Location techniques for pico- and femto-satellites, with applications for space weather monitoring

Space weather phenomena have a significant impact on satellite communications but are not well understood. In-situ measurements of the ionospheric environment would significantly improve the understanding of the origins and progressions of these phenomena. Whilst previous scientific satellites have measured the ionospheric plasma, they only provide a limited view due to their small number. It has previously been suggested that a swarm of femto-satellites (PCBsats) could be used to collect high quality temporal and spatial measurements, whilst being financially effective. To give the measurements any scientific value, the location and time of each measurement needs to be accurately recorded. The PCBsat prototype used a solution that, due to export requirements and fundamental limitations with the device, would not be capable of working in space. Several location and timing solutions have been investigated, with none matching the precision, accuracy, power consumption and physical size of a GNSS receiver (i.e. a receiver of GPS, GLONASS, Galileo etc. signals). To further reduce the power consumption, a novel distributed GNSS receiver has been designed and built, where the largest computational burden (calculating the receivers position) is offloaded to a relaying node. This use of distributed computing has been shown to reduce the power consumption of the receiver by between 5:6% and 13:3% - which is equivalent to between 2 and 5 times the power consumption of the PCBsat’s main processor. In addition to this, this novel approach has the additional benefit of being used in a hybrid scheme. Where information required to calculate a receiver’s position is stored so that it can be used with higher precision ephemerides that are publicly available but are delayed by up to three weeks. This has many applications as it can increase the utility of collected data, at a reduced cost. As the intended femto-satellite application relies on a link to relaying satellites, the dynamics, in particular the dispersion, of the intended constellation needs to be known. This has been modelled using a novel orbit simulator. The orbit simulator is the first of its kind to model multidimensional free molecular drag to simulate the effects of the low density atmosphere on a satellite. This allows the dispersion of a constellation of satellites to be investigated with maximum separations for the PCBsat being presented.