HARMONI is the first light visible and near-IR integral field spectrograph for the ELT. It covers a large spectral range from 470nm to 2450nm with resolving powers from 3300 to 18000 and spatial sampling from 60mas to 4mas. It can operate in two Adaptive Optics modes - SCAO (including a High Contrast capability) and LTAO - or with NOAO. The project is preparing for Final Design Reviews.



The core of HARMONI is the Integral Field Spectrograph (IFS) which is composed of different subsystems including the IFS Pre-Optics (IPO). The IPO main objective is to take light from the focal plane relay system and reformat and condition it to be a suitable input for the rest of the instrument. The IPO in HARMONI includes the IFS Pre-Optics Fast Shutter (POFS), a mechanical cryogenic fast shutter which will be used with both the visible and infrared detectors. This mechanism has been designed to be fast and reliable and its design has already passed the Critical Design Review (CDR) but specific issues that require further analysis have been identified. The functioning of this element is a critical part in HARMONI and, consequently, a prototype has been used to analyze possible improvements in the CDR design and to perform extensive testing before the Final Design Review (FDR).



In this work we present the design of the IFS Pre-Optics Fast Shutter and the test results obtained with the prototype developed at the facilities of the Instituto de Astrofísica de Canarias (IAC).