Short answer twice. Long answer: He went once as part of Scott's team, but was sent home after getting sick on an expedition. He later went back himself as the leader of an expedition to be the first to walk from one side of the Antarctic to the other, but didnt achieve it.
Earnest Shackleton participated in several expeditions, notably one
in the early 1900s when he led a team to the 'farthest south' -- a
goal that motivated other explorers who followed him, to be the
first to set foot at the South Pole.
As well, Shackleton is known for his preservation of human life…