A U.S. satellite is at risk of exploser and needs to be de-orbited from urgence.

– January 23, 2020 – Science

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DirecTV is alerting the federal authorities about one of its satellites, which has suffered a serious battery anomaly. It must be de-orbited without delay and placed in a scrap orbit, as it could explode at the end of February.

This is typically the kind of event that could feed into a B-series script. Except that this time, fiction has been overtaken by reality: at 36,000 km altitude, in orbit around the Earth, an American satellite could end up exploding because of a serious failure in the functioning of its batteries. If such a detonation were to occur, thousands of pieces of debris would be propelled in all directions, further polluting the Earth’s space environment and endangering other satellites in operation.

Fortunately, this cannot happen before February 25, 2020, when the spring eclipse season begins, which leaves a bit of leeway to act – a very relative leeway, however, because the manoeuvres will take… 21 days, which actually leaves just a few days – and move the spacecraft to a scrap orbit, where it will no longer be a risk to space operations. The waste orbit is nearly 300 km above the geostationary orbit, which is exactly 35,786 km above sea level.

L’ombre formée sur la Terre au cours de l’éclipse. // Source : ESO/L.Calcada (photo recadrée)

The shadow formed on the Earth during the eclipse // Source: ESO/L.Calcada (cropped photo)

A perilous rocker on faulty batteries

But how is it that eclipses can cause the destruction of a satellite? First of all, it is necessary to specify what these eclipse seasons are: in the case of satellites that have a stationary position, i.e. an orbit that moves at the same rate as the Earth’s rotation, the spring eclipse season runs roughly from February 26 to April 13. At that point, satellites can no longer rely on their Solar panels which are their primary source of power. They must then switch to their batteries while they are in the shadows.

But that’s when the batteries are fully operational. However, in the case of the Spaceway-1 satellite, they have not been operating normally since December 2019. The nature of the incident is not known: the documentation that was forwarded to the FCC – the Federal Communications Commission a U.S. agency that oversees space activities involving the United States – simply states that the spacecraft “suffered a major anomaly that resulted in irreversible thermal damage to its batteries.

“Boeing, the satellite manufacturer, has concluded, based on all available data, that there is no guarantee that the battery cells will withstand the pressures necessary to ensure the safe operation of the satellite during eclipse operations; rather, there is a significant risk that these battery cells could burst,” the paper, which was highlighted by SpaceNews, continued. In principle, therefore, there is no reason why the FCC should deny DirecTV, the company that operates this satellite and a subsidiary of telecom giant AT&T, emergency de-orbiting.

Des antennes opérées par DirecTV. // Source : Eric Lumsden

Antennas operated by DirecTV // Source: Eric Lumsden

Time is running out

But there’s a little subtlety: in principle, the FCC requires satellite operators to empty the propellant – the fuel they carry on board that they can use to correct their orbit or maneuver to avoid a possible collision – from the spacecraft going into the scrap orbit. Turns out Spaceway-1 still has 73 kilograms of propellant in the hold. And considering the calendar, DirecTV won’t have time to get rid of it before February 25th. Hence the urgent request to the FCC to skip a few steps.

“Now that its operational activities have ended, the space vehicle has sufficient power margin to avoid the use of batteries during operations in direct sunlight,” writes DirecTV. “However, use of the batteries during the eclipse is unavoidable and it is not possible to isolate damaged battery cells. The risk of catastrophic battery failure makes it urgent to completely de-orbit and decommission Spaceway-1 before the start of the eclipse season on February 25. The ball’s in the FCC’s court.

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