Iranian National Observatory (INO) project is approaching completion, with the first light of the flagship 3.4m optical telescope, INO340, planned for 2022. The observatory is located in central Iran on Mt Gargash at 3600m, benefiting from an excellent atmospheric seeing and suitable weather conditions. The observatory comprises the 3.4m optical telescope, the enclosure and auxiliaries, a service building hosting a control room, offices and mirror coating hall, a lens array system for wide-field monitoring, and a site monitoring station equipped with a weather station and an automatic seeing monitor, and essential utilities. The Alt-Az telescope benefits from hydrostatic bearing in the Azimuth, an active optics system to support and deform the primary mirror and a hexapod to position the secondary mirror. This report will provide an overview of the project development, manufacturing and installing the telescope and its enclosure.
An active optics algorithm is developed for the Iranian National Observatory 3.4 [m] telescope (INO340). The primary mirror (M1) and the secondary mirror (M2) are considered flexible and rigid, respectively. M1-Support consists of 60 active axial actuators (AAC), 32 passive lateral actuators (LAC), three axial hard-points (AHP), and three lateral hardpoints (LHP); and an accurate hexapod supports M2. M1 surface shape and M2 positions are actively controlled using an active optics system (AOS) to reach the best image quality. Correction can be done using either a look-up table in open-loop control or the wavefront error in closed-loop control. This paper presents the algorithm and the strategy of INO340 active optics. In this regard, relevant extracted matrices for the INO340 active optics algorithm are derived. The Shack-Hartmann sensor probes the accumulated aberrations and provides a square matrix as feedback. By decomposing the aberrations into the Zernike polynomials, tip-tilt, defocus, and coma aberrations are eliminated by adjustment of M2 positions and other aberrations are removed by deforming the flexible M1. The effective mechanical modes of M1 are selected based on the AACs’ force amplitude, and root mean square (RMS) of the residual surface. The percentage of residual surface error and set of axial forces are shown for each mechanical mode. As a result, mechanical modes No. 1 to 9 and No. 12 to 16 can be corrected. Finally, the algorithm is used to remove the remained aberration after the polishing process, which shows the residual surface after compensation and the required set of AACs’ force.
The Active Optics System (AOS) of the Iranian National Observatory 3.4 m telescope (INO340) is designed to support and deform the M1 and to adjust the position of the M2 with the purpose of optical aberrations’ compensation. Sixty active axial pneumatic actuators and 32 passive lateral actuators support M1 axially and laterally, respectively. The arrangement and force vectors of the lateral actuators are optimized in such a way that minimum deformation on M1 occurs. There are 3 axial and 3 lateral fixed-points as positioning detectors for M1, and an accurate hexapod keeps M2 in the appropriate position. M1 surface shape and M2 positions are actively controlled by AOS during telescope operations using either a look-up table in open-loop control or the wavefront error in closed-loop control to achieve the best image quality. There are three levels of the control loop in AOS: 1- A proportional controller for a single actuator, 2- Inner-loop control to equilibrate M1 within the bandwidth of 1 [Hz], 3- Outer-loop control to remove optical aberrations within the bandwidth of 0.01 [Hz]. A test setup for the axial actuator and an Alt-simulator setup are provided to design and optimize a proportional controller for a single actuator and to test the inner-loop control. In this paper, the mechanical, control, and software designs for INO340 AOS are presented.
The Iranian National Observatory (INO) 3.4 m optical telescope (INO340), has been installed on Mt Gargash peak at an altitude of 3600 m in central Iran. The optical design of the telescope is Ritchey-Chretien Cassegrain type on an altitude-azimuth mount and offers an unvignetted field of view of 20 arcmin and the focal ratio of f/11.25. It has a total mass of 85 tons with a height of 11 m and a maximum diameter of 7.5 m. The telescope design was optimized to achieve 0.2 arcsec tracking accuracy and 3 arcsec blind pointing accuracy. The finite element analyses have been carried out during the design phase to make sure of the functionality and safety of the telescope. This paper presents the mechanical design, analysis and manufacturing of the telescope.
The INO340 enclosure design follows recent developments in enclosure and dome design which aims at minimum enclosed air with suitable temperature and humidity control as well as an efficient air flushing to reduce the mirror seeing. The INO340 enclosure performance indicates a quality design and construction which meets the desired specifications. This report will review the design details of INO340 enclosure building architecture and anatomy. It will also describe some back design philosophies that drove design details and construction of the enclosure. We briefly report on the development and installation of the dome.
The Iranian National Observatory site is under construction at an altitude of 3600m at Mount Gargash in central Iran. It offers a promising site for optical and near-IR observations with a 0.7 arcsec median seeing and thus a number of observing facilities have been planned. The largest facility is a 3.4m Alt- Az reflecting Ritchey-Chretien optical telescope under development with an exit focal ratio of ~f/11 providing a generous 20 arcmin field of view at the main Cassegrain focus. This telescope will be equipped with high resolution medium-wide field imaging camera as well as medium and high resolution spectrographs. The telescope will benefit from an active support for the primary mirror. The primary mirror has been manufactured, polished and delivered. In this project overview, the design parameters for the 3.4m telescope and the current status of the project are presented.
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