What is Euclid’s (obscure) question?


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Artist’s impression of the Euclid mission in space. The spacecraft is white and gold and is made up of three main elements: a flat parasol, a large cylinder into which light from space will enter and a “square” bottom containing the instruments. The spacecraft is shown half in shadow, because the canopy will always face the sun and thus protect the telescope from sunlight. The background is a realistic representation of a deep-field view of the night sky, with many galaxies visible. In the lower half of the image, an artist’s impression of the cosmic web is superimposed over the galaxies. The cosmic web is the scaffolding of the cosmos on which galaxies are built, made up mostly of dark matter and laced with gas. The cosmic web is represented here 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

Currently, approximately halfway through Euclid’s simulation campaign, the primary focus in the main control room is Initial Launch and Orbit Phase (LEOP) and spacecraft commissioning.


These are the two most critical moments in the life of a mission; as he wakes up after the rigors of the launch, he makes his first maneuvers towards his target destination and as his instruments are put into service.

Stress when Euclid thrusters fail

Joe Bush, head of simulations for Euclid, spent months meticulously planning all the ways Euclid could fail. From problems on the spaceship to human problems like team cohesion, trust and morale.


You’d be forgiven if you think March 23 of this year has gone 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.

“Suddenly, a suspected mechanical failure meant that one of Euclid’s attitude thrusters was stuck, producing no force, forcing us to use the backup set of thrusters. But then, the orbit control thrusters, part of that spare set, it started behaving strangely, one performing 10% more and the other performing less by the same amount,” recalls Tiago Loureiro, director of flight operations at Euclid.

Structural and thermal model of the Euclid satellite. Credit: ESAS. Corvaia


The team discussed a potential hybrid solution that would make use of both sets of thrusters, but no procedure existed for this, and creating one would require input and advice from the scientific project at ESA’s technical heart (ESTEC) and the partner industry. While not involved in this previous simulation, these teams have now joined the simulations and will, of course, be available throughout Euclid’s life in space.

“I wanted the teams to get used to making decisions on very short notices, and having two sets of bad power units definitely did that,” explains Joe.

“The twin thruster nightmare scenario underlined how successful mission operations include a diverse range of experts and specialists, able to support and brainstorm with our control teams for the plethora of potential issues that may arise.”


Tiago adds to this: “The simulation campaign is all about teamwork, no one can lead a mission alone. Knowing who or what to rely on for information and advice and when, to support us in those high-stakes decision-making moments, is an important skill in mission operations, but also in life!”

It would be unfortunate for such a thing to actually happen, but it’s certainly not impossible. Whether it be Euclid’s thrusters, solar arrays, or any number of other critical spacecraft components, the ability of teams to remain calm but decisive in the midst of a serious problem, to know who to call and to rely what time, will be vital to mission accomplished.

The Bullet Cluster is a much-studied pair of galaxy clusters, which collided head-on. One went through the other, like a bullet going through an apple. In the bullet cluster, this is happening across our line of sight, so we can see the two clusters clearly. Optical image from Magellan and the Hubble Space Telescope shows the galaxies in orange and white in the background. The hot gas, which contains most of the normal matter in the cluster, is shown by the Chandra X-ray image, which shows the hot gas inside the cluster (pink). Gravitational lensing, the distortion of background images by mass in the cluster, reveals that the mass of the cluster is dominated by dark matter (blue), an exotic form of matter abundant in the universe, with very different properties than normal matter . This was the first clear separation observed between normal and dark matter. Credits: X-Ray: NASA/CXC/CfA/M.Markevitch, Optical Map and Lens: NASA/STScI, Magellan/U.Arizona/D.Clowe, Lens Map: ESO WFI


Engineers to soothe a sensitive soul

Euclid’s exceptionally sensitive 1.2-metre telescope will capture light that is ten billion years old, originating in the early universe and only now reaching us. In doing so, it will shed light on a simple question for which we still don’t have an answer: what is the universe made of? Surprisingly, this is now a cosmic mystery.

The matter we are made of and the light that makes us see, make up just 5% of the universe. The rest is dark: with dark energy making up about 70% and dark matter the remaining about 25%.

But what are dark matter and dark energy? Euclid hopes to find out, but his instruments are only as sensitive as their operations allow them to be. ESA’s mission control engineers will need to protect the unshielded telescope during and after launch, making sure it is not hit by direct sunlight. They will then have to calibrate and aim the spacecraft very precisely, to make sure it can see clearly.


From launch to Lagrange

Euclid will launch on a SpaceX Falcon 9 rocket from Cape Canaveral, Florida, US, no earlier than July. A trajectory correction maneuver will propel it to “Lagrange point 2”, one of five points around the Sun and Earth where the gravitational forces between the two bodies balance out, creating gravitational “plateaus” around which objects can orbit , steadily, without too much work to keep them in place.

All of this will be tested in ongoing simulations taking place at ESA’s ESOC mission control centre, first with local teams and later by bringing science teams together at ESA’s ESTEC technical heart, SpaceX, earth and Thales Industry.


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