A massive release of passive-surveillance satellite data of nighttime lights could help researchers in fields ranging from agriculture to epidemiology. Researchers at Penn State and the University of Southampton in the UK have provided open access to detailed satellite data on brightness for five cities in Niger and Nigeria from 2000 to 2005, as well as detailed methods for analyzing the data to track seasonal population movements. A paper describing the data and methods, which can be applied to other populations and other similar data sets, is available in the online, open-access journal Scientific Data.