**1. Introduction**

The Barcelona Expert Centre (BEC) is a joint initiative between the Spanish Research Council (CSIC) and the Universitat Politècnica de Catalunya (UPC) that was created in 2007. Since its foundation until January 2016, the head of the BEC was professor Jordi Font. The original purpose of the BEC was to provide support to the Spanish activities on the Soil Moisture and Ocean Salinity (SMOS) European mission, professor Font being the co-principal investigator of SMOS and being in charge of the sea salinity part of the mission. SMOS is a European Space Agency (ESA) mission and was the first 2D synthetic aperture interferometric radiometer operating in the microwave L-band ever put in orbit. SMOS was put in orbit on 2 November 2009 and was designed to fulfill two specific goals: to measure sea-surface salinity (SSS) with 1*<sup>o</sup>* spatial resolution and monthly temporal resolution and an accuracy of 0.1 PSU over the sea [1], and to measure soil moisture (SM) with 25 km spatial resolution and daily temporal resolution within a maximum uncertainty of 4% [2]. Initially, BEC missions were to provide assessments to the ESA as a level 2 ocean salinity expert support laboratory, to contribute to SMOS radiometric calibration and validation activities, and to develop and validate new algorithms for the generation of added-value products at levels 3 and 4.

Since 2016, Antonio Turiel has been the head of BEC that nowadays consists of four departments, whose areas are SMOS (salinity and land), ocean winds, cryosphere, and ocean currents. The activities developed at BEC has been diversified, as hav its main objectives, which currently are:


BEC is now a large team of highly motivated and remote sensing specialist people carrying out the scientific and operational activities in all processing levels of different missions. At the moment we are around 20 people; among us are permanent staff, post-doctoral contracts, visiting scientists, and Ph.D. students working on a wide variety of topics:


This book aims to be a tribute to the work done over the last 10 years at the BEC and to the entire team that has made the BEC one of the main remote sensing centers in Spain.
