HARMONI is the high angular resolution optical and near-IR integral field spectrograph for the Extremely Large telescope (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. The Instrument Pre-Optics (IPO), a sub-system under the responsibility of the Instituto de Astrofísica de Canarias (IAC), consists of several opto-mechanical mounts operating at cryogenic temperatures. Among these, toroidal mirrors stand out as the most sensitive and accurate elements of the IPO. An athermal design has been achieved by combining different materials for both the mount and the pads that define the position of the optical element. This design compensates the differential contractions during cooling, which allows the optical element alignment to be maintained within the tight tolerance when transitioning from warm to cryogenic operating temperatures. This paper presents the design of the athermal toroidal mirror mount, the tests carried out on its prototype and the final optomechanical mount.
Infrared instruments for astronomy require many bearings for motion that must move in cryogenic conditions. There are poor and expensive options for this, and the companies with qualified bearings only supply after a long time. To attend these constrains, the Instituto de Astrofísica de Canarias (IAC) started to develop a procedure to upgrade commercial bearing to operate to cryogenic conditions.
The initial attempts involved sprinkling molybdenum disulfide (MoS2) inside the bearing without disassembling it after cleaning. However, this method prevented uniform lubrication, leading to potential failures. The IAC mechanical team diligently refined the procedure, which included disassembling the bearings and replacing the cage by a technical polyamide cage.
This innovative approach significantly enhances efficiency; however, it comes at a higher cost due to high price of some technical polyamides such as Vespel. Additional research and testing have demonstrated that the pre-lubrication the bearing races with MoS2 significantly increases bearing life, although it involves a laborious process.
In recent years our focus has been on exploring more cost-effective material and how to improve bearing life.
This presentation discusses these techniques and the selected material for bearing preparation and presents the results of the latest cryogenic temperature life tests conducted on the produced bearings, along with the conclusions reached.
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.
HARMONI is the first light visible and near-IR integral field spectrograph for the ELT. It covers a large spectral range from 450 nm to 2450 nm with resolving powers from 3500 to 18000 and spatial sampling from 60 mas to 4 mas. 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. HARMONI is a work-horse instrument that provides efficient, spatially resolved spectroscopy of extended objects or crowded fields of view. The gigantic leap in sensitivity and spatial resolution that HARMONI at the ELT will enable promises to transform the landscape in observational astrophysics in the coming decade. The project has undergone some key changes to the leadership and management structure over the last two years. We present the salient elements of the project restructuring, and modifications to the technical specifications. The instrument design is very mature in the lead up to the final design review. In this paper, we provide an overview of the instrument's capabilities, details of recent technical changes during the red flag period, and an update of sensitivities.
HARMONI is the first light, adaptive optics assisted, integral field spectrograph for the European Southern Observatory’s Extremely Large Telescope (ELT). A work-horse instrument, it provides the ELT’s diffraction limited spectroscopic capability across the near-infrared wavelength range. HARMONI will exploit the ELT’s unique combination of exquisite spatial resolution and enormous collecting area, enabling transformational science. The design of the instrument is being finalized, and the plans for assembly, integration and testing are being detailed. We present an overview of the instrument’s capabilities from a user perspective, and provide a summary of the instrument’s design. We also include recent changes to the project, both technical and programmatic, that have resulted from red-flag actions. Finally, we outline some of the simulated HARMONI observations currently being analyzed.
HARMONI is the first light visible and near-IR integral field spectrograph for the Extremely Large Telescope (ELT). It covers a large spectral range from 450nm to 2450nm with resolving powers from 3500 to 18000 and spatial sampling from 60mas to 4mas. The IFS Pre-Optics (IPO), sub-system under the responsibility of the Institute of Astrophysics of the Canary Islands (IAC), contains 30 opto-mechanical mounts working at cryogenic temperatures and are classified into three types depending on the mirror shape: [1] - Sprung kinematic mount for flat mirrors: By spring loading, the mirror is constrained radially against a Vee-groove. - Thermally compensated kinematic sprung mount for power mirrors: It is similar to the previous mount but the radial pads compensate mirror radial movement. - Bonded mount for toroidal mirrors: The mirror is bonded to a rear invar pad, which serves as an interface to the support. This work describes the designs developed for the opto-mechanical modules of the Instrument IPO in order to comply with the sub-system requirements. We also present the prototypes developed to prove some of the adopted concepts in the design.
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