43 research outputs found
Hierarchichal-segmented AO in order to attain wide field compensation in the visible on an 8m class telescope
We describe the preliminary optimized layout for a partially optimized
concept of an optical-8m class VLT-like 2x2 segmented camera where each channel
is assisted by an equivalent of an MCAO system where the ground layer
correction is commonly employed while the high altitude ones is performed in an
open-loop fashion. While we derive the basic relationships among the Field of
View and attainable correction with a pre-defined choice for the hardware, we
discuss sky coverage and wavefront sensing issues employing natural and
artificial references, involving the latest stateof-the-art in the development
of wavefront sensing. We show that a flexible approach allow for a compensated
Field of View that is variable and can be properly tuned matching the current
turbulence situation and the requirement in term of quality of the
compensation. A preliminary description of the overall optomechanical package
is given as well along with a rough estimates of the efforts required to
translates such a concept into reality.Comment: 6 pages, 4 figures, in AO4ELT5 Proceeding
Multiple Spatial Frequencies Pyramid WaveFront Sensing
A modification of the pyramid wavefront sensor is described. In this conceptually new class of devices, the perturbations are split at the level of the focal plane depending upon their spatial frequencies, and then measured separately. The aim of this approach is to increase the accuracy in the determination of some range of spatial frequency perturbations, or a certain classes of modes, disentangling them from the noise associated to the Poissonian fluctuations of the light coming from the perturbations outside of the range of interest or from the background in the pupil planes; the latter case specifically when the pyramid wavefront sensor is used with a large modulation. While the limits and the effectiveness of this approach should be further investigated, a number of variations on the concept are shown, including a generalization of the spatial filtering in the point-diffraction wavefront sensor. The simplest application, a generalization to the pyramid of the well-known spatially filtering in wavefront sensing, is showing promise as a significant limiting magnitude advance. Applications are further speculated in the area of extreme adaptive optics and when serving spectroscopic instrumentation where “light in the bucket” rather than Strehl performance is required
Ingot Laser Guide Stars Wavefront Sensing
We revisit one class of z-invariant WaveFront sensor where the LGS is fired
aside of the telescope aperture. In this way there is a spatial dependence on
the focal plane with respect to the height where the resonant scattering
occurs. We revise the basic parameters involving the geometry and we propose
various merit functions to define how much improvement can be attained by a
z-invariant approach. We show that refractive approaches are not viable and we
discuss several solutions involving reflective ones in what has been nicknamed
"ingot wavefront sensor" discussing the degrees of freedom required to keep
tracking and the basic recipe for the optical design.Comment: 6 pages, 4 figures, AO4ELT5 Conference Proceeding, 201
A Holographic Diffuser Generalised Optical Differentiation Wavefront Sensor
The wavefront sensors used today at the biggest World's telescopes have
either a high dynamic range or a high sensitivity, and they are subject to a
linear trade off between these two parameters. A new class of wavefront
sensors, the Generalised Optical Differentiation Wavefront Sensors, has been
devised, in a way not to undergo this linear trade off and to decouple the
dynamic range from the sensitivity. This new class of WFSs is based on the
light filtering in the focal plane from a dedicated amplitude filter, which is
a hybrid between a linear filter, whose physical dimension is related to the
dynamic range, and a step in the amplitude, whose size is related to the
sensitivity. We propose here a possible technical implementation of this kind
of WFS, making use of a simple holographic diffuser to diffract part of the
light in a ring shape around the pin of a pyramid wavefront sensor. In this
way, the undiffracted light reaches the pin of the pyramid, contributing to the
high sensitivity regime of the WFS, while the diffused light is giving a sort
of static modulation of the pyramid, allowing to have some signal even in high
turbulence conditions. The holographic diffuser zeroth order efficiency is
strictly related to the sensitivity of the WFS, while the diffusing angle of
the diffracted light gives the amount of modulation and thus the dynamic range.
By properly choosing these two parameters it is possible to build a WFS with
high sensitivity and high dynamic range in a static fashion. Introducing
dynamic parts in the setup allows to have a set of different diffuser that can
be alternated in front of the pyramid, if the change in the seeing conditions
requires it.Comment: 11 pages, 5 figure
Daedalus-CAM Project Plan
Through its Open Space Innovation Platform, in August 2019 ESA opened a campaign for novel ideas to address detecting, mapping and exploring lunar caves and lava tubes.
Amongst these ideas, ESA selected the project “Daedalus” to participate in its Concurrent Design Facility (CDF) to study the feasibility and planning the mission. The Mission is planned to last one full lunar day (12+2 contingency), with the possibility to extend the mission time within the cave and to rely on communication with Earth in the following lunar day. The CDF Internal Final Report on Daedalus is now available on request.
The Daedalus robot hosts two payloads, one lidar (responsibility University of WĂĽrzburg) and one stereoscopic panoramic camera (Daedalus-CAM, responsibility INAF).
The present document has been issued to describe the Project Plan of the Daedalus–CAM imaging payload
Multiple spatial frequencies wavefront sensing
We describe the concept of splitting spatial frequency perturbations into
some kind of pupil planes wavefront sensors. Further to the existing approach
of dropping higher spatial frequency to suppress aliasing effects (the
so-called spatial filtered Shack-Hartmann), we point out that spatial
frequencies splitting and mixing of these in a proper manner, could be handled
in order to exhibit some practical or fundamental advantages. In this framework
we describe the idea behind such class of concepts and we derive the
relationship useful to determine if, by which extent, and under what kind of
merit function, these devices can overperform existing conventional sensors.Comment: 6 pages, 3 figures, in AO4ELT5 Proceeding
Prospects of Deep Field Surveys with Global-MCAO on an ELT
Several astronomical surveys aimed at the investigation of the extragalactic
components were carried out in order to map systematically the universe and its
constituents. An excellent level of detail is needed, and it is possible only
using space telescopes or with the application of adaptive optics (AO)
techniques for ground-based observatories. By simulating K-band observations of
6000 high-redshift galaxies in the Chandra Deep Field South region, we have
already shown how an extremely large telescope can carry out photometric
surveys successfully using the Global-MCAO, a natural guide stars based
technique that allows the development of extragalactic research, otherwise
impracticable without using laser guide stars. As the outcome of the analysis
represents an impact science case for the new instruments on upcoming
ground-based telescopes, here we show how the investigation of other observed
deep fields could profit from such a technique. Further to an overview of the
surveys suitable for the proposed approach, we show preliminary estimations
both on geometrical (FoV and height) and purely AO perspectives (richness and
homogeneity of guide stars in the area) for planned giant telescope.Comment: 8 pages, 6 figures, AO4ELT5 conferenc
SHARK-NIR, the coronagraphic camera for LBT, moving toward construction
SHARK-NIR is one of the two coronagraphic instruments proposed for the Large
Binocular Telescope. Together with SHARK-VIS (performing coronagraphic imaging
in the visible domain), it will offer the possibility to do binocular
observations combining direct imaging, coronagraphic imaging and coronagraphic
low resolution spectroscopy in a wide wavelength domain, going from 0.5{\mu}m
to 1.7{\mu}m. Additionally, the contemporary usage of LMIRCam, the
coronagraphic LBTI NIR camera, working from K to L band, will extend even more
the covered wavelength range. In January 2017 SHARK-NIR underwent a successful
final design review, which endorsed the instrument for construction and future
implementation at LBT. We report here the final design of the instrument, which
foresees two intermediate pupil planes and three focal planes to accomodate a
certain number of coronagraphic techniques, selected to maximize the instrument
contrast at various distances from the star. Exo-Planets search and
characterization has been the science case driving the instrument design, but
the SOUL upgrade of the LBT AO will increase the instrument performance in the
faint end regime, allowing to do galactic (jets and disks) and extra-galactic
(AGN and QSO) science on a relatively wide sample of targets, normally not
reachable in other similar facilities.Comment: 8 pages, 6 figures, AO4ELT5 conference proceeding