1. Introduction
Lightning is a spectacular and direct response to strong thundercloud electric fields, which in turn are generated by intense atmospheric moist convection and (normally) the onset of active precipitation processes involving ice particles [Saunders , 2008]. Since lightning is inherently coupled to storm microphysics and dynamics, it can be used as a valuable tool to help remotely probe the developmental state, severity, and evolution of thunderstorms and thunderstorm complexes [e.g., Yoshida et al. , 2017; Darden et al. , 2009 and references therein]. Because a lightning discharge produces lightning nitrogen oxides (LNOx), which in turn affect greenhouse gas concentrations (such as ozone), lightning also serves as a key indicator for monitoring long-term climate change [Williams , 2020], and plays an important role in affecting air quality forecasts [Koshak et al. , 2014a,b; Koshak et al. , 2015]. Overall, lightning provides useful information about a variety of atmospheric processes and offers vital scientific insight across a broad range of disciplines, such as weather, climate, atmospheric chemistry, and lightning physics. In addition, lightning itself is a direct threat to public safety, and also frequently impacts equipment and infrastructure on the ground.
The Lightning Imaging Sensor (LIS) on the International Space Station (ISS) plays a special role in improving our understanding of these complex interrelationships by providing global measurements of total lightning at high spatial and temporal resolution. This optically based lightning detection instrument was launched to the ISS in February of 2017, and has successfully operated with limited downtime since then. The ISS, which is in a low-Earth orbit (LEO) inclined near 55°, has been increasingly used as a host for a number of Earth-observing instruments due to its accessibility; ample space, power, and data bandwidth; and ability to precess through the diurnal cycle.
This paper will describe the ISS LIS instrument and its data products, document key performance metrics and science results from its first three years on orbit, discuss applications enabled by near-realtime ISS LIS data, and point toward new opportunities for cross-platform science that are enabled by using ISS LIS in conjunction with other Earth-observing instruments.