William Lahoz’s main interests are data assimilation and Earth Observation. He has numerous publications in leading scientific journals and book chapters. He has organized international symposia, conferences and Summer Schools, and been an invited speaker. William is an ACP editor. He contributed to the 1998 WMO Ozone Assessment. He has been on several international scientific committees. William currently leads NILU land data assimilation activities. He co-funded the UK-DARC, of which he was Deputy Director, and led the prestigious European project on Envisat data assimilation, ASSET. Boris Khattatov’ primary area of expertise involves applications of optimal control, estimation, and inverse problem theory to problems in the numerical modelling of the Earth’s atmosphere and satellite data analysis. Boris led a US Air Force sponsored effort on advancing modelling capabilities for nowcasting and forecasting ionospheric "weather". He has numerous publications in leading scientific journals, and has contributed to books and patents. Richard Ménard has been involved in data assimilation for nearly 20 years. Thereafter, he joined the NASA Global Modeling and Assimilation Office and then joined Environment Canada in 2000. He was awarded his Ph.D. on Kalman filtering of Burgers’ equation (Roger Daley, advisor). He has made several contributions in the field of Kalman filtering, chemical data assimilation, covariance modelling, validation of assimilation systems, and chemical-dynamical coupling.