The MODIS Terra MOD09A1 Version 6.1 product provides atmospherically corrected Surface Reflectance for MODIS Bands 1â7 at 500 m spatial resolution. The reflectance values are corrected for atmospheric effects including gases, aerosols, and Rayleigh scattering. The dataset is produced as an 8-day composite, where for each pixel the most suitable observation is selected from all acquisitions within the compositing period based on criteria such as cloud conditions and solar zenith angle. When multiple observations meet these criteria, the pixel with the lowest value in Band 3 (blue) is selected. The product also includes two quality assurance layers and four observation bands to support data quality assessment and interpretation.