaning their orbits cannot be lowered at the end of their mission to ensure a timely re-entry.
Speakers at the conference were careful not to criticize the cubesat sector, which has become an important source of innovation in the space enterprise. Part of the reason is they are wary of regulations that might curb the appetite for cubesats and other nanosatellites among universities and entrepreneurial companies.
That puts the onus on cubesat stakeholders — those who build, operate and launch them — to be proactive with measures to reduce the debris threat. One option is to design relatively inexpensive hardware that would deploy at the end of a cubesat’s mission to increase drag to ensure that it re-enters within 25 years. This hardware could be sold in kits, the inclusion of which could mandated in launch agreements, much like buyers of certain household appliances such as dishwashers must also buy accessories to get them professionally installed.
Another, though perhaps more expensive, option is to more aggressively pursue development of cubesat propulsion systems. These systems would make cubesats more capable, in addition to giving their owners a means to dispose of them at the end of a mission.
In the meantime, the IADC should develop debris mitigation guidelines tailored specifically to cubesats, whose proliferation was not considered in drafting the current rules. This will be helpful to cubesat and nanosat project planners, while sending the message that they too have a stake in preserving the orbital environment.
Individual governments could set the proper example by insisting that taxpayer-funded nanosatellite projects include satellite end-of-life disposal plans. This could have the added benefit of helping drive the development — and ultimately reducing the cost — of debris mitigation technologies and strategies.
In short, there are plenty of measures the cubesat community can and should be taking to minimize its contribution to orbital clutter. Allowing the problem to fester could invite government-imposed regulation, potentially at the cost of sapping the energy from one of the space industry’s most dynamic sectors.