I have done some studies related to spectral reflectance signatures of the identified end members of Level 2, sentinel 2 and sentinel 3 satellite images. the study area was the open ocean so basically the water. i used the (753 nm to 1020 nm) wavelength for sentinel 3 and (783 nm to 2190 nm) for sentinel 2. the linear spectral unmixing generated the minus values and over 1 values. i selected the region form 0 to 1 and analyzed for my study to generate the spectral reflectance signatures of the identified endmembers. the sentinel level 2 data i used were already subjected to baseline atmospheric correction. i just want to clear about the uncertainty exists in the level 2 baseline atmospherically corrected sentinel data to certify the accuracy of my results. if i take a material spectral reflectance in the lab and using the sentinel level 2 baseline atmospherically corrected data within the same IR wave length regions what is the possible uncertainty factor??is there a document i can refer to take an initial understanding about this without taking any other measurements?