GAIA is the new astrometric mission of the European Space Agency (http://www.esa.int/esaSC/120377_index_0_m.html). GAIA ‘Concept and Technology Study’ was approved in 1996, the mission was technically re-assessed at the end of 2001 and is scheduled to be launched in 2011. The objective of GAIA is to study the galaxy and its formation, the physics behind the stars and its evolution, the galactic dynamics, as well as to generate a detailed astrophysical objects census, ending up in the largest and most complete three-dimensional map of our Galaxy. In order to accomplish those objectives, GAIA will observe more than one billion stars and other objects with unprecedented accuracy, providing a sample of more than 1% of the stellar content of our Galaxy. Such a mission implies generation of data at very high rates (hundreds of stars per second) that is to be sent to the ground stations on Earth. The GAIA payload, with about 100 CCDs will typically generate more than 400000 Mb of data per day, while the download capability is limited to about 200000 Mb per day. One of the challenges of the GAIA mission is therefore the data compression, with very strict requirements. In order to solve this issue the GOCA (GAIA Optimum Compression Algorithm) project was entrusted by ESA to GTD (project prime) and IEEC (scientific partner), aimed in providing a deep understanding of the GAIA compression problem and offering a complete data compression system, both at an algorithm and implementation level. The main objectives of GOCA not only encompassed the review and evaluation of the already proposed compression scheme but the design of new algorithms for the mission. Project requirement are very demanding as it is required a balance between high compression ratios for all data (star) packages and very los CPU consumption ratios (lower thab 5% aprox). GOCA was divided into two main development stages: prototyping and industrialisation. The GOCA prototyping stage started in March of 2007, and on summer a prototype version of a GAIA tailored compression system was ready. The prototype GOCA Software included the development of a compressor, a calibrator, a decompressor, and several tools for data analysis and platform adaptation. The industrialisation processes that started just after the prototyping stage produced an optimised version of the compressor, ready to be integrated and boarded into the final GAIA platform. The industrial GOCA Software achieved lossless compression, high compression rates and low CPU consumption simultaneously. On December 2007 GTD presented a fully validated GAIA compression system, being reviewed and accepted by ESA. Final presentation at ESA/ESTEC in Noordwijk was performed the 15th of January 2008, exactly nine months after GOCA kick-off. The methodologies followed and the lessons learned during the execution of the GOCA project not only justify the software produced to be ready and prepared to be boarded, but opens the door for GTD to continue working within GAIA or similar missions. The GTD experience and methodology applied from the Spatial and Aeronautic domain combined with leasons learnd along the GOCA project execution may justify not only the quality of the software produced to be on-board in the GAIA Mision but also the oportinunity to work forwards within GAIA or in another related satellite scientific missions. (i.e LISA Pathfinder,…)
