Engineers and scientists from both Landsat and Sentinel missions are working together to calibrate observation data and validate its quality to improve the science using these resources.
 

On board Landsat 8 are two sensors that capture data about earth's surface. Here is an explanation of the instruments that capture every pixel.
 

Once the ground stations receive data from Landsat, there's still a lot of processing to make every pixel usable. Here's an overview of some of that work.