If you have read my introduction then you know that I am a scientist who is working on some aspects of the data processing of the ESA Gaia satellite mission. Gaia will scan the entire sky 24/7 for more than 5 years down to magnitude 20. Magnitude 20 means that these objects are 5,000 times fainter as the stars you can observe with your naked eye – on a very dark sky. More than one billion objects are expected to be detected and will be observed 40-250 times. This will yield a huge amount of data that cannot be processed on-board. It is even worse, this amount of raw data collected cannot even be downlinked to Earth in its entity. Useful data has to be extracted on-board and needs to be compressed before the downlink to Earth can happen.
Therefore, the main data processing has to happen on Earth. This will be under responsibility of the Gaia DPAC (Data Processing and Analysis Consortium). Learn more about how this consortium is organized and its tasks by the following article of the DPAC chair Anthony Brown that is part of the official ESA launch blog for the Gaia mission: http://blogs.esa.int/gaia/2013/09/23/gaia-data-processing/
By the way, I am a member of CU5 and CU9 of the DPAC. More about this in one of the following blog entries.