Unlike many natural hazards, volcanoes usually give warnings of impending eruptions that can be detected from hours to years prior to any hazardous activity [Sparks et al., 2012]. The Eyjafjallajökull eruption, for example, was preceded by several discrete episodes of subsurface magma accumulation that highlighted the potential for future eruption. Once it begins, an eruption can last for up to decades, during which time the changing conditions of associated hazards—like ash plumes and lava flows—must be continuously assessed. Unfortunately, the resources and infrastructure needed to conduct ground-based monitoring of a volcano—especially those located in remote areas of Earth that might still have the potential to impact air traffic, like in the north Pacific—are extreme, and less than 10% of the world’s volcanoes are monitored in any systematic way. Space-based methods offer a means of bridging this monitoring gap.