## 1 Introduction  
Vegetation fire, as an important component of biogeochemical cycles, combusts fuels on the land and releases water vapor, trace gases, and aerosol emissions into the atmosphere [1]. Global biomass burning contributes a substantial amount of emissions that significantly affect the atmospheric carbon budget, weather conditions, air quality, and climate [2, 3]. For example, global fires annually burn an area of \(\sim\)350-422 Mha [4, 5] and release -2.2 Pg carbon [6], among which 67% (burned area) and 52% (carbon) are, respectively, contributed by biomass burning in Africa alone [4, 6]. Fire emissions are likely underestimated from satellite observations due to a substantial number of undetected small fires [6, 7, 8]. One of the most important fire parameters observed from satellites is fire radiative power (FRP)--the instantaneous fire radiative energy [9]. FRP has been increasingly used to understand fire characteristics [10, 11, 12], analyze impacts of fire weather conditions on fire activity [13], and predict smoke injection height [14, 15]. More importantly, FRP is a proxy of the rates of biomass combustion and emissions [9; 16; 17], which has been confirmed in lab-based combustion experiments [18], prescribed fires [19], and landscape wildfires [20; 21; 22; 23]. Thus, satellite-based FRP provides an effective way to quantify biomass-burning emissions. Among all satellite-based FRP products, the most commonly used and scientifically reliable one is from the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the NASA Earth Observing System (EOS) Aqua and Terra satellites. The MODIS active fire products have provided FRP data since 2000, which has been widely applied to estimate regional-to-global trace gases and aerosol emissions [24; 25; 26; 27; 28; 29]. However, global applications of MODIS FRP are affected by the MODIS sampling limitations and the equatorial swath gaps. First, the MODIS sensor is able to detect a fire pixel of above 10 MW confidently at nadir but its fire detection capability decreases quickly at off-nadir angles due to degrading pixel resolution [30; 31; 32]. Thus, MODIS could miss observations of fires (at off-nadir angles) that are detectable at nadir, which results in the underestimation of MODIS FRP and emissions estimates. To mitigate FRP underestimation caused by the sampling limitation-, a quadratic model has been proposed separately for Aqua MODIS and Terra MODIS [30], and a mapping method has been developed based on cumulative distribution function (CDF) [33]. Both methods assume that MODIS FRP or FRP CDF in all scan angles should be the same as that at nadir if MODIS pixel size is the same across all angles. This assumption would be valid only if fires burn consistently in the same locations with constant FRP values during a long period when the sensor senses the fires in all angles with the same observation frequency. It could be the case for gas flares but not landscape wildfires because wildfires evolve fast with environmental conditions and its intensity is very dynamic [34]. [PERSON] et al. [35] mitigate the underestimation of emissions at MODIS large view angles in the Northern Hemisphere of Africa, by using emissions estimated with the smallest view angle within \(\pm\)2 days, assuming persistent burning patterns during the same period. This may not work well because burning sites could vary largely due to human activity [36]. Second, due to MODIS swath gaps between adjacent orbits at low latitudes, MODIS needs two days to provide a full coverage of the equatorial regions between \(\sim\)30\({}^{\circ}\)S and \(\sim\)30\({}^{\circ}\)N [37]. As a result, MODIS misses observations of fires daily inside its swath gaps, which has been known in fire detection [38; 39] and emissions estimation [40]. Due to the lack of comparable reference data, the effects of swath-gap-caused missing fire observations on FRP and emissions estimates are poorly understood quantitatively.