###Answer the question from the input provided. Please answer from input only.

###Input: From the late 1340s onwards, people in the countryside suffered from frequent natural disasters such as droughts, floods and the resulting famines, and the government's lack of effective policy led to a loss of popular support. In 1351, the Red Turban Rebellion started and grew into a nationwide uprising. In 1354, when Toghtogha led a large army to crush the Red Turban rebels, Toghun Temür suddenly dismissed him for fear of betrayal. This resulted in Toghun Temür's restoration of power on the one hand and a rapid weakening of the central government on the other. He had no choice but to rely on local warlords' military power, and gradually lost his interest in politics and ceased to intervene in political struggles. He fled north to Shangdu from Khanbaliq (present-day Beijing) in 1368 after the approach of the forces of the Míng dynasty (1368–1644), founded by Zhu Yuanzhang in the south. He had tried to regain Khanbaliq, which eventually failed; he died in Yingchang (located in present-day Inner Mongolia) two years later (1370). Yingchang was seized by the Ming shortly after his death. Some royal family members still lived in Henan today.

A rich cultural diversity developed during the Yuan dynasty. The major cultural achievements were the development of drama and the novel and the increased use of the written vernacular. The political unity of China and much of central Asia promoted trade between East and West. The Mongols' extensive West Asian and European contacts produced a fair amount of cultural exchange. The other cultures and peoples in the Mongol World Empire also very much influenced China. It had significantly eased trade and commerce across Asia until its decline; the communications between Yuan dynasty and its ally and subordinate in Persia, the Ilkhanate, encouraged this development. Buddhism had a great influence in the Yuan government, and the Tibetan-rite Tantric Buddhism had significantly influenced China during this period. The Muslims of the Yuan dynasty introduced Middle Eastern cartography, astronomy, medicine, clothing, and diet in East Asia. Eastern crops such as carrots, turnips, new varieties of lemons, eggplants, and melons, high-quality granulated sugar, and cotton were all either introduced or successfully popularized during the Yuan dynasty.

Western musical instruments were introduced to enrich Chinese performing arts. From this period dates the conversion to Islam, by Muslims of Central Asia, of growing numbers of Chinese in the northwest and southwest. Nestorianism and Roman Catholicism also enjoyed a period of toleration. Buddhism (especially Tibetan Buddhism) flourished, although Taoism endured certain persecutions in favor of Buddhism from the Yuan government. Confucian governmental practices and examinations based on the Classics, which had fallen into disuse in north China during the period of disunity, were reinstated by the Yuan court, probably in the hope of maintaining order over Han society. Advances were realized in the fields of travel literature, cartography, geography, and scientific education.

The first recorded travels by Europeans to China and back date from this time. The most famous traveler of the period was the Venetian Marco Polo, whose account of his trip to "Cambaluc," the capital of the Great Khan, and of life there astounded the people of Europe. The account of his travels, Il milione (or, The Million, known in English as the Travels of Marco Polo), appeared about the year 1299. Some argue over the accuracy of Marco Polo's accounts due to the lack of mentioning the Great Wall of China, tea houses, which would have been a prominent sight since Europeans had yet to adopt a tea culture, as well the practice of foot binding by the women in capital of the Great Khan. Some suggest that Marco Polo acquired much of his knowledge through contact with Persian traders since many of the places he named were in Persian.

The Yuan undertook extensive public works. Among Kublai Khan's top engineers and scientists was the astronomer Guo Shoujing, who was tasked with many public works projects and helped the Yuan reform the lunisolar calendar to provide an accuracy of 365.2425 days of the year, which was only 26 seconds off the modern Gregorian calendar's measurement. Road and water communications were reorganized and improved. To provide against possible famines, granaries were ordered built throughout the empire. The city of Beijing was rebuilt with new palace grounds that included artificial lakes, hills and mountains, and parks. During the Yuan period, Beijing became the terminus of the Grand Canal of China, which was completely renovated. These commercially oriented improvements encouraged overland and maritime commerce throughout Asia and facilitated direct Chinese contacts with Europe. Chinese travelers to the West were able to provide assistance in such areas as hydraulic engineering. Contacts with the West also brought the introduction to China of a major food crop, sorghum, along with other foreign food products and methods of preparation.



###Question: What astronomer worked for Kublai?

###Answer: {'answer':'Guo Shoujing'}