The Humidity Sounder for Brazil (HSB) was a 4-channel microwave sounder provided by Brazil to obtain humidity profiles throughout the atmosphere. HSB allowed humidity measurements even under conditions of heavy cloudiness and haze. HSB was one of four instruments comprising the Atmospheric Infrared Sounder (AIRS) Project Instrument Suite aboard NASA’s Aqua satellite. 

HSB had four channels: Three channels spanned the strongly opaque water vapor absorption line at 183 GHz and provided data on atmospheric humidity, while the fourth channel at 150 GHz enabled deeper penetration through the atmosphere for moisture data at Earth’s surface. The HSB instrument failed on February 5, 2003.