The Euclid Visible Instrument Shutter

The Visible Imaging Channel (VIS) provides high quality images to carry out the weak-lensing galaxy shear measurements. As shown in the figure below, the VIS is constituted of several subsystems.

All the main units within the VIS instrument (credits: The VIS Consortium)

The Focal-Plane Assembly (FPA) is a thermal-mechanical structure that supports the 6x6 CCDs and its associated Read-Out Electronics unit (ROE). 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 Calibration Unit (CU) is designed to allow flat fields of the visible channel. The scope of the VIS Read-out Shutter Unit (RSU) is preventing direct light from falling onto the CCDs of the VIS instrument during the closed phase while allowing the fine guidance sensors to be exposed to light continuously. A single hatch concept has been adopted after extensive trade-off. The hatch is closed and opened by a single stepper motor. A counter mass and a flywheel have been implemented to counter the disturbance loads. A launch-lock mechanism maintains firmly the RSU in the open position during launch. The shutter is driven by a dedicated commanding electronics, the PMCU. Some sketches of the present RSU design are shown below.

The University of Geneva is currently developing and manufacturing the RSU in collaboration with APCO Technology (Switzerland).

Sketches of the present RSU design (credits: University of Geneva)