His speciality is atmospheric characterization of transiting exoplanets. As exoplanet observations have played an ever increasing important role in Hubble’s overall science programme, Ken Sembach, Space Telescope Science Institute (STScI) Director, formed an Advisory Committee to explore the priorities in exoplanet research and provide advice for implementing an exoplanet science programme with Hubble. The committee, of which David is part, is chaired by Professor Drake Deming.