The University of Southampton

Space junk threatens future satellites

30 October 2009

Close encounters between objects in orbit could increase by 50 per cent in the next decade and 250 per cent in 50 years, scientists at the University of Southampton have predicted.

An increase in space debris means satellite operators will have to step up screening and tracking measures to avoid collisions, according to Dr Hugh Lewis of the University's School of Engineering Sciences.

Space debris, which includes fragments of rockets and spacecraft, represents a significant risk to satellite operations because of the possibility of damaging or catastrophic collisions. The Southampton research explored the impact of the increase in debris on the management of satellites.

The amount of space debris has increased by 40 per cent in the past four years, although 'space-faring' nations have now introduced measures to limit the amount of new debris they produce. According to NASA figures, there are approximately 19,000 objects larger than 10cm, with estimates of more than 500,000 smaller pieces, in orbit. Services, such as the industry database SOCRATES, are used by spacecraft operators to avoid the potentially catastrophic consequences of close approaches and to mitigate risk.

Dr Lewis and colleagues Dr Graham Swinerd and Rebecca Newland, also from the School of Engineering Sciences, used SOCRATES data from 2005 to 2009 to understand the relationship between the amount of debris produced by recent fragmentation events and the number of occasions spacecraft have come within five kilometres of each other or debris. Using the predicted growth in the debris population over the next 50 years, the team then estimated the number of close approaches that are set to occur.

Compared with the 13,000 close approaches per week that occur now, their projection showed that there will be 20,000 a week in 2019 and more than 50,000 a week in 2059.

Dr Lewis says: "Previous studies of the future debris environment have often focused on the evolution of the gross characteristics, such as the number of objects or the number of collisions, without necessarily considering the effect the changing environment has on satellite operations.

"In this work, we have explored the impact that an increasing debris population might have on close approach screening results, and decisions relating to tracking campaigns and collision avoidance manoeuvres.

"The results suggest a 50 per cent increase in the number of close approaches in the next 10 years and a 250 per cent increase in the next 50 years. Satellites and constellations of satellites, especially those in high-risk altitude bands, will require significant operational support as a consequence of these new close approaches.

"In spite of tracking campaigns to reduce uncertainty, each satellite is likely to require at least one collision avoidance manoeuvre in the next 10 years, and five manoeuvres in the next 50 years."

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