John is the Science Area Leader for the National Time Scale Group. He joined NPL in 1986 after completing a PhD in ammonia masers at Keele University.
John initially worked on the development of an optically pumped caesium clock. He then moved to working on satellite time transfer methods, using television signals, GNSS and two-way methods using communication satellites. This involved collaborative work with other National Measurement Institutes, along with UK industry, including the collaborative development of a timing GNSS receiver.
John has worked on the developments on Kalman-filter-based clock ensembles, steering algorithms and clock predictors, in particular the modelling of clocks and measurement noise.
Much of John’s later work has been on a range of collaborations with other National Measurement Institutes, and organisations in the UK with interests in time and frequency. This has included work on the Galileo reference time scale, time scale aspects of GNSS vulnerability, and the design of time scales for the Square Kilometre Array radio telescope.
John’s work is currently focused on the development of a distributed time scale within the National Timing Centre programme.
Areas of interest
- Development of clock and time scale algorithms including ensemble and steering algorithms
- Kalman filters, clock and time transfer models
- GNSS systems
- Time and frequency transfer and dissemination techniques
- Design and development of robust time scales
Key publications
- Square Kilometre Array: the radio telescope of the XXI century
Keith Grainge, Bassem Alachkar, Shaun Amy, Domingos Barbosa, Murali Bommineni, Paul Boven, Ralph Braddock, John Davis, Praveen Diwakar, Vishal Francis, Robert Gabrielczyk, Romeo Gamatham, Simon Garrington, Tim Gibbon, David Gozzard, Simon Gregory, Yichen Guo, Yashwant Gupta, Jill Hammond, David Hindley, Uli Horn, Richard Hughes-Jones, Michelle Hussey, Sam Lloyd, Siju Mammen, Vivek Mohile, Jaco Muller, Swami Natarajan, John Nicholls, Richard Oberland, Mike Pearson, Tim Rayner, Sascha Schediwy, Richard Schilizzi, Supriya Sharma, Simon Stobie, Mark Tearle, Bo Wang, Bruce Wallace, Lijun Wang, Rajesh Warange, Richard Whitaker, Althea Wilkinson, Neil Wingfield
Astronomy Reports 61, 288 (2017)
- Local representations of UTC in national laboratories
P B Whibberley, J A Davis and S L Shemar
Metrologia 48, S154 (2011)
- A Kalman filter clock algorithm for use in the presence of flicker frequency modulation noise
J A Davis, C A Greenhall and P W Stacey
Metrologia 42, 1 (2005)
- European Two-Way Satellite Time Transfer Experiments Using the INTELSAT (VA-F13) Satellite at 307°E
J A Davis, P R Pearce, D Kirchner, H Ressler, P Hetzel, A Soering, G DeJong, P Grudler, F Baumont and L Veenstra,
IEEE Transactions on Instrumentation and Measurement 44, 90 (1995)
Email John Davis