Why does a spacecraft staring at the sun get a cloudy vision?

Earth’s host star can be quite moody, forcing astronomers to launch satellites and probe missions to closely observe the sun’s massive flares. But instruments aimed at the sun tend to have a blurred vision, a result of a mysterious layer that has baffled scientists for years.

NASA’s Onboard Instruments Solar Dynamics Observatory (SDO), which has been monitoring the Sun since 2010, degraded by 40% within five years of its launch. Today, a group of scientists may finally have pinpointed the reason behind the spacecraft’s hazy look: water.

said Robert Berg, a researcher at the US National Institute of Standards and Technology (NIST) and one of the authors behind the new research. Stady Posted in HeliophysicsAnd In an email to Gizmodo. Previous studies, he added, “described oxidation as one of several possible causes, but water has not been suggested as an oxidizing agent.”

In order to decipher the code, the scientists behind the new study used a room-sized particle accelerator to replicate conditions imposed by space weather. They found that oxygen atoms from water molecules combine with aluminum from spacecraft instruments to produce a hazy layer of aluminum oxide that blocks rays from the sun.

In new research published Thursday, scientists from the National Institute of Standards and Technology (NIST) and the Laboratory for Atmospheric and Space Physics at the University of Colorado Boulder detail these important new findings. “We weren’t able to expose years of radiation, but combined with the oxide growth model, we showed very convincingly that water vapor combined with ultraviolet light can cause the observed losses,” says Charles Tarrio, a physicist from NIST. (NIST) and lead author of the new study, explained in an email.

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Sun-observing spacecraft use aluminum filters — each smaller than a postage stamp and thinner than a human hair — to collect extreme ultraviolet light, a wavelength of light emitted by the sun that is too short for the human eye to see. Although the EUV makes up a small part of the total amount of light emitted by the Sun, it plays a vital role in notifying scientists when a star is about to collapse.

The sun sometimes releases bursts of energy known as Coronal mass ejection–Huge explosions of charged particles which extend away from the sun like hot whips. These events can affect us here on Earth, creating geomagnetic storms that cause disruptions to power grids and navigation systems.

By observing the sun using solar probes and satellites, scientists can get a better handle on its outburst schedule. Unfortunately, spacecraft facing the sun tend to lose their ability to capture ultraviolet light within a few years of entering service. A spacecraft filter typically transmits about 50% of the EUV light through its detector at the start of its mission, dropping to 25% within one year and 10% within five years, according to nest. The researchers based this on their study of SDO, but say other spacecraft have suffered the same fate.

Other examples of spacecraft degradation include the LYRA instrument aboard the European PROBA2 satellite, the SOLSPEC instrument aboard the International Space Station’s SOLAR payload, which was used to measure solar energy, and the Solar Diameter Imager and Surface Mapper telescope aboard the PICARD spacecraft, according to Berg.

For years, scientists thought the filters were developing a layer of carbon, the result of contamination on spacecraft. But the same group of scientists is behind the new research This theory is disproved in 2021 Before going back to the drawing board. “The other thing that points to oxidation is that spacecraft instruments have been built to be cleaner and cleaner over the past few decades, with the goal of eliminating the sources of organic molecules that lead to carbon deposition,” Tarrio said. However, many tools still show significant degradation. This takes away from carbon growth.”

Using a particle accelerator to generate EUV light, the researchers diverted that light into the spacecraft’s filters using mirrors while also exposing them to water vapor. After 20 days, the filters had developed a layer of aluminum oxide. The layer was not thick enough to impede the filters’ ability to capture EUV light, but it likely got thicker over a longer period of time. Scientists have also created theoretical models that are consistent with what happens to spacecraft in real life.

So how did the oxide layer form in the first place? Scientists believe that water from the spacecraft’s thermal blanket, which is used to control the spacecraft’s temperature, reacts with the aluminum in the filter to produce the anodized layer that prevents light from traveling through the detector.

The new research could help better design spacecraft that look toward the sun in the future to help prevent its rapid deterioration. One thing the researchers suggested is adding a layer of carbon to stop the movement of aluminum ions, as well as tubes that prevent water vapor from entering.

more: A spacecraft orbiting the sun takes amazing pictures of a coronal mass ejection