Warming up a space telescope can clear ice from its mirrors and create another problem: the structure expands, disturbing the alignment needed to measure distant galaxies.
That trade-off shaped a repair to ESA's Euclid telescope in March 2024. A thin layer of ice was reducing the light reaching its visible-light instrument. The water had come from Earth, absorbed during assembly and slowly released by spacecraft materials into the vacuum. Some of it settled on the cold optics.
Heating the whole spacecraft was an available option. But ESA said the structure might not return to precisely the same state after cooling, leaving several weeks of fine recalibration before the telescope could recover its required precision.
The team instead planned to warm selected mirrors separately and measure how much light came back after each step. That made the repair a way to locate the contamination, while limiting how much of the telescope had to change temperature.
ESA's March 26 report describes heating the main suspect, a cold mirror behind the telescope's main optics, from -147°C to -113°C. Still far below freezing on Earth, but warm enough in a vacuum to remove the ice. The team reported receiving 15% more light almost immediately.
The early success meant they could identify where the ice had collected and target that area again. Water was expected to keep escaping from the spacecraft's materials, so this was maintenance Euclid would need repeatedly. A selective warm-up offered a way to restore its view without routinely heating the entire structure and paying the recalibration cost.
Sources:
https://www.esa.int/Science_Exploration/Space_Science/Euclid/Euclid_s_sight_restored
https://www.esa.int/Science_Exploration/Space_Science/Euclid/Operations_begin_to_de-ice_Euclid_s_vision
Image: AI-generated editorial still life of an optical mirror, not Euclid hardware or a photograph of the repair.
That trade-off shaped a repair to ESA's Euclid telescope in March 2024. A thin layer of ice was reducing the light reaching its visible-light instrument. The water had come from Earth, absorbed during assembly and slowly released by spacecraft materials into the vacuum. Some of it settled on the cold optics.
Heating the whole spacecraft was an available option. But ESA said the structure might not return to precisely the same state after cooling, leaving several weeks of fine recalibration before the telescope could recover its required precision.
The team instead planned to warm selected mirrors separately and measure how much light came back after each step. That made the repair a way to locate the contamination, while limiting how much of the telescope had to change temperature.
ESA's March 26 report describes heating the main suspect, a cold mirror behind the telescope's main optics, from -147°C to -113°C. Still far below freezing on Earth, but warm enough in a vacuum to remove the ice. The team reported receiving 15% more light almost immediately.
The early success meant they could identify where the ice had collected and target that area again. Water was expected to keep escaping from the spacecraft's materials, so this was maintenance Euclid would need repeatedly. A selective warm-up offered a way to restore its view without routinely heating the entire structure and paying the recalibration cost.
Sources:
https://www.esa.int/Science_Exploration/Space_Science/Euclid/Euclid_s_sight_restored
https://www.esa.int/Science_Exploration/Space_Science/Euclid/Operations_begin_to_de-ice_Euclid_s_vision
Image: AI-generated editorial still life of an optical mirror, not Euclid hardware or a photograph of the repair.