## 2 Requirements Specifications and Measurements Gaps
This means that for instruments in polar LEO orbits (typically Sun-Synchronous Orbits, SSO) with off-side acquisition capacity, the coverage of the polar regions is limited by the swath of the instrument and by the number of satellites considered. The latency of the data is also an issue for near real-time products. Moreover, a very small subset of EU or cooperating missions can provide sea ice thickness, sea ice type, sea ice concentration, sea ice cover, sea ice drift and extent at the resolutions required by end-users. Therefore, sea ice monitoring with a short revisit time, short latency time and high spatial resolution are the main requirements, the mission shall support sea ice products (e.g., sea ice type, cover, extent, drift, thickness and iceberg tracking) with a revisit time \(<\)3 h and latency time \(<\) 1 h [4]. The use case \"fishing pressure and fish stock assessment\" promises also new prospects for the system in the maritime domain and would benefit from a reduction in access and revisit times for the provision of appropriate oceanic conditions (e.g., sea surface temperature, ocean chlorophyll concentration) and fishing pressure (e.g., vessel tracking). Ocean chlorophyll concentrations are related to the presence of planktonic life, which is the base of the marine food chain. In this regard, this parameter brings information on the health and productivity of marine ecosystems. Therefore, these data are valuable and help to develop strategies for sustainable and productive commercial fishery. Another important measurement to cover is Sea Surface Temperature (SST) in this time frame. The SST over polar regions in a global context is essential for climate modeling, weather forecast, as well as for the fishing and maritime industry. Missions with optical instruments (in the visible and infrared domains) provide information on the sea surface composition (e.g., ocean chlorophyll concentration, color dissolved organic matter) and sea surface temperature. One of the main difficulties of these types of techniques is that they are directly impacted by cloud coverage and depend on solar illumination conditions. The current Copernicus infrastructure provides about 24-48 h of latency for those measurements. From the side of contributing missions in geostationary orbits, these provide data every 30 min (shorter revisit time), but with a coarse resolution of 5 km. Geostationary satellites are essential in equatorial and mid-latitude areas, but for high latitudes, image distortion and atmospheric effects are too large for effective use. In the context of the fishing pressure and fish stock assessment, data on fish farming cages (density) and vessel's identity and location (position, speed and direction) are potentially valuable for emergency and management services. For instance, the provision of these observations will help to improve ship routing services, offshore operations and search and rescue operations, thus contributing to marine safety. This type of data can be provided by using an Automatic Identification System (AIS). The ESA has promoted the use of AIS systems on Satellites (SAT-AIS) [5] through of Advanced Research in Telecommunications Systems (ARTES) program. In the horizon 2020-2030, only the NORSAT-2 and Triton-2 missions carrying AIS have been planned [6]. The \"agriculture and forestry (hydric stress)\" use case is based on methods enabling precision agriculture, efficient irrigation, fire prevention, forest protection and impacts on hydrological basins, supporting agronomic research and production, assessment of population food security and sovereignty and environmental impact evaluation. Soil moisture is a key parameter for the hydrological cycle, meteorology, climatology and agriculture production. The role of soil moisture for meteorology lies in the global transfer of water and energy between the Earth's surface and the atmosphere. In the agricultural context, the amount of soil moisture is an important element affecting production and plant growth.