There was a one-time opportunity to obtain nearly coincident coverage from both Landsat 5 and Landsat 7 as Landsat 7 drifted to its final orbital position during the initialization and verification phase following launch. During the underfly period, Landsat 7 Enhanced Thematic Mapper Plus (ETM+) data were collected using the U.S Landsat 7 ground station network and the solid-state recorder, while agreements were established with Space Imaging/EOSAT and various international ground stations to collect corresponding Landsat 5 Thematic Mapper (TM) data. Approximately 750 coincident scenes were collected during the underfly from 1-3 June 1999. Underfly data are intended to play a major role in developing cross-calibrations to bridge the results derived from historical Landsat 5 TM data with research performed with current Landsat 7 ETM+ data. The purpose of this paper is to provide an overview of the underfly experiment, and to provide some early comparative results between Landsat 5 and 7 data sets. Initial results indicate that products produced using TM and ETM+ data are very similar.
