Aaron Lemmer | Search arXiv

arXiv2026

Initial modeling and testbed feasibility studies of WaveDriver: a laser guide star AO system for HWO

The Habitable Worlds Observatory (HWO) will require $>100\times$ greater wavefront stability than achieved by JWST, pushing conventional telescope architectures to picometer-level performance limits. WaveDriver is a mission concept that relaxes these constraints by employing an external laser guide star (LGS) spacecraft flying in formation with HWO to enable wavefront sensing and control. Early results from the High Contrast Testbed demonstrate feasibility of required stability using coronagraphs, multiple deformable mirrors, and a suite of wavefront sensors. We report mission design analyses, initial testbed stability metrics, compare sensor performance, and present an optical model that quantifies LGS brightness, conjugation errors, and field errors arising from finite beacon separation.

astro-ph.IM↗

arXiv2026

On-sky results from REDWOODS, a platform at Lick/ShaneAO for testing second stage AO technologies

REDWOODS is a new sub-testbed within the Shane Adaptive Optics (AO) system at Lick observatory, developed to test second stage AO wavefront sensing and control technologies, including a Self-Coherent Camera with optional broadband Wynne corrector, two different three-sided fully reflective highly broadband pyramid wavefront sensor modes, and multi-wavefront sensor single conjugate AO control. We present project results to date, including on-sky data.

astro-ph.IM↗

arXiv2024

The Focal-plane Actualized Shifted Technique Realized for a Shack Hartmann Wavefront Sensor (fastrSHWFS)

Astronomical adaptive optics (AO) is a critical approach to enable ground-based diffraction-limited imaging and high contrast science, with the potential to enable habitable exoplanet imaging on future extremely large telescopes. However, AO systems must improve significantly to enable habitable exoplanet imaging. Time lag between the end of an exposure and end of deformable mirror commands being applied in an AO loop is now the dominant error term in many extreme AO systems (e.g., Poyneer et al. 2016), and within that lag component detector read time is becoming non-negligible (e.g., Cetre et al. 2018). This term will decrease as faster detector readout capabilities are developed by vendors. In complement, we have developed a modified Shack Hartmann Wavefront Sensor (SHWFS) to address this problem called the Focal-plane Actualized Shifted Technique Realized for a SHWFS (fastrSHWFS). The novelty of this design is to replace the usual lenslet array with a bespoke pupil-plane phase mask that redistributes the spot pattern on the detector into a rectangular array with a custom aspect ratio (in an extreme case, if the detector size can accommodate it, the array can be a single line). We present the fastrSHWFS concept and preliminary laboratory tests. For some detectors and AO systems, the fastrSHWFS technique can decrease the read time per frame compared to a regular SHWFS by up to 30x, supporting the goal of reduced AO lag needed to eventually enable habitable exoplanet imaging.

astro-ph.IM↗