The Aristarchos 2.3 m Telescope is a Ritchey-Chrétien telescope at the

Chelmos Observatory The Helmos or Chelmos Observatory () is an observatory located at the top of mount Chelmos, near Kalavryta, southern Greece. It is the largest research infrastructure of the National Observatory of Athens and IAASARS. The observatory was complet ...

on Mount Chelmos,

Greece Greece, officially the Hellenic Republic, is a country in Southeast Europe. Located on the southern tip of the Balkan peninsula, it shares land borders with Albania to the northwest, North Macedonia and Bulgaria to the north, and Turkey to th ...

. It is the largest telescope in the country and it had its first light test in 2005. It is operated by the

Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing The Institute for Astronomy, Astrophysics, Space Applications, and Remote Sensing (IAASARS/National Observatory of Athens, NOA; ) is a non-profit research institute in Greece with expertise in multidisciplinary Astrophysics, astrophysical, Space s ...

of the

National Observatory of Athens The National Observatory of Athens (NOA; ) is a research institute in Athens, Greece. Founded in 1842, it is the oldest List of research institutes in Greece, research foundation in Greece. The Observatory was the first scientific research insti ...

History

The New Greek Telescope project of the

(NOA) was funded by the

European Commission The European Commission (EC) is the primary Executive (government), executive arm of the European Union (EU). It operates as a cabinet government, with a number of European Commissioner, members of the Commission (directorial system, informall ...

and the General Secretariat for Research and Technology of the Hellenic Ministry of Development. The telescope had its first light test in 2005, and became the largest telescope in

when it became fully operational at the

site in 2007. The telescope is operated by the Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing (IAASARS) of the NOA. It is the largest telescope located in the

Balkans The Balkans ( , ), corresponding partially with the Balkan Peninsula, is a geographical area in southeastern Europe with various geographical and historical definitions. The region takes its name from the Balkan Mountains that stretch throug ...

and the second largest in

mainland Europe Continental Europe or mainland Europe is the contiguous mainland of Europe, excluding its surrounding islands. It can also be referred to ambiguously as the European continent, – which can conversely mean the whole of Europe – and, by so ...

Design

The telescope, built by

Carl Zeiss AG Zeiss ( ; ) is a German manufacturer of optical systems and optoelectronics, founded in Jena, Germany, in 1846 by optician Carl Zeiss. Together with Ernst Abbe (joined 1866) and Otto Schott (joined 1884) he laid the foundation for today's ...

, has a Ritchey-Chrétien configuration with a primary mirror with a diameter of 2.3 m. At the main f/8 Cassegrain focus, the corrected field of view is approximately one degree, with a plate scale of 1.17 arcsec/mm. It has an

Altazimuth mount An altazimuth mount or alt-azimuth mount is a simple two- axis mount for supporting and rotating an instrument about two perpendicular axes – one vertical and the other horizontal. Rotation about the vertical axis varies the azimuth (compass b ...

. The telescope is housed in a tower 35 meters away from the control building, so that heat and vibrations from human activity, automobiles and computers will not affect the telescope's performance. It was designed to support remote observation.

Research

OPTICON-RadioNet

The Aristarchos telescope is a full member of the OPTICON-Radionet Pilot (ORP) project since January 1, 2016. ORP is funded by the

European Union The European Union (EU) is a supranational union, supranational political union, political and economic union of Member state of the European Union, member states that are Geography of the European Union, located primarily in Europe. The u ...

and its main goal is to promote cooperation between experts from the astronomy community. It is the largest and most comprehensive network of facilities and observatories across

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

. The Aristarchos telescope has made quite a few observations under ORP awarded time, like a stellar occultation of

Neptune Neptune is the eighth and farthest known planet from the Sun. It is the List of Solar System objects by size, fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 t ...

's moon

Triton Triton commonly refers to: * Triton (mythology), a Greek god * Triton (moon), a satellite of Neptune Triton may also refer to: Biology * Triton cockatoo, a parrot * Triton (gastropod), a group of sea snails * ''Triton'', a synonym of ''Triturus' ...

and a transit of exoplanet

WASP-12b WASP-12b is a hot Jupiter (a class of extrasolar planets) orbiting the star WASP-12, discovered in April of 2008, by the SuperWASP planetary transit survey. The planet takes only a little over one Earth day to orbit its star, in contrast to abo ...

Space communications

All the activities concerning

optical Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultravio ...

quantum In physics, a quantum (: quanta) is the minimum amount of any physical entity (physical property) involved in an interaction. The fundamental notion that a property can be "quantized" is referred to as "the hypothesis of quantization". This me ...

, and deep space communications carried out at the Chelmos Observatory are identified by project HOTSPOT. The Aristarchos telescope was selected in August 2020 as the first ground-based station of the ScyLight program of

ESA The European Space Agency (ESA) is a 23-member international organization devoted to space exploration. With its headquarters in Paris and a staff of around 2,547 people globally as of 2023, ESA was founded in 1975 in the context of European ...

. ScyLight supports the research, development and evolution of optical communication, photonics and quantum communication technologies, and provides flight opportunities for their in-orbit verification. On 23 July 2021, the installation of the equipment for the project was completed; and a test was successfully performed for cummunication with the

Alphasat Inmarsat-4A F4, also known as Alphasat and Inmarsat-XL, is a large geostationary communications I-4 satellite operated by United Kingdom-based Inmarsat in partnership with the European Space Agency. Launched in 2013, it is used to provide mobile ...

satellite. The Aristarchos telescope was also selected for another project, the Deep Space Optical Communications (DSOC) demonstration of

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

. On 7 July 2025, the telescope achieved

laser communication Free-space optical communication (FSO) is an optical communication technology that uses light propagating in free space to wirelessly transmit data for telecommunications or computer networking over long distances. "Free space" means air, oute ...

with the

Psyche Psyche (''Psyché'' in French) is the Greek term for "soul" ( ψυχή). Psyche or La Psyché may also refer to: Psychology * Psyche (psychology), the totality of the human mind, conscious and unconscious * ''Psyche'', an 1846 book about the unc ...

spacecraft while it was on its way to the

main asteroid belt The asteroid belt is a torus-shaped region in the Solar System, centered on the Sun and roughly spanning the space between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies called asteroids ...

. A high-powered laser was fired from the nearby

Kryoneri Observatory The Kryoneri Observatory (Greek: Αστεροσκοπείο Κρυονερίου), also known as the Kryoneri Astronomical Station (Αστρονομικός Σταθμός Κρυονερίου), is an astronomical observatory in Corinthia, Greece ...

and the Aristarchos telescope received the spacecraft's response. These two observatories were the only ones in Europe participating in this experiment. The Aristarchos telescope will communicate with Psyche again on 21 July, 28 July and 4 August.

Other studies

The Aristarchos telescope has been operating for many years and has made multiple contributions to science. Just to name a few, in 2013 it helped discover the

exoplanets An exoplanet or extrasolar planet is a planet outside the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first detec ...

WASP-113b and WASP-114b, and in 2022 it proved that 55

asteroids An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...

believed to belong to a 4 Gyr

collisional family In astronomy, a collisional family is a group of objects that are thought to have a common origin in an impact (collision). They have similar compositions and most share similar orbital elements. Known or suspected collisional families include nu ...

share a common origin and thus do form a collisional family. Another contribution of the telescope is that it has provided a measurement of the distance to the planetary nebula

KjPn 8 KjPn 8 is a bipolar planetary nebula which was discovered by M.A. Kazaryan and Eh. S. Parsamyan in 1971 and independently by Luboš Kohoutek in 1972. Very little was published about this nebula until 1995, when it was realized that KjPn 8 sits ...

.NASA ADS
Bibliographic record

References

External links

*{{Commons category inline
OPTICON Network
Reflecting telescopes Astronomy in Greece