### Observational Data
#### 2.1.1 Remote Sensing Data
In addition, the ICEYE satellite constellation consists of over 25 microsatellites equipped with SAR operating at X-band frequencies, enabling all-weather, day-and-night Earth observation with high spatial resolution (e.g., 25 cm-1 m at dwell imaging modes). These data have been used in applications such as flood monitoring [30] and oil spill detection [31]. GNSS-R In contrast to Synthetic Aperture Radar (SAR), which actively emits signals, Global Navigation Satellite System Reflectometry (GNSS-R) has emerged as a novel passive remote sensing technology utilizing signals from existing GNSS constellations like Global Positioning System [32; 33]. These signals are transmitted by GNSS satellites, reflected from the ocean surface, and then captured by a GNSS-R receiver. By analyzing the reflected signals and the direct signals, GNSS-R enables the retrieval of ocean parameters such as wind speed and wave height, achieving sea surface measurement at a lower cost compared to active radar systems. TechDemoSat-1 (TDS-1) was one of the pioneering satellite missions to demonstrate the feasibility of employing GNSS-R for Earth observation and has been successfully used for monitoring sea ice coverage, estimating sea ice thickness, and determining sea ice concentration [34; 35]. Building on the success of TDS-1, the Cyclone Global Navigation Satellite System (CYGNSS) was launched in 2016 by the National Aeronautics and Space Administration (NASA). CYGNSS, originally designed for sea surface wind and tropical cyclone monitoring, has been expanded to broader ocean studies such as wave height estimation and oil spill detection, showcasing the versatility of GNSS-R technology [36; 37]. Passive microwave remote sensing detects naturally emitted microwave radiation from the Earth's surface. Compared to optical sensors, passive microwave radiometers are much less affected by cloud cover and atmospheric aerosols, making them particularly valuable for continuous monitoring of ocean surface conditions under all weather and illumination conditions. Sensors such as the Advanced Microwave Scanning Radiometer 2 (AMSR-2), onboard the Global Change Observation Mission--Water satellite, operate across a broad range of frequency channels (e.g., 6.9 to 89 GHz) and enable the retrieval of key oceanographic parameters, including sea surface temperature, sea ice concentration, and surface wind speed [38; 39]. These observations play a critical role in climate monitoring, numerical weather prediction, and operational oceanography. LiDAR  
Light Detection and Ranging (LiDAR) is an active remote sensing technology that uses laser pulses to measure ocean targets with exceptional precision. By emitting laser light and analyzing the return signals, LiDAR generates detailed information about the ocean surface [40]. A notable example is the ICESat-2 satellite, which utilizes the Advanced Topographic Laser Altimeter System (ATLAS) to measure ice sheet elevations, track changes in sea ice, and monitor surface water levels with remarkable accuracy [41]. X-band marine radars operate within the frequency range of 8-12 GHz, with a wavelength of around 3 cm, delivering high spatial resolution in applications like wave monitoring and current measurements [42]. Commonly installed on ships or coastal stations, these radar systems provide real-time assessments of ocean dynamics, making them valuable for ocean observation and maritime operations [43]. Moving to even longer wavelengths, high-frequency (HF) radar systems operate at wavelengths of 10-100 m and are widely used for nearshore currents and wave measurements [44]. For instance, the National Oceanic and Atmospheric Administration (NOAA) Integrated Ocean Observing System HF Radar network offers real-time monitoring of coastal currents along the U.S. coastline, providing critical information for coastal management. Although HF radar excels in large-scale, continuous observations, its main drawback is lower spatial resolution compared to optical and X-band marine radar systems.