ESA's Sentinel-1A satellite has beenstruck by a space particle while orbiting at a height of 700 km (435miles) above the Earth. Theparticle is estimated to have measured only a few millimeters across,yet the impact caused a dent in the solar panel of the spacecraft 40cm (15.7 inches) in diameter. It is not yet known whether the debriswas manmade or natural in origin.
The Sentinel-1A satellite is taskedwith monitoring the health of Earth's oceans, highlighting changes inthe use of land, and providing data for emergency response efforts inthe wake of natural disasters, as part of the European Union'sCopernicus Program.
At 17:07 GMT August 23, mission operators detected a minute drop-off in power outputfrom the satellite's twin solar panels, which, combined with a slightalteration in the probe's orbital trajectory, indicated that thespacecraft may have been struck by a piece of orbital debris. Toconfirm the impact, the team decided to switch on the probe's side-facing cameras.
The cameras had been mounted on eitherside of the satellite in order to provide visual confirmation thatSentinel-1A's delicate solar arrays had successfully deployed in thehours following its launch. Having completed their initial taskadmirably following orbital insertion in April 2014, missioncontrollers had deactivated the cameras, with no intention of turningthem back on again.
Following the events of the 23rd, thecameras were commanded into life once more, granting technicians aclear view of where the particle had struck the 10 m (32.8ft) solar array, leaving the large dent in the process.
"Such hits, caused by particles ofmillimeter size, are not unexpected," comments Holger Krag, head ofESA's Space Debris Office in Darmstadt, Germany. "These very smallobjects are not trackable from the ground, because only objectsgreater than about 5 cm can usually be tracked and, thus, avoided bymaneuvering the satellites."
Thankfully, Sentinel-1A has emergedfrom the ordeal intact, and able to continue its mission unhindered.However, space debris represents a very real problem for those hopingto operate in the increasingly crowded environment of low-Earth orbit(LEO), which is frequented by swarms of telecommunication, militaryand basically every other form of satellite.
Decades of orbital operations has ledto over 500,000 pieces of manmade debris larger than a marblewhizzing around in LEO. This number gets a lot higher the smaller thegauge of debris. No matter how small a piece of space trash is, whenit's moving at over 17,500 mph (28,162kmph) it is going todamage whatever it hits, with potentially catastrophic results.
These collisions do happen. In the pastwhole satellites have collided with one another, creating vast cloudsof debris capable of crippling a spacecraft, or in a worst-casescenario, a manned outpost such as the International Space Station.
Space agencies across the globe areaware of this growing issue, and regulations have been put in placerequiring satellites and launch vehicles to be designed with a thecapacity to either de-orbit themselves, or to push themselves into adistant "graveyard" orbit.
There are also numerous concepts underdevelopment with the potential to de-orbit the multitude of debrisand derelict satellites already present in LEO. Netting andharpooning space junk are two techniques that could be employed tode-clutter LEO, while using gas clouds and lasers to zap the orbitaltrash are also under consideration.
Hopefully, these new technologies willreduce mankind's inevitable footprint in orbit, and avoid a Kessler effect, whereby debris in LEO causes a cascade of collisions thatwould render the operation of satellites in certain orbitsimpossible.
Source: ESA
