Defunct NASA satellite to crash back to Earth, with a small risk of falling debris

A defunct NASA satellite that launched 14 years ago to study Earth’s radiation belts is expected to crash back to the planet on Tuesday.

The roughly 1,323-pound spacecraft, known as the Van Allen Probe A, is projected to plunge through the atmosphere at approximately 7:45 p.m. EDT, based on predictions from the U.S. Space Force. Although it will be an uncontrolled re-entry — meaning NASA has no way to steer the probe — the agency expects most of the satellite to burn up as it makes the fiery trip through the atmosphere.

The agency said in a statement, however, that “some components are expected to survive re-entry.”

“The risk of harm coming to anyone on Earth is low — approximately 1 in 4,200,” NASA said. “NASA and Space Force will continue to monitor the re-entry and update predictions.”

It’s not uncommon for out-of-commission satellites, spent rocket parts and smaller bits of space debris to fall back to Earth. In fact, these types of objects re-enter the planet’s atmosphere on an almost daily basis, according to the European Space Agency.

In most cases, the hardware burns up harmlessly in the atmosphere, but occasionally some parts can make it through. Even in those instances, it’s rare for space debris to fall over land and cause damage because oceans cover around 71% of Earth’s surface.

Accurate predictions of when and where an uncontrolled spacecraft will fall back to Earth can be difficult to make because the process is influenced by atmospheric dynamics, space weather and the probe’s positioning as its orbit degrades. The Space Force’s predictions for the Van Allen Probe A’s re-entry timing include an uncertainty of plus or minus 24 hours.

The Van Allen Probe A — along with its twin, the Van Allen Probe B — launched into space on Aug. 30, 2012. The pair was designed to fly through and study rings of high-energy radiation particles that are trapped by Earth’s magnetic field. These enormous, doughnut-shaped zones make up the planet’s permanent radiation belts, called the Van Allen belts.

The Van Allen belts shield Earth from solar storms, cosmic radiation and constant waves of charged particles known as solar wind. Without them, high-energy radiation particles from the sun could bombard satellites in orbit, damage human health and knock out power grids on the ground. But astronauts must fly through the Van Allen belts to reach outer space, which exposes them to harmful radiation.

The Van Allen Probe A and Van Allen Probe B were developed to better understand the belts and how they came to be. The mission made numerous discoveries about the features and composition of radiation belts and even uncovered a “transient” third radiation belt that can form during periods of intense solar activity.

The twin probes operated until 2019, when they ran out of fuel. NASA ended the mission after that, and they have been languishing in orbit ever since.

Originally, NASA thought the two probes would re-enter Earth’s atmosphere in 2034, but higher-than-normal solar activity in recent years has increased atmospheric drag on the probes. When the sun is more active and releases more energy, it increases density in parts of the atmosphere, which can slow satellites or degrade their orbits.

The Van Allen Probe B, however, is not expected to re-enter Earth’s atmosphere before 2030.

Satellite re-entries like this highlight the broader problem of space debris, especially as launches become more frequent. Tens of thousands of pieces of space junk — and millions more smaller bits of orbital debris — are cluttered in low-Earth orbit, the narrow band of space around the planet where many telecommunications and GPS satellites operate.

Bits of space debris fly through orbit at up to 18,000 mph, threatening to collide with functioning spacecraft and posing safety risks to astronauts on the International Space Station.

This article was originally published on NBCNews.com