An artist’s view of Swarm, the European Space Agency’s first constellation of Earth observation satellites. Credit: ESA-P. Karel, 2013
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Pressure is mounting on the European Space Agency’s mission control center. A European Space Agency (ESA) satellite evaded a mysterious piece of space junk that was spotted just hours before a potential collision.
This means that an important step in the spacecraft’s continued journey to safer skies will have to be rescheduled immediately, as violent solar activity associated with the intensification of the solar cycle distorts Earth’s atmosphere and threatens to drag satellites out of orbit…
herd? from a bug?
not exactly – flock It’s actually the ESA’s job to detect Earth’s magnetic field puzzle. It consists of three satellites, A, B and C – known as Alpha, Bravo and Charlie.
What has happened?
A tiny piece of man-made trash orbiting our planet – known as outer space debris – Seen hurtling towards Alpha at 16:00 CET (10:00 EDT), on June 30. From the trajectory, a potential collision was predicted just eight hours later, just after midnight. The chance of the collision was big enough that Alpha needed it to get out of the way — fast.
constellation flock. Swarm is the European Space Agency’s first constellation of Earth observation satellites. Its mission is to uncover one of the most mysterious aspects of our planet: the magnetic field. Credit: ESA-P. Karel, 2013
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There’s trash in space?
that much. Fragments of old rockets and satellites and little debris left over from past collisions and chaotic avalanches swirl around our planet. Each small piece can cause major damage to the satellite, while a larger satellite can destroy the satellite and create massive amounts of new debris.
Is this the first time this has happened?
that day? Can. Once? Impossible. Each ESA satellite must perform an average of two evasive maneuvers per year – and that’s not counting all the warnings they receive that ultimately don’t require evasive action.
The image shows the Sentinel-1A solar array before and after the millimeter particle collision on the second panel. The diameter of the damaged area is about 40 cm, which corresponds to this structure with an impact fraction of less than 5 mm in size. ESA Credit
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Then what’s the problem?
Taking evasive actions – known as “Maneuver to avoid collision– This requires a lot of planning. You need to check that you are not moving the satellite to a new orbit that exposes it to the risk of further collisions and that you must calculate how to return to your original orbit using the least amount of fuel and losing as little scientific data as possible. .
The European Space Agency’s Space Debris Office analyzes data from the US space monitoring network and raises a potential collision warning to ESA’s flight control and flight dynamics team, usually more than 24 hours before the piece of debris approaches the satellite.
In this case, we only received eight hours notice.
Worse, the warning meant Team Swarm was now suddenly racing against two hours. Another maneuver was planned just hours after the potential collision and had to be aborted to give Alpha enough time to get away from the wreckage. This maneuver is also very time sensitive and must be completely re-planned, recalculated and executed in one day.
What are the other maneuvers?
Alpha and Charlie hike to escape the wrath of the sun. The two satellites will need to perform 25 maneuvers over 10 weeks to reach their new, higher orbits. One of Alpha’s maneuvers was planned for several hours after the possible collision.
Solar Cycle 25 Forecast, NOAA, July 2022. The number of sunspots on the Sun’s surface increases and decreases in a solar cycle of about 11 years. Our star is currently entering a very active period of the 25th solar cycle. credit: NOAA
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Wait, the sun kills the satellite?
Our sun enters a very active part of thesolar cycle‘ Direct. This activity increases the density of the Earth’s upper atmosphere. Satellites travel through “thicker” air, which slows them down and requires them to use limited fuel on board to stay in orbit. Alpha and Charlie move to a less dense part of the atmosphere where they can stay in orbit and hopefully collect years of scientific data and expand the mission!
What would have happened if not for this maneuver?
Alpha could be hovering over Charlie and the orbits of the two satellites would soon cross. This would make Swarm’s overall mission ‘intersection’, limiting its ability to do science until a set of maneuvers realigned Alpha and Charlie.
Is the herd okay now?
Team Swarm gets reaction time for the Olympic sprinter competition. Working with the Flight Dynamics team at ESA’s Mission Control Center, they plan and execute evasive actions in just four hours, and then re-plan and execute other maneuvers within 24 hours.
Alpha is now safe from crashing into the debris and has completed her ascent to safer skies with Charlie. But there’s a lot of debris out there, and it shows with little warning that it could threaten satellites.
The European Space Agency’s (ESA) Laser Measurement Station on Tenerife points its green laser at the sky. Credit: ESA
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How does your team keep up with all these crash alerts?
With new technology, more sustainable behavior and taking responsibility for space debris very seriously. ESA is build new technology To track more debris, expand New math tool This will help us plan, execute and act on the rapidly growing number of evasive maneuvers guiding rules Which limits the amount of new junk that we and other satellite operators add to the problem. We’re even looking at ways to capture larger debris and get it out of orbit using “outer claws“.
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