The recent popularity of building and launching small simple research satellites, known as CubeSats, could lead to hazards for all space users unless preventive measures are taken.
Speaking at the 65th International Astronautical Congress in Toronto, Southampton University researcher Hugh Lewis pointed to the inability of CubeSats, most of which are around 10x10x10cm in size, to manoeuvre to avoid in-orbit collisions.
This lack of manoeuvrability means the CubeSats can’t be safely disposed of at the end of their lifetime either by being sent to burn in the Earth’s atmosphere or pushed up into the so-called graveyard orbit.
Tens of CubeSats thus remain in the Earth’s orbit hurtling at enormous velocities, posing risk to other spacecraft.
"To reduce the risks, some effort is needed to engage with the growing small satellite community,” Lewis said. “All space users, not just those in the CubeSat community, who are taking the right steps should be encouraged to continue and, ultimately, lead on sustainable practices and debris mitigation activities.”
Since 2003, about 160 CubeSats have been launched around the world. The technology gained popularity among smaller companies, enabling them to break into the space data and communications industries.
Although international guidelines require satellites to deorbit within 25 years, more than a third of the existing CubeSats are predicted to remain in orbit for a longer period of time. That is especially the case of satellites launched into higher orbits from where the descent back to the Earth takes longer, potentially several hundreds of years.
"By far the greatest risk comes from those with long lifetimes at altitudes of about 750km,” Lewis explained. “If CubeSats continue to be launched into long-lived orbits without any means of disposing of them, then they will contribute to the growing space debris hazard.”
Since 2005, CubeSats have been involved in more than 360,000 close approaches of less than 5km with other orbiting objects.
Lewis and his team used their Debris Analysis and Monitoring Architecture to the Geosynchronous Environment (DAMAGE) model to simulate three future CubeSat launch traffic scenarios until the year 2043. By comparing these with close approach data from 2005 to 2013, the team found CubeSats are estimated to be involved in millions of close approaches over the next 30 years, with a handful leading to a collision.
Analysis of the close approaches found that most of the collision risk from CubeSats comes from high-speed encounters with large spacecraft. In addition, many of these encounters were in Sun-synchronous orbits that are popular with remote sensing and Earth science satellites.
“It's probably a matter of changing the perceptions of the risks and helping them (the operators) to understand that there is a collective responsibility to ensure that outer space activities are sustainable so that future generations have the same opportunities to use space as we do."