The Visible and Near Infrared Imaging Channels instrument provides shape measurements. It is optimised to fulfill the needs of its primary scientific goal, weak lensing. Euclid Instrument Channels starts after the telescope M3. Two electronics boxes are associated to the instrument and integrated on the Payload, the Payload Data Handling Unit (PDHU) and the Payload Mechanism Control Unit (PMCU).
The focal plane of VIS is composed of 4 x 9 CCDs with 12 µm pixels (baseline e2v CCD203-82 CCD with optimized packaging for field of view gap) that covers the 0.5 deg² visible field of view. The baseline CCDs are full frame types of 4096 x 4096 pixels. They are used in conjunction with the mechanical shutter in the optical path to prevent image smearing during readout. The CCDs are butted with minimum gaps between the sensitive areas but still require dithering pattern to provide maximum gap filling of the visible field of view in order to prevent specific loss of information at inter CCD spatial frequencies.
Thermal Mechanical design of VIS channel
The architecture of the proposed electronics to control and read out the 36 CCDs has been developed from experience with previous projects, most notably Gaia. Unlike Gaia where the CCDs are all operated independently, the Euclid VIS CCDs are all operated in synchronism. This simplifies the sub-system design. Each CCD is served by a proximity electronics module (PEM). Each row of PEMs is served by an interconnect module (IM). Because an individual clock sequence generators for each CCD is not needed for Euclid, it is beneficial to combine the PEM & IM functions into one unit. This unit is called a Read Out Electronics (ROE) unit.