GALILEO MULTISPECTRAL IMAGING OF EARTH

Nearly 6000 multispectral images of Earth were acquired by the Galileo spacecraft during its two flybys. The Galileo images offer a unique p erspective on our home planet through the spectral capability made pos sible by four narrowband near-infrared filters, intended for observati ons of methane in Jupiter's atmosphere, which are not incorporated in any of the currently operating Earth orbital remote sensing systems. S pectral variations due to mineralogy, vegetative cover, and condensed water are effectively mapped by the visible and near-infrared multispe ctral imagery, showing a wide variety of biological, meteorological, a nd geological phenomena. Global tectonic and volcanic processes are cl early illustrated by these images, providing a useful basis for compar ative planetary geology. Differences between plant species are detecte d through the narrowband IR filters on Galileo, allowing regional meas urements of variation in the ''red edge'' of chlorophyll and the depth of the 1-mu m water band, which is diagnostic of leaf moisture conten t. Although evidence of life is widespread in the Galileo data set, on ly a single image (at similar to 2 km/pixel) shows geometrization plau sibly attributable to our technical civilization Water vapor can be un iquely imaged in the Galileo 0.73-mu m band, permitting spectral discr imination of moist and dry clouds with otherwise similar albedo. Surfa ce snow and ice can be readily distinguished from cloud cover by narro wband imaging within the sensitivity range of Galileo's silicon CCD ca mera. Ice grain size variations can be mapped using the weak H2O absor ption at 1 mu m, a technique which may find important applications in the exploration of the moons of Jupiter. The Galileo images have the p otential to make unique contributions to Earth science in the areas of geological, meteorological and biological remote sensing, due to the inclusion of previously untried narrowband IR filters. The vast scale and near global coverage of the Galileo data set complements the highe r-resolution data from Earth orbiting systems and may provide a valuab le reference point for future studies of global change.