Sam Ragland
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View article: The Simultaneous Operation of a Controllable Segmented Primary Mirror and Single Conjugate Adaptive Optics System part 2 -- Simulated Operation
The Simultaneous Operation of a Controllable Segmented Primary Mirror and Single Conjugate Adaptive Optics System part 2 -- Simulated Operation Open
There are scientific and technological needs to improve the co-phasing of the primary mirrors of segmented telescopes. We have developed a methodology for using the wavefront sensor of an adaptive optics (AO) system to disentangle the phas…
View article: AI-powered low-order focal plane wavefront sensing in infrared
AI-powered low-order focal plane wavefront sensing in infrared Open
Adaptive optics (AO) systems are crucial for high-resolution astronomical observations by compensating for atmospheric turbulence. While laser guide stars (LGS) address high-order wavefront aberrations, natural guide stars (NGS) remain vit…
View article: The instrumentation program at the Large Binocular Telescope Observatory in 2024
The instrumentation program at the Large Binocular Telescope Observatory in 2024 Open
The Large Binocular Telescope, with its expansive collecting area, angular resolving power, and advanced optical design, provides a robust platform for development and operation of advanced instrumentation for astronomical research. The LB…
View article: Pele meets Pillan:  Demonstration of a new method for monitoring surface changes on Io
Pele meets Pillan:  Demonstration of a new method for monitoring surface changes on Io Open
A new development in the field of adaptive optics (AO) on ground-based telescopes enables routine monitoring of changes on Io's surface at scales down to ~80km (achieved), or even down to ~50km (in the limit).  Our observations, taken…
View article: Observation of Io's Resurfacing via Plume Deposition Using Ground‐Based Adaptive Optics at Visible Wavelengths With LBT SHARK‐VIS
Observation of Io's Resurfacing via Plume Deposition Using Ground‐Based Adaptive Optics at Visible Wavelengths With LBT SHARK‐VIS Open
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes on Io's surface have been monitored from both spacecraft and ground‐based telescopes. Here, we present the highest spatial resolution images of Io ever…
View article: LBT SHARK-VIS Observes a Major Resurfacing Event on Io
LBT SHARK-VIS Observes a Major Resurfacing Event on Io Open
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes on Io's surface have been monitored from both spacecraft and ground-based telescopes. Here, we present the highest spatial resolution images of Io ever…
View article: Keck Planet Imager and Characterizer Emission Spectroscopy of WASP-33b
Keck Planet Imager and Characterizer Emission Spectroscopy of WASP-33b Open
We present Keck Planet Imager and Characterizer (KPIC) high-resolution ( R ∼35,000) K -band thermal emission spectroscopy of the ultrahot Jupiter WASP-33b. The use of KPIC’s single-mode fibers greatly improves both blaze and line-spread st…
View article: Keck/KPIC Emission Spectroscopy of WASP-33b
Keck/KPIC Emission Spectroscopy of WASP-33b Open
We present Keck/KPIC high-resolution ($R\sim35,000$) $K$-band thermal emission spectroscopy of the ultra-hot Jupiter WASP-33b. The use of KPIC's single-mode fibers greatly improves both blaze and line-spread stabilities relative to slit sp…
View article: Architecting, Implementing and Observing with a Metasurface vector Zernike wavefront sensor on the Keck Telescope
Architecting, Implementing and Observing with a Metasurface vector Zernike wavefront sensor on the Keck Telescope Open
The ability to directly detect faint companions orbiting around nearby stars using ground-based telescopes has made incredible strides in the past couple of decades. This has been enabled by a suite of methods working closely and in concer…
View article: Enabling high resolution visible AO at the W.M. Keck Observatory
Enabling high resolution visible AO at the W.M. Keck Observatory Open
The W. M. Keck Observatory has generated an observatory wide strategic plan for 2035. This plan has identified visible Adaptive Optics (AO) as an attractive science path for the observatory. Given the 10-meter aperture of the Keck telescop…
View article: From Demonstration to Operation: High Contrast Imaging Tools at Keck Observatory
From Demonstration to Operation: High Contrast Imaging Tools at Keck Observatory Open
High contrast imaging (HCI) is limited in practice by uncorrected wavefront errors within traditional adaptive optics (AO). Keck observatory experiences roughly 130nm of unacoounted residual wavefront error even with well calibrated AO. Mu…
View article: Retrieving C and O Abundance of HR 8799 c by Combining High- and Low-resolution Data
Retrieving C and O Abundance of HR 8799 c by Combining High- and Low-resolution Data Open
The formation and evolution pathway for the directly imaged multiplanetary system HR 8799 remains mysterious. Accurate constraints on the chemical composition of the planetary atmosphere(s) are key to solving the mystery. We perform a deta…
View article: Retrieving C and O Abundance of HR 8799 c by Combining High- and Low-Resolution Data
Retrieving C and O Abundance of HR 8799 c by Combining High- and Low-Resolution Data Open
The formation and evolution pathway for the directly-imaged multi-planetary system HR 8799 remains mysterious. Accurate constraints on the chemical composition of the planetary atmosphere(s) are key to solving the mystery. We perform a det…
View article: A Clear View of a Cloudy Brown Dwarf Companion from High-resolution Spectroscopy
A Clear View of a Cloudy Brown Dwarf Companion from High-resolution Spectroscopy Open
Direct imaging studies have mainly used low-resolution spectroscopy ( R ∼ 20–100) to study the atmospheres of giant exoplanets and brown dwarf companions, but the presence of clouds has often led to degeneracies in the retrieved atmospheri…
View article: AIROPA II: modeling instrumental aberrations for off-axis point spread functions in adaptive optics
AIROPA II: modeling instrumental aberrations for off-axis point spread functions in adaptive optics Open
Images obtained with single-conjugate adaptive optics (AO) show spatial variation of the point spread function (PSF) due to both atmospheric anisoplanatism and instrumental aberrations. The poor knowledge of the PSF across the field of vie…
View article: Phase II of the Keck Planet Imager and characterizer: system-level laboratory characterization and preliminary on-sky commissioning
Phase II of the Keck Planet Imager and characterizer: system-level laboratory characterization and preliminary on-sky commissioning Open
The Keck Planet Imager and Characterizer (KPIC) is a series of upgrades for\nthe Keck II Adaptive Optics (AO) system and the NIRSPEC spectrograph to enable\ndiffraction-limited, high-resolution ($R>30,000$) spectroscopy of exoplanets\nand …
View article: A Clear View of a Cloudy Brown Dwarf Companion from High-Resolution Spectroscopy
A Clear View of a Cloudy Brown Dwarf Companion from High-Resolution Spectroscopy Open
Direct imaging studies have mainly used low-resolution spectroscopy ($R\sim20-100$) to study the atmospheres of giant exoplanets and brown dwarf companions, but the presence of clouds has often led to degeneracies in the retrieved atmosphe…
View article: Daytime calibration and testing of the Keck All sky Precision Adaptive Optics Tomography System
Daytime calibration and testing of the Keck All sky Precision Adaptive Optics Tomography System Open
The development of the Keck All sky Precision Adaptive optics (KAPA) project was initiated in September 2018 to upgrade the Keck I adaptive optics (AO) system to enable laser tomography adaptive optics (LTAO) with a four laser guide star (…
View article: AIROPA III: Testing Simulated and On-Sky Data
AIROPA III: Testing Simulated and On-Sky Data Open
Adaptive optics images from the W. M. Keck Observatory have delivered numerous influential scientific results, including detection of multi-system asteroids, the supermassive black hole at the center of the Milky Way, and directly imaged e…
View article: Predictive wavefront control on Keck II adaptive optics bench: on-sky coronagraphic results
Predictive wavefront control on Keck II adaptive optics bench: on-sky coronagraphic results Open
The behavior of an adaptive optics (AO) system for ground-based high contrast imaging dictates the achievable contrast of the instrument. In conditions where the coherence time of the atmosphere is short compared with the speed of the AO s…
View article: On-sky Reconstruction of Keck Primary Mirror Piston Offsets Using a Zernike Wavefront Sensor
On-sky Reconstruction of Keck Primary Mirror Piston Offsets Using a Zernike Wavefront Sensor Open
The next generation of large ground- and space-based optical telescopes will have segmented primary mirrors. Co-phasing the segments requires a sensitive wavefront sensor capable of measuring phase discontinuities. The Zernike wavefront se…
View article: Analyzing long-term performance of the Keck-II adaptive optics system
Analyzing long-term performance of the Keck-II adaptive optics system Open
We present an analysis of the long-term performance of the W. M. Keck observatory laser guide star adaptive optics (LGS-AO) system and explore factors that influence the overall AO performance most strongly. Astronomical surveys can take y…
View article: Predictive wavefront control on Keck II adaptive optics bench: on-sky coronagraphic results
Predictive wavefront control on Keck II adaptive optics bench: on-sky coronagraphic results Open
The behavior of an adaptive optics (AO) system for ground-based high contrast imaging (HCI) dictates the achievable contrast of the instrument. In conditions where the coherence time of the atmosphere is short compared to the speed of the …
View article: On-sky reconstruction of Keck Primary Mirror Piston Offsets using a\n Zernike Wavefront Sensor
On-sky reconstruction of Keck Primary Mirror Piston Offsets using a\n Zernike Wavefront Sensor Open
The next generation of large ground- and space-based optical telescopes will\nhave segmented primary mirrors. Co-phasing the segments requires a sensitive\nwavefront sensor capable of measuring phase discontinuities. The Zernike\nwavefront…
View article: Retrieving the C and O Abundances of HR 7672 AB: A Solar-type Primary Star with a Benchmark Brown Dwarf
Retrieving the C and O Abundances of HR 7672 AB: A Solar-type Primary Star with a Benchmark Brown Dwarf Open
A benchmark brown dwarf (BD) is a BD whose properties (e.g., mass and chemical composition) are precisely and independently measured. Benchmark BDs are valuable in testing theoretical evolutionary tracks, spectral synthesis, and atmospheri…
View article: Retrieving the C and O Abundances of HR 7672~AB: a Solar-Type Primary Star with a Benchmark Brown Dwarf
Retrieving the C and O Abundances of HR 7672~AB: a Solar-Type Primary Star with a Benchmark Brown Dwarf Open
A benchmark brown dwarf (BD) is a BD whose properties (e.g., mass and chemical composition) are precisely and independently measured. Benchmark BDs are valuable in testing theoretical evolutionary tracks, spectral synthesis, and atmospheri…
View article: An Imaging Search for Post-main-sequence Planets of Sirius B
An Imaging Search for Post-main-sequence Planets of Sirius B Open
We present deep imaging of Sirius B, the closest and brightest white dwarf, to constrain post-main-sequence planetary evolution in the Sirius system. We use Keck/NIRC2 in L ′ band (3.776 μ m) across three epochs in 2020 using the technique…
View article: An Imaging Search for Post-Main-Sequence Planets of Sirius B
An Imaging Search for Post-Main-Sequence Planets of Sirius B Open
We present deep imaging of Sirius B, the closest and brightest white dwarf, to constrain post-main-sequence planetary evolution in the Sirius system. We use Keck/NIRC2 in L'-band (3.776 $μ$m) across three epochs in 2020 using the technique…
View article: Point spread function reconstruction of adaptive-optics imaging: meeting the astrometric requirements for time-delay cosmography
Point spread function reconstruction of adaptive-optics imaging: meeting the astrometric requirements for time-delay cosmography Open
Astrometric precision and knowledge of the point spread function are key ingredients for a wide range of astrophysical studies including time-delay cosmography in which strongly lensed quasar systems are used to determine the Hubble consta…