HARMONI is the first light visible and near-infrared (450 – 2450 nm, λ/Δλ = 3,000 – 17,000) integral field spectrograph for the European Southern Observatory’s Extremely Large Telescope. The path for scientific light includes pre-optics to set the field of view (4 – 60 mas), an integral field unit to reformat the rectangular field into four 540 mm long slits, and four spectrographs which collimate, disperse, and image the light. The spectrographs collimate the input slits using a system of three off-axis, aspheric mirrors which lack a common optical axis. We have demonstrated the alignment procedure of this three-mirror anastigmat in numerical simulations. We will initially align the collimator mirrors by measuring reference features with a coordinate measuring machine (CMM). We will then use an interferometer to measure the wavefront error (WFE) at positions along the input slit. These WFE measurements will be entered into a numerical model to optimize available compensators, and the corresponding adjustments will be applied to the collimator. This process of measuring WFE, using a model to determine optimal compensator adjustments, and applying the adjustments will be repeated until the performance has converged. As an initial demonstration of this method, we have simulated the full alignment procedure. The modelled systems include manufacturing errors, account for the uncertainty of values reported by mirror manufacturers, and simulate the CMM and interferometer alignment steps. Nearly all of 1000 instances meet our requirements after two iterations of the optical alignment, and all were found to satisfy our requirements after five iterations.
HARMONI is the first light visible and near-infrared (NIR) integral field spectrograph for the Extremely Large Telescope(ELT). The HARMONI spectrograph will have four near-infrared cameras and two visible, both with seven lenses of various materials and diameters ranging from 286 to 152 mm. The lens mounts design has been optimized for each lens material to compensate for thermal stresses and maintain lens alignment at the operational temperature of 130 K. We discuss their design and mounting concept, as well as assembly and verification steps. We show initial results from two prototypes and outline improvements in the mounting procedures to reach tighter lens alignments. To conclude, we present a description of our future work to measure the decentering of the lenses when cooled down and settled.
HARMONI is the adaptive optics assisted, near-infrared and visible light integral field spectrograph for the Extremely Large Telescope (ELT). A first light instrument, it provides the work-horse spectroscopic capability for the ELT. As the project approaches its Final Design Review milestone, 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, provide a summary of the instrument’s design, including plans for operations and calibrations, and provide a brief glimpse of the predicted performance for a specific observing scenario. The paper also provides some details of the consortium composition and its evolution since the project commenced in 2015.
HARMONI is the first light visible and near-IR integral field spectrograph for the ELT. It covers a large spectral range from 450nm to 2450nm with resolving powers from R (≡λ/Δλ) 3500 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 instrument uses a field splitter and image slicer to divide the field into 4 sub-units, each providing an input slit to one of four nearly identical spectrographs. This proceeding presents the final opto- mechanical design and the AIV plan of the spectrograph units.