and has 5m focal length. Its tube is mounted on a so-called German-type equatorial mounting and it is housed in a new dome not far from the Sinas building. The Doridis refractor was extensively used for observations of planets, comets, and the moon, as well as for astrometry and photometry of variable stars. In 2014, thanks to a generous donation from Cosmote, the telescope was fully restored and it is used for the purposes of education and public outreach. HellENIc GeoMagnetic Array The National Observatory of Athens operates ENIGMA (HellENIc GeoMagnetic Array), a ground-based magnetometer array in the area of south-eastern Europe (central and southern Greece) for space weather applications. The four existing stations are latitudinally equi-spaced between 30° and 33° corrected geomagnetic latitude and cover the areas of Thessaly, Central Greece and the Peloponnese. Each station is equipped with a state-of-the-art vector fluxgate magnetometer. In the near future another station will be installed in Macedonia or Thrace, and there are plans for the installation of an additional station in Crete by mid-2010s. One of the primary research objectives assigned to ENIGMA is the study of geomagnetic field line resonances (FLRs). ENIGMA is also part of the SuperMAG network. Ionospheric Station – Athens Digisonde The Athens Digisonde is an infrastructure for remote sensing of the Earth's Ionosphere, operated by NOA in Penteli since September 2000. The Digisonde is a Digital Portable Sounder with four receiving antennas (DPS-4), spaced about one wavelength apart. Data are collected and retrieved in real time (24/7 operation) and are openly available through the main portal of the Ionospheric Group of IAASARS/NOA. The Athens Digisonde is part of the following international networks: GIRO, ESPAS, WDC for Solar-Terrestrial Physics (RAL) and IPS/WDC The Athens Digisonde participates systematically in cal/val campaigns for LEO satellites. Its measurements are used in a variety of services (i.e. ESA space situational awareness). Atmospheric Remote Sensing Station Since February 2009, IAASARS has been operating a ground-based Atmospheric Remote Sensing Station (ARSS) to monitor ground solar radiation levels and particulate pollution over the city of Athens, Greece. ARSS is located on the roof of the Biomedical Research Foundation of the Academy of Athens (37.9 N, 23.8 E) at an elevation of 130 m above mean sea level. The site is located close to the Athens city centre and 10 km from the sea. ARSS is equipped with a CIMEL CE318-NEDPS9 solar photometer for the