Carl Sagan served as the David Duncan Professor of Astronomy and Space Sciences and Director of the Laboratory for Planetary Studies at Cornell University. He played a leading role in the Mariner, Viking, Voyager, and Galileo spacecraft expeditions, for which he received the NASA Medals for Exceptional Scientific Achievement and (twice) for Distinguished Public Service.His Emmy- and Peabody–winning television series, Cosmos, became the most widely watched series in the history of American public television. The accompanying book, also called Cosmos, is one of the bestselling science books ever published in the English language. Dr. Sagan received the Pulitzer Prize, the Oersted Medal, and many other awards—including twenty honorary degrees from American colleges and universities—for his contributions to science, literature, education, and the preservation of the environment. In their posthumous award to Dr. Sagan of their highest honor, the National Science Foundation declared that his “research transformed planetary science . . . his gifts to mankind were infinite.” Dr. Sagan died on December 20, 1996.