creating an electrical signal which indicated the location and size of the hole in the plastic; precise calibration allowed information about the collision, such as particle speed and size, to be extracted from the signal. These calibrations took place from 1985 until 1989. This device was used on Vega 1 and Vega 2 spacecraft to Halley's Comet in 1986, and earned him the Gagarin Medal for Space Exploration that year for his contribution towards the success of the Vega mission, as his instruments had been the only ones from the United States to encounter the comet. Accomplishments John Alexander Simpson is known for inventions such as the "gas flow α-particle proportional counter", which measures plutonium yields in the presence of high intensity fission products, and the neutron monitor. His obituary in The Guardian noted that he was one of the most prolific inventors of scientific instruments for space exploration. The first of his instruments launched into space occurred in 1958; the last two were launched in 1999, one aboard the spacecraft Ulysses and the other aboard Stardust. In 1959, Simpson was elected to the National Academy of Sciences. In 1968, he held the first Ryerson Chair and was made Distinguished Service Professor at the University of Chicago; in 1974, he was the first to be appointed to the Compton Chair, and in 1986 he became Emeritus. Simpson is the recipient of the 1986 Gagarin Medal for Space Exploration for his contribution towards the success of the Vega program, which sent satellites to Halley's Comet earlier that year. In 1991, he was awarded the Bruno Rossi Prize by the American Astronomical Society for his contributions towards high-energy astrophysics, and in 1993 was awarded the Arctowski Medal of the National Academy of Sciences. In 1999, he was awarded the Leo Szilard Lectureship Award for his role in educating scientists, members of the United States Congress, and the public on the importance of civilian control of nuclear policy and his critical efforts in planning and execution of the International Geophysical Year. In 2000, he was also additionally awarded the William Bowie Medal which is the highest award given by the American Geophysical Union, for his extensive explorations of the cosmic rays and other energetic particles which bombard Earth. He was known an outstanding professor, having throughout the course of his academic career supervised the research of 34 doctoral students, many who are now