Question: Who was the discoverer of the island country where the islet of Vasafua is located?

full_context: Document 1: Tuvalu: The next European to visit was Arent Schuyler de Peyster, of New York, captain of the armed brigantine or privateer Rebecca, sailing under British colours, which passed through the southern Tuvaluan waters in May 1819; de Peyster sighted Nukufetau and Funafuti, which he named Ellice's Island after an English Politician, Edward Ellice, the Member of Parliament for Coventry and the owner of the Rebecca's cargo. The name Ellice was applied to all nine islands after the work of English hydrographer Alexander George Findlay.
Document 2: Fualopa: Fualopa is an islet of Funafuti, Tuvalu. It is part of the Funafuti Conservation Area, established in 1996 with the aim of preserving the natural fauna and flora of the area. Fualopa hosts a breeding colony of black noddy ("Anous minutus" or white-capped noddy).
Document 3: Tuvalu: In 1568, Spanish navigator Álvaro de Mendaña was the first European to sail through the archipelago, sighting the island of Nui during his expedition in search of Terra Australis. In 1819 the island of Funafuti was named Ellice's Island; the name Ellice was applied to all nine islands after the work of English hydrographer Alexander George Findlay. The islands came under Britain's sphere of influence in the late 19th century, when each of the Ellice Islands was declared a British Protectorate by Captain Gibson of HMS Curacoa between 9 and 16 October 1892. The Ellice Islands were administered as British protectorate by a Resident Commissioner from 1892 to 1916 as part of the British Western Pacific Territories (BWPT), and then as part of the Gilbert and Ellice Islands colony from 1916 to 1974.
Document 4: Marshall Islands: Micronesian colonists gradually settled the Marshall Islands during the 2nd millennium BC, with inter-island navigation made possible using traditional stick charts. Islands in the archipelago were first explored by Europeans in the 1520s, with Spanish explorer Alonso de Salazar sighting an atoll in August 1526. Other expeditions by Spanish and English ships followed. The islands derive their name from British explorer John Marshall, who visited in 1788. The islands were historically known by the inhabitants as "jolet jen Anij" (Gifts from God).
Document 5: Faiava Lasi: Faiava Lasi is an islet of Nukufetau, Tuvalu, which is immediately to the south of Lafaga islet at the North East of Nukufetau atoll.
Document 6: Tuvalu: Funafuti is the largest atoll of the nine low reef islands and atolls that form the Tuvalu volcanic island chain. It comprises numerous islets around a central lagoon that is approximately 25.1 kilometres (15.6 miles) (N–S) by 18.4 kilometres (11.4 miles) (W-E), centred on 179°7'E and 8°30'S. On the atolls, an annular reef rim surrounds the lagoon with several natural reef channels. Surveys were carried out in May 2010 of the reef habitats of Nanumea, Nukulaelae and Funafuti and a total of 317 fish species were recorded during this Tuvalu Marine Life study. The surveys identified 66 species that had not previously been recorded in Tuvalu, which brings the total number of identified species to 607.
Document 7: Vasafua: Vasafua is an islet of Funafuti, Tuvalu. Vasafua is part of the Funafuti Conservation Area, established in 1996 with the aim of preserving the natural fauna and flora of the area.
Document 8: Marshall Islands: Spanish explorer Alonso de Salazar was the first European to see the islands in 1526, commanding the ship Santa Maria de la Victoria, the only surviving vessel of the Loaísa Expedition. On August 21, he sighted an island (probably Taongi) at 14°N that he named "San Bartolome".
Document 9: Tuvalu: In 1892 Captain Davis of the HMS Royalist reported on trading activities and traders on each of the islands visited. Captain Davis identified the following traders in the Ellice Group: Edmund Duffy (Nanumea); Jack Buckland (Niutao); Harry Nitz (Vaitupu); John (also known as Jack) O'Brien (Funafuti); Alfred Restieaux and Emile Fenisot (Nukufetau); and Martin Kleis (Nui). During this time, the greatest number of palagi traders lived on the atolls, acting as agents for the trading companies. Some islands would have competing traders while dryer islands might only have a single trader.
Document 10: Funafuti: Funafuti is an atoll and the capital of the island nation of Tuvalu. It has a population of 6,025 people, making it the country's most populated atoll, with 56.6 percent of Tuvalu's population. It is a narrow sweep of land between 20 and 400 metres (66 and 1,312 feet) wide, encircling a large lagoon (Te Namo) 18 km (11 miles) long and 14 km (9 miles) wide. The average depth in the Funafuti lagoon is about 20 fathoms (36.5 metres or 120 feet). With a surface of 275 square kilometres (106.2 sq mi), it is by far the largest lagoon in Tuvalu. The land area of the 33 islets aggregates to 2.4 square kilometres (0.9 sq mi), less than one percent of the total area of the atoll. Cargo ships can enter Funafuti's lagoon and dock at the port facilities on Fongafale.
Document 11: Funafala: Funafala is an islet of Funafuti, Tuvalu that is inhabited by five families, with a church also located on the islet. Funafala means 'the pandanus of Funa', the name of a chief, after whom also the group has been named Funafuti.
Document 12: Guam: The Chamorros, Guam's indigenous people, settled the island approximately 4,000 years ago. Portuguese explorer Ferdinand Magellan was the first European to visit the island on March 6, 1521. Guam was colonized in 1668 with settlers, like Diego Luis de San Vitores, a Catholic missionary. Between the 1500s and the 1700s, Guam was an important stopover for the Spanish Manila Galleons. During the Spanish–American War, the United States captured Guam on June 21, 1898. Under the Treaty of Paris, Spain ceded Guam to the United States on December 10, 1898. Guam is amongst the seventeen Non-Self-Governing Territories of the United Nations.
Document 13: Tuvalu: Captain John Byron passed through the islands of Tuvalu in 1764 during his circumnavigation of the globe as captain of the Dolphin (1751). Byron charted the atolls as Lagoon Islands. Keith S. Chambers and Doug Munro (1980) identified Niutao as the island that Francisco Mourelle de la Rúa sailed past on 5 May 1781, thus solving what Europeans had called The Mystery of Gran Cocal. Mourelle's map and journal named the island El Gran Cocal ('The Great Coconut Plantation'); however, the latitude and longitude was uncertain. Longitude could only be reckoned crudely as accurate chronometers were unavailable until the late 18th century.
Document 14: Funamanu: Funamanu is a small narrow island that is part of Funafuti atoll in Tuvalu. It is a motu (islet) or very small island and is located 2.6 miles southwestward of the southwest tip of Funafuti. The islet is known to be covered in coconut trees which grow 70 feet high. Te Ava Pua Pua is the passage through the reef, with a least depth of 12.7 metres, between the islets of Funamanu to the north and Fale Fatu to the south, in the southeast of Funafuti atoll.
Document 15: Guam: The indigenous Chamorros settled the island approximately 4,000 years ago. Portuguese explorer Ferdinand Magellan, while in the service of Spain, was the first European to visit the island, on March 6, 1521. Guam was colonized by Spain in 1668 with settlers, including Diego Luis de San Vitores, a Catholic Jesuit missionary. Between the 16th century and the 18th century, Guam was an important stopover for the Spanish Manila Galleons. During the Spanish -- American War, the United States captured Guam on June 21, 1898. Under the Treaty of Paris, Spain ceded Guam to the United States on December 10, 1898. Guam is among the seventeen non-self - governing territories listed by the United Nations.
ground_truth: Álvaro de Mendaña
sub_queries: Vasafua >> country Answer: Tuvalu
Who was the discoverer of Tuvalu ? Answer: Álvaro de Mendaña