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Yayın 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.Yayın DAG 4m telescope: assembly, integration and testing(SPIE-Int Soc Optical Engineering, 2018-07-06) Pirnay, Olivier; Lousberg, Grégory P.; Gabriel, Eric; Marchiori, Gianpietro; Busatta, Andrea; Yeşilyaprak, Cahit; Keskin, OnurAMOS with EIE as a main subcontractor, was awarded a contract in November 2014 for the design, manufacturing and installation of a 4m-class telescope for the Turkish Eastern Anatolia Observatory (DAG) situated at 3170 m above the sea level in Palandöken mountains. The telescope is based on a Ritchey-Chretien configuration with two folded Nasmyth focal planes and a focal length of 56m. Diffraction-limited performances will be reached thanks to the combination of the active optics system and the adaptive optics system that will be implemented on one of the Nasmyth ports. The active optics system aims at controlling the shape of the primary mirror by means of 66 axial force actuators and positioning actively the secondary and tertiary mirrors by means of hexapods. More than 30 years of experience in testing instruments and telescopes, including optical testing, alignment, metrology, mechanical static and dynamic measurements, system identification, etc. allow to implement an adequate verification strategy combining component level verifications with factory and site test in the most efficient and reliable manner. As a main contractor, AMOS is in charge of the overall project management, the system engineering, the optical design and the active optics development. As a main sub-contractor and partner of AMOS, EIE is in charge of the development of the mount. The factory test therefore takes place in EIE premises. In this paper is shortly presented the overall design of the telescope with a review of the specification, the optical design and a description of the major sub-systems, including the optics. The assembly, integration et test plan is outlined. The assembly sequence and the tests of the active optics and the mount are discussed. Finally, the site integration and tests are explained. The process to assess the image quality of the telescope and the verification instrument developed for this purpose by AMOS are presented.Yayın DAG 4m telescope: optics completion, on-site integration and test(SPIE, 2022) Pirnay, Olivier; Albart, Pierre; Bastin, Christian; De Ville, Jonathan; Gabriel, Eric; Leseur, Thibault; Lousberg, Grégory P.; Méant, Laurence; Orban, Sabrina; Tortolani, Jean-Marc; Amalfi, Manfredi; Marchiori, Gianpietro; Rampini, Francesco; Busatta, Andrea; Yeşilyaprak, Cahit; Keskin, OnurAMOS with EIE as main subcontractor has recently completed the erection of the 4 m telescope located at the Turkish Eastern Anatolia Observatory (DAG) set up by the Ataturk University Astrophysics Research and Application Centre (ATASAM) of Erzurum. The telescope design is based on a Ritchey-Chrétien configuration with two folded Nasmyth focal planes and a focal length of 56m. The optical train is composed of three mirrors: the primary mirror (M1) with an optical aperture of 4m, a convex secondary mirror (M2), and a large flat folding mirror (M3). Diffraction-limited performances in optical and near infrared spectral bands will be achieved thanks to the combination of active and adaptive optics systems. The active optics system is controlling the shape of the primary mirror by means of 66 axial force actuators and position actively the secondary and tertiary mirrors by means of hexapods. The adaptive optics system will be implemented at one of the two Nasmyth ports. As main contractor, AMOS is in charge of the overall project management, the system engineering, the optical design and the active optics development. As main sub-contractor and partner of AMOS, EIE is in charge of the development of the mount. Following the factory acceptance in Europe, the telescope was dismounted and delivered in early 2021. The activities onsite were carried out according to the assembly, integration and verification plan (AIV plan). In the meantime, the fabrication of the 4 m primary mirror was completed, and the full set of mirrors was forwarded on-site before the end of the year 2021. In this paper is presented a brief description of the design and performances of the telescope followed by the project progress status at the time the optics are being integrated in the telescope for the first time. This includes the review of the mirrors as-built quality and the excepted performances of the telescope mount after alignment and tuning. The path forward final acceptance is explained with the presentation of the optical alignment method and the test carried-out on-sky.Yayın Modelling and simulation studies on adaptive controller for alt-azimuth telescopes despite unknown wind disturbance and mass(SAGE Publications, 2020-09-15) Keskin, Onur; Ünal, Ali Cem; Kararsız, Gökhan; Yılmaz, Tuğrul; Yeşilyaprak, CahitNumerous ground-based observatories are using small sized ground telescopes for scientific research purposes. The telescopes that are available on the market have three main problems. These issues can be listed as: positioning repeatability, tuning requirement according to different wind speeds for different seasons, and the mass changing via different scientific equipments added to the telescope. This study is aimed at resolving these issues for ground based small alt-azimuth telescopes. Establishing of a set and forget system is performed by designing an adaptive controller. Motor dynamics are taken into consideration for a realistic mathematical model. The Wind-Gust model that consists of a sum of sinusoidal disturbances with unknown phase, amplitude and frequency is used for the wind model. The purposed controller cancels the disturbance effects on the plant while operational positioning and also the makes the plant insensitive to mass changes. The Lyapunov approach is utilised when proving the asymptotic stability. The proposed controller’s success is illustrated with thorough numerical evaluation.Yayın Project management of DAG: Eastern Anatolia Observatory(SPIE, 2016) Keskin, Onur; Yeşilyaprak, Cahit; Yerli, Sinan Kaan; Zago, Lorenzo; Güver, Tolga; Aliş, SinanThe four meter DAG (Eastern Anatolia Observatory in Turkish) telescope is not only the largest telescope in Turkey but also the most promising telescope in the northern hemisphere with a large potential to offer scientific observations with its cutting edge technology. DAG is designed to be an AO telescope which will allow both infrared and visible observations with its two Nasmyth platforms dedicated to next generation focal plane instruments. In this paper, status updates from DAG telescope will be presented in terms of; (i) in house optical design of DAG, (ii) tender process of telescope, (iii) tender process of enclosure, and (iv) tender process of the observatory building. Also status updates from the focal plane instruments project and possible collaboration activities will be presented.Yayın Eastern Anatolia Observatory (DAG): Recent developments 2017(SPIE-INT Soc Optical Engineering, 2018-07-06) Yeşilyaprak, Cahit; Keskin, OnurEast Anatolia Observatory (DAG) is the new observatory of Turkey with the optical (VIS) and near-infrared (NIR) largest telescope (4 m mirror) and its robust observing site infrastructure. This national project consists of three phases with DAG (telescope, enclosure, building, infrastructure), FPI (Focal Plane Instruments and Adaptive Optics) and MCP (Mirror Coating Plant) and is supported by the Ministry of Development of Turkey. Almost all infrastructure (roads, geological and atmospheric surveys, electricity, fiber optics, water, generator, etc.) of DAG site (Erzurum/Turkey, 3170 m altitude) have been completed. The recent developments (telescope, enclosure, mirror, focal plane instruments, building, atmospheric studies, etc.) of DAG and its site in 2017 and 2018 were presented for the future possible collaborations for various astronomical instruments and telescopes which can be set up in DAG site.Yayın Adaptive backstepping approach for 2-DOF telescopes despite unknown wind disturbance(Institute of Electrical and Electronics Engineers Inc., 2019-07) Ünal, Ali Cem; Yılmaz, Cemal Tuğrul; Kararsız, Gökhan; Keskin, Onur; Yeşilyaprak, CahitSmall ground telescopes on the marked are widely used in many space observatories and scientific researches. There are three main problems in such telescopes; positioning of the focal point and the need of tuning for both different seasonal wind speeds and mass changes of the telescope arm. This study focuses on eliminating those problems for 2-DOF altazimuth configuration small telescopes. An adaptive controller is designed to create a set and forget system. The mathematical model of the telescope is derived based on RR type joint configuration. For a realistic approach, motor dynamics is considered in the mathematical model. The wind disturbance is modeled according to the Wind-Gust model which is a sum of sinusoidal with unknown amplitude, frequency and phase. The controller aims to cancel the effect of the disturbance on focal point of the telescope while positioning. The asymptotic stability is proven with the Lyapunov approach. The numerical study is illustrated to success of the proposed controller.Yayın DAG: A new observatory and a prospective observing site for other potential telescopes(SPIE, 2016) Yeşilyaprak, Cahit; Yerli, Sinan Kaan; Keskin, Onur; Güçsav, Bülent BurakDAG (Eastern Anatolia Observatory is read as "Dogu Anadolu Gözlemevi" in Turkish) is the newest and largest observatory of Turkey, constructed at an altitude of 3150 m in Konakll/Erzurum provenience, with an optical and nearinfrared telescope (4 m in diameter) and its robust observing site infrastructure. This national project consists of three main phases: DAG (Telescope, Enclosure, Buildings and Infrastructures), FPI (Focal Plane Instruments and Adaptive Optics) and MCP (Mirror Coating Plant). All these three phases are supported by the Ministry of Development of Turkey and funding is awarded to Atatürk University. Telescope, enclosure and building tenders were completed in 2014, 2015 and 2016, respectively. The final design of telescope, enclosure and building and almost all main infrastructure components of DAG site have been completed; mainly: road work, geological and atmospheric surveys, electric and fiber cabling, water line, generator system, cable car to summit. This poster explains recent developments of DAG project and talks about the future possible collaborations for various telescopes which can be constructed at the site.Yayın DAG rotating enclosure final erection and acceptance tests(SPIE, 2024) Marchiori, Gianpietro; Rampini, Francesco; Amalfi, Manfredi; Bressan, Riccardo; Ghedin, Leonardo; Battistel, Cristina; Manfrin, Cristiana; Vio, L.; Niero, Tiziano; Marchiori, Tommaso; Yeşilyaprak, Cahit; Keskin, OnurThe DAG (Dogu Anadolu Gözlemevi) observatory is the largest observatory in Turkey and is composed by the 4m-class infrared Telescope, the Rotating Enclosure, the dome fixed structure and the auxiliary building. It is mounted on the top of Karakaya Mountain at 3170m altitude, close to Erzurum, in Turkey. This presentation refers to the DAG Rotating Enclosure. The Rotating Enclosure is octagonal sized steel structure with eight trolleys acting on a rai of 18.6 meters diameter. The structure is and 14.5m high over a pillar 9.0m. It is equipped with an observing slit door composed by two L-Shaped elements. Six sliding ventilation doors, about 3.7x6.5m each, that can be opened independently and with different degrees of aperture allow for optimizing the internal airflow. Immediately Inside the observing slit doors, there is a windscreen consisting of 3 panels that, in case of wind, are raised in accordance with the telescope elevation to protect it. The panels have a specific degree of air permeability to still allow ventilation for the telescope. A 6.5tons overall bridge crane allows to move pieces in every zone of the rotating enclosure for the maintenance of the telescope optics. At the beginning of November 2023, EIE carried out all acceptance tests with the end customer and delivered the rotating enclosure to ATASAM. This paper provides the results of the final erection and reports the procedures and results of the Acceptance Tests performed by EIE for the DAG Rotating Enclosure activities. 4m class telescopes and related Domes represent nowadays a consolidated part of EIE core-business, a low costs standard product able to satisfy the most critical observational requirements of astronomers.
