The 2012 David Bates Medal is awarded to Hans Rickman for his fundamental contributions to cometary physics and the analysis of non-gravitational forces in comets.
Hans Rickman was born in 1949 in Uppsala, Sweden. His scientific career has been devoted to cometary physics, a field in which he has become one of the few leading international experts. Rickman conducted physical studies of comets, on the gas flow from their nucleus, on the production and kinematics of CO, on the formation of stable dust mantles that can make comets inactive, on comet size distribution and the link between total magnitude and nuclear magnitude. Another major aspect of his work was related to cometary dynamics. Rickman investigated in detail the dynamic evolution of long-period comets, addressing the problem of the origin of the Oort cloud, and the role of the galactiv environment on this flux. He made a major contribution in showing, in connection with the Nice Model, that the scattered disk of TNOs is a more likely source for Jupiter-family comets than the Kuiper Belt. Bridging physical and dynamical approaches, he made pioneering contributions to the study of non-gravitational forces in comets, the modeling of which is up to now the only successful tool for estimating the cometary masses. In particular, by inverting his model, he inferred the properties of comet 9P/Tempel 1 from the observations of non-gravitational perturbations of its orbit. Another outstanding aspect of Hans Rickman’s career is his commitment in serving the community. In parallel with his research activities, Rikman played a major role in organizing the cometary community by starting the series of “Asteroids Comets Meteors” Conferences, which first took place in Uppsala. This meeting was a breakthrough in bringing together the comet and asteroid communities, and proved so popular that it is now organized regularly every second year. At a more general level, the entire international astronomical community is indebted to him for his service and leadership within the International Astronomical Union (IAU). He has held several important positions within the IAU, first as a member of several commissions, then as the Assistant General Secretary (2000-2003), then as General Secretary (2003-2006). In addition to his IAU activities, Rickman has served in a number of other high profile positions of leadership including the Royal Swedish Academy of Sciences, the European Astronomical Society and the European Space Agency. Hans Rickman is the author of over 260 articles, including more than 100 refereed articles, more than 75 as a first author, and more of 20 invited reviews. He has also published a book of lectures (“Collisional Processes in the Solar system”, by M. Marov and H. Rickman) and more than 60 popular astronomy articles. Rickman also has a rich teaching experience as a Professor of Uppsala University. He has taught about 50 undergraduate courses and 16 graduate courses in astronomy, and he has been the supervisor of 7 PhD students at Uppsala University. In summary, Rickman has made an outstanding contribution to planetary and astronomical science, through his major research contributions in cometary science, but also through his deep involvement in the scientific community at the highest international level.