The Euclid spacecraft, the European Space Agency’s (ESA) instrument for delving into the mysteries of the dark universe, has successfully overcome a cosmic misidentification issue and is back on course. This marks a significant step in its mission to explore the enigmatic realms of dark matter and dark energy, two of cosmology’s most profound puzzles. Dark matter, which constitutes a staggering 85% of the universe’s matter, remains invisible, while dark energy drives the universe’s relentless expansion.
Euclid embarked on its mission on July 1, embarking on a four-week journey to reach Lagrange point 2, a gravitationally stable location in the Earth-sun system. Upon reaching its destination, however, the spacecraft encountered an unexpected challenge. While capturing its initial breathtaking images of the cosmos, Euclid’s Fine Guidance Sensor struggled to locate its guiding stars, essential for precise navigation and targeting specific regions of the sky.
The root cause of this problem was identified as cosmic rays – charged particles emitted by the sun during periods of heightened solar activity. These cosmic rays interfered with the Fine Guidance Sensor, generating signals that Euclid mistakenly interpreted as stars. Additionally, stray sunlight and solar X-rays added to the interference, causing artifacts to outnumber actual stars in Euclid’s observations. Consequently, the spacecraft couldn’t discern the star patterns necessary for accurate navigation.
One notable consequence of this hiccup was evident in an image of a distant star field, which displayed unusual loops and lassos, captivating but unhelpful in the quest to uncover subtle patterns in distant galaxies and star clusters, which could offer insights into dark energy and dark matter.
Such challenges are common during the commissioning phase of a spacecraft’s operations, prompting ESA’s mission control teams to work tirelessly in adapting the craft to the rigors of space.
A software patch was developed and initially tested on a terrestrial model of Euclid before being deployed on the actual spacecraft, located roughly 1 million miles (1.5 million kilometers) from Earth at Lagrange point 2. Following ten days of orbital testing, the Fine Guidance Sensor has been successfully restored to full functionality, and Euclid’s guide stars have been precisely located once more.
Micha Schmidt, Euclid spacecraft operations manager, explained, “Our industrial partners – Thales Alenia Space and Leonardo – reworked the way the Fine Guidance Sensor identifies stars. After a substantial effort and a remarkable speed of execution, we received new onboard software for installation on the spacecraft. We meticulously tested the software update step by step under real flight conditions, with input from the Science Operations Centre for observation targets.”
With these issues resolved, Euclid is poised to resume its crucial performance verification phase, which had been temporarily halted in August. This phase, expected to extend until late November, represents the final hurdle before Euclid can delve into the mysteries of the dark universe.
Giuseppe Racca, Euclid project manager, remarked, “The performance verification phase that was interrupted in August has now fully restarted, and all the observations are carried out correctly. We are confident that the mission performance will prove to be outstanding, and the regular scientific survey observations can start thereafter.”
Euclid’s mission involves surveying approximately one-third of the sky from its vantage point near Earth and looking back in time over 10 billion years of cosmic history. Its objective is to construct 3D models of galaxies, shedding light on the evolution of the 13.8 billion-year-old universe and the role of dark matter in shaping it. Euclid will also investigate large-scale galactic disruptions to comprehend the influence of dark energy, which propels galaxies apart at an ever-increasing rate.
Carole Mundell, ESA’s director of science, expressed excitement about the upcoming phase, stating, “Now comes the exciting phase of testing Euclid in science-like conditions, and we are looking forward to its first images showcasing how this mission will revolutionize our understanding of the dark universe.”
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