HARMONI is the high angular optical and near-IR integral field spectrograph (IFS) for the ELT. The instrument covers a large spectral range from 470 to 2450nm with resolving powers from 3300 to 18000 and spatial sampling from 60 to 4mas. A workhorse instrument designed to operate in two Adaptive Optics modes - Single-Conjugate Adaptive Optics (SCAO, including a High Contrast capability) and Laser Tomography Adaptive Optics (LTAO) - or without adaptive optics. HARMONI project is now finishing phase C, ready for Final Design Reviews of all subsystems.

The Instrument Pre-Optics (IPO) is one of the HARMONI subsystems. It distributes the telescope light received from the adaptative optics systems. The main objective of the IPO is to format the field for the selected spatial scales feeding the Integral Field Unit (IFU). IPO is under the responsibility of the Institute of Astrophysics of the Canary Islands (IAC). This optical subsystem implements 30 Opto-mechanical mounts working at cryogenic temperatures. The mounts may be classified into two types based on the features of the optics they support: (1) Sprung Kinematic Mount (SKM) for flat mirrors, and (2) Thermally Compensated Kinematic Sprung Mounts (TCKSM) for power mirrors (toroidal mirrors, offaxis parabolas, and cameras). Designed to maintain optical alignment at cryogenic temperatures, the mounts maintain optical surface deformation within the limits specified by the error budget, ensuring compliance with requirements even worst-case scenarios.

This work describes the verification tests performed to the engineering models of the Opto-mechanical mounts of the IPO to validate compliance with the sub-system optical and mechanical requirements at both room and cryogenic temperatures.