Radiometric Characterization and Performance Assessment of the Ali Using Bulk Trended Data

The Earth Observing-1 (EO-1) Advanced Land Imager (ALI), developed as part of NASA’s New Millennium Program, utilizes advances in imaging technologies and techniques to provide high-quality image data compatible with that produced from currently available Landsat Thematic Mapper (TM) technology. As opposed to the Landsat 7 Enhanced Thematic Mapper Plus (ETM+) focal plane design that uses 136 detector elements in eight spectral bands, the ALI focal plane contains 15,360 detector elements in ten spectral bands, divided among four sensor chip assemblies (SCA). To develop the ability to process the resulting volumes of data for the ALI (and any future Landsat Data Continuity Mission (LDCM) sensors derived from an ALI-like design), a new processing system has been implemented in a joint collaboration between the U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center and researchers at NASA Goddard Space Flight Center (GSFC) and South Dakota State University (SDSU). One component of this processing system is designed to extract basic information related to detector performance—bias levels, histogram statistics from image data, and response to internal calibration sources operated at known radiance levels—from every typical ALI data collect and store the results into a central database for later study. Analyses under development will provide the ability to thoroughly characterize the ALI’s radiometric behavior at the individual detector level as well as the SCA level over both single-orbit and lifetime intervals. For example, initial results from a lifetime bias level analysis of the trended data indicate that any given detector can possess as many as seven distinct bias “states.”