What's the (dark) matter with Euclid?

Currently about halfway through the Euclid simulations campaign, the key focus in the Main Control Room is the Launch and Early Orbit Phase (LEOP) and spacecraft commissioning.

These are the two most critical moments in a mission's life; as it wakes up after the rigors of launch, makes its first maneuvers towards its target destination and as its instruments are commissioned. Stress as Euclid thrusters fail Joe Bush, simulations officer for Euclid, has spent months meticulously planning all the ways that Euclid could fail. From problems on the spacecraft to human issues like team cohesion, confidence and morale. You'd be forgiven for thinking, that on 23 March this year, he went too far. Joe broke not just one, but two sets of thrusters on the Euclid spacecraft simulator. It was up to the Flight Control and Flight Dynamics Teams to decide which they could and should use.

"All of a sudden, a suspected mechanical failure meant one of Euclid's attitude thrusters was stuck shut, producing no force at all, forcing us to use the backup set of thrusters. But then, the orbit control thrusters, part of that backup set, began behaving strangely, one overperforming by 10% and the other underperforming by the same amount," recalls Tiago Loureiro, Euclid Flight Operations Director. The team discussed a potential hybrid solution that would make use of both sets of thrusters, but for this, there was no procedure in place, and to create one would require input and advice from the Science project at ESA's Technical heart (ESTEC) and industry partners. While not involved in this earlier simulation, these teams have now joined simulations and of course, will be on hand throughout Euclid's life in space.

Artist impression of the Euclid mission in space. The spacecraft is white and gold and consists of three main elements: a flat sunshield, a large cylinder where the light from space will enter, and a 'boxy' bottom containing the instruments. The spacecraft is shown half in the shadow, because the sunshield will always be faced in the direction of the Sun and thus protecting the telescope from the light of the Sun. The background is a realistic representation of a deep field view of the night sky, with many galaxies visible. On the bottom half of the image, an artistic representation of the cosmic web is overlayed over the galaxies. The cosmic web is the scaffolding of the cosmos on which galaxies are built, consisting primarily of dark matter and laced with gas. The cosmic web is here represented with a grid and a two-dimensional representation of a cosmological simulation. Credit: ESA/Euclid/Euclid Consortium/NASA. Background galaxies: NASA, ESA, and S. Beckwith (STScI) and the HUDF Team, CC BY-SA 3.0 IGO Read more

Structural and thermal model of the Euclid satellite. Credit: ESA–S. Corvaja Read more

The Bullet Cluster is a much-studied pair of galaxy clusters, which have collided head on. One has passed through the other, like a bullet travelling through an apple. In the Bullet Cluster, this is happening across our line of sight, so we can clearly see the two clusters. The optical image from the Magellan and the Hubble Space Telescope shows galaxies in orange and white in the background. Hot gas, which contains the bulk of the normal matter in the cluster, is shown by the Chandra X-ray image, which showst the hot intracluster gas (pink). Gravitational lensing, the distortion of background images by mass in the cluster, reveals the mass of the cluster is dominated by dark matter (blue), an exotic form of matter abundant in the universe, with very different properties compared to normal matter. This was the first clear separation seen between normal and dark matter. Credit: X-ray: NASA/CXC/CfA/M.Markevitch, Optical and lensing map: NASA/STScI, Magellan/U.Arizona/D.Clowe, Lensing map: ESO WFI Read more