These are just off the top of my head and would very much be interested to hear what other peoples opinions/suggestions are.
Locate and investigate the nearest habitable planet.
Continue exploration and documentation of the universe.
Carry out scientific research in all fields.
Aid scientific research being carried out from Earth
Locate and exploit mineral rich bodies.
Establish a permanent base on the habitable planet.
Document the planet.
Maintain a permanent communication system with Earth.