The VIS instrument

The visible (VIS) instrument in under the responsibility of the Euclid Consortium. VIS at imaging all galaxies of the Euclid survey with very high image quality. It will be used to measure the shapes of galaxies and derive the gravitational lensing effects induced by large scale structures of the universe on distant background galaxies. It will probe how the dark matter is distributed and how its distribution changed over the last 10 billion years.

The different subsystems of the VIS instruments are shown on the image below. The VIS focal plane is composed of a matrix of 6×6 4096×4132 12 micron pixel e2v CCDs (Charge Coupled Devices), specially optimised for the Euclid mission (CCD273 ). The first 4 VIS flight CCDs were delivered by e2v in February 2017 (see the EC News pages). The VIS fiocal plane covers a field of view of 0.57 deg2 (twice the angular size of the full Moon and about 450 times the field of view of the Hubble Space Telescope ACS camera) with 0.1 arc-second pixels.

VIS will be equipped with one single very broad band filter covering the wavelength range from 550 nm to 900 mn with a mean image quality of about 0.23 arc-second.

The overall throughput of the VIS instrument will enable scientists to measure shapes of galaxies with sufficient accuracy, compliant with the requirements. VIS will be able to get a signal-to-noise ratio of at least 10 for 1.5 billion galaxies down to magnitude 24.5 in 4000 seconds.

Overview of the elements composing the VIS instrument- Courtesy Euclid Consortium/VIS team
Overview of the subsystems composing the VIS instrument – Top, from left to right: VIS Calibration Unit, VIS Focal Plane and an expanded view of the Focal Plane Array, with the 36 CCD273 at the front, showing details of the focal plane structure, the ReadOut Electronics, the electronic structure and the Power Supply units. Bottom, from left to right: VIS Shutter Unit and the Power and Mechanisms Control Unit and Command and Data Porcessing Unit boxes. Courtesy Euclid Consortium/VIS team

Last update : Feb 08, 2017