The problem was that a small amount of unwanted sunlight reached Euclid. Visible Instrument (VIS) At certain angles, even the spacecraft’s sunshield (its back) turns toward the sun.

Artist's impression of Euclid in spaceArtist's impression of Euclid in space

Artist’s impression of Euclid in space

“The original plan was for Euclid to point its sunshield at the Sun. But immediately after launch, the problem arose. Sunlight was detected in test imagesexplains Ismail Tereno of the University of Lisbon in Portugal and head of the Euclid Survey Operation Support Team working in collaboration with the Portuguese Space Agency.

“After extensive troubleshooting, science, engineering, and industrial teams found that for this light to disappear, Euclid needed to observe with a different orientation (attitude) to the Sun. This means “It was that the original survey design would no longer work. We had to quickly come up with a new strategy, implement it, and test it,” says Joao Denis, from the University of Lisbon. Also from Portugal who and Ismail were responsible for the (re)design of the survey.

To reduce the effect of ‘stray’ sunlight, the teams found that Euclid needed to observe with a more restricted rotation angle, such that the sun shield was not directly facing the sun, a direction I have a small but impactful inclination. With this new limiting behavior, parts of the sky could not be reached from any point in Euclid. Orbit around L2. “Finding a good survey solution proved very difficult, and we had to go back to the drawing board,” recalls Ismail.

A giant puzzle

This was the start of a very intense phase for Joao, Ismail and the survey operations and science teams. “Joao immediately had insight into what needed to change, and then worked around the clock to come up with a workable redesign proposal,” Ismail says.

Designing the Euclid survey was a big puzzle. In addition to scientific goals and the perspective from which Euclid needed to observe, there are many other factors to consider.

The largest part of the mission’s observations will be devoted to a ‘broad’ survey, covering more than a third of the sky. Completion of extensive survey a In-depth survey, taking about 10% of the total observation time. In addition, routine calibration observations had to be scheduled to fit the puzzle.

Xavier Dupac, ESA survey scientist at the Science Operations Center at ESAC in Spain, ensured that the survey designed by João, Ismael and team could be completed. “For example, we have to take into account the time it takes for the spacecraft to travel from one observation point to another. These times need to be factored into the survey design in addition to the actual observation time,” Xavier said. Tells.

In the end, the teams came up with a workable solution that meant there was more overlap between adjacent observations. The Euclid survey is now slightly less efficient, but all the necessary areas of the sky can be reached and the overall loss in the survey area is kept to a minimum.

“The teams worked very hard to redesign the survey in a short time, which is a great achievement,” says Valeria Petorino, Euclid Project Scientist for ESA. “And that’s not the end of the story. As the mission progresses and scientific results begin to come in, the teams will continue to refine the survey, and be prepared to adapt it if needed.”

Looking ahead to the year of Euclid’s first survey.

Today, Euclid officially began his survey. The telescope currently has to observe 130 square degrees – 500 times the area of ​​the full moon – over the next 14 days. This patch is in the direction of the constellations Caelum and Pictor in the Southern Hemisphere.

Euclid's broad and deep surveysEuclid's broad and deep surveys

Euclid’s broad and deep surveys

Euclid will cover about 15% of its survey in the coming year. This first year of cosmology data will be released to the community in the summer of 2026. Deep field observations The forecast is for spring 2025.

Source: European Space Agency