New observations of sprites from the space shuttle

We present the results of space-based observations of sprites obtained during the Mediterranean Israeli Dust Experiment (MEIDEX) sprite campaign conducted on board the space shuttle Columbia during its STS-107 mission in January 2003. A total of ∼6 hours of useful data were saved from 21 different orbits, of which 1/5 contained lightning. We imaged sprites from an altitude of 280 km using a calibrated multispectral camera above thunderstorms in various geographical locations, mainly in central Africa, northern Australia, and South America, and also over the Pacific and Indian Oceans. In this paper we report on sprites observed from ranges 1600-2000 km from the shuttle, at altitudes of 40-90 km above the ground. Their brightness was in the range of 0.3-1.7 mega-Rayleighs (MR) in the 665 nm filter and 1.44-1.7 MR in the 860 nm filter. On the basis of the frequency of observed events and the number of tropical thunderstorms, we estimate the sprite rate in the tropics to be of the order of several per minute.