Who is Sir Ernest Shackleton, leader from Endurance: Shackleton's Incredible Voyage and what is their importance?

Ernest Shackleton is an Irish explorer knighted for the successful command of the 1907-09 British Antarctic Expedition. Subsequent to that expedition he becomes interested in traversing the Antarctic continent by dog sledge, a feat not actually accomplished until 1958. By the time period considered in the text, Shackleton is an experienced polar explorer, having travelled to the Antarctic in 1901-1902 under Robert Scott and having led a 1907-1909 expedition. As Shackleton envisioned, the expedition sets out from England in August, 1914, and reaches the Weddell Sea in January, 1915. Whalers at South Georgia Island warn Shackleton that ice conditions are worse than normal—their prescient advice is disregarded, however, and Endurance is trapped in ice and lost by late October, 1915. Under Shackleton's undaunted leadership, the men survive several months on the drifting pack ice before reaching Elephant Island.