27 research outputs found
Open-Loop Woofer-Tweeter Control on the LAO Multi-Conjugate Adaptive Optics Testbed
Advances in micro deformable mirror (DM) technologies such as MEMs, have
stimulated interest in the characteristics of systems that include a high
stroke mirror in series with a high actuator count mirror. This arrangement is
referred to as a woofer-tweeter system. In certain situations it may be
desirable or necessary to operate the woofer DM in open-loop. We present a
simple method for controlling a woofer DM in open loop provided the device
behaves in an approximately linear fashion. We have tested a mirror that we
believe meets our criterion, the ALPAO DM52 mirror. Using our open-loop method
we fit several test Kolmogorov wavefronts with the mirror and have achieved an
accuracy of approximately 25 nm rms surface deviation over the whole clear
aperture, and 20 nm rms over 90% of the aperture. We have also flattened the
mirror in open loop to approximately 11 nm rms residual.Comment: 5 pages, 3 figures, to be published in proceedings of The 6th
International Workshop on Adaptive Optics for Industry and Medicin
Initial concepts for CELT adaptive optics
The California Extremely Large Telescope (CELT) project has recently completed a 12-month conceptual design phase that has investigated major technology challenges in a number of Observatory subsystems, including adaptive optics (AO). The goal of this effort was not to adopt one or more specific AO architectures. Rather, it was to investigate the feasibility of adaptive optics correction of a 30-meter diameter telescope and to suggest realistic cost ceilings for various adaptive optics capabilities. We present here the key design issues uncovered during conceptual design and present two non-exclusive "baseline" adaptive optics concepts that are expected to be further developed during the following preliminary design phase. Further analysis, detailed engineering trade studies, and certain laboratory and telescope experiments must be performed, and key component technology prototypes demonstrated, prior to adopting one or more adaptive optics systems architectures for realization
Adaptive optics for the Thirty Meter Telescope
Adaptive Optics (AO) will be essential for at least seven of the eight science instruments currently planned for the Thirty Meter Telescope (TMT). These instruments include three near infra-red (NIR) imagers and spectrometers with fields of view from 2 to 30 arc seconds, a mid-IR echelle spectrometer, a planet formation imager/spectrometer, a wide field optical spectrograph, and a NIR multi-object spectrometer with multiple integral field units deployable over a 5 arc minute field of regard. In this paper we describe the overall AO reference design that supports these instruments, which consists of a facility AO system feeding the first three instruments and dedicated AO systems for the remaining four. Key design challenges for these systems include very high-order, large-stroke wavefront correction, tip-tilt sensing with faint natural guide stars to maximize sky coverage, laser guidestar wavefront sensing on a very large aperture, and achieving extremely high contrast ratios for the detection of extra-solar planets and other faint companions of bright stars. We describe design concepts for meeting these challenges and summarize our supporting plans for AO component development
Initial concepts for CELT adaptive optics
The California Extremely Large Telescope (CELT) project has recently completed a 12-month conceptual design phase that has investigated major technology challenges in a number of Observatory subsystems, including adaptive optics (AO). The goal of this effort was not to adopt one or more specific AO architectures. Rather, it was to investigate the feasibility of adaptive optics correction of a 30-meter diameter telescope and to suggest realistic cost ceilings for various adaptive optics capabilities. We present here the key design issues uncovered during conceptual design and present two non-exclusive "baseline" adaptive optics concepts that are expected to be further developed during the following preliminary design phase. Further analysis, detailed engineering trade studies, and certain laboratory and telescope experiments must be performed, and key component technology prototypes demonstrated, prior to adopting one or more adaptive optics systems architectures for realization
Gemini north and south laser guide star systems requirements and preliminary designs
In the near future, the Gemini Observatory will offer Laser Guide Star Adaptive Optics (LGS AO) observations on both Gemini North and South telescopes. The Gemini North AO system will use a 10W-class sodium laser to produce one laser guide star at Mauna Kea, Hawaii, whereas the Gemini South AO System will use up to five such lasers or a single 50W-class laser to produce one to five sodium beacons at Cerro Pachon, Chile. In this paper we discuss the similarities and differences between the Gemini North and South Laser Guide Star Systems. We give a brief overview of the Gemini facility Adaptive Optics systems and the on-going laser research and development program to procure efficient, affordable and reliable lasers. The main part of the paper presents the top-level requirements and preliminary designs for four of the Gemini North and South Laser Guide Star subsystems: the Laser Systems (LS), Beam Transfer Optics (BTO), Laser Launch Telescopes (LLT), and their associated Periscopes
On-sky wide field adaptive optics correction using multiple laser guide stars at the MMT
We describe results from the first astronomical adaptive optics system to use
multiple laser guide stars, located at the 6.5-m MMT telescope in Arizona. Its
initial operational mode, ground-layer adaptive optics (GLAO), provides uniform
stellar wavefront correction within the 2 arc minute diameter laser beacon
constellation, reducing the stellar image widths by as much as 53%, from 0.70
to 0.33 arc seconds at lambda = 2.14 microns. GLAO is achieved by applying a
correction to the telescope's adaptive secondary mirror that is an average of
wavefront measurements from five laser beacons supplemented with image motion
from a faint stellar source. Optimization of the adaptive optics system in
subsequent commissioning runs will further improve correction performance where
it is predicted to deliver 0.1 to 0.2 arc second resolution in the
near-infrared during a majority of seeing conditions.Comment: 13 pages, 1 table, 7 figures. Accepted for publication in
Astrophysical Journal. Expected March 200
eXtreme Adaptive Optics Planet Imager: overview and status
As adaptive optics (AO) matures, it becomes possible to envision AO systems oriented towards specific important scientific goals rather than general-purpose systems. One such goal for the next decade is the direct imaging detection of extrasolar planets. An "extreme" adaptive optics (ExAO) system optimized for extrasolar planet detection will have very high actuator counts and rapid update rates - designed for observations of bright stars - and will require exquisite internal calibration at the nanometer level. In addition to extrasolar planet detection, such a system will be capable of characterizing dust disks around young or mature stars, outflows from evolved stars, and high Strehl ratio imaging even at visible wavelengths. The NSF Center for Adaptive Optics has carried out a detailed conceptual design study for such an instrument, dubbed the eXtreme Adaptive Optics Planet Imager or XAOPI. XAOPI is a 4096-actuator AO system, notionally for the Keck telescope, capable of achieving contrast ratios >10^7 at angular separations of 0.2-1". ExAO system performance analysis is quite different than conventional AO systems - the spatial and temporal frequency content of wavefront error sources is as critical as their magnitude. We present here an overview of the XAOPI project, and an error budget highlighting the key areas determining achievable contrast. The most challenging requirement is for residual static errors to be less than 2 nm over the controlled range of spatial frequencies. If this can be achieved, direct imaging of extrasolar planets will be feasible within this decade
Os saberes a ensinar e para ensinar matemática e suas relações com o ensino industrial brasileiro
Disponível em: http://revistas.upel.edu.ve/index.php/paradigma/article/view/6907/0Este trabalho é parte de uma pesquisa de doutorado que se preocupa em investigar o ensino de matemática no Liceu e na Escola Industrial de Florianópolis no período de 1937 a 1961. O objetivo é identificar os saberes a ensinar e para ensinar nos cursos do Liceu Industrial e da Escola Industrial de Florianópolis e quais as principais mudanças no ensino de Mat emática destas instituições de ensino industrial. Foram utilizados como referenciais teóricos Chervel (1990) sobre história das disciplinas escolares, Julia (2001) sobre cultura escolar , Hofstetter & Valente (2017) a respeito dos saberes a ensinar , Hofstet ter et al . (2017) na definição dos experts e Cellard (2008) para a análise documental . Percebeu - se que o ensino de Matemática era voltado para cálculos básicos, pois o enfoque era formar o aluno para a indústria, apesar de se intensificar o ensino de Álgeb ra e Trigonometria no início dos anos de 1940. Palavras - chave: Ensino Industrial. História da Educação Matemática. Experts . Saberes a ensinar. Saberes para ensinar