9 research outputs found
Battle of the Predictive Wavefront Controls: Comparing Data and Model-Driven Predictive Control for High Contrast Imaging
Ground-based high contrast exoplanet imaging requires state-of-the-art
adaptive optics (AO) systems in order to detect extremely faint planets next to
their brighter host stars. For such extreme AO systems (with high actuator
count deformable mirrors over a small field of view), the lag time of the
correction (which can impact our system by the amount the wavefront has changed
by the time the system is able to apply the correction) which can be anywhere
from ~1-5 milliseconds, can cause wavefront errors on spatial scales that lead
to speckles at small angular separations from the central star in the final
science image. One avenue for correcting these aberrations is predictive
control, wherein previous wavefront information is used to predict the future
state of the wavefront in one-system-lag's time, and this predicted state is
applied as a correction with a deformable mirror. Here, we consider two methods
for predictive control: data-driven prediction using empirical orthogonal
functions and the physically-motivated predictive Fourier control. The
performance and robustness of these methods have not previously been compared
side-by-side. In this paper, we compare these predictors by applying them as
post-facto methods to simulated atmospheres and on-sky telemetry, to
investigate the circumstances in which their performance differs, including
testing them under different wind speeds, C_n^2 profiles, and time lags. We
also discuss future plans for testing both algorithms on the Santa Cruz Extreme
AO Laboratory (SEAL) testbed
SHIMM as an atmospheric profiler on the Nickel Telescope
Optimal atmospheric conditions are beneficial for detecting exoplanets via
high contrast imaging (HCI), as speckles from adaptive optics' (AO's) residuals
can make it difficult to identify exoplanets. While AO systems greatly improve
our image quality, having access to real-time estimates of atmospheric
conditions could also help astronomers use their telescope time more
efficiently in the search for exoplanets as well as aid in the data reduction
process. The Shack-Hartmann Imaging Motion Monitor (SHIMM) is an atmospheric
profiler that utilizes a Shack-Hartmann wavefront sensor to create spot images
of a single star in order to reconstruct important atmospheric parameters such
as the Fried parameter (), profile and coherence time. Due to its
simplicity, the SHIMM can be directly used on a telescope to get in situ
measurements while observing. We present our implementation of the Nickel-SHIMM
design for the one meter Nickel Telescope at Lick Observatory. We utilize an
HCIPy simulation of turbulence propagating across a telescope aperture to
verify the SHIMM data reduction pipeline as we begin on-sky testing. We also
used on-sky data from the AO system on the Shane Telescope to further validate
our analysis, finding that both our simulation and data reduction pipeline are
consistent with previously determined results for the Fried parameter at the
Lick Observatory. Finally, we present first light results from commissioning of
the Nickel-SHIMM.Comment: Conference Proceedings for 2023 SPIE Optics and Photonics, Techniques
and Instrumentation for Detection of Exoplanets X
Using the Gerchberg-Saxton algorithm to reconstruct non-modulated pyramid wavefront sensor measurements
Adaptive optics (AO) is a technique to improve the resolution of ground-based
telescopes by correcting, in real-time, optical aberrations due to atmospheric
turbulence and the telescope itself. With the rise of Giant Segmented Mirror
Telescopes (GSMT), AO is needed more than ever to reach the full potential of
these future observatories. One of the main performance drivers of an AO system
is the wavefront sensing operation, consisting of measuring the shape of the
above mentioned optical aberrations. Aims. The non-modulated pyramid wavefront
sensor (nPWFS) is a wavefront sensor with high sensitivity, allowing the limits
of AO systems to be pushed. The high sensitivity comes at the expense of its
dynamic range, which makes it a highly non-linear sensor. We propose here a
novel way to invert nPWFS signals by using the principle of reciprocity of
light propagation and the Gerchberg-Saxton (GS) algorithm. We test the
performance of this reconstructor in two steps: the technique is first
implemented in simulations, where some of its basic properties are studied.
Then, the GS reconstructor is tested on the Santa Cruz Extreme Adaptive optics
Laboratory (SEAL) testbed located at the University of California Santa Cruz.
This new way to invert the nPWFS measurements allows us to drastically increase
the dynamic range of the reconstruction for the nPWFS, pushing the dynamics
close to a modulated PWFS. The reconstructor is an iterative algorithm
requiring heavy computational burden, which could be an issue for real-time
purposes in its current implementation. However, this new reconstructor could
still be helpful in the case of many wavefront control operations. This
reconstruction technique has also been successfully tested on the Santa Cruz
Extreme AO Laboratory (SEAL) bench where it is now used as the standard way to
invert nPWFS signal
Visible extreme adaptive optics on extremely large telescopes: Towards detecting oxygen in Proxima Centauri b and analogs
Looking to the future of exo-Earth imaging from the ground, core technology
developments are required in visible extreme adaptive optics (ExAO) to enable
the observation of atmospheric features such as oxygen on rocky planets in
visible light. UNDERGROUND (Ultra-fast AO techNology Determination for
Exoplanet imageRs from the GROUND), a collaboration built in Feb. 2023 at the
Optimal Exoplanet Imagers Lorentz Workshop, aims to (1) motivate oxygen
detection in Proxima Centauri b and analogs as an informative science case for
high-contrast imaging and direct spectroscopy, (2) overview the state of the
field with respect to visible exoplanet imagers, and (3) set the instrumental
requirements to achieve this goal and identify what key technologies require
further development.Comment: SPIE Proceeding: 2023 / 12680-6
Predictive wavefront control on Keck II adaptive optics bench: on-sky coronagraphic results
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 AO system, the servo-lag error can become the dominant error term of the AO
system. While the AO system measures the wavefront error and subsequently
applies a correction (typically taking a total of one or a few milliseconds),
the atmospheric turbulence above the telescope has changed resulting in the
servo-lag error. In addition to reducing the Strehl ratio, the servo-lag error
causes a build-up of speckles along the direction of the dominant wind vector
in the coronagraphic image, severely limiting the contrast at small angular
separations. One strategy to mitigate this problem is to predict the evolution
of the turbulence over the delay time. Our predictive wavefront control
algorithm minimizes, in a mean square sense, the wavefront error over the delay
and has been implemented on the Keck II AO bench. In this paper, we report on
the latest results of our algorithm and discuss updates to the algorithm
itself. We explore how to tune various filter parameters based on both daytime
laboratory tests and on-sky tests. We show a reduction in the
residual-mean-square wavefront error for the predictor compared to the leaky
integrator (the standard controller for Keck) implemented on Keck for three
separate nights. Finally, we present contrast improvements for daytime and
on-sky tests for the first time. Using the L-band vortex coronagraph for Keck's
NIRC2 instrument, we find a contrast gain of up to 2 at a separation of 3
lambda/D and up to 3 for larger separations (3-7 lambda/D).Comment: Accepted to JATIS May 20 2022. 34 pages, 15 Figures. arXiv admin
note: substantial text overlap with arXiv:2108.0893
Liposomal Delivery Improves the Efficacy of Prednisolone to Attenuate Renal Inflammation in a Mouse Model of Acute Renal Allograft Rejection
Background.Systemic exposure to high-dose corticosteroids effectively combats acute rejection after kidney transplantation, but at the cost of substantial side effects. In this study, a murine acute renal allograft rejection model was used to investigate whether liposomal-encapsulated prednisolone (LP) facilitates local exposure to enhance its therapeutic effect.Methods.Male BalbC recipients received renal allografts from male C57BL/6J donors. Recipients were injected daily with 5 mg/kg cyclosporine A and received either 10 mg/kg prednisolone (P), or LP intravenously on day 0, 3, and 6, or no additional treatment. Functional magnetic resonance imaging (fMRI) was performed on day 6 to study allograft perfusion and organs were retrieved on day 7 for further analysis.Results.Staining of polyethylene-glycol-labeled liposomes and high performance liquid chromatography analysis revealed accumulation in the LP treated allograft. LP treatment induced the expression of glucocorticoid responsive gene Fkbp5 in the allograft. Flow-cytometry of allografts revealed liposome presence in CD45(+) cells, and reduced numbers of F4/80(+) macrophages, and CD3(+) T-lymphocytes upon LP treatment. Banff scoring showed reduced interstitial inflammation and tubulitis and fMRI analysis revealed improved allograft perfusion in LP versus NA mice.Conclusions.Liposomal delivery of prednisolone improved renal bio-availability, increased perfusion and reduced cellular infiltrate in the allograft, when compared with conventional prednisolone. Clinical studies should reveal if treatment with LP results in improved efficacy and reduced side effects in patients with renal allograft rejection.Diabetes mellitus: pathophysiological changes and therap
Critical role for complement receptor C5aR2 in the pathogenesis of renal ischemia-reperfusion injury
The complement system, and specifically C5a, is involved in renal ischemia-reperfusion (IR) injury. The 2 receptors for complement anaphylatoxin C5a (C5aR1 and C5aR2) are expressed on leukocytes as well as on renal epithelium. Extensive evidence shows that C5aR1 inhibition protects kidneys from IR injury; however, the role of C5aR2 in IR injury is less clear as initial studies proposed the hypothesis that C5aR2 functions as a decoy receptor. By Using wild-type, C5aR1(-/-), and C5aR2(-/-) mice in a model of renal IR injury, we found that a deficiency of either of these receptors protected mice from renal IR injury. Surprisingly, C5aR2(-/-) mice were most protected and had lower creatinine levels and reduced acute tubular necrosis. Next, an in vivo migration study demonstrated that leukocyte chemotaxis was unaffected in C5aR2(-/-) mice, whereas neutrophil activation was reduced by C5aR2 deficiency. To further investigate the contribution of renal cell-expressed C5aR2 vs. leukocyte-expressed C5aR2 to renal IR injury, bone marrow chimeras were created. Our data show that both renal cell-expressed C5aR2 and leukocyte-expressed C5aR2 mediate IR-induced renal dysfunction. These studies reveal the importance of C5aR2 in renal IR injury. They further show that C5aR2 is a functional receptor, rather than a decoy receptor, and may provide a new target for intervention
Visible extreme adaptive optics on extremely large telescopes: towards detecting oxygen in Proxima Centauri b and analogs
International audienceLooking to the future of exo-Earth imaging from the ground, core technology developments are required in visible Extreme Adaptive Optics (ExAO) to enable the observation of atmospheric features such as oxygen on rocky planets in visible light. UNDERGROUND (Ultra-fast AO techNology Determination for Exoplanet imageRs from the GROUND), a collaboration built in Feb. 2023 at the Optimal Exoplanet Imagers Lorentz Workshop, aims to (1) motivate oxygen detection in Proxima Centauri b and analogs as an informative science case for high-contrast imaging and direct spectroscopy, (2) overview the state of the field with respect to visible exoplanet imagers, and (3) set the instrumental requirements to achieve this goal and identify what key technologies require further development
Chasing rainbows and ocean glints: Inner working angle constraints for the Habitable Worlds Observatory
International audienceNASA is engaged in planning for a Habitable Worlds Observatory (HabWorlds ), a coronagraphic space mission to detect rocky planets in habitable zones and establish their habitability. Surface liquid water is central to the definition of planetary habitability. Photometric and polarimetric phase curves of starlight reflected by an exoplanet can reveal ocean glint, rainbows, and other phenomena caused by scattering by clouds or atmospheric gas. Direct imaging missions are optimized for planets near quadrature, but HabWorlds ' coronagraph may obscure the phase angles where such optical features are strongest. The range of accessible phase angles for a given exoplanet will depend on the planet's orbital inclination and/or the coronagraph's inner working angle (IWA). We use a recently created catalog relevant to HabWorlds of 164 stars to estimate the number of exo-Earths that could be searched for ocean glint, rainbows, and polarization effects due to Rayleigh scattering. We find that the polarimetric Rayleigh scattering peak is accessible in most of the exo-Earth planetary systems. The rainbow due to water clouds at phase angles of ~20â - 60â would be accessible with HabWorlds for a planet with an Earth equivalent instellation in ~46 systems, while the ocean glint signature at phase angles of ~130â - 170â would be accessible in ~16 systems, assuming an IWA = 62 mas (3λ/D). Improving the IWA = 41 mas (2λ/D) increases accessibility to rainbows and glints by factors of approximately 2 and 3, respectively. By observing these scattering features, HabWorlds could detect a surface ocean and water cycle, key indicators of habitability