Research Topics
GPS Timing
Space Weather
Scintillation
GPS receiver design
Modern technology relies heavily on precise timing.
What is Time?
“The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.”
Reference: http://www.npl.co.uk/educate-explore/what-is-the-time/
Accurate time, why?
As we rely on more and more technology and demand faster applications, it is imperative to have highly accurate timing and synchronisation.
GPS timing applications
- Mobile phones
- Internet
- Banking
- Power supply grids
- ...and much more.
When radiation from the Sun reaches the layer of the Earth's atmosphere known as the Ionosphere, it excites the atoms, causing electrons to be released. The electrons have a charge and can interfere with radio waves: e.g. GPS signals. The more free electrons there are the more more disruption there is. Sometimes the Sun ejects large bursts of radiation, which bombard the Earth and can adversely affect worldwide telecommunications systems more so than normal.
High TEC values (orange/red colours) show a large amount of free electrons in the Earth's Ionosphere. GPS signals travel through the Earth's ionosphere before they reach our GPS receiver on the surface. High amounts of free electrons can seriously delay or weaken the GPS signals. This can stop your Satellite Navigation 'SatNav' from providing your position and time accurately and in severe cases it can completely prevent a fix on your location and time.
Figure (left): Global map of the Total Electron Content (TEC) of the ionosphere at 12:00 hrs on the 27 October 2003.
Legend:
TEC: Total Electron Content
Blue = Low TEC
Green/Yellow = Medium TEC
Red = High TEC
Radio wave scintillation is characterised by amplitude and phase fluctuations which are imposed upon a signal as it propagates through the ionosphere. Electron density irregularities are typically to blame for this effect.
Scintillation can seriously disrupt navigation, radio astronomy and communications systems.
Thus there is a need to produce a real-time and local ionospheric monitoring system, providing information leading to the use of alternate resources for example, should there be signal outages during times of severe scintillation fading.
Design of a next generation GPS receiver for a Low Earth Orbit (LEO) satellite
The aim is to design a low-cost dual frequency GNSS radio occultation receiver.
It should be able to:
Locate scintillation and large space weather events.
Forecast weather in near-real time.
Monitor climate change.
