Euclid’s vision fogs due to thin layers of water ice in space

The European Space Agency's Euclid telescope is facing an issue that spacecraft normally experience once in space. Layers of water ice, as thin yet impactful as a strand of DNA, have begun to degrade its vision, posing a significant hurdle for a mission that requires remarkable precision.

According to the agency, this problem stems from water molecules absorbed from Earth's atmosphere during the telescope's assembly. Once in space, the vacuum conditions coax these water molecules out of the spacecraft's components. In the cold environment where Euclid operates, these molecules freeze upon contact with the first surface they encounter. Unfortunately, when they adhere to the optics of this sensitive mission, they can significantly impede its ability to study the cosmos.

The accumulation of water ice on Euclid's optics was anticipated, given the challenges of completely eliminating Earth's atmospheric moisture from the spacecraft before launch.

"For this reason, there was an 'outgassing campaign' shortly after launch where the telescope was warmed up by onboard heaters and also partially exposed to the Sun, sublimating most of the water molecules present at launch on or very near Euclid's surfaces. A considerable fraction, however, has survived, by being absorbed in the multi-layer insulation, and is now being slowly released in the vacuum of space," ESA said in a statement.

With small quantities of water expected to continue emanating from within Euclid throughout its mission, finding an efficient long-term solution to de-ice its optics is critical.

"Most other space missions don't have such demanding requirements on 'thermo-optical stability' as Euclid," expalined Andreas Rudolph, Euclid Flight Director at ESA's mission control.

ESA's Euclid mission is designed to explore the composition and evolution of the dark Universe. The mission's key goal is to make a 3D map of the Universe by observing billions of galaxies out to 10 billion light-years,

A few layers of water ice – the width of a strand of DNA – are starting to impact @ESA_Euclid's vision. This is a common issue for spacecraft in the freezing cold of space, but it's a potential problem for this highly sensitive mission that requires precision to investigate the… pic.twitter.com/CIxVCHs94J

— ESA (@esa) March 19, 2024