spaceSpace and Physics

A European Satellite Just Had To Dodge An Unknown Piece Of Space Junk In Orbit


Jonathan O'Callaghan

Senior Staff Writer

CryoSat-2 was launched in 2010. ESA/P. Carril

A European satellite had to be moved on Monday, July 9, when a piece of space debris came a little too close for comfort, as picked up by

The CryoSat-2 spacecraft, which orbits at a height of 700 kilometers (435 miles) and travels at 27,000 kilometers per hour (17,000 miles per hour), was found to have a 1 in 10,000 chance of colliding with an unknown object. So to avoid it, engineers fired the thrusters on the satellite, ensuring it safely passed 120 meters (400 feet) above the piece of debris.


“Chances of collision went [up to] 1/10000 so a Collision Avoidance Manoeuvre (CAM) was performed!” ESA said on Twitter.

“The unknown object, or 'chaser', was approaching from behind & below CryoSat, so spacecraft operations engineers sent the commands, CryoSat 2 fired its thrusters, and it passed safely, 120 metres [390 feet] over the unknown [chaser].”


ESA noted this was actually the second time this year CryoSat-2 has had to avoid space debris, and the 14th CAM in total since the satellite launched in 2010. The team will now perform another maneuver tomorrow to get the spacecraft back into its original orbit.

CryoSat-2 is an Earth observation mission, tasked with measuring the thickness of polar sea ice and monitoring changes in the ice sheets of Greenland and Antarctica. The first satellite in the program was lost during a launch failure in 2005, meaning CryoSat-2 is technically the first satellite in this mission, despite the name.


The spacecraft flies at an angle of 88 degrees from north to south, which allows it to get a view of both poles. It uses an instrument called a Synthetic Aperture Interferometric Radar Altimeter (SIRAL) to measure changes in the ice, bouncing radar off the surface to detect differences as small as 1 centimeter (0.3 inches).

This latest incident highlights the problem of space junk, though. Last week a report from ESA found that almost 20,000 pieces of space junk were orbiting the planet, with a combined mass of 8,135 tons. This has forced engineers to look into ways of removing space junk.

One obvious way is to ensure satellites are directed to burn up in the atmosphere at the end of their life. But for those that lose contact with the ground, or smaller pieces that can’t be controlled, there are a number of removal methods being tested including a net or harpoon.

Even the International Space Station (ISS) has to be moved on occasion to avoid debris. And there have been a few collisions between satellites and debris in the past – although thankfully for CryoSat-2, this wasn’t one of them.




spaceSpace and Physics
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