DOCSLIB.ORG

Adaptive Optics for Satellite Imaging and Earth Based Space Debris Manoeuvres

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Adaptive Optics for Satellite Imaging and Earth Based Space Debris Manoeuvres ADAPTIVE OPTICS FOR SATELLITE IMAGING AND EARTH BASED SPACE DEBRIS MANOEUVRES Doris Grosse(1,2), Francis Bennet(1,2), Michael Copeland(1,2),Celine´ d’Orgeville(1,2), Franc¸ois Rigaut(1,2), and Ian Price(1) (1)Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611, Australia, Email: [email protected] (2)SERC Limited, Mount Stromlo, Weston Creek, Australia ABSTRACT 1. INTRODUCTION Space Debris is becoming a more and more urgent issue As hundreds of thousands of space debris objects are ac- and action needs to be taken to both actively reduce the cumulating and the risk of collisions in space as predicted amount of debris in space, and prevent space debris ac- by Kessler [8] increases, more attention and efforts need cumulation caused by collisions of existing debris. To to be brought to Space Situational Awareness. It is the investigate and mitigate the risk of collisions of space de- aim of the Space Environment Research Centre (SERC) bris and satellites, a Cooperative Research Centre man- to create a more detailed data catalogue of satellites and aged by the Space Environment Research Centre (SERC) space debris in order to calculate, determine and predict has been established in Australia supported by the Aus- their positions more accurately, so that functional satel- tralian government and national and international part- lites can manoeuvre more efficiently around the debris. ners. The aim of the project is to improve orbital track- As those satellite manoeuvres are costly and shorten the ing and predictions and build an instrument to demon- life of satellites, SERC is also developing measures to strate remote manoeuvre by means of photon pressure prevent collisions by means of remote Earth based space and to perform high resolution Adaptive Optics (AO) im- debris manoeuvres by moving the debris object and not agery. The Research School of Astronomy and Astro- the satellite into unoccupied orbits. Furthermore, the ex- physics (RSAA) from the Australian National University pertise developed to achieve more accurate orbit deter- (ANU) is one of the partners of the SERC collaboration mination and prediction will be applied to determine the and is developing AO systems for this purpose. There are success of the photon pressure experiment. currently two AO systems being developed. An adaptive As a partner of SERC, the Research School of Astron- optics imaging (AOI) system and an adaptive optics sys- omy and Astrophysics (RSAA) of the Australian Na- tem for tracking and pushing (AOTP). Both systems will tional University provides Adaptive Optics (AO) exper- be operating with a laser guide star. The AOI system will tise to help achieve these goals. With the help of data image satellites and debris in lower Earth orbits providing that will be collected by an AO imaging system that is information about the satellites’ shape, attitude and posi- currently being developed at the RSAA [3], the shape, tion. It will also conduct astrometric measurements of structure and attitude of satellites will be modelled more geostationary satellites determining their position down a precisely, which in turn will help to improve orbit deter- few meters. The AOTP system will target debris in lower mination and prediction. To mitigate the risk of collisions Earth orbits and employ a 10 to 20 kW CW laser in or- directly, an Earth based remote manoeuvre is being de- der to push the debris with photon pressure in different veloped [10] that is designed to perturb orbits of space orbits. Both the AOI and AOTP systems will be mounted debris objects to prevent possible collisions. In order to on a 1.8 m telescope operated by another SERC partner achieve this, a high power laser aimed at the debris can be Electro Optic Systems (EOS) on Mt Stromlo near Can- propagated through the atmosphere. As the atmosphere berra, Australia. This paper outlines the current status of distorts the wavefronts, an AO system is being developed both systems and presents results of an earlier AO imag- that compensates for this distortion and helps focus the ing system implemented on a 1 m telescope with which laser beam onto the object in space. images resolving satellite features and orientation were We provide an overview of the AO systems that have been successfully taken. and are currently developed at the RSAA for these pur- poses. After giving a brief overview of the principle of AO in section 2, we review in section 3 the AO Satellite Keywords: Space Situational Awareness; Adaptive Op- imaging systems for a 1 m and 1.8 m telescope both sit- tics; Optical Telescopes; Satellite Imaging; Earth Based uated on Mount Stromlo, Canberra, Australia. The 1 m Space Debris Manoeuvre. and 1.8 m telescope AO systems are detailed in subsec- Proc. 7th European Conference on Space Debris, Darmstadt, Germany, 18–21 April 2017, published by the ESA Space Debris Office Ed. T. Flohrer & F. Schmitz, (http://spacedebris2017.sdo.esoc.esa.int, June 2017) tion 3.1 and subsection 3.2 respectively. Both telescopes deformable mirror that corrects for the distortions to a are run by EOS Space Systems, another SERC partner. wavefront sensor. The wavefront sensor measures the The 1.8 m telescope will also host the Earth based debris error of this correction and sends it to the control com- manoeuvre system that is currently being developed at the puter, where it is transformed into deformable mirror RSAA to target the debris, which is detailed in section 4. commands and sent to the deformable mirror, thats com- pensates for it again. The corrected wavefront is sent to the high-resolution camera recording the corrected and improved images for the scientific purpose. As the at- 2. ADAPTIVE OPTICS mosphere is constantly changing, the system needs to be running in real time, usually at several hundred Hz. Many reference books, such as [1, 7, 9], explore the operational Adaptive Optics is a technology that compensates for principle and design of AO systems with a wide range of phase distortions of light waves in real time. Atmo- applications in astronomy in more detail. The applica- spheric turbulence distorts any wavefronts of light pass- tion of AO systems for satellite imaging and space debris ing through Earth’s atmosphere, effectively limiting the manoeuvres distinguishes itself from astronomical appli- resolution of the ground-based telescope. The theoreti- cations in particular by its requirement of being able to cal resolution limit of a telescope is set by diffraction and compensate for atmospheric turbulence despite of the fast defined by the ratio of wavelength λ to telescope diame- movement of the telescope’s field of view through the at- ter D, λ/D. The resolution that is achievable in practice mosphere. The following section focuses on the system without the application of an AO system is however given specifications of the AO systems for satellite imaging and by the atmospheric seeing above the telescope and is de- provides an overview of the AO systems that are being fined by λ/r0, which takes the optical coherence length, developed in this field with the RSAA. also called Fried parameter r0 into account. This param- eter provides a measure for the atmosphere to maintain a constant refractive index over a certain distance and usu- ally takes values between 5 to 20 cm in the visible for 3. SATELLITE IMAGING WITH ADAPTIVE OP- poor or good sites respectively. This means however that TICS telescopes that are significantly larger in diameter than r0 will always be affected by the seeing. An AO instrument Optical telescopes can be used to precisely track satel- is capable of correcting for these distortions and of restor- lites and space debris and determine their position with ing the resolution close to the diffraction limited value of satellite laser ranging [4, 6]. They can also be used for the telescope. imaging satellites, but the resolution of features is see- The AO instrument receives the distorted light that prop- ing limited unless it is compensated for with the help of agated through the atmosphere and compensates for the an Adaptive Optics System. To help characterise satel- distortions so that high resolution measurements can be lites in lower Earth orbit (LEO), the RSAA is developing recorded. Figure 1 details the AO operational princi- Adaptive Optics Imaging Systems. ple. The light collected by the telescope is sent via a As satellites are fast moving objects in the night sky, the AO system has special design requirements that are de- tailed in the following two sections. Section 3.1 pro- vides an overview and shows results of an existing satel- lite imaging system designed to image satellites in LEO with a 1 m telescope [2], section 3.2 provides an overview of a satellite imaging system designed to image satellites with a 1.8 m and to support astrometric measurements of satellite positioning in Geostationary orbit (GEO) [3]. 3.1. Adaptive Optics Satellite Imaging System for a 1 m Telescope The Adaptive Optics imaging system that was developed for imaging of satellites in LEO can achieve a Strehl ratio of 20% at an altitude of 1000 km, but can also perform in lower altitudes down to 600 km. The system is depicted Figure 1. Operational principle of Adaptive Optics: the in Figure 2. It uses the reflected sunlight from the satel- distorted wavefront is corrected by the deformable mirror lites in the visible as natural guide star light for the wave- and the residual error is measured by the wavefront sen- front sensor and the infrared part for imaging. The entire sor. The measurement is translated into further correc- light collected by the telescope is reflected via a beam tion commands to the deformable mirror by the control expander and scaled down to suit 1’ optics.
Load more

Recommended publications
  • 8. Adaptive Optics 299
    8. Adaptive Optics 299 8.1 Introduction Adaptive Optics is absolutely essential for OWL, to concentrate the light for spectroscopy and imaging and to reach the diffraction limit on-axis or over an extended FoV. In this section we present a progressive implementation plan based on three generation of Adaptive Optics systems and, to the possible extent, the corresponding expected performance. The 1st generation AO − Single Conjugate, Ground Layer, and distributed Multi-object AO − is essentially based on Natural Guide Stars (NGSs) and makes use of the M6 Adaptive Mirror included in the Telescope optical path. The 2nd generation AO is also based on NGSs but includes a second deformable mirror (M5) conjugated at 7-8 km – Multi-Conjugate Adaptive Optics − or a post focus mirror conjugated to the telescope pupil with a much higher density of actuators -tweeter- in the case of EPICS. The 3rd generation AO makes use of single or multiple Laser Guide Stars, preferably Sodium LGSs, and should provide higher sky coverage, better Strehl ratio and correction at shorter wavelengths. More emphasis in the future will be given to the LGS assisted AO systems after having studied, simulated and demonstrated the feasibility of the proposed concepts. The performance presented for the AO systems is based on advances from today's technology in areas where we feel confident that such advances will occur (e.g. the sizes of the deformable mirrors). Even better performance could be achieved if other technologies advance at the same rate as in the past (e.g. the density of actuators for deformable mirrors).
    [Show full text]
  • Subaru Super Deep Field (SSDF) with AO
    Subaru Super Deep Field (SSDF) using Adaptive Optics Yosuke Minowa （NAOJ） on behalf of Yoshii, Y. (IoA, Univ. of Tokyo; PI) and SSDF team: Kobayashi, N. (IoA, Univ. of Tokyo), Totani, T. (Kyoto Univ.), Takami, H., Takato, N. Hayano, Y., Iye, M. (NAOJ). Subaru UM (1/30/2007) SSDF project: What? { Scientific motivation 1. Study the galaxy population at the unprecedented faint end (K’=23-25mag) to find any new population which may explain the missing counterpart to the extragalactic background light. 2. Study the morphological evolution of field galaxies in rest-frame optical wavelengths to find the origin of Hubble sequence. Æ high-resolution deep imaging of distant galaxies SSDF project: How? { Deep imaging of high-z galaxies with AO. z Improve detection sensitivity. Peak intensity: with AO ~ 10-20 times higher 0”.07 without AO z Improve spatial 0”.4 resolution FWHM < 0”.1 AO is best suited for the deep imaging study of high-z galaxies which requires both high-sensitivity and high-resolution. z SSDF project: Where? { Target field: a part of “Subaru Deep Field” (SDF) z Originally selected to locate near a bright star for AO observations (Maihara+01). z Optical~NIR deep imaging data are publicly available. { Enable the SED fitting of detected galaxies. Æ phot-z, rest-frame color, (Maihara+01) stellar mass… Observations { AO36+IRCS at Cassegrain z K’-band (2.12um) imaging with 58mas mode z providing 1x1 arcmin2 FOV AO36 IRCS To achieve unprecedented faint-end, we concentrated on K’-band imaging of this 1arcmin2 field, rather than wide-field or multi-color imaging.
    [Show full text]
  • Modern Astronomical Optics 1
    Modern Astronomical Optics 1. Fundamental of Astronomical Imaging Systems OUTLINE: A few key fundamental concepts used in this course: Light detection: Photon noise Diffraction: Diffraction by an aperture, diffraction limit Spatial sampling Earth's atmosphere: every ground-based telescope's first optical element Effects for imaging (transmission, emission, distortion and scattering) and quick overview of impact on optical design of telescopes and instruments Geometrical optics: Pupil and focal plane, Lagrange invariant Astronomical measurements & important characteristics of astronomical imaging systems: Collecting area and throughput (sensitivity) flux units in astronomy Angular resolution Field of View (FOV) Time domain astronomy Spectral resolution Polarimetric measurement Astrometry Light detection: Photon noise Poisson noise Photon detection of a source of constant flux F. Mean # of photon in a unit dt = F dt. Probability to detect a photon in a unit of time is independent of when last photon was detected→ photon arrival times follows Poisson distribution Probability of detecting n photon given expected number of detection x (= F dt): f(n,x) = xne-x/(n!) x = mean value of f = variance of f Signal to noise ration (SNR) and measurement uncertainties SNR is a measure of how good a detection is, and can be converted into probability of detection, degree of confidence Signal = # of photon detected Noise (std deviation) = Poisson noise + additional instrumental noises (+ noise(s) due to unknown nature of object observed) Simplest case (often
    [Show full text]
  • Adaptive Optics: an Introduction Claire E
    1 Adaptive Optics: An Introduction Claire E. Max I. BRIEF OVERVIEW OF ADAPTIVE OPTICS Adaptive optics is a technology that removes aberrations from optical systems, through use of one or more deformable mirrors which change their shape to compensate for the aberrations. In the case of adaptive optics (hereafter AO) for ground-based telescopes, the main application is to remove image blurring due to turbulence in the Earth's atmosphere, so that telescopes on the ground can "see" as clearly as if they were in space. Of course space telescopes have the great advantage that they can obtain images and spectra at wavelengths that are not transmitted by the atmosphere. This has been exploited to great effect in ultra-violet bands, at near-infrared wavelengths that are not in the atmospheric "windows" at J, H, and K bands, and for the mid- and far-infrared. However since it is much more difficult and expensive to launch the largest telescopes into space instead of building them on the ground, a very fruitful synergy has emerged in which images and low-resolution spectra obtained with space telescopes such as HST are followed up by adaptive- optics-equipped ground-based telescopes with larger collecting area. Astronomy is by no means the only application for adaptive optics. Beginning in the late 1990's, AO has been applied with great success to imaging the living human retina (Porter 2006). Many of the most powerful lasers are using AO to correct for thermal distortions in their optics. Recently AO has been applied to biological microscopy and deep-tissue imaging (Kubby 2012).
    [Show full text]
  • A Review of Astronomical Science with Visible Light Adaptive Optics
    A review of astronomical science with visible light adaptive optics Item Type Article Authors Close, Laird M. Citation Laird M. Close " A review of astronomical science with visible light adaptive optics ", Proc. SPIE 9909, Adaptive Optics Systems V, 99091E (July 26, 2016); doi:10.1117/12.2234024; http:// dx.doi.org/10.1117/12.2234024 DOI 10.1117/12.2234024 Publisher SPIE-INT SOC OPTICAL ENGINEERING Journal ADAPTIVE OPTICS SYSTEMS V Rights © 2016 SPIE. Download date 30/09/2021 19:37:34 Item License http://rightsstatements.org/vocab/InC/1.0/ Version Final published version Link to Item http://hdl.handle.net/10150/622010 Invited Paper A Review of Astronomical Science with Visible Light Adaptive Optics Laird M. Close1a, aCAAO, Steward Observatory, University of Arizona, Tucson AZ 85721, USA; ABSTRACT We review astronomical results in the visible (λ<1μm) with adaptive optics. Other than a brief period in the early 1990s, there has been little (<1 paper/yr) night-time astronomical science published with AO in the visible from 2000-2013 (outside of the solar or Space Surveillance Astronomy communities where visible AO is the norm, but not the topic of this invited review). However, since mid-2013 there has been a rapid increase visible AO with over 50 refereed science papers published in just ~2.5 years (visible AO is experiencing a rapid growth rate very similar to that of NIR AO science from 1997-2000; Close 2000). Currently the most productive small (D < 2 m) visible light AO telescope is the UV-LGS Robo-AO system (Baranec, et al.
    [Show full text]
  • Adaptive Optics
    Adaptive Optics Ruobing Dong Large portion is adopted from Claire Max’s lecture in UCSC 03/30/2011 Why is adaptive optics needed? Turbulence in earth’s atmosphere makes stars twinkle More importantly, turbulence spreads out light; makes it a blob rather than a point Even the largest ground-based astronomical telescopes have no better resolution than an 8" telescope Atmospheric perturbations cause distorted wavefronts Rays not Patten changes parallel at time scale of ~10ms each small parallel beam makes a Index of diffraction limited Plane spot on the image refraction Distorted plane Wave variations Wavefront Characterize turbulence strength by quantity r0 Wavefront of light r0 Primary mirror of telescope • “Coherence Length” r0 : Diameter of the circular pupil for which the diffraction limited image and the seeing limited image have the same angular resolution. (r0 ~ 15 - 30 cm at good observing sites • Pupil larger than r0, images are seeing dominated. Real time sequence from a A much larger small telescope with telescope, aperture aperture the size of r0 contains many r0 Schematic of adaptive optics system Feedback loop: next cycle corrects the (small) errors of the last cycle How does adaptive optics help? (cartoon approximation) Adaptive optics increases peak intensity of a point source Lick Observatory" No AO" With AO" Intensity" No AO" With AO" AO produces point spread functions with a “core” and “halo” Definition of “Strehl”: Ratio of peak intensity to that of “perfect” optical system" " Intensity x" When AO system performs well,
    [Show full text]
  • What Is Adaptive Optics ?
    6. Adaptive Optics Introduction to Adaptive Optics Brief introduction to adaptive optics: why, how ? AO for high contrast imaging Components of an AO system Types of AO systems Atmospheric Turbulence Useful references: Adaptive Optics in Astronomy (2004), by Francois Roddier (Editor), Cambridge University Press Adaptive Optics for Astronomical Telescopes (1998), by John W. Hardy, Oxford University Press 1 Why Adaptive Optics ? Gains offered by AO : Angular resolution: Resolve small features on Sun, Moon, planets, disks, galaxies Improved sensitivity for faint objects: Detection of faint objects is a background-limited problem. By making the image smaller, the AO system limits amount of background mixed with image, and improves sensitivity. Efficiency with AO goes as D4 instead of D2 without AO. This is especially important in infrared, as sky glows, and AO work well. Astrometry: Measuring the position of a source. For example: measuring the mass of the black hole in the center of our galaxy. Confusion limit: Astronomical imaging of sources is often confusion limited. Better angular resolution helps ! For example: studying stellar populations in nearby galaxies. High contrast imaging (Extreme-AO) 2 Direct imaging of exoplanets and disks What is Adaptive Optics ? Atmospheric turbulence limits size of images to ~1” (1/3600 of a degree) Diffraction limit of large telescopes is 0.1” to 0.01” → 10x to 100x smaller ! With AO Without AO AO uses a deformable mirror to correct atmospheric turbulence 3 Wavefront control for High contrast imaging
    [Show full text]
  • A Status Report on the Thirty Meter Telescope Adaptive Optics Program
    J. Astrophys. Astr. (2013) 34, 121–139 c Indian Academy of Sciences A Status Report on the Thirty Meter Telescope Adaptive Optics Program B. L. Ellerbroek TMT Observatory Corporation, 1111 S. Arroyo Pkwy., Ste. 200, Pasadena, CA 91107, USA. e-mail: [email protected] Received 15 March 2013; accepted 24 May 2013 Abstract. We provide an update on the recent development of the adap- tive optics (AO) systems for the Thirty Meter Telescope (TMT) since mid-2011. The first light AO facility for TMT consists of the Narrow Field Infra-Red AO System (NFIRAOS) and the associated Laser Guide Star Facility (LGSF). This order 60 × 60 laser guide star (LGS) multi- conjugate AO (MCAO) architecture will provide uniform, diffraction- limited performance in the J, H and K bands over 17–30 arcsec diameter fields with 50 per cent sky coverage at the galactic pole, as is required to support TMT science cases. The NFIRAOS and LGSF subsystems completed successful preliminary and conceptual design reviews, respec- tively, in the latter part of 2011. We also report on progress in AO component prototyping, control algorithm development, and system per- formance analysis, and conclude with an outline of some possible future AO systems for TMT. Key words. Adaptive optics—extremely large telescope. 1. Introduction The first light facility AO system for TMT is the Narrow Field Infra-Red AO Sys- tem (NFIRAOS), which will provide diffraction-limited performance in the J, H and K bands over 17–30 arcsec diameter fields with 50 per cent sky coverage at the galactic pole. This is accomplished with order 60 × 60 wavefront sensing and cor- rection, two deformable mirrors (DMs) conjugate to ranges of 0 and 11.2 km, six sodium Laser Guide Stars (LGSs) in an asterism with a diameter of 70 arcsec, and three low order (tip/tilt or tip/tilt/focus), infra-red Natural Guide Star (NGS) Wave- Front Sensors (WFSs) deployable within a 2 arcminute diameter patrol field.
    [Show full text]
  • Successful Tests of Adaptive Optics
    No. 58 - December 1989 Successful Tests of Adaptive Optics . F. MERKLE, ESO P. KERN, P. LENA, F. RIGAUT, Observatoire de Paris, Meudon, France. ' J. C. FONTANELLA, G. ROUSSET, ONERA, Chitillon-Sous-Bagneux, ~rance I%^. C. BOYER, J. P. GAFFARD, P. JAGOUREL, LASERDOT, Marcoussis, France g ., .I An old dream of ground-based as- A Break-through in Optical The extensive tests showed that it tronomers has finally come true, thanks Technology was possible to effectively "neutralize" to the joint development of a new tech- the atmospherically induced smearing nique in astronomical imaging - called In a major technological break- of a stellar image by a closed-loop adaptive optics -, by ESO and Obser- through in ground-based astronomy the correction system. In this way stellar vatoire de Paris, ONERA (Office National VLT Adaptive Optics Prototype System images were obtained at infrared d'Etudes et de Recherches Aerospatia- (also referred to as Come-On) has now wavelengths whose sharpness was only les), LASERDOT (formerly CGE) in proved its ability to overcome this natur- limited by the telescope aperture, i. e. France. al barrier during a series of successful diffraction limited images. It has been demonstrated that this tests in the period 12-23 October 1989. On each of the ten nights, infrared technique effectively eliminates the ad- They were performed at the coude exposures were made of about 10 bright verse influence of atmospheric turbu- focus of the 1.52-m telescope at the stars ranging from the visible magnitude lence on images of astronomical ob- Observatoire de Haute-Provence (OHP), 0.7 to 4.7 (including Capella, Deneb, jects, yielding images almost as sharp France.
    [Show full text]
  • Building the Gateway to the Universe 3
    B UILDING THE GATEWAY TO T HE UN IVERSE T HIRTY M ETER TEL ESCOPE 42581_Book.indd 2 10/12/10 11:11 AM CONTENTS 02 The Story of TMT is the History of the Universe 04 Breakthroughs and Discoveries in Astronomy 08 Grand Challenges of Astronomy 12 A Brief History of Astronomy and Telescopes 14 The Best Window on the Universe 16 The Science and Technology of TMT 26 Technology, Innovation, and Science 28 Turning Starlight into Insight On the cover Artist’s concept of the Thirty Meter Telescope. The unique dome design optimizes TMT’s view while minimizing its size. The louvered openings surrounding the dome enable the observatory to balance the air temperature inside the dome with that of the surrounding atmosphere, ensuring the best possible image with the telescope. Photo-illustration: Skyworks Digital 42581_Book.indd 3 10/12/10 11:11 AM B UILDING THE GATEWAY TO T HE UN IVERSE 42581_Book.indd 1 10/12/10 11:11 AM THE STORY OF TMT IS THE HISTORY OF THE U N IVERSE The Thirty Meter Telescope (TMT) will take us on an exciting journey of dis- covery. The TMT will explore the origin of galaxies, reveal the birth and death of stars, probe the turbulent regions surrounding supermassive black holes, and uncover previously hidden details about planets orbiting distant stars, including the possibility of life on these alien worlds. 2 T HIRTY METERT ELESCO PE 42581_Book.indd 2 10/12/10 11:11 AM Photo-illustration: Dana Berry MAUNA KEA HAWAII SELECTED AS PREFERRED SITE FULLY INTEGRATED LASER GUIDE STAR ADAPTIVE OPTICS INTERNATIONAL SCIENCE PARTNERSHIP BUILDING THE GATEWAY TO THE UNIVERSE 3 42581_Book.indd 3 10/12/10 11:11 AM B REAKTHROUG HS A ND DISCOV ERI ES I N ASTRONOMY Research in astronomy has revealed exciting details about our place in the cosmos.
    [Show full text]
  • The Close Circumstellar Environment of Betelgeuse-Adaptive Optics
    Astronomy & Astrophysics manuscript no. ms12521 c ESO 2018 August 29, 2018 The close circumstellar environment of Betelgeuse⋆ Adaptive optics spectro-imaging in the near-IR with VLT/NACO P. Kervella1, T. Verhoelst2, S. T. Ridgway3, G. Perrin1, S. Lacour1, J. Cami4, and X. Haubois1 1 LESIA, Observatoire de Paris, CNRS UMR 8109, UPMC, Universit´eParis Diderot, 5 place Jules Janssen, 92195 Meudon, France 2 Instituut voor Sterrenkunde, K. U. Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium 3 National Optical Astronomy Observatories, 950 North Cherry Avenue, Tucson, AZ 85719, USA 4 Physics and Astronomy Dept, University of Western Ontario, London ON N6A 3K7, Canada Received ; Accepted ABSTRACT Context. Betelgeuse is one the largest stars in the sky in terms of angular diameter. Structures on the stellar photosphere have been detected in the visible and near-infrared as well as a compact molecular environment called the MOLsphere. Mid-infrared observations have revealed the nature of some of the molecules in the MOLsphere, some being the precursor of dust. Aims. Betelgeuse is an excellent candidate to understand the process of mass loss in red supergiants. Using diffraction-limited adaptive optics (AO) in the near-infrared, we probe the photosphere and close environment of Betelgeuse to study the wavelength dependence of its extension, and to search for asymmetries. Methods. We obtained AO images with the VLT/NACO instrument, taking advantage of the “cube” mode of the CONICA camera to record separately a large number of short-exposure frames. This allowed us to adopt a “lucky imaging” approach for the data reduction, and obtain diffraction-limited images over the spectral range 1.04 − 2.17 µm in 10 narrow-band filters.
    [Show full text]
  • Adaptive Optics for the Thirty Meter Telescope
    Adaptive Optics for the Thirty Meter Telescope Brent Ellerbroek Thirty Meter Telescope Observatory Corporation Presentation to NAOC Beijing, June 23, 2011 TMT.AOS.PRE.11.085.REL01 1 Presentation Outline TMT adaptive optics (AO) requirements The first light TMT AO system design – Narrow Field Infra-Red AO System (NFIRAOS) – Laser Guide Star Facility (LGSF) AO component development Summary TMT.AOS.PRE.11.085.REL01 2 The Thirty Meter Telescope (TMT) Project Intends to build a Thirty Meter Telescope for ground based, visible and near infra-red astronomy Is a collaboration of: – The Association of Canadian Universities for Research in Astronomy (ACURA) – The University of California – The California Institute of Technology Construction scheduled to – NAOJ (participant), NAOC begin in 2012-13 (participant), and India (observer) First light to follow after a 7- Is now concluding a Design and year construction schedule Development Phase (DDP) to – Establish the system design – Determine the cost and schedule – Select a site (Mauna Kea 13N) 3 TMT.AOS.PRE.11.085.REL01 The TMT Design Ritchey-Chretien optical design form D = 30 m, f/1 primary 492 1.42m segments 3.05 m convex secondary f/15 output focal ratio 15 arc min unvignetted FOV Articulated tertiary Nasmyth-mounted instrumentation TMT.AOS.PRE.11.085.REL01 4 Many TMT Observations Require High Angular Resolution Studying the spatial structure and star formation regions of distant galaxies Precision astrometry and photometry of crowded star fields – Has been used to determine star orbital dynamics and “weigh” the black hole at the center of our galaxy Direct detection and characterization of extra-solar planets – Expected star-to-planet contrast ratios from 106 to 109 Real-time atmospheric turbulence compensation via adaptive optics (AO) enables high resolution observations such as these from the ground 5 TMT.AOS.PRE.11.085.REL01 Sample AO Results on Large Telescopes Galactic Center Astrometry (Keck LGS AO) Multi-Conjugate AO on a 2’ FoV (VLT) Classical AO MCAO LGS AO Science Papers vs.
    [Show full text]