While being assembled on Earth, it is always the case that even with lots of dry rooming, and careful prep, space ‘scopes (and spacecraft, more generally), retain at least a tiny fraction of the water molecules naturally present in the air, in between the layers of the various sub-assemblies.
And since space is. . . a vast vacuum — it sucks those little water molecules (from the inside, outward), toward the surfaces of the ‘scope — and then, in the near negative 290 degrees, they tend to freeze onto the nearest flatish surfaces. And the mirrors are a very large — and nearly flat — natural collecting surface. So it is that Euclid will now have to de-ice the mirrors, with its pre-installed heaters, from time to time. Heating however, in deep space… amounts to raising the temp to only minus three or so.
But that will be enough for the water to detach and float away. . . it is believed. Here’s that story, from ESA.int:
…A few layers of water ice — about the width of a strand of DNA — are starting to impact Euclid’s vision; a common issue for spacecraft in the freezing cold of space, but a potential problem for this highly sensitive mission that requires remarkable precision to investigate the nature of the dark Universe. After months of research, Euclid teams across Europe are now testing a newly designed procedure to de-ice the mission’s optics.
If successful, the operations will validate the mission teams’ plan to keep Euclid’s optical system as ice-free as possible for the rest of its life in orbit….
What a time to be alive… and “awake” — pushing back against the dark of ignorance, is the bright face of mirrored space science. Or… “woke“, if you prefer. Smile….
नमस्ते
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