Instrumental Conception

The Payload Module

Euclid Payload Module view and instruments location

The Euclid payload consists of a 1.2 m aperture telescope with two instruments: the visual imager (VIS) and the near-infrared spectrometer and photometer (NISP). VIS provides high quality images to carry out the weak lensing galaxy shear measurements. NISP performs imaging photometry to provide NIR photometric measurements for photometric redshifts, and also carries out slitless spectroscopy to obtain spectroscopic redshifts.

 The VIS instrument

View of the components of the VIS instrument

The Visible Imaging Channel (VIS) is an assembly of the following units:

  • The Focal Plane Assembly (FPA) is a thermal-mechanical structure that supports the 6 x 6 CCDs (each have 4096 x 4096 pixels of 2 x 2 µm) covering the field of view of 0,5 deg² and its associated Read Out Electronics units (ROE) which together comprise the visible focal plane array. In addition to providing structural support of the massive focal plane array, the FPA structure ensures mechanical and thermal stability of the CCD array and accurate location of the CCD array with respect to the optical beam image plane.
  • The VIS Calibration Unit (CU) is designed to allow flat fields of the visible channel. This structure encloses a

    12-LEDs panel illuminating a diffusing panel inside an integrating sphere.

  • A Shutter Unit (SU) stops the light beam before entering the VIS focal plane assembly in order to prevent trails in the images during visible detector array readout in normal operations and flat field calibration

  • Two electronics units are associated with the instrument: the Control and Data Processing Unit (CDPU) and the Power and Mechanism Control Unit (PMCU). The CDPU controls the instrument and compresses the scientific data before transfer to the payload mass memory. The PMCU controls the instrument mechanisms and calibration units.

The NISP instrument

View of the NISP instrument

The NISP instrument has two main observing modes: the photometric mode, for the acquisition of images with broad band filters, and the spectroscopic mode, for the acquisition of slitless dispersed images on the detectors. A Wheel composed by 4 grisms enables to select the spectroscopic observing bands as well as the orientation of the spectrum (0 deg or 90 deg).. Another wheel composed by 3 filters enables to select the photometric observing broad bands.

The main elements of the NISP instrument are listed

  • Structure Assembly (SA)
  • Optical Assembly (OA): This holds the optical elements and the Focal Plane Array
  • Filter Wheel Assembly (FWA): This holds the three filters for the photometric mode and it allows them to be placed in the optical beam. It provides also a closed and open position.
  • Grism Wheel Assembly (GWA): This holds the four dispersing elements for the spectroscopic mode and it allows them to be placed in the optical beam

These two wheels are equipped by a cryogenic engine to ensure the rotation and the accurate positioning of the optics

  • Calibration Unit (CU): This injects calibration signal in the optical beam for calibration purposes
  • Thermal Control (TC) whose goal is to control the optics at a temperature of 140K ±0.3 K during its lifetime.


CEA implication

The Euclid System engineer lead is J. Amiaux

The Euclid Coordination & Manager support lead is M. Berthé

IRFU is in charge of several unit of these two instruments:

- The Focal Plane Assembly of the VISible imager and the associated Power and Mechanism Control Unit (PMCU)
- The cryogenic engines to ensure the rotation of the filter in the Near-Infrared Spectrometer 

SAp Members involved in the instrumental activity are:
Amiaux Jérôme, Berthe Michel, Boulade Olivier, Cara Christophe, Cuillandre Jean-Charles, Doumayrou Eric, Dumaye Luc, Fontignie Jean, Goetschy Alain, Herviou Christian, Horeau Benoit, Huynh Duc Dat, Ketchaso Christian, Leberrurier Frederic, Lortholary Michel, Martignac Jerome, Moreau Vincent, Motisi Maxime, Mulet Patrick, NICO François, Orduna Thierry, Renaud Diana, Ronayette Samuel,Visticot François, Tourette Thierry, 

SIS Members involved in the instrumental activity are:
Alberi Anthony, Bachet Damien, Bargueden Patrick, Barriere Jean-christophe, Boudouin Romain, Carty Michaël, Charon Patrice, Contrepois Pascal, Dorlin Téo, Duboue Bruno, Hennion Vincent, Leboeuf Didier, Le Noa Yannick, Le Pouhalec Philippe, Reinert Yann, Rousse Jean-Yves


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Last modified in February 4th, 2015  by Sandrine Pires