ESA Euclid mission will study Dark Energy

An artist's concept of the ESA's Euclid misssion to study dark energy.

Credit: ESA/C. Carreau

Euclid is an ESA mission to map the geometry of the dark Universe.

The Euclid mission will investigate the distance-redshift relationship and the evolution of cosmic structures by measuring shapes and redshifts of galaxies and clusters of galaxies out to redshifts ~2, or equivalently to a look-back time of 10 billion years.

To accomplish the Euclid mission ESA has selected Thales Alenia Space (see also the ESA press release) for the construction of the satellite and its Service Module and Airbus Defence and Space (EADS ex-Astrium) for the Payload Module.

Euclid will be equipped with a 1.2 m diameter Silicon Carbide (SiC) mirror telescope made by EADS feeding 2 instruments, VIS and NISP, built by the Euclid Consortium :

• a high quality panoramic visible imager (VIS), 
• a near infrared 3-filter (Y, J and H) photometer (NISP-P) and 
• a slitless spectrograph (NISP-S). 

With these instruments physicists will probe the expansion history of the Universe and the evolution of cosmic structures by measuring the modification of shapes of galaxies induced by gravitational lensing effects of dark matter and the 3-dimension distribution of structures from spectroscopic red­shifts of galaxies and clusters of galaxies.

The satellite will be launched by a Soyuz ST-2.1B rocket and then travel to the L2 Sun-Earth Lagrangian point for a 6 years mission.

Members of the Euclid Consortium at the Euclid Meeting in Leiden.

Credit: ESA

In this way, Euclid will cover the entire period over which dark energy played a significant role in accelerating the expansion.

NASA will also participate in the ESA's Euclid mission in conjunction with it's own WFIRST-AFTA mission, searching for Dark Energy.

Last year, NASA nominated 40 American scientists to join the 14 American scientists already part of the international Euclid Consortium, the team responsible for the science, data production and instruments for the mission. NASA will also provide 16 infrared detectors for the telescope.

Euclid's goal is to understand the nature of dark energy and its role in the expansion of the universe. To do so, it plans to use two complimentary probes to study the phenomenon. The first probe will study weak gravitational lensing, while the second will examine BAOs.

Orbiting at the second Lagrangian point, Euclid will use two instruments to study a wide region of the sky free from the contaminating light from the solar system and the galaxy. It will also observe two "Euclid Deep Fields" of the early universe.

Of the approximately 10 billion sources Euclid intends to observe, more than 1 billion will be studied for weak lensing, while tens of millions of galaxies will be measured for clustering caused by BAOs.

"WFIRST-AFTA and Euclid will make complimentary observations, with WFIRST-AFTA observing fainter galaxies and Euclid observing more sky," Nasa project manager Gehrels said.

"The combined data set will be much larger and more accurate than any other BAO measurement."

When combined with ground-based observations over a variety of wavelengths, the new observations that WFIRST-AFTA and Euclid provide, should bring significant insights into dark energy and the expansion of the universe.

"The best constraints on dark energy in the 2020s will come from a combination of Euclid, WFIRST and ground-based data," WFIRST project manager Rhodes said.