Sun-facing satellites monitor the Sun’s ultraviolet (UV) light to give us advance warning of solar storms. But over the course of just a year or two, the metal filters in the detectors mysteriously lose their ability to transmit UV light. Now, scientists have found the first evidence indicating that carbonization is not the problem.

Sun-facing satellites monitor the Sun’s ultraviolet (UV) light to give us advance warning of solar storms, both big ones that could cause a Carrington-like event as well as the smaller, more common disturbances that can temporarily disrupt communications. One key piece of equipment used in these detectors is a tiny metal filter that blocks out everything except the UV signal researchers need to see.

But for decades, there has been a major problem: Over the course of just a year or two, these filters mysteriously lose their ability to transmit UV light, «clouding up» and forcing astronomers to launch expensive annual recalibration missions. These missions involve sending a freshly calibrated instrument into space to make its own independent observations of the sunlight for comparison.

A leading theory has been that the filters were developing a layer of carbon, whose source is contaminants on the spacecraft, that blocked incoming UV light. Now, NIST scientists and collaborators from the Laboratory for Atmospheric and Space Physics (LASP) in Boulder, Colorado, have found the first evidence indicating that carbonization is not the problem, and it must be something else, such as another possible stowaway from Earth. The researchers describe their work in Solar Physics today.

«To my knowledge, it’s the first quantitative, really solid argument against carbonization as the cause of the filter degradation,» said NIST physicist Charles Tarrio.

What Are They Good For? Absolutely Everything

Most of the light produced by the Sun is visible and includes the rainbow of colors from red (with a wavelength of around 750 nanometers) to violet (with a wavelength of about 400 nm). But the Sun also produces light with wavelengths too long or short for the human eye to see. One of these ranges is extreme ultraviolet (EUV), extending from 100 nm down to just 10 nm.

Story Source: Materials provided by National Institute of Standards and Technology (NIST). Original written by Jennifer Lauren Lee. Note: Content may be edited for style and length.