How do I know if a hotspot/fire detection was missed due to cloud or missing data?
An indication of cloud cover or missing data is not yet included in FIRMS. If you want to know whether the MODIS Rapid Response system may have failed to report some hotspots/fires due to cloud or missing data, you can look on the MODIS Rapid Response Real-Time website. There you can view the MODIS near-real-time level 2 browse images which clearly show satellite coverage and cloud at the time of overpass. To take cloud and missing data in to account, it may be more appropriate to use one of the 1-km Level 3 or CMG fire products.