Sentinel-1A Satellite Takes A Direct Hit From Millimetre Size Particle

One of the worst things that can happen during an orbital mission is an impact. Near-Earth orbit is literally filled with debris and particulate matter that moves at very high speeds. At worst, a collision with even the smallest object can have catastrophic consequences. At best, it can delay a mission as technicians on the ground try to determine the damage and correct for it.

This was the case when, on August 23rd, the European Space Agency’s Sentinel-1A satellite was hit by a particle while it orbited the Earth. And after several days of reviewing the data from on-board cameras, ground controllers have determined what the culprit was, identified the affected area, and concluded that it has not interrupted the satellite’s operations.

The Sentinel-1A mission was the first satellite to be launched as part of the ESA’s Copernicus program – which is the worlds largest single earth observation program to date. Since it was deployed in 2014, Sentinel-1A has been monitoring Earth using its C-band Synthetic Aperture Radar, which allows for crystal clear images regardless of weather or light conditions.

The picture shows Sentinel-1A’s solar array before and after the impact of a millimetre-size particle on the second panel. The damaged area has a diameter of about 40 cm, which is consistent on this structure with the impact of a fragment of less than 5 millimetres in size. Credit: ESA
Picturing obtained by one of the Sentinel-1A’s onboard cameras, showing the solar array before and after the impact of a millimeter-size particle on the second panel. Credit: ESA

In addition to tracking oil spills and mapping sea ice, the satellite has also been monitoring the movement of land surfaces. Recently, it provided invaluable insight into the earthquake in Italy that claimed at least 290 lives and caused widespread damage. These images were used by emergency aid organizations to assist in evacuations, and scientists have begun to analyze them for indications of how the quake occurred.

The first indication that something was wrong came on Tuesday, August 23rd, at 17:07 GMT (10:07 PDT, 13:07 EDT), when controllers noted a small power reduction. At the time, the satellite was at an altitude of 700 km, and slight changes in it’s orientation and orbit were also noticed.

After conducting a preliminary investigation, the operations team at the ESA’s control center hypothesized that the satellite’s solar wing had suffered from an impact with a tiny object. After reviewing footage from the on-board cameras, they spotted a 40 cm hole in one of the solar panels, which was consistent with the impact of a fragment measuring less than 5 mm in size.

However, the power loss was not sufficient to interrupt operations, and the ESA was quick to allay fears that this would result in any interruptions of the Sentinel-1A‘s mission. They also indicated that the object’s small size prevented them from advanced warning.

Artist's impression of Sentinel-1A, showing its solar panels fully deployed. Credit and copyright: ESA–P. Carril, 2014
Artist’s impression of Sentinel-1A, showing its solar panels fully deployed. Credit and copyright: ESA–P. Carril, 2014

As Holger Krag – Head of the Space Debris Office at ESA’s establishment in Darmstadt, Germany – said in an agency press release:

“Such hits, caused by particles of millimeter size, are not unexpected. These very small objects are not trackable from the ground, because only objects greater than about 5 cm can usually be tracked and, thus, avoided by maneuvering the satellites. 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.

While it is not clear if the object came from a spent rocket or dead satellite, or was merely a tiny clump of rock, Krag indicated that they are determined to find out. “Analysis continues to obtain indications on whether the origin of the object was natural or man-made,” he said. “The pictures of the affected area show a diameter of roughly 40 cm created on the solar array structure, confirming an impact from the back side, as suggested by the satellite’s attitude rate readings.”

In the meantime, the ESA expects that Sentinel-1A will be back online shortly and doing the job for which it was intended. Beyond monitoring land movements, land use, and oil spills, Sentinel-1A also provides up-to-date information in order to help relief workers around the world respond to natural disasters and humanitarian crises.

The Sentinel-1 satellites, part of the European Union’s Copernicus Program, are operated by ESA on behalf of the European Commission.

Further Reading: Sentinel-1

Watch Live: Next-Gen Environment Satellite Aims For Space

UPDATE, APRIL 4: The satellite safely made it into space! Watch the launch replay and successful satellite separation here.

Just in case you aren’t already in French Guiana, here’s your chance to watch a European environment radar satellite take a rocket ride. Tune into the webcast above to see Sentinel-1A’s launch. If the schedule holds, the launch will be at 5:02 p.m. EDT (9:02 p.m. UTC) on April 3, 2014. Watch live above!

ESA heralds Sentinel-1 as a “new era in Earth observation” because the satellite duo (yes, it will be eventually two satellites) will vastly improve their ability to send out information on natural disasters and quick-moving Earth observation events. Sentinel-1 will in fact be the first of a satellite series feeding into the same information system.

Once the second half of the duo launches in 2016, Sentinel-1 will have a wide swath of geographical coverage, could go to the same areas quickly, and would send data out quickly. Repeatable and rapid Earth observations will bring data quickly into the hands of the authorities who could make decisions about evacuations and other things. 

This information will be fed into Copernicus, a new system that will co-ordinate all of the Sentinel satellites for users to gain information.

“The Sentinels will provide a unique set of observations, starting with the all-weather, day and night radar images from Sentinel-1 to be used for land and ocean services,” ESA stated in an explanation about Copernicus.

“Sentinel-2 will deliver high-resolution optical images for land services and Sentinel-3 will provide data for services relevant to the ocean and land. Sentinel-4 and Sentinel-5 will provide data for atmospheric composition monitoring from geostationary and polar orbits, respectively.”

And here are a few of the other applications ESA foresees it would be useful for: sea-ice measurements, looking for oil spills, tracking ships, flagging land with “motion risks” and also doing mapping for the forestry industry.

As far as the webcast, there’s a schedule of speeches and events beforehand at the European Space Agency’s space operations center in Darmstadt, Germany. Be sure to tune in a bit earlier at 3:30 p.m. EST (7:30 p.m. UTC) to see the ceremonies.

Source: European Space Agency