One of the major difficulties with using computer models to forecast the weather is keeping the models constantly updated with what the weather is actually doing. There have been enormous advances in recent years that have considerably improved the ability of numerical weather prediction models. The models are able to ingest all manner of weather observations; measurement on the ground, measurements from space, measurements from weather balloons to name a few. However, the computer models will only ever be as good as the input data that is used to represent the state of the atmosphere. As the resolution and ability of the models improve, (related to the size of the grid) to get the benefit of the model improvement, the input data must also be improved. Particularly important in computer modelling is the transportation of moisture in the atmosphere since this is a key factor in the formation of severe rain storms which can lead to flooding. Currently there is almost no instrument capable of making routine remote measurements of moisture in the lower few kilometres of the atmosphere over an area the size of the UK. With the grid-length of computer models used in research as small as 1 km, the search is on to find instruments that can provide measurements on a similar scale in order to get the very best results from the model. The aim of this project is to develop an inexpensive instrument that can measure moisture in the atmosphere. A key novelty of this proposal is that it makes use of existing digital radio and television signals broadcasts. The basic concept is simple: the more water vapour along the path between the transmitter and receiver, the longer it takes for the signal to travel. Assuming the location of the receiver is kept fixed, changes in the signal time can be related to changes in water vapour. To accomplish this there are many technical challenges that first need to be solved. The radio signals were not designed to be used in this way so a consdiderable amount of signal processing is required. In addition because the time of flight of the signal is very small it is difficult to measure and requires a very stable clock. The advantage of this approach is that it is inexpensive, consumes relatively little power and requires no additional signals to be transmitted in order to make the measurements.

Abstracts are not currently available in GtR for all funded research. This is normally because the abstract was not required at the time of proposal submission, but may be because it included sensitive information such as personal details.

Although GNSS systems now underpin a significant part of modern infrastructure, such as financial markets, telecoms, power generation and distribution as well as transport and emergency services, they suffer from a number of known vulnerabilities. One such shortcoming relates to an ionospheric disturbance known as scintillation. The phenomenon of scintillation is familiar to most people through the twinkling of star light as it crosses the atmosphere. Ionospheric scintillation causes amplitude and phase variations on signals from GNSS satellites when they cross the ionised upper atmosphere (the ionosphere). Currently, GNSS receivers are not robust against radio scintillation; effects range from degradation of positioning accuracy to the complete loss of signal tracking. During scintillation events, required levels of accuracy and continuity, as well as availability, may not be met, thus compromising commercial operations, such as maritime navigation, geophysical exploration and airplane navigation during airport precision approach. The project will quantify the problem of ionospheric scintillation over the forthcoming solar maximum (2010-2013) and develop algorithms to reduce the impact on the users. The research will lead to improved GNSS receiver design that will enable robust performance of receivers that are compromised by effects of the natural environment through ionospheric scintillation.

Abstracts are not currently available in GtR for all funded research. This is normally because the abstract was not required at the time of proposal submission, but may be because it included sensitive information such as personal details.

Time is the quantity, which can be measured to the highest precision of all metrological quantities. We all benefit from this extraordinary precision in our everyday lives, as precision time enables synchronization of data packets in ultrafast broadband communication and the determination of our position by computing the flight times of radiofrequency signals in Satellite Navigation to nanosecond precision. These economically important applications rely on microwave atomic clocks, which in their commercial form are precise to 1 part in 10^14. We are currently facing a revolution in timing accuracy due to the invention of optical clocks and accessible ways of counting optical frequencies, which has already been recognised by the Nobel Price in Physics in 2005. These novel clocks already reach stabilities beyond 1 part in 10^18, more than 4 orders of magnitude beyond the state-of-the art. However, while the clock technology is progressing rapidly, there is still a lot to learn about how such a precision can be transferred to the user community in a practical and efficient way. Microwave links, such as used in current satellite time transfers, are impractically slow for such precision, while optical fibre links need expensive dedicated fibre connections and are limited to a few 100 km, making intercontinental connections impractical. In addition, at 10^-18 precision, effects such as general relativity coupling gravity to frequency are coming into play and make the transfer dependent on deformation of the continental plates in Earth tides and larger rain falls. ICON brings together world leading transportable optical clocks and world leading optical link space infrastructure to explore the limits of precision time transfer. Including work on making transportable clocks more compact and robust with world-leading atom chip concepts, we are aiming at bringing precision time to everyone - first researchers relying on precision oscillators and later in commercial applications for the benefit of wider society.