An actinometric platform has been installed and measuring at National Observatory of Athens on since 2016 (Latitude: 37.9 deg, Longitude: 23.7 deg, Altitude: 130m a.s.l.). The system consists of two sun photometers (PANDORA, and PSR- Presicion Spectral Radiometer), both of which measure the sun spectrum at very high resolution, providing high temporal information of the radiation field and the aerosol variability.

PANDORA is a spectrometer which records direct Irradiance at the spectral region of 290-520 nm (0.12nm step), with 1min frequency. PANDORA is part of the PANDONIA global network (Athens-NOA) and has been used for satellite (TropOMI) validation activities. Measurements of th PANDONIA network are freely accessible online in real time (

PSR Is a spectroradiometer with two input optics in order to record both direct and Global (total) Irradiance, which end up at the same spectrometer. The instrument measures in the range 300-1020 nm, with a sampling step of 0.7 nm. Absolute Calibration of the instrument was provided by the World Radiation Center (PMOD-WRC) guaranteeing very low uncertainty. Integrated spectral irradiance measurements have been used for solar energy validation and health and agricultural related applications.



  •      Spectral solar global (GHI) and direct (DNI) irradiance
  •      Spectral aerosol optical depth
  •      Atmospheric water vapor
  •      Total column O3 and NO2
  •      Tropospheric column NO2
  •      Solar radiation related quantities for solar energy, biological and agricultural applications

Tropomi validation activities: