What did Drake intend to do when he set sail on the Golden Hind in December 1577?

Drake in 1577 was sent by Elizabeth I on an expedition to the Pacific coast of America on the 100-ton four-mast flagship "Pelican", which during the expedition was renamed "Golden Hinde". The official purpose of the trip was the discovery of new lands. But additionally, Drake had to get as much Spanish gold as possible for England.