at the ICOS Ecosystem Stations. The following variables are included: - Incoming short-wave radiation (SW_IN) - Outgoing short-wave radiation (SW_OUT) - Diffuse short-wave radiation (SW_DIF) - Incoming long-wave radiation (LW_IN) - Outgoing long-wave radiation (LW_OUT) - Incoming photosynthetic photon flux density (PPFD_IN) - Outgoing photosynthetic photon flux density (PPFD_OUT) - Diffuse photosynthetic photon flux density (PPFD_DIF) - Below canopy photosynthetic photon flux density (PPFD_BC_IN) All the following requirements and specifications apply to Class 1 and Class 2 ICOS Ecosystem Stations, unless otherwise mentioned. This document is structured in four different sections with the aim to facilitate the use and application: - Measurements: sensors, setup and methods to correctly collect the data and respective info are described. It includes instructions on the sampling design. - Maintenance: all the maintenance and calibration guidelines are described, including the general timeline for sensors calibration and maintenance. - Submission: it is the section related to the data preparation and submission to the ETC. It includes the list of all the parameters, the correct formatting and the way to submit them to the database. It is linked to the BADM system needed to submit the metadata and non-continuous measurements - Processing: this section is for internal use of the ETC and describes the processing applied to the single variable/info/sample submitted. It is important to remind that the exact application of the protocol at site level is also discussed with ETC in order to find agreed solutions for specific cases. If a specific part is relevant only for a specific ecosystem or site Class this is also reported in the document.