50,000 bits of space debris pose a risk, experts warn

"The fragments from the explosion spread around the Earth forming a band, which can be crossed by spacecraft with orbits that are quite different from the one of DMSP-F13," says Francesca Letizia. (Credit: University of Southampton)

Despite their tiny size, bits of space debris from a US meteorological satellite that exploded in orbit on February 3 could still pose a threat to other spacecraft and missions.

When the DMSP F13 satellite exploded, it produced an estimated 100 pieces of space debris that were detected using radar. In assessing how debris created by the explosion might affect their spacecraft, the European Space Agency and other satellite operators concluded that it would pose little risk to their missions.

Defense Meteorological Satellite System
Defense Meteorological Satellite System (DMSP) spacecraft. (Credit: US Air Force )

But new research suggests the explosion also created more than 50,000 small fragments larger than 1mm that couldn’t be detected using radar based on the ground.

“The fragments from the explosion spread around the Earth forming a band, which can be crossed by spacecraft with orbits that are quite different from the one of DMSP-F13,” says Francesca Letizia, a PhD student at University of Southampton who led the research.

What’s the collision risk?

For the study, published in the Journal of Guidance, Control, and Dynamics, researchers developed a new technique called CiELO (debris Cloud Evolution in Low Orbits) to assess the collision risk to space missions from small-sized debris.

They produced a collision probability map showing a peak in the risk at altitudes just below the location of the DMSP-F13 explosion. The map was created by treating the debris cloud produced by the explosion as a fluid, whose density changes under the effect of atmospheric drag.

“Treating the fragment band as a fluid allows us to analyze the motion of a large number of fragments very quickly, and much faster than conventional methods,” says Camilla Colombo, lecturer in the aeronautics research group. “In this way, the presence of small fragments can be easily taken into account to obtain a refined estimation of the collision probability due to an explosion or a collision in space.”

“This map can be used with a database of spacecraft or space debris objects to identify the targets that are most exposed, Letizia says. “For example, in the map we show the top ten spacecraft at risk from the fragments generated by the explosion of DMSP-F13 according to our model. They are mainly US and Russian satellites in sun-synchronous or polar orbits.”


The aim of the team’s research is to gain a deeper insight into the dynamics of small debris fragments and their contribution to collision risk in the Earth orbital environment.

“Even though many of these objects will be no bigger than the ball in a ballpoint pen, they can disable a spacecraft in a collision because of their enormous speed,” says Hugh Lewis, senior lecturer in aerospace engineering.

“In the case of the DMSP-F13 explosion, our work has shown that the introduction of a new cloud of small-sized debris into orbit will have increased the risks for other spacecraft in the vicinity, even if the risk from the larger fragments has been discounted.”

Source: University of Southampton