This is the third and final Earth flyby for Rosetta. It will provide exactly the boost Rosetta needs to continue into the outer solar system. The spacecraft is scheduled for a close encounter with asteroid 21 Lutetia in July 2010, before it goes into hibernation early in 2011, only to wake up in early 2014 for approach to 67P/Churyumov-Gerasimenko.
NASA has contributed an ultraviolet instrument (Alice); a plasma instrument (the Ion and Electron Sensor), and a microwave instrument (Microwave Instrument for the Rosetta Orbiter), among other contributions to this international mission. JPL manages NASA's participation in the Rosetta mission.
Learn more about NASA's contribution to Rosetta at: http://rosetta.jpl.nasa.gov