The Impact of Segment Vibrations on Adaptive Optics at the Keck Telescope

2007 ◽  
Author(s):  
Ralf Flicker ◽  
Christopher Neyman
Keyword(s):  
Adaptive Optics ◽  
The Impact

scholarly journals Binary asteroid (31) Euphrosyne: ice-rich and nearly spherical

2020 ◽  
Vol 641 ◽  
pp. A80
Author(s):  
B. Yang ◽  
J. Hanuš ◽  
B. Carry ◽  
P. Vernazza ◽  
M. Brož ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Family Formation ◽  
Large Fraction ◽  
Imaging Study ◽  
Spherical Shape ◽  
Hydrostatic Equilibrium ◽  
Main Belt ◽  
Binary Asteroid ◽  
Water Ice ◽  
The Impact

Aims. Asteroid (31) Euphrosyne is one of the biggest objects in the asteroid main belt and it is also the largest member of its namesake family. The Euphrosyne family occupies a highly inclined region in the outer main belt and contains a remarkably large number of members, which is interpreted as an outcome of a disruptive cratering event. Methods. The goals of this adaptive-optics imaging study are threefold: to characterize the shape of Euphrosyne, to constrain its density, and to search for the large craters that may be associated with the family formation event. Results. We obtained disk-resolved images of Euphrosyne using SPHERE/ZIMPOL at the ESO 8.2 m VLT as part of our large program (ID: 199.C-0074, PI: Vernazza). We reconstructed its 3D shape via the ADAM shape modeling algorithm based on the SPHERE images and the available light curves of this asteroid. We analyzed the dynamics of the satellite with the Genoid meta-heuristic algorithm. Finally, we studied the shape of Euphrosyne using hydrostatic equilibrium models. Conclusions. Our SPHERE observations show that Euphrosyne has a nearly spherical shape with the sphericity index of 0.9888 and its surface lacks large impact craters. Euphrosyne’s diameter is 268 ± 6 km, making it one of the top ten largest main belt asteroids. We detected a satellite of Euphrosyne – S/2019 (31) 1 – that is about 4 km across, on a circular orbit. The mass determined from the orbit of the satellite together with the volume computed from the shape model imply a density of 1665 ± 242 kg m−3, suggesting that Euphrosyne probably contains a large fraction of water ice in its interior. We find that the spherical shape of Euphrosyne is a result of the reaccumulation process following the impact, as in the case of (10) Hygiea. However, our shape analysis reveals that, contrary to Hygiea, the axis ratios of Euphrosyne significantly differ from those suggested by fluid hydrostatic equilibrium following reaccumulation.

New View of the Solar Chromosphere

2019 ◽  
Vol 57 (1) ◽  
pp. 189-226 ◽  
Author(s):  
Mats Carlsson ◽  
Bart De Pontieu ◽  
Viggo H. Hansteen
Keyword(s):  
High Resolution ◽  
Adaptive Optics ◽  
Numerical Models ◽  
Transverse Magnetic ◽  
Solar Photosphere ◽  
Solar Chromosphere ◽  
Image Reconstruction Techniques ◽  
New Instrumentation ◽  
Field Unit ◽  
The Impact

The solar chromosphere forms a crucial, yet complex and until recently poorly understood, interface between the solar photosphere and the heliosphere. ▪ Advances in high-resolution instrumentation, adaptive optics, image reconstruction techniques, and space-based observatories allow unprecedented high-resolution views of the finely structured and highly dynamic chromosphere. ▪ Dramatic progress in numerical computations allows 3D radiative magnetohydrodynamic forward models to take the place of the previous generation of 1D semiempirical atmosphere models. These new models provide deep insight into complex nonlocal thermodynamic equilibrium chromospheric diagnostics and enable physics-based interpretations of observations. ▪ This combination of modeling and observations has led to new insights into the role of shock waves, transverse magnetic waves, magnetic reconnection and flux emergence in the chromospheric energy balance, the formation of spicules, the impact of ion-neutral interactions, and the connectivity between chromosphere and transition region. ▪ During the next few years, the advent of new instrumentation (integral-field-unit spectropolarimetry) and observatories (ALMA, DKIST), coupled with novel inversion codes and expansion of existing numerical models to deal with ever more complex physical processes (including multifluid approaches), is expected to lead to major new insights into the dominant heating processes in the chromosphere and beyond.

scholarly journals SUPER

2018 ◽  
Vol 620 ◽  
pp. A82 ◽  
Author(s):  
C. Circosta ◽  
V. Mainieri ◽  
P. Padovani ◽  
G. Lanzuisi ◽  
M. Salvato ◽  
...  
Keyword(s):  
Star Formation ◽  
Adaptive Optics ◽  
High Redshift ◽  
Spectral Energy Distribution ◽  
Host Galaxy ◽  
Spectral Energy ◽  
Distribution Fitting ◽  
X Ray ◽  
Narrow Component ◽  
The Impact

Theoretical models of galaxy formation suggest that the presence of an active galactic nucleus (AGN) is required to regulate the growth of its host galaxy through feedback mechanisms, produced by, for example, AGN-driven outflows. Although many observational studies have revealed that such outflows are common both at low and high redshift, a comprehensive picture is still missing. In particular, the peak epoch of galaxy assembly (1 <  z <  3) has been poorly explored so far, and current observations in this redshift range are mostly limited to targets with high chances to be in an outflowing phase. This paper introduces SUPER (a SINFONI Survey for Unveiling the Physics and Effect of Radiative feedback), an ongoing ESO’s VLT/SINFONI Large Programme. SUPER will perform the first systematic investigation of ionized outflows in a sizeable and blindly-selected sample of 39 X-ray AGN at z ∼ 2, which reaches high spatial resolutions (∼2 kpc) thanks to the adaptive optics-assisted IFS observations. The outflow morphology and star formation in the host galaxy will be mapped through the broad component of [O III]λ5007 and the narrow component of Hα emission lines. The main aim of our survey is to infer the impact of outflows on the on-going star formation and to link the outflow properties to a number of AGN and host galaxy properties. We describe here the survey characteristics and goals, as well as the selection of the target sample. Moreover, we present a full characterization of its multi-wavelength properties: we measure, via spectral energy distribution fitting of UV-to-FIR photometry, stellar masses (4 × 109 − 2 × 1011 M⊙), star formation rates (25 − 680 M⊙ yr−1) and AGN bolometric luminosities (2 × 1044 − 8 × 1047 erg s−1), along with obscuring column densities (up to 2 × 1024 cm−2) and luminosities in the hard 2 − 10 keV band (2 × 1043 − 6 × 1045 erg s−1) derived through X-ray spectral analysis. Finally, we classify our AGN as jetted or non-jetted according to their radio and FIR emission.

scholarly journals Comparison of Multiscale Imaging Methods for Brain Research

Cells ◽  
2020 ◽  
Vol 9 (6) ◽  
pp. 1377
Author(s):  
Jessica Tröger ◽  
Christian Hoischen ◽  
Birgit Perner ◽  
Shamci Monajembashi ◽  
Aurélien Barbotin ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Brain Research ◽  
Super Resolution ◽  
Synaptic Proteins ◽  
Physiological Status ◽  
Basic Set ◽  
Recent Developments ◽  
Quantitative Manner ◽  
The Impact ◽  
The Brain

A major challenge in neuroscience is how to study structural alterations in the brain. Even small changes in synaptic composition could have severe outcomes for body functions. Many neuropathological diseases are attributable to disorganization of particular synaptic proteins. Yet, to detect and comprehensively describe and evaluate such often rather subtle deviations from the normal physiological status in a detailed and quantitative manner is very challenging. Here, we have compared side-by-side several commercially available light microscopes for their suitability in visualizing synaptic components in larger parts of the brain at low resolution, at extended resolution as well as at super-resolution. Microscopic technologies included stereo, widefield, deconvolution, confocal, and super-resolution set-ups. We also analyzed the impact of adaptive optics, a motorized objective correction collar and CUDA graphics card technology on imaging quality and acquisition speed. Our observations evaluate a basic set of techniques, which allow for multi-color brain imaging from centimeter to nanometer scales. The comparative multi-modal strategy we established can be used as a guide for researchers to select the most appropriate light microscopy method in addressing specific questions in brain research, and we also give insights into recent developments such as optical aberration corrections.

Binocular adaptive optics visual simulator: understanding the impact of aberrations on actual vision

2010 ◽  
Author(s):  
Enrique J. Fernández ◽  
Pedro M. Prieto ◽  
Pablo Artal
Keyword(s):  
Adaptive Optics ◽  
The Impact

scholarly journals Performance Enhancement of DWDM-FSO Optical Fiber Communication Systems Based on Hybrid Modulation Techniques under Atmospheric Turbulence Channel

Photonics ◽  
2021 ◽  
Vol 8 (11) ◽  
pp. 464
Author(s):  
Mohammed R. Hayal ◽  
Bedir B. Yousif ◽  
Mohamed A. Azim
Keyword(s):  
Optical Fiber ◽  
Atmospheric Turbulence ◽  
Adaptive Optics ◽  
Communication Systems ◽  
Optical Fiber Communication ◽  
Passive Optical Network ◽  
Communication Link ◽  
Fiber Communication ◽  
Digital Pulse ◽  
The Impact

In this paper, we enhance the performance efficiency of the free-space optical (FSO) communication link using the hybrid on-off keying (OOK) modulation, M-ary digital pulse position modulation (M-ary DPPM), and M-pulse amplitude and position modulation (M-PAPM). This work analyzes and enhances the bit error rate (BER) performance of the moment generating function, modified Chernoff bound, and Gaussian approximation techniques. In the existence of both an amplified spontaneous emission (ASE) noise, atmospheric turbulence (AT) channels, and interchannel crosstalk (ICC), we propose a system model of the passive optical network (PON) wavelength division multiplexing (WDM) technique for a dense WDM (DWDM) based on the hybrid fiber FSO (HFFSO) link. We use eight wavelength channels that have been transmitted at a data rate of 2.5 Gbps over a turbulent HFFSO-DWDM system and PON-FSO optical fiber start from 1550 nm channel spacing in the C-band of 100 GHz. The results demonstrate (2.5 Gbps × 8 channels) 20 Gbit/s-4000 m transmission with favorable performance. In this design, M-ary DPPM-M-PAPM modulation is used to provide extra information bits to increase performance. We also propose to incorporate adaptive optics to mitigate the AT effect and improve the modulation efficiency. We investigate the impact of the turbulence effect on the proposed system performance based on OOK-M ary- PAPM-DPPM modulation as a function of M-ary DPPM-PAPM and other atmospheric parameters. The proposed M-ary hybrid DPPM-M-PAPM solution increases the receiver sensitivity compared to OOK, improves the reliability and achieves a lower power penalty of 0.2–3.0 dB at low coding level (M) 2 in the WDM-FSO systems for the weak turbulence. The OOK/M-ary hybrid DPPM-M-PAPM provides an optical signal-to-noise ratio of about 4–8 dB of the DWDM-HFFSO link for the strong turbulence at a target BER of 10−12. The numerical results indicate that the proposed design can be enhanced with the hybrid OOK/M-DPPM and M-PAPM for DWDM-HFFSO systems. The calculation results show that PAPM-DPPM has increased about 10–11 dB at BER of 10−12 more than the OOK-NRZ approach. The simulation results show that the proposed hybrid optical modulation technique can be used in the DWDM-FSO hybrid links for optical-wireless and fiber-optic communication systems, significantly increasing their efficiency. Finally, the use of the hybrid OOK/M-ary DPPM-M-PAPM modulation schemes is a new technique to reduce the AT, ICC, ASE noise for the DWDM-FSO optical fiber communication systems.

scholarly journals Identifying optical turbulence profiles for realistic tomographic error in adaptive optics

2019 ◽  
Vol 488 (1) ◽  
pp. 213-221 ◽  
Author(s):  
O J D Farley ◽  
J Osborn ◽  
T Morris ◽  
T Fusco ◽  
B Neichel ◽  
...  
Keyword(s):  
Vertical Distribution ◽  
Adaptive Optics ◽  
Compute Tomographic ◽  
Distribution Profile ◽  
Statistical Sample ◽  
Large Telescopes ◽  
The Impact ◽  
First Time ◽  
The Vertical Distribution ◽  
Performance Estimates

ABSTRACT For extremely large telescopes, adaptive optics will be required to correct the Earth’s turbulent atmosphere. The performance of tomographic adaptive optics is strongly dependent on the vertical distribution (profile) of this turbulence. An important way in which this manifests is the tomographic error, arising from imperfect measurement and reconstruction of the turbulent phase at altitude. Conventionally, a small number of reference profiles are used to obtain this error in simulation; however these profiles are not constructed to be representative in terms of tomographic error. It is therefore unknown whether these simulations are providing realistic performance estimates. Here, we employ analytical adaptive optics simulation that drastically reduces computation times to compute tomographic error for 10 691 measurements of the turbulence profile gathered by the Stereo-SCIDAR instrument at ESO Paranal. We assess for the first time the impact of the profile on tomographic error in a statistical manner. We find, in agreement with previous work, that the tomographic error is most directly linked with the distribution of turbulence into discrete, stratified layers. Reference profiles are found to provide mostly higher tomographic error than expected, which we attribute to the fact that these profiles are primarily composed of averages of many measurements resulting in unrealistic, continuous distributions of turbulence. We propose that a representative profile should be defined with respect to a particular system, and that as such simulations with a large statistical sample of profiles must be an important step in the design process.

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