The MODIS Aqua MYD09A1 Version 6.1 product provides atmospherically corrected Surface Reflectance for MODIS Bands 1â7 at 500 m spatial resolution. The data are corrected for atmospheric effects including gases, aerosols, and Rayleigh scattering. The product is generated as an 8-day composite, where for each pixel the best 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 a quality assurance layer and four observation bands to support data reliability and interpretation.