## 1 Introduction  
The agricultural sector is of fundamental importance, and it is one of sectors that is the most vulnerable to climate change [1]. At the same time, intensive and unsustainable agricultural practices deplete and degrade natural resources and key ecosystem services. In fact, in European countries, extreme events are responsible for reducing crop yields by 9% and 3.1% [2]. The European Union (EU) is significantly promoting sustainable agricultural practices [3]. One of the most important instruments provided by the EU is the Common Agricultural Policy (CAP), which aims to improve environmental protection and climate sustainable practices. The management of the EU's CAP involves Member States through national paying agencies, which are responsible for monitoring the use of funding by the farming community [4]. The availability of information on agriculture and crops is crucial for successful agronomic planning and sustainable agriculture management [5]. However, official statistics on crop areas are often provided at the end of the season or later and are therefore not useful for supporting in-season crop management [6]. CAP regulations encourage the development of regular and systematic monitoring services [7]. Earth Observation (EO) has been used for agricultural monitoring since the early 1970s. The Copernicus Sentinel constellation allows the integration of SAR and optical sensors for agricultural applications, overcoming their specific limitations (i.e., dependence on the sun and clouds for optical and signal noise and stability for SAR) [8]. Optical sensors are sensitive to canopy response and photosynthetic characteristics, while SAR sensors are more sensitive to plant biomass, soil moisture, and surface texture [6]. Based on the above, [PERSON] et al. (2021) asked institutional users to indicate the most important environmental and climate-related requirements in terms of current agro-environmental legislation and assessed the potential of current European EO technology to meet their monitoring needs. The results of this work show that users request the development of consolidated agricultural EO products, the provisioning of seasonal and annual information on crop production, and in-season indicators of crop development and status. Furthermore, they express the need to monitor the degree of diversification of agri-environmental measures in the agricultural sector in order to support green direct payments [7]. Thus, an effective multi-temporal cropland mapping is fundamental for the correct management of natural resources and for the prevention of risks due to climatic conditions such as drought. In fact, 14% and 12% of users indicated an interest in agricultural and water resources domains, respectively, and in the development of new EO products in these domains [7]. Optical sensors have demonstrated their ability to distinguish different crops [9; 10], and in recent years, Synthetic Aperture Radar (SAR) sensors have also been used for crop mapping and monitoring [11; 12; 13]. Several authors have investigated the capabilities of SAR data in crop mapping. Successful results have been obtained with the C band, which is particularly valuable for rice phenology analysis [14]. Additionally, techniques based on X-band sensors showed encouraging results, especially dual-pol imagery [15]. Other types of crops mapped using SAR data include winter wheat, irrigated grassland, and summer cereals [11; 16; 17]. However, in addition to backscatter values, optical data can provide relevant and complementary information at the field and crop level [12; 18]. Several authors investigated the synergic use of SAR and optical data, demonstrating that radar is very sensitive to soil moisture, especially in VV polarization, while optical data are very useful for determining vegetation characteristics [8; 19; 20].