One CATOBAR carrier: São Paulo is a Clemenceau-class aircraft carrier currently in service with the Brazilian Navy. São Paulo was first commissioned in 1963 by the French Navy as Foch and was transferred in 2000 to Brazil, where she became the new flagship of the Brazilian Navy. During the period from 2005–2010, São Paulo underwent extensive modernization. At the end of 2010, sea trials began, and as of 2011[update] São Paulo had been evaluated by the CIASA (Inspection Commission and Training Advisory). She was expected to rejoin the fleet in late 2013, but suffered another major fire in 2012.
Try to answer this question if possible (otherwise reply "unanswerable"): What did Sao Paulo undergo during the period from 2005-2010?
extensive modernization