Iranian National Observatory (INO) is an Iranian astronomical observatory inaugurated in 2021. It has reported the capture of its first light on 15 October 2022 upon the commissioning of the home-grown optical telescope with a primary mirror of 3.4 m, making it by far the country's largest astronomical research facility.
Background
The project aimed at the construction of observing facilities for astronomical research and education purpose. The primary goal is the design and construction of a 4 m-class optical telescope and other smaller observing facilities to respond to a growing demand. INO is executed at the Institute for Research in Fundamental Sciences (IPM), one of the leading research institutes in fundamental sciences in Iran.
The training capabilities in observational astronomy in Iran in late 2000s was unable to meet the growing demand due to a rapid growth in higher education. While almost every big university in Iran has an astronomy department or group, the existing observational facilities consist of a number of small telescopes in various university campus observatories generally used for undergraduate and graduate training.
A medium-size optical telescope is thought to be a step to facilitate research in astronomy and observational cosmology. The geographic location of Iran, relatively dry climate, and high-altitude mountains offer suitable locations for optical telescopes to carry out surveys and time-critical observations.
At the present, the flagship of the INO observing facilities, a 3.4-m optical telescope known as INO340, is in commissioning state. Iranian scientists see the project as a platform to catch up with the science and technological developments in the field of astronomy and cosmology.
Site selection
The site selection activities began in 2000 before the formal approval of the project in 2004. Over 30 sites were visited, and seeing observations were conducted at some of them. Later, four sites were chosen for simultaneous seeing monitoring for two years. With two sites in hand after the conclusion of the site selection (2000–2007), INO made seeing measurements to be able to compare the two sites, Dinava (~3000 m) and Gargash (~3610 m). In 2011, INO announced Mount Gargash as the site for this project. The site became road accessible in 2016.
Telescope design
Optics
The telescope is a Ritchey–Chrétien f/11 which provides an unvignetted 20-arcmin field of view at the main Cassegrain focus. In addition, three broken side foci are also provided, each with a field of view of 8 arcmin. The main mirror (M1) is a single-segment fast f/1.5 mirror with a diameter of 3.4 m, which makes INO340 one of the most compact telescopes for its size. M1 is a meniscus shape 18 cm thick made of a Zerudor ceramic with a 700-mm central hole. The M1 is polished to 1-nm roughness. It is supported by 60 actuators which are actively controlled to hold the mirror at the correct shape. The 600-mm secondary mirror reflects the light from the primary mirror and is also controlled by a hexapod. The mirror is made of a Zerodur ceramic and has a hyperbolic surface geometry.
The structure
The telescope mount is altitude over azimuth (alt-az) which allows the telescope to be compact and provides direct load paths from the telescope down through the structure to the pier and foundations. The drive motors used to move the telescope in azimuth and elevation will be servo motors with position feedback provided by linear tape encoders.
Telescope Control System (TCS)
The TCS is responsible for controlling a number of subsystems such as the mount control system (MCS), which is responsible for pointing and tracking the targets, and the mirrors control system or active control systems (ACS). MCS receives commands from the user interface.
Telescope enclosure and the dome
The telescope enclosure is a cylindrical structure composed of a concrete ring 16 m in diameter, at the centre of which a 6-m diameter telescope pier is located. On top of the concrete building there is a rotating cylindrical structure of approximately 200 tons, with a 5-m shutter to facilitate the exposure of the primary mirror to the light from the dark night objects and five windows to allow air flow inside the dome. The dome and a lower floor are chilled during the day to improve the mirror seeing.