arXiv subjects

Guillermo Mercant Rubio

Publications and source records attributed to Guillermo Mercant Rubio.

3 recordsLinked to original sources

arXiv2026

HARMONI at ELT: Design & Test on the current status of Low Order Wavefront Subsystem Pick Off Arm Engineering Model (LPOA-EM)

HARMONI is the first-light, adaptive-optics-assisted, near-infrared integral field spectrograph for the ELT, covering 800 to 2450 nm with resolving powers from 3000 to 7000. The Low Order Wavefront Sensor subsystem (LOWFS) provides field stabilisation by measuring the motion of the instrument focal plane relative to the telescope wavefront sensors. Following a rescope process in 2025, LOWFS has been updated to operate three LOWFS Pick-Off Arms (LPOA) simultaneously within a shared volume. We present first results from the LPOA Engineering Model (EM) characterisation campaign on two rotary joints, shoulder and elbow, including measurements of angular resolution, discrete step tracking validated by independent metrology, rotation axis wobble, and radial and axial runout of the bearing assembly.

astro-ph.IM↗

arXiv2026

HARMONI at ELT: LPOU calibrations for a micron-level pointing accuracy

HARMONI is the first light, adaptive optics assisted, near-IR integral field spectrograph for the ELT [1]. It covers a spectral range from 800 nm to 2450 nm with resolving powers from 3000 to 7000 and spatial sampling of 25 mas and 6mas. It can operate in two adaptive optics modes, SCAO (including a high contrast capability) and MCAO. The project is resuming its final design phase after a rescope design phase in 2025. To achieve its optimal image quality, HARMONI needs to perform pointing error measurement by means of three guide probes. Each guide probe is a robotic arm with a shoulder-elbow stage that is optically equivalent to two periscopes connected together. Since any systematic positioning error of the shoulder-elbow motors will result in a measurement error of the pointing error itself, an appropriate geometric calibration reference is necessary. In previous designs, this calibration reference took the form of a deployable calibration mask that could be inserted in the telescope's focal plane. However, this approach prevents the guiding sensors from distinguishing motor contributions from other effects caused by the instrument optics. In this work, we explore the possibility of inserting the calibration mask as close to the guide probes as possible, along with the addition of the necessary refocus optics in the light path of the guiding sensors. We discuss different variations of this idea, their effect on the image quality, and their ability to resolve positioning errors smaller than 1 μm. The results of these analyses were cross-validated by means of optical simulations in RayZaler, and will be used to put bounds to the expected calibration accuracy achievable by this design.

astro-ph.IM↗

arXiv2026

HARMONI at ELT: Reoptimization of the NGSS natural guide star sensors system for MCAO compatibility

HARMONI is the first-light, adaptive optics assisted, near-IR integral field spectrograph for the ELT. It covers a spectral range from below 800nm to 2400nm with resolving powers from 3000 to 7000 and spatial sampling of 25mas and 6mas. It can operate in three adaptive optics (AO) modes: single conjugate AO (SCAO), high-contrast AO (HCAO), and multi-conjugate AO (MCAO). The project is resuming its final design phase after a rescope design phase that has lasted two years. This paper describes the impact of the rescope on the natural guide star sensors (NGSS) system, imposing wide-ranging changes in particular to the low-order wavefront sensors (LOWFS) previously optimized for LTAO operation as well as on the external support and enclosure (ESE) whose external interfaces have changed. The high-contrast module (HCM) is also deeply affected due to the modified plate scale of the instrument, and the single-conjugate AO sensor (SCAOS) benefits from a reduced patrol field requirement. Description of the changes will be given together with the associated system analysis involving requirements flow-down, revisited functional analysis, and updated product breakdown structure. Elements of the new system management structure and work breakdown will also be included.

astro-ph.IM↗