I know ;p It's because of numerous data layers. There are 13 different sensors on the satellites recording wave-frequencies in different parts of the electromagnetic spectrum. These are then released in one large file from the same location at the same time. So that you can process different files together and produce images that help you see what is interesting to you. The program produces well over 5 Terabytes of image data daily. which will increase a lot more in years to come.