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Öğe Adaptive optics for DAG telescope(Türk Astronomi Derneği, 2020-12-11) Keskin, Onur; Jolissaint, LaurentWhat we propose for DAG is therefore a natural guide star GLAO system, that can be turned into a highly efficient AO system. Thus the working principle and expected performance analysis will be shown. In this manner most DAG users will be able to make some use of the DAG AO. Later, it will be possible to upgrade the system by changing th algorithm and adding 1 or 2 additional DM, and even laser guide stars.Öğe Advances for the 4m DAG Telescope in Flange derotator(SPIE, 2020-12-13) Keskin, Onur; Ünal, Ali Cem; Koç, İlker Murat; Jolissaint, Laurent; Yeşilyaprak, CahitThe purpose of this study is expressing advances in design stages for in flange optical field derotator system for 4 meters DAG Telescope. In-Flange Derotator KORAY (K-mirror OpticalRelAY) is designed, analysed and manufactured to meet the specifications of DAG telescope. DAG telescope, situated at Erzurum/Karakaya summit at 3150m altitude, is the first Turkish optical telescope with VIS(Visible) and IR (Infrared) observation capability. DAG, designed by Turkish engineers at FMV Isik University, is also the largest telescope (4m diameter) in Turkey and in European continent. Being one of the 2023 vision projects; the first light of DAG is expected to take place in 2021. This purpose brings some real-life challenges such as design limitations, material selection and electronic integration.Öğe Design of a derotator for the 4 m DAG telescope(SPIE-Int Soc Optical Engineering, 2016-08-09) Baudet, Jeremie; Jolissaint, Laurent; Keskin, Onur; Yeşilyaprak, Cahit; Yerli, Sinan KaanThis paper Silt our work on the design of a field derotator for the adaptive optics instruments platform of DAG (Dogu Anadolu Cozier vi), a new 4 in telescope for astronomical observations near the city of krzurum, l'urkey. While the telescopefollows an astronomical object, its pupil sees a rotation of the object around the optical axis which depends n the telescope geographic coordinate and the object sky coordinate. This effect is called the field rotation. This rotation needs to be compensated during the astronomical object data acquisition. In this report we demonstrate the feasibility of placing the derotator (a. K-mirror design) in the telescope fork central hole and propose a preliminary design, considering flexures.Öğe The design of an adaptive optics telescope: the case of DAG(SPIE, 2016-07-27) Jolissaint, Laurent; Keskin, Onur; Zago, Lorenzo; Yerli, Sinan Kaan; Yeşilyaprak, Cahit; Mudry, Emeric; Lousberg, Grégory P.In this paper, we describe in detail the optical design of DAG, a new 4 m telescope for Turkey. DAG is an "adaptive optics friendly" telescope, in a sense that each design decision is taken considering the potential impact on the AO performance (vibrations, static aberrations etc.) The objective is to make this telescope fully ready for AO at first light. It is designed as a Ritchey-Chretien combination, 56 m focal length, with Nasmyth foci only, and active optics. Its total RMS error is expected to be 45 nm up to Zernike mode 78, and 26 nm for the higher, non AO corrected modes. A final design optimization has been done by the telescope manufacturers, demonstrating that our AO-based requirements can be satisfied, without much difficulty.Öğe Design of the near infrared camera DIRAC for East Anatolia Observatory(SPIE, 2022) Zhelem, Ross; Content, Robert; Churilov, Vladimir; Kripak, Yevgen; Waller, Lew; Case, Scott; Mali, Slavko; Muller, Rolf; Gonzalez, Mario; Adams, Dave; Binos, Nick; Chin, Timothy; Farrell, Tony; Klauser, Urs; Kondrat, Yuriy; Kunwar, Nirmala; Lawrence, Jon; Lorente, Nuria; Luo, Summer; McDonald, Erica; McGregor, Helen; Nichani, Vijay; Pai, Naveen; Vuong, Minh; Zahoor, Jahanzeb; Zheng, Jessica; Norris, Barnaby; Bryant, Julia; Vaccarella, Annino; Herrald, Nick; Gilbert, James; Yeşilyaprak, Cahit; Güçsav, Bülent; Coker, Deniz; Keskin, Onur; Jolissaint, LaurentThe 4m DAG telescope is under construction at East Anatolia Observatory in Turkey. DIRAC, the " DAG InfraRed Adaptive optics Camera", is one of the facility instruments. This paper describes the design of the camera to meet the performance specifications. Adaptive and auxiliary optics relay the telescope F/14 input 1:1 into DIRAC. The camera has an all refractive design for the wavelength range 0.9 - 2.4 micron. Lenses reimage the telescope focal plane 33 x 33 as (9 x 9 mm) on a 1k x 1k focal plane array. With magnification of 2x, the plate scale on the detector is 33 mas/pixel. There are 4 standard filters (Y, J, H, K) and 4 narrowband continuum filters. A 12 position filter wheel allows installation of 2 extra customer filters for specific needs; the filter wheel also deploys a pupil viewer lens. Optical tolerancing is carried out to deliver the required image quality at polychromatic Strehl ratio of 90% with focus compensator. This reveals some challenges in the precision assembly of optics for cryogenic environments. We require cells capable of maintaining precision alignment and keeping lenses stress free. The goal is achieved by a combination of flexures with special bonding epoxy matching closely the CTE of the lens cells and crystalline materials. The camera design is very compact with object to image distance <220 mm and lens diameters <25 mm. A standalone cryostat is LN2 cooled for vibration free operation with the bench mounted adaptive optics module (TROIA) and coronagraph (PLACID) at the Nasmyth focus of the DAG telescope.Öğe Eastern Anatolia Observatory (DAG): the status in 2022, towards the first light(SPIE, 2022) Yeşilyaprak, Cahit; Keskin, Onur; Jolissaint, LaurentEast Anatolian Observatory's DAG telescope, with its 4m diameter primary mirror and VIS/IR observation capability, Eastern Anatolian Observatory's 4m diameter class DAG telescope, with VIS/IR observation capability, will be located on the Konakll-Karaya summit at an altitude of 3170 m, near the city of Erzurum, Turkey. DAG contains both active optics (aO) and adaptive optics (AO) systems. With the enclosure assembly nearly done, and the dummy mirror integration including the M1 cell integration performed at the end of 2021; DAG telescope's AIV is planned to take place by the end of May/2022 and the Provisional Acceptance by November/2022. DAG is equipped with an in-flange derotator-KORAY (K-mirror Optical RelAY) that will direct the light to the seeing limited Nasmyth platform containing TROIA (TuRkish adaptive Optics system for Infrared Astronomy). The scientific instruments that DAG will receive in 2022, are but not limited to, a stellar coronagraph and a 30"NIR diffraction limited camera. In his paper, a global status update and expected optical performance characteristics will be presented.Öğe The flexible adaptive optics concept(Instituto de Astrofisica de Canarias, 2017) Jolissaint, Laurent; Eikenberry, Stephen Steve; Bouxin, Audrey; Keskin, Onur; Yeşilyaprak, CahitThe availability of small deformable mirrors with large number of actuators and stroke, on one hand, and versatile wavefront sensors (pyramid WFS), on the other, allows the development of AO systems whose equivalent pitch can be adapted freely to the guide stars and seeing conditions. On moderately large telescopes (4 m class) this exibility allows a performance (Strehl and limiting magnitude) always better than what a classical, frozen Shack-Hartman design would allow. Moreover, adding several natural guide star wavefront sensors, we believe a single system could do anything from extreme AO to GLAO, i.e using the same hardware, and adapting the control software parameters to the observation mode. Taking advantage of such a system requires the use of a zoom optics in the imager in order to optimally match the plate scale with the PSF. We demonstrate that sub-optimal pixel size would result in a significant loss in term of science data reduction, in particular object detectability. The raison d'etre of such a versatile system is to popularize AO in community of astronomers not familiar with it, by allowing, on the same telescope, high resolution as well as seeing improved observations. This is particularly important for countries where very few large telescopes are available. On the long term, we think that most moderate size telescopes will have this sort of exible multi-purpose AO systems as a default. The exible AO concept will be implemented on the new 4 m Turkish telescope, DAG. © 2017 Instituto de Astrofisica de Canarias. All rights reserved.Öğe A flexible adaptive optics concept for general purpose high angular resolution science on the DAG 4m telescope(SPIE-Int Soc Optical Engineering, 2018) Jolissaint, Laurent; Bouxin, Audrey; Gökay, Ulaş Sabahattin; Keskin, Onur; Rigaut, Francois; Yeşilyaprak, CahitThanks to the availability of high actuator density deformable mirrors (ALPAO 468 DM), the high versatility of the pyramid wavefront sensor and above all, the venue of essentially no noise EMCCD detectors, it becomes possible to fully adapt the degree of correction of an adaptive optics system for a given guide star brightness and atmospheric condition. Indeed, when the conditions are very good, the high actuator density of the DM allows to reach a high Strehl by using all the modes, and when the conditions are less favorable, the spatial sampling, i. the number of modes, and the sensitivity of the detector allows to maximize the Strehl beyond what would be possible with a classical, frozen SH-WFS based system. Beside, oversampling the detector allows to relax the specification on the pupil images given by the pyramid on the detector, which in turn relaxes the pyramid prism manufacturing specifications. We are now designing an AO system for the DAG 4 m telescope that will allow, on the same system, ExAO as well as low order improved seeing observations. This article reports on the AO performance analysis, the final optical design and the design of the double prism achromatic pyramid.Öğe Observing with DAG: performance metrics of imaging and spectroscopy(Türk Astronomi Derneği, 2020-12-11) Jolissaint, Laurent; Zago, Lorenzo; Keskin, OnurDAG telescope will be designed as a telescope with adaptive optics and seeing limited modes of observation. Its primary mirror will be a thin meniscus, controlled in shape by an active optics system. This implies specific requirements for the mirrors manufacturing errors tolerancing, studied and defined in this document.Öğe Optical design of the adaptive optics system for DAG, the new 4 m Turkish telescope(SPIE, 2020) Bouxin, Audrey; Jolissaint, Laurent; Keskin, Onur; Yeşilyaprak, Cahit; Spanò, PaoloWe present the design of the Adaptive Optics System for the new Turkish 4-m telescope (DAG). The AO will use a pyramid WFS, with a double prism and a no noise EM-CCD camera to allow for oversampling of the pupil images and a relaxation of the prism manufacturing tolerances. In order to use the high modal resolution of the P-WFS allowed by the adjustment of the modulation angle, we implement a high order deformable mirror with 468 actuators, which will permit to use the system in extreme AO correction mode. The P-WFS optical design has been largely inspired by NFIRAOS truth WFS. The number of optical surfaces has been reduced to the bare minimum. An atmospheric dispersion compensator is introduced around the tip-tilt modulation mirror. In this proceeding, we present the detail of the optical design steps for all the components of the system.Öğe Project management and status update for DAG (Eastern Anatolia Observatory) the 4 meter VIS/IR optical telescope(SPIE-Int Soc Optical Engineering, 2018) Keskin, Onur; Yeşilyaprak, Cahit; Jolissaint, LaurentThe new 4 m Turkish telescope, DAG (East Anatolian Observatory, Fig. 2), will be located on the summit of the mountain Konakli-Karakaya, at an altitude of 3170 m, near the city of Erzurum, Turkey. First light is expected for August 2020. The telescope is a multi-purpose instrument, and will run observations both in the visible (VIS) and near infrared (NIR) domains, in seeing limited (SL) and adaptive optics (AO) correction mode. In his paper, status updates from DAG telescope will be presented in terms of; (i) DAG telescope optics, (ii) Nasmyth focal planes and platforms, (iii) current progress of the telescope, (iii) current progress of enclosure, (iv) current progress of the observatory building, (v) current process of the astronomical instruments & tendering phase, and (Vi) status of the Optomechatronics Research Laboratory - OPAL.Öğe TROIA adaptive optics system for DAG Telescope(SPIE, 2020-12-13) Keskin, Onur; Jolissaint, Laurent; Bouxin, Audrey; Yeşilyaprak, CahitThis paper presents the specifications of TROIA-TuRkish adaptive Optics system for Infrared Astronomy system, the science rationale for these specifications, and description of the site technical and environmental conditions to be taken into account in the adaptive optics (AO) system design for the Eastern Anatolia Observatory-DAG telescope. With it's 468 actuators, EMCCD camera, and the pyramid wavefront sensor configuration; TROIA is able to adapt the degree of correction to a given guide star (GS) brightness during observations. The high actuator density of TROIA AO system will allow DAG to perform astronomical observations at ExAO performances.Öğe TROIA Adaptive optics system for DAG telescope; assembly and laboratory performance prior to on-sky assessment(SPIE, 2022-08-29) Keskin, Onur; Jolissaint, Laurent; Bouxin, Audrey; Yeşilyaprak, CahitIn this article, we describe the current status of the development of TROIA* a pyramid wavefront sensor based adaptive optics system designed for DAG, a new 4 m telescope located in Eastern Anatolia, Turkey. The wavefront uses a no-noise electron-multiplied CCD camera, and the deformable mirror has a large actuators density, allowing coronagraphic science in one hand, but also system optimization for low light level or bad seeing conditions thanks to the versatility of the P-WFS. We describe the optical design, the mounting and alignment procedure and our loop control concept. Closed loop results are described, showing that while there are still many issues to fix before the sky version, the system behaves as expected.Öğe Turkey's next big science project: DAG the 4 meter telescope(SPIE-INT Soc Optical Engineering, 2014) Keskin, Onur; Yeşilyaprak, Cahit; Yerli, Sinan Kaan; Zago, Lorenzo; Jolissaint, LaurentThe DAG (Turkish for Eastern Anatolia Observatory) 4-m telescope project has been formally launched in 2012, being fully funded by the Government of Turkey. This new observatory is to be located on a 3170 m altitude ridge near the town of Erzurum in Eastern Anatolia. First light is scheduled for late 2017. The DAG team's baseline design of the telescope consists of a Ritchey-Chretien type with alt-az mount, a focal length of 56 m and a field of view up to 30 arcmin. Multiple instruments will be located at the Nasmyth foci. The optical specifications of the telescope are set by DAG team for diffraction limited performance with active and adaptive optics. Modern mirror control technologies will allow defining in a most cost effective way the figuring requirements of the optical surfaces: the low order figuring errors of the combined optical train constituted of M1-M2-M3 are defined in terms of Zernike coefficients and referred to the M1 surface area. The high order figuring errors are defined using the phase structure functions. Daytime chilling of the closed enclosure volume and natural ventilation through suitable openings during observations will be used to ensure optimal mirror and dome seeing. A design of a ground layer adaptive optics (GLAO) subsystem is developed concurrently with the telescope. In this paper, main design aspects, the optical design and expected performance analysis of the telescope will be presented.
