# Development of the User Requirements for the Canadian WildFireSat Satellite Mission
## 1 Introduction
In recent years, wildfire smoke has been the dominant cause of poor air quality for large portions of Canada [24]. The impacts of smoke on communities can necessitate an evacuation, even without a direct threat from wildfire [25; 26; 27]. This led to the development of methods to derive emissions from satellite-detected wildfires, and to use the emission estimates in smoke dispersion [28; 29] and air quality [30] forecast systems. These automated systems require the provision of timely and reliable wildfire activity data, with an emphasis on wildfire events that produce large long-range transportation of smoke, or wildfire events near communities. With additional development, these systems can evolve to incorporate Fire Radiative Power (FRP; MW) measurements as an additional source for the estimation of wildfire emissions (e.g., [31; 32]), as is becoming increasingly common throughout the world (e.g., Global Fire Assimilation System (GFAS); [33]. Under climate change a substantial increase in the frequency and intensity of wildfires is expected [34; 35]. In particular, northern regions such as Canada are expected to see an increase of wildfire activity related to increases in conditions conducive to extreme wildfire weather [19; 36; 37; 38; 39; 40; 41]. Consequently, frequency of extreme burning days where wildfires are able to escape is also projected to increase [42; 41]. In 2019 the Canadian Space Agency (CSA) initiated the development of a dedicated wildfire monitoring satellite \"WildFireSat\" mission [43]. WildFireSat (WFS) intends to leverage uncooled microbolometer technology developed by the CSA and Institut National d'Optique (INO). An earlier version of this technology called the New InfraRed Sensor Technology (NIRST) was the first mid-wave infrared (IR) microbolometer used in space-based wildfire remote sensing on the 2011 Aquarius SAC-D mission [44]. Following the NIRST experiment, the same technology was used in a feasibility study (referred to as \"Phase 0\") to demonstrate the technical feasibility of a cost-effective, dedicated Canadian Wildland Fire Monitoring System (CWFMS) [45]. Since then, the detector technology has continued to evolve (e.g., [46]), while new Low Earth Orbit (LEO) wildfire products (e.g., from the Visible Infrared Imaging Radiometer Suite (VIIRS) and Sea and Land Surface Temperature Radiometer (SLSTR); [47; 48]) have filled some temporal coverage gaps (Figure 1), which will improve the feasibility of a targeted wildfire monitoring mission. Phase-A of the WFS mission is driven by the Mission Requirements [49] which extend from the User Requirements. However, the User Requirements defined in CWFMS [50] required substantial revisions to accommodate the new context of this mission. The aim of this study is to trace the process used to update and re-scope the CWFMS User Requirements for WFS through consideration of emerging science and ongoing end-user consultation (e.g., [51]). This study presents the WFS User Requirements and provides cross reference to their heritage in CWFMS where applicable. We trace the two primary phases of this process: (1) Canadian wildfire management needs are assessed through direct engagement of wildfire management end-users, leading to a set of key Fire Management Functionalities (FMFs); (2) User Requirements for the WFS mission are refined through the integration of the wildfire management needs with the best available scientific techniques. The result of this study is the definition of User Requirements for the first dedicated operational wildfire monitoring satellite, forming the foundation for later stages of mission development. Figure 1: Active-fire satellite overpass time in relation to the diurnal wildfire activity cycle. Wildfire activity varies throughout the day in relation to the changing solar elevation and resulting changes in atmospheric moisture, ambient temperatures, and wind speeds.