The spacecraft-killing anomaly over the South Atlantic

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EXCERPTS: . . . thanks to a quirk in Earth’s magnetic field, a region called the South Atlantic Anomaly (SAA) regularly exposes orbiting spacecraft to high levels of dangerous particles. Over the years, the SAA has been responsible for several spacecraft failures and even dictates when astronauts can and can’t perform spacewalks. As the space around Earth becomes filled with an increasing number of craft, what does the SAA mean for the future of spaceflight?

[...] Earth’s magnetic field itself extends tens of thousands of miles into space, and the area in which the magnetic field interacts with charged particles is called the magnetosphere. The magnetosphere protects life on Earth by deflecting solar wind and cosmic rays, which would otherwise strip away much of the atmosphere, among other detrimental effects.

But not all incoming particles are deflected. Some instead become trapped in two doughnut-shaped regions called the Van Allen Radiation Belts. The inner of the two Van Allen Belts sits an average of about 400 miles (645 kilometers) above the surface of Earth. But the Van Allen Belts are located symmetrically about Earth’s magnetic axis, which is not perfectly aligned with Earth’s rotational axis. The result: The Belts’ distance from Earth’s surface varies around the globe.

The SAA is the region where the inner Van Allen Belt dips closest to Earth — a mere 120 miles (190 km) above the surface. At that altitude, spacecraft in low Earth orbit (LEO) may periodically pass through the SAA, exposing them (and, in the case of manned missions, their occupants) to large amounts of trapped high-energy particles — i.e., potentially damaging doses of radiation.

[...] It’s not just satellites that have had problems, either. Computers and instruments aboard Skylab, the International Space Station (ISS), the space shuttle, and even SpaceX’s Dragon craft have all experienced glitches or other issues when passing through the SAA. ... Because the ISS does occasionally pass through the SAA, it was constructed with ample radiation shielding to protect astronauts from harm. ... As scientists and engineers have gained more experience ... they’ve developed strategies to counter the potential damage ... although this often increases spacecraft weight and, in turn, pumps up launch costs... (MORE - details)

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