Spaceflight Insider

Europe’s Earth-observing Sentinel-1A satellite hit by space debris

The picture shows Sentinel-1A’s solar array before and after the impact of a millimeter-size particle on the second panel.

The picture shows Sentinel-1A’s solar array before and after the impact of a millimeter-size particle on the second panel. Photo Credit: ESA

The European Space Agency (ESA) reported its Earth-observing Sentinel-1A satellite was apparently hit by a space particle Aug. 23. The tiny speck of space debris struck one of the spacecraft’s solar panels, causing a small power reduction and slight changes in Sentinel-1A’s orientation and orbit.

According to ESA, controllers noticed something was wrong at 1:07 p.m. EDT (17:07 GMT) Aug. 23. That was when they detected a sudden small loss of power. In order to determine the cause of this anomaly, engineers decided to turn on the spacecraft’s onboard cameras to check if everything is fine with solar arrays.

The pictures acquired by the cameras, which were placed there to monitor the initial deployment of the solar wings, allowed engineers to identify that something indeed had hit one of the two power-generating panels.

Artist's rendering of the Sentinel-1A satellite.

Artist’s rendering of the Sentinel-1A satellite. Image Credit: ESA/ATG medialab

“In this case, assuming the change in attitude and the orbit of the satellite at impact, the typical speed of such a fragment, plus additional parameters, our first estimates indicate that the size of the particle was of a few millimeters,” said Holger Krag, head of the Space Debris Office at ESA’s establishment in Darmstadt, Germany.

He added that such small objects, like the one that struck the solar array, are not trackable from the ground. Current technology allows controllers to detect only debris greater than about two inches, which can be easily avoided in advance.

ESA has not yet determined the origin of the object that hit its satellite. It could be a micrometeoroid or a tiny part of a defunct spacecraft.

“Analysis continues to obtain indications on whether the origin of the object was natural or man-made,” Krag said, “The pictures of the affected area show a diameter of roughly 40 centimeters created on the solar array structure, confirming an impact from the back side, as suggested by the satellite’s attitude rate readings.”

More than 500,000 pieces of space junk are currently zipping around Earth. They are threats to spacecraft and communications systems. In May of this year, a tiny piece of space debris, possibly a paint flake or small metal fragment no bigger than a few thousandths of a millimeter across, struck one of the windows on the International Space Station.

Although last week’s hit affected the spacecraft’s onboard power and position, it did not interrupt the satellite’s routine operations and, according to ESA, the spacecraft is continuing its normal work.

Launched Apr. 3, 2014, Sentinel-1A is a polar-orbiting, all-weather, day-and-night radar imaging satellite for land and ocean services. It is one of the two Sentinel-1 spacecraft orbiting the Earth 180 degrees apart. The duo image the entire planet every six days.

Sentinel satellites are part of the Copernicus program, funded jointly by the European Commission and ESA. The project uses accurate and timely data to provide key information services to improve the way the environment is managed, to help mitigate the effects of climate change, and to ensure civil security.


Tomasz Nowakowski is the owner of Astro Watch, one of the premier astronomy and science-related blogs on the internet. Nowakowski reached out to SpaceFlight Insider in an effort to have the two space-related websites collaborate. Nowakowski's generous offer was gratefully received with the two organizations now working to better relay important developments as they pertain to space exploration.

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