Buckingham Centre for Astrobiology, University of Buckingham, UK.
University of Buckingham, UK.
University of Ruhuna, Sri Lanka.
University of Peradeniya, Sri Lanka.
Sir John Kotelawala Defence University, Sri Lanka.
National Institute of Fundamental Studies, Sri Lanka.
Editor in Chief,
Journal of Astrobiology and Outreach.
Institute for the Study of Panspermia and Astroeconomics.
California Institute of Technology, 1965.
Professor of Mathematics,
Vidyodaya University of Ceylon, 1966.
Universities of Arizona and Maryland USA, 1966-1970.
Yukawa Institute, Kyoto University, Japan, 1969.
Tutor and Supervisor in Mathematics,
Jesus College, Cambridge.
Member of the Graduate Staff,
Institute of Theoretical Astronomy, University of Cambridge, 1966-1973.
University of Western Ontario, London, Ontario, Canada, 1974 and 1976.
Institute of Fundamental Studies, Sri Lanka, 1982-1984.
President of Sri Lanka, 1982-1984.
Institute of Space and Astronautical Studies, Japan, 1993.
University of the West Indies, Mona, Kingston, 1994.
Professor and Head of the Dept.of Applied Maths and Astronomy,
University College, Cardiff, 1973-1989
Professor of Applied Mathematics and Astronomy,
Cardiff University, 1990-2006
Professor and Director,
Cardiff Centre for Astrobiology 2006-2011
Churchill College, Cambridge 2015-2016.