Question: Helmer Julius Hanssen, was a Norwegian sailor, pilot and polar explorer, he participated in three of the polar expeditions led by Roald Engelbregt Gravning Amundsen, was a Norwegian explorer of polar regions, he was the leader of the Antarctic expedition of 1910–12, which was the first to reach the South Pole, on which date?

Context articles: Helmer Hanssen
Albert P. Crary
Roald Amundsen
Mount Amundsen
Mullins Valley
Amundsen Bay
Richard E. Byrd
Evans Névé
Amundsen Coast
Robert Falcon Scott

Helmer Julius Hanssen (24 September 1870 – 2 August 1956) was a Norwegian sailor, pilot and polar explorer.
 He participated in three of the polar expeditions led by Roald Amundsen and was one of the first five explorers to reach the South Pole.
Albert Paddock Crary (July 25, 1911 – October 29, 1987), was a pioneer polar geophysicist and glaciologist.
 He was the first person to have stepped foot on both the North and South Poles, having made it to the North Pole on May 3, 1952 (with Joseph O. Fletcher and William P. Benedict) and then to the South Pole on February 12, 1961 as the leader of a team of eight.
 The South Pole expedition set out from McMurdo Station on December 10, 1960, using three Snowcats with trailers.
 Crary was the seventh expedition leader to arrive at the South Pole by surface transportation (the six others before him were—in sequence—Amundsen, Scott, Hillary, Fuchs, a Russian expedition in 1959/60 from Vostok base, and Antero Havola).
 He was widely admired for his intellect, wit, skills and as a great administrator for polar research expeditions.
Roald Engelbregt Gravning Amundsen (] ; 16 July 1872 – c. 18 June 1928) was a Norwegian explorer of polar regions.
 As the leader of the Antarctic expedition of 1910–12, which was the first to reach the South Pole, on 14 December 1911, he was a key expedition leader during the Heroic Age of Antarctic Exploration.
 In 1926, he was the first expedition leader for the air expedition to the North Pole, making him the first person, without dispute, to reach both poles.
 He is also known as having the first expedition to traverse the Northwest Passage (1903–06) in the Arctic.
Mount Amundsen is a nunatak lying east of Denman Glacier, about 11 nautical miles (20 km) northeast of Mount Sandow.
 It was discovered by the Western Base Party of the Australasian Antarctic Expedition (1911–14) under Mawson, and named by Mawson for Roald Amundsen, the Norwegian polar explorer, who was the first to attain the South Pole.
Mullins Valley ( ) is a four mile long valley located at 5,400 ft elevation in the McMurdo Dry Valleys.
 It is one of the few dry valleys in the world to contain rock glaciers.
 US Antarctic Program (USAP) research has dated the subsurface ice in Mullins Valley at 4 million years old making it among the oldest ice on earth.
 United States Antarctic Program (USAP) research has also shown the rock glaciers in the valley to be analogous to the Arsia Mons region on Mars.
 Named for Jerry L. Mullins, Physical Scientist, Director, Polar Programs, Antarctic and Arctic Program for United States Geological Survey (USGS), National Science Foundation Antarctic geophysical research, and U.S Scientific Committee (SCAR) delegate to SCAR SCAGI committee.
 Appointed by the National Academy of Sciences, Polar Research Board.
 His was responsible for Antarctic field research in the Transantarctic Mountains, McMurdo Dry Valleys, Shackleton Mountains, Beardmore Mountains, Antarctic Peninsula, Mount Siple, Amundsen-Scott South Pole station and at deep field research locations in West Antarctica.
 His program conducted research in the disciplines of global positioning systems, geodesy, crustal motion, glacial geophysics, airborne geospatial systems, airborne geophysics, seismology, light radar (lidar), topographic mapping and he managed the USGS South Pole winter-over program from 1989 to 1994.
 He was appointed by the National Academy of Sciences, Polar Research Board as a US delegate to the Scientific Committee on Antarctic Research Geosciences Standing Scientific Group from 1995–July 2012 and was appointed as a member of the Advisory Committee on Antarctic Names in 1994.
 Mullins Valley appears in the Antarctic research literature, on the maps from the British expedition of Captain Scott and in aerial photographs from the United States expedition Operation Highjump by Admiral Byrd.
 Mullins Valley, Mullins Lake, Mullins Glacier, and Mullins Geodetic Station, Antarctica are named for United States polar explorer and researcher Jerry L. Mullins.
Amundsen Bay, also known as Ice Bay, is a long embayment 24 mi wide, close west of the Tula Mountains in Enderby Land, Antarctica.
 The bay was seen as a large pack-filled recession in the coastline by Sir Douglas Mawson on January 14, 1930.
 Seen by Captain Hjalmar Riiser-Larsen in charge of a Norwegian expedition during an airplane flight on January 15 and subsequently mapped nearer its true position by the Norwegians.
 The bay was mapped in detail by an Australian National Antarctic Research Expeditions party landed by aircraft in 1956 and another landed by launch from "Thala Dan" in February 1958.
 It was named by Mawson after Roald Amundsen, the Norwegian explorer who was first to reach the South Pole.
Rear Admiral Richard Evelyn Byrd Jr., USN (October 25, 1888 – March 11, 1957) was an American naval officer who specialized in feats of exploration.
 He was a recipient of the Medal of Honor, the highest honor for valor given by the United States, and was a pioneering American aviator, polar explorer, and organizer of polar logistics.
 Aircraft flights in which he served as a navigator and expedition leader crossed the Atlantic Ocean, a segment of the Arctic Ocean, and a segment of the Antarctic Plateau.
 Byrd claimed that his expeditions had been the first to reach both the North Pole and the South Pole by air.
 However, his claim to have reached the North Pole is disputed.
Evans Névé ( ) is a large névé which nourishes Tucker Glacier, Mariner Glacier, Aviator Glacier, Rennick Glacier and Lillie Glacier in Victoria Land, Antarctica.
 The névé was named in honor for Edgar Evans of the ill-fated British Antarctic Expedition, 1910–13, by the Northern Party of the New Zealand Geological Survey Antarctic Expedition, 1963–64.
 Evans, along with Edward Adrian Wilson, Lawrence Oates and Henry Robertson Bowers, accompanied Captain Robert F. Scott to the Geographic South Pole, January 17, 1912.
 All five perished on the return journey after failing to beat Norwegian explorer Roald Amundsen to the 90th parallel.
 This glaciological feature lies situated on the Pennell Coast, a portion of Antarctica lying between Cape Williams and Cape Adare.
Amundsen Coast is that portion of the coast to the south of the Ross Ice Shelf lying between Morris Peak, on the east side of Liv Glacier, and the west side of the Scott Glacier.
 Named by New Zealand Antarctic Place-Names Committee in 1961 for Captain Roald Amundsen, the Norwegian explorer who led his own expedition in 1910–12 to the Antarctic.
 Setting up a base at Framheim at the edge of the Ross Ice Shelf, he sledged southward across the shelf and discovered a route up the Axel Heiberg Glacier along this coast to reach the polar plateau.
 He was the first to reach the South Pole, December 14, 1911.
Captain Robert Falcon Scott, (6 June 1868 – 29 March 1912) was a British Royal Navy officer and explorer who led two expeditions to the Antarctic regions: the Discovery Expedition (1901–1904) and the ill-fated Terra Nova Expedition (1910–1913).
 On the first expedition, he set a new southern record by marching to latitude 82°S and discovered the Polar (Antarctic) Plateau, on which the South Pole is located.
 On the second venture, Scott led a party of five which reached the South Pole on 17 January 1912, four weeks after Roald Amundsen's Norwegian expedition.
 On their return journey, Scott's party discovered plant fossils, proving Antarctica was once forested and joined to other continents.
 A planned meeting with supporting dog teams from the base camp failed, despite Scott's written instructions, and at a distance of 150 miles from their base camp and 11 miles from the next depot, Scott and his companions perished.