Satellite Earth Observation represents an important tool for mapping and quantifying wetland inundation dynamics at the basin scale. Given its capacity for wide coverage and repetitive observations, satellite remote sensing is the most feasible way to map wetland inundation dynamics. Passive and active microwave systems, GNSS (Global Navigation Satellite System) altimeters, and optical systems have all been previously used at various temporal and spatial scales [9; 10; 11; 12; 13; 14; 15]. Optical remote sensing systems are inherently limited when mapping inundation within tropical wetland ecosystems as vegetation canopy cover can obscure the signal from the ground surface, making the detection of water inundation difficult or impossible. Additionally, optical imagery is affected by cloud cover, often persistent in tropical regions, particularly during wet season conditions. Microwave remote sensing systems are not affected by cloud cover and are able to image both day and night. Furthermore, microwave pulses from radar systems can penetrate vegetation canopy cover, under certain conditions and sensor types, enabling the detection of standing water beneath the canopy. Passive microwave systems are capable of detecting inundation under vegetation canopies due to a reduction in microwave emissivity where surface water is present, but this is limited to a coarse spatial resolution (\(\sim\)25 km) [13; 14; 15]. Attempts have mainly employed the US Defense Meteorological Satellite Program operated Special Sensor Microwave/Imager (SSM/I) and the Special Sensor Microwave Imager Sounder (SSMIS), producing the SWAMPS and GIEMS products [13; 14] that provide global monthly inundation estimates at a 25 km resolution. Satellite EO approaches, using thermal imaging [16] or signals from global navigation systems such as CYGNSS [17], can map both open water and inundated vegetation at spatial resolutions of about 1.1 km. These data provide high temporal frequency maps of inundation, revealing important intra- and inter-annual trends. Their relatively coarse spatial resolution means that key hydrological features that may be key to routing water through a wetland system, such as anabranching channels and smaller tributaries, might not be captured [18]. As such, we cannot use these data to understand the hydrological processes that govern their dynamics. Efforts were made to downscale the GIEMS dataset to create the GIEMS-D3 product [15], providing average yearly minimum and maximum global inundation extent at a 90 m resolution. Despite the improved spatial scale, this product lacks the monthly granularity of the original GIEMS product, limiting its use for quantifying temporal dynamics in inundation. Active Synthetic Aperture Radar (SAR) systems can provide high-resolution observations (i.e., 3-100 m) of inundation compared to passive systems. Open water acts as a specular-like reflector of an incident radar pulse, providing a distinct (low) backscatter signal [9; 10; 11; 12; 19; 20; 21; 22; 23; 24; 25]. Therefore, SAR imagery has been widely used for the mapping of open water (i.e., without the presence of emergent or floating vegetation), particularly in the context of floodwater mapping [19; 20; 21; 22]  
The potential for SAR systems to detect inundation underneath vegetation canopies is due to a double-bounce interaction between the vertical structure of the vegetation and the surface of the water beneath [9; 10; 12; 24; 25; 26; 27]. In forested wetlands in the Amazon Basin, this mechanism was demonstrated by [PERSON] et al. [28] by comparing L-band backscatter signals from the JERS-1 system with transects of field observations within seasonally flooded (igapo) forests. The circumstances under which this backscatter mechanism occurs depends on a number of factors but is largely a function of the wavelength and polarisation used by the SAR system and the type of vegetation that is inundated.