65th International Astronautical Congress | Cubesat Revolution, Spotty Compliance with Debris Rules Fuel Dangerous Congestion in Low Earth Orbit
TORONTO — The world’s rocket and satellite owners are doing a mediocre job in respecting debris-mitigation rules, especially in low Earth orbit, where debris proliferation is the ugly underside of the fast-growing small-satellite and microsatellite market, government and industry officials said.
Twelve years after a grouping of the world’s space powers published what it thought were modest guidelines asking that satellite and rocket owners take steps to remove their hardware from low Earth orbit within 25 years after its mission, a sizable portion of them are paying little attention to the rule.
The French space agency, CNES, studied 12 years of debris-mitigation practices, 2000-2012, and found that 40 percent of satellites and rocket bodies are left in low Earth orbit at altitudes high enough to make it impossible for them to re-enter within the 25-year window specified in the rules.
“There is no clear trend toward improvement over the years,” said Juan Carlos Dolado Perez of CNES, who presented the results of the study at the 65th International Astronautical Congress here. “There is still a real effort to be done.”
Raising or lowering a satellite or rocket stage’s orbit to remove it from the busiest orbital highways takes fuel, which a satellite owner would prefer to use to extend mission life. Launch services providers would like to use that energy to carry more satellite payload.
Bad enough when satellite operations deal mainly with multimillion-dollar spacecraft, the situation threatens to get worse as Moore’s Law — which predicts that the number of transistors on a computer microprocessor will double every two years or so — enables ever-smaller nests of technologies to be placed on small-satellite platforms for a price that universities and startup companies can afford.
The owners of some of these satellites have not registered with the International Telecommunication Union even though the spacecraft are broadcasting signals, creating potential interference issues. Many are launched in groups, on shoestring budgets, with no onboard propulsion to assure they can be sufficiently lowered at the end of their operating lives to meet the 25-year rule.
“Most [debris] mitigation guidelines were not meant for these very small satellites,” said Heiner Klinkrad, director of the European Space Agency’s Space Debris Office in Darmstadt, Germany. “Cubesats are slipping through the net. They are all going to the same altitudes, which means they will constitute a kind of curtain, which increases collision risks.”
Objects deployed from the international space station, or near the station’s 400-kilometer altitude, will naturally be drawn into Earth’s atmosphere and destroyed well within 25 years. It is at higher altitudes, above 500 kilometers, where lies the problem.
“Many of the cubesats are going to altitudes higher than 500 kilometers,” said Marcello Valdatta of the University of Bologna, Italy. He said the rules regarding cubesats — a generic term for satellites usually weighing less than 2 kilograms — are vague.
The only solution may be to design an inexpensive, lightweight “plug and fly” kit that would deploy at the end of the cubesat’s life, creating drag and forcing its atmospheric re-entry within 25 years.
Several researchers, presenting the results of their analysis of what has been happening with the microsatellites launched in recent years — the relatively high failure rates in orbit, the mounting debris — adopted an almost apologetic tone, saying they did not want to smother a young and dynamic industry with regulations.
“It’s not about bashing the cubesat community at all,” said Hugh G. Lewis of Britain’s University of Southampton, who studied the orbits and disposition of cubesats in recent years as part of a project funded by the European Commission’s Framework Seven Program for Research.
Lewis’ data came from’s catalog of orbital objects and from work done by T.S. Kelso, senior research astrodynamicist at Analytical Graphics’ Center for Space Standards and Innovation in Colorado Springs, Colorado.
The data point to more than 350,000 “conjunctions,” or close encounters in which a cubesat and another space object came to within 5 kilometers of each other, between 2005 and June of this year. As the number of cubesats in orbit has increased, so has the number of conjunctions involving them.
Only 1 percent of conjunctions in 2007 involved a cubesat, Lewis said. For the first nine months of 2014, cubesats accounted for 5 percent of the total.
Depending on a satellite’s size and shape, it is all but certain to remain in orbit more than 25 years after retirement if its altitude is above 650 kilometers.
Some 160 cubesats were launched between 2003 and 2013. Their launch rate has increased sharply since then. One-third of them operate in orbits that are too high to meet the 25-year rule, and in many cases they could not meet a 50-year rule, Lewis said.
Phil Smith, senior analyst at the Tauri Group space consultancy of Alexandria, Virginia, in a presentation on the dynamism of the cubesat sector — a 300 percent increase in launches between 2012 and 2013, and a 63 percent increase, to 150 satellites, expected in 2014 — agreed that many of these satellites are heading into orbits that are inconsistent with the 25-year rule.
Several speakers said cubesat owners will need to come up with a debris-mitigation solution on their own, or face the risk that an in-orbit collision in a popular orbit for weather or science or military satellites leads to government regulations that could cripple the industry.
The proliferation of cubesats and nanosats was also a subject of discussion at the Advanced Maui Optical and Space Surveillance Technologies conference in Maui, Hawaii, in September, where experts considered the question of whether a licensing regime is needed.
“We have to operate safely, but not stifle the innovation,” said Josef Koller, space policy adviser for the deputy assistant secretary of defense for space policy.
U.S. Strategic Command, which provides space situational awareness information for the Defense Department, has said it can track items as small as about 10 centimeters, the standard length of the side of a cubesat. While a new ground-based S-band radar known as the Space Fence is expected to enable Strategic Command to track even smaller objects, it is not yet clear how many cubesats would be added to the catalog.
One issue is that because cubesats are often launched in tandem into close-proximity orbits, it can be difficult to distinguish one from another.
The Secure World Foundation, a nonprofit organization dedicated to space sustainability, plans to develop a handbook for new operators in the next year — rules of the road that, if adopted by organizations from universities to governments, would help reduce the threat.
The book is necessary because some cubesat owners “may not have a lot of experience in doing this in a responsible manner,” said Brian Weeden, technical adviser at the Secure World Foundation.