Aerial reconnaissance
Hot towers were first detected by radar in the 1950s. Aerial reconnaissance was used to probe hot towers, though planes avoided the most dangerous cores of hot towers due to safety concerns. The launch of the Tropical Rainfall Measuring Mission (TRMM) in 1997 provided the resolution and coverage necessary to systematically catalog hot towers and precisely assess their structure globally. Prior to 1997, the small size and short duration of hot towers limited studies of hot towers to aerial observations as the resolutions of satellite sensors at microwave and infrared wavelengths were to coarse to properly resolve details within hot towers.