A European satellite that has been scrambling to escape premature death in Earth’s atmosphere due to bad space weather has narrowly avoided a collision with a random piece of space debris.
Swarm, the satellite system that had a terrible day recently, is actually composed of three satellites A (Alpha), B (Bravo), and C (Charlie). To perform their mission of studying Earth’s magnetic field, the three satellites must fly in close coordination and maintain distance from one another.
So there was a bit of panic when the Swarm team got notice that Alpha had a very high likelihood of getting hit by an unknown piece of space debris in less than eight hours.
Swarm has been climbing to a higher altitude after it experienced increased drag due to changes in the density of the upper layers of Earth’s atmosphere that occurred in response to solar activity.
One of the 25 maneuvers planned to avoid this fate for Alpha was to take place only a few hours after the satellite was forced to dodge this incoming space debris. The impeding dodge put a hold on that step in the process, but holding off for too long would cause issues in maintaining satellite formation.
The maneuver, which intended to raise the satellite’s altitude by 28 miles (45 kilometers) over a 10-week period, had to be suspended after a piece of space debris raised an alarm at mission control.
So the ESA engineers and scientists did what engineers and scientists occasionally have to do when projects are threatened – they “got to work with a reaction time to rival an Olympic sprinter,” according to a press release. They had planned and executed an orbital change within four hours to avoid the debris. Less than twenty-four hours later, they performed an updated maneuver to put Swarm back on track to get out of the slowly thickening atmosphere.
Avoiding space debris will only grow in importance to satellites, lest we become a civilization affected by Kessler syndrome. The technology and resources are in place to ensure that collision with space debris doesn’t happen. Now we must continue to utilize them correctly, no matter how bad the weather is.
The incident, which happened on June 30, according to a European Space Agency (ESA) statement (opens in new tab), required the ground control team to immediately perform an avoidance maneuver to dodge the piece of debris.
According to ESA, the incident highlights the precarious situation in Earth orbit. The problem of space debris has been getting worse and worse, with hundreds of thousands of fragments large enough to kill a satellite currently known to be hurtling around the planet.
Avoiding space debris is common among all satellites – on average, an ESA satellite has to dodge about two pieces per year, with many, many more potential warnings coming down the pipeline from ESA’s Space Debris Office and the US Space Surveillance Network. Usually, those warnings come with at least 24-hour notice, so an eight-hour timeline was much tighter than usual.
As the density of the upper atmosphere increases, satellites have to plod through the thickening gas as if they were flying against wind. Satellite operators therefore need to use on-board propulsion to prevent the satellites from spiraling back down to Earth.
Part of the reason that time crunch matters is how difficult it is to pick where and how to dodge. Considerations like other potential collisions, fuel consumption, the safe distance needed from the space debris, and many other factors are all included in the decision-making process. Making those decisions in a few hours would be stressful for anybody.
On top of that, experts predict that these same air density changes will lead to a temporary increase in the amount of debris fragments in low Earth orbit, as those fragments face the same increased drag as the satellites, Hugh Lewis, a professor of engineering and physical sciences at the University of Southampton in the U.K. and one of Europe’s leading space debris experts, told Space.com in an earlier interview. Unlike the satellites, these fragments are completely out of control.
Right now, the Sun is undergoing an increase in solar activity as part of one of the spikes in its solar cycle, creating more drag for Swarm than it had previously been affected by.
Over the medium term, this could have caused Alpha and Charlie to switch places in their orbits, effectively stopping the mission from being able to collect data. Even worse, if left unchecked, the satellites themselves could have been slowed enough to a point where they were wholly dragged out of the sky.