(Paris) Invasive frost clouds the vision of the European Euclid space telescope, nicknamed by researchers “detective of the Dark Universe”: scientists have started operations to try to eliminate this thin layer of ice… with a little heating .
This is the latest technical problem for this six-year mission, launched in July 2023 to map the stars and galaxies covering a third of the observable sky.
With this mission, scientists hope to learn more about the nature of dark energy and dark matter, two entities never before observed and believed to make up 95% of the Universe.
As early as last November, ground teams noticed that a telescope instrument, which produces images in visible light, was receiving less light than expected, Ralf Kohley, head of instrument operations, told AFP.
Observation of some stars revealed that they appeared less bright than they should be. An impossibility for stars whose stability is measured in millions of years.
The ESA thinks this ‘big problem’ with vision, according to the scientist, comes from a thin layer of ice, the thickness of a strand of DNA, which accumulates on the optics of the imager .
All instruments sent into space carry with them minute quantities of water vapor, which freeze in the cold of space. Scientists believe a substantial amount of water vapor became lodged in the device’s layers of insulating materials.
Shortly after Euclid’s launch, scientists partially exposed it to sunlight. And above all activated on-board radiators, supposed to heat the telescope to rid it of possible traces of water.
Some setbacks
This operation could be repeated, but it is not without drawbacks. “Heating everything up will disrupt the mission a lot,” explains Ralf Kohley. The heat, by expanding the materials, would require a recalibration of the entire telescope for at least a month.
This is why the ESA started heating two of the telescope’s three mirrors last week. Scheduled until March 21, its result will not be known before mid-April, according to Mr. Kohley.
In the event of failure, there will remain the solution of heating the entire Euclid telescope. By dropping it from -140 degrees Celsius to -3 degrees.
Part of the problem is that scientists don’t know exactly where the frost layer is accumulating, or even exactly how much.
And even if the heating operation proves successful, there is no guarantee that water molecules will not freeze again on one of the telescope’s mirrors, warns Mr. Kohley. In which case Euclid would be subjected to annual full heating, which would ultimately remove six months of observations over the six years of the mission.
This scenario remains at this stage “purely speculative”, indicates the scientist, who still hopes it is possible to “get rid of this problem in a more elegant way”.
Euclid has had its share of setbacks since its launch. Firstly with the influence of cosmic rays, by definition impossible to predict or avoid, which disrupted the spacecraft’s guidance system. And imposed a complicated update of its computer system.
Stray sunlight also interfered with his observations. This problem was fixed with a small rotation of the telescope.
The telescope officially began its scientific observations in February, after delivering the first breathtaking images in November of galaxies located in the depths of the cosmos.