The calculation of the characteristics of the air refractive index fluctuations along line of sight for multiconjugated adaptive optics

AbstractWe present our effort to measure the proper motions of satellites in the halo of the Milky Way with mainly ground based telescopes as a precursor on what is possible with Gaia. For our first study, we used wide field optical data from the LBT combined with a first epoch of SDSS observations, on the globular cluster Palomar 5 (Pal 5). Since Pal 5 is associated with a tidal stream it is very useful to constrain the shape of the potential of the Milky Way. The motion and other properties of the Pal 5 system constrain the inner halo of the Milky Way to be rather spherical. Further, we combined adaptive optics and HST to get an absolute proper motion of the globular cluster Pyxis. Using the proper motion and the line-of-sight velocity we find that the orbit of Pyxis is rather eccentric with its apocenter at more than 100 kpc and its pericenter at about 30 kpc. The dynamics excludes an association with the ATLAS stream, the Magellanic clouds, and all satellites of the Milky Way at least down to the mass of Leo II. However, the properties of Pyxis, like metallicity and age, point to an origin from a dwarf of at least the mass of Leo II. We therefore propose that Pyxis originated from an unknown relatively massive dwarf galaxy, which is likely today fully disrupted. Assuming that Pyxis is bound to the Milky Way we derive a 68% lower limit on the mass of the Milky Way of 9.5 × 1011 M⊙.

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Measuring line-of-sight sodium density structure using laser guide stars

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa808 ◽

2020 ◽

Vol 494 (2) ◽

pp. 2798-2808

Author(s):

Joschua A Hellemeier ◽

Domenico Bonaccini Calia ◽

Paul Hickson ◽

Angel Otarola ◽

Thomas Pfrommer

Keyword(s):

Adaptive Optics ◽

Continuous Wave ◽

Line Of Sight ◽

Fibre Laser ◽

Modulation Amplitude ◽

Density Structure ◽

Laser Guide Star ◽

Laser Guide Stars ◽

Guide Star ◽

Laser Guide

ABSTRACT The performance of adaptive optics systems employing sodium laser guide stars can be improved by continuously monitoring the vertical density structure of mesospheric sodium along the line of sight. We demonstrate that sodium density profiles can be retrieved by amplitude modulation of continuous wave (CW) lasers. In an experiment conducted at the Large Zenith Telescope (LZT), ESO’s Wendelstein Raman-fibre laser was amplitude-modulated with a pseudo-random binary sequence and profiles were obtained by cross-correlation of the modulation pattern with the observed return signal from the laser guide star. For comparison, high-resolution profiles were obtained simultaneously using the lidar system of the LZT. The profiles obtained by the two techniques show noise contamination, but were found to agree to within the measurement error. As a further check, a comparison was also made between several lidar profiles and those obtained by simultaneous observations using a remote telescope to image the laser plume from the side. The modulated CW lidar technique could be implemented by diverting a small fraction of the returned laser light to a photon counting detector. Theoretical analysis and numerical simulations indicate that, for 50 per cent modulation strength, the sodium centroid altitude could be retrieved every 5 s from a single laser guide star, with an accuracy which would induce a corresponding wavefront error of 50 nm for the Extremely Large Telescope and less than 30 nm for the Thirty Meter Telescope and Giant Magellan Telescope. If multiple laser guide stars are employed, the required modulation amplitude will be smaller.

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ASTROCLIMATIC STATISTICS AT THE SAYAN SOLAR OBSERVATORY

Solnechno-Zemnaya Fizika ◽

10.12737/szf-61202012 ◽

2020 ◽

Vol 6 (1) ◽

pp. 126-133

Author(s):

Artem Shikhovtsev ◽

Pavel Kovadlo ◽

Aleksandr Kiselev

Keyword(s):

Adaptive Optics ◽

Solar Observatory ◽

Line Of Sight ◽

Solar Telescope ◽

Vertical Profiles ◽

Minimum Level ◽

Optical Turbulence ◽

Low Intensity ◽

Spatial Features ◽

Adaptive Optics System

The paper analyzes meteorological and optical characteristics of the atmosphere at the Sayan Solar Observatory (SSO) and the future 3 m Large Solar Telescope (LST-3). We examine spatial features of changes in astroclimatic characteristics for the Sayan Solar Observatory and Baikal Astrophysical Observatory (BAO). We have obtained a vertical profile of the structural characteristic of air refractive index fluctuations for a low intensity optical turbulence along the line of sight. This profile is an important result because it will allow us to adjust the adaptive optics system of LST-3 to the best astroclimatic conditions when the correction efficiency is maximal. In order to analyze vertical profiles of optical turbulence characteristics and to assess the contribution of individual atmospheric layers to the isoplanatic angle for a minimum level of total turbulence, we give recommendations for the design of multi-conjugated adaptive optics in general and for LST-3 in particular.

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Closer to the Theoretical Limit: Spherical Corrections to Aplanatic Solid Immersion Imaging with Adaptive Optics

ISTFA 2012: Conference Proceedings from the 38th International Symposium for Testing and Failure Analysis ◽

10.31399/asm.cp.istfa2012p0006 ◽

2012 ◽

Author(s):

Y. Lu ◽

E. Ramsay ◽

C.R. Stockbridge ◽

A. Yurt ◽

F. H. Köklü ◽

...

Keyword(s):

Refractive Index ◽

Adaptive Optics ◽

Spherical Aberration ◽

Deformable Mirror ◽

Substrate Thickness ◽

Spot Intensity ◽

Theoretical Limit ◽

Thickness Tolerance ◽

Theory And Experiment ◽

Good Agreement

Abstract Aplanatic solid immersion lens (SIL) microscopy is required to achieve the highest possible resolution for next generation silicon IC backside inspection and failure analysis. However, aplanatic SILs are susceptible to spherical aberration introduced by substrate thickness mismatch. We have developed a wavefront precompensation technique using a MEMS deformable mirror and demonstrated an increase in substrate thickness tolerance in aplanatic SIL imaging. Good agreement between theory and experiment is achieved and spot intensity increases by at least a factor of two to three are demonstrated for thicknesses deviating several percent from ideal. This technique is also capable of fixing aberrations due to SIL fabrication, off-axis imaging and refractive index mismatch.

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