Geosynchronous SAR for Terrain & atmosphere with short revisit (GeoSTARe)

Geo STA Re would be a mission combining the continuous view capabilities from geostationary orbits of super-continental areas with the all-day, all-weather imaging capabilities of Synthetic Aperture Radar. It would complement Copernicus Sentinel-1 bringing the repeat time from days down to hours. In that, it would provide novel and unique observations. The well proven potentials of Radar in sensing roughness, deformations, and moisture, combined with the short time to get any image, from minutes to an hour, and the immediate data download and exploitation (thanks to the geostationary orbit) makes GeoSTARe a game changer in those fields where hourly-to-daily monitoring is a must

Coherent change detection with GNSS-based SAR -Experimental study-

Bistatic Synthetic Aperture Radar (BSAR) systems are under an increasing amount of research activity over the last years. The possibility of the use of transmitters of opportunity has increased the flexibility and the applications of radar systems. One of the options is the use of Global Navigation Satellite Systems (GNSS) as transmitters, such as GPS, GLONASS or the forthcoming Galileo and Beidou, that is used in this study. This thesis is the result of the study of a GNSS-based SAR used for detection of changes that may occur in a scene. Although passive SAR is outclassed by active SAR in terms of SAR imaging performance, Coherent Change Detection applications in passive SAR can be promising. A proof-of-concept study is presented in this thesis. The connection between spatial target change and the level of coherence before and after the change is investigated. The stages of theoretical analysis and experimental setup are described in detail. Simulated scenarios are presented and the experimental results are analysed

Active and Passive Multi-Sensor Radar Imaging Techniques Exploiting Spatial Diversity

The work here presented reports several innovative SAR and ISAR radar imaging techniques exploiting the spatial diversity offered by multi-sensor systems in order to improve the performance with respect to the conventional, single channel cases. Both the cases of dedicated transmitters and exploitation of opportunity transmitters are considered

Active and Passive Multi-Sensor Radar Imaging Techniques Exploiting Spatial Diversity

The work here presented reports several innovative SAR and ISAR radar imaging techniques exploiting the spatial diversity offered by multi-sensor systems in order to improve the performance with respect to the conventional, single channel cases. Both the cases of dedicated transmitters and exploitation of opportunity transmitters are considered

Synchronising coherent networked radar using low-cost GPS-disciplined oscillators

This text evaluates the feasibility of synchronising coherent, pulsed-Doppler, networked, radars with carrier frequencies of a few gigahertz and moderate bandwidths of tens of megahertz across short baselines of a few kilometres using low-cost quartz GPSDOs based on one-way GPS time transfer. It further assesses the use of line-of-sight (LOS) phase compensation, where the direct sidelobe breakthrough is used as the phase reference, to improve the GPS-disciplined oscillator (GPSDO) synchronised bistatic Doppler performance. Coherent bistatic, multistatic, and networked radars require accurate time, frequency, and phase synchronisation. Global positioning system (GPS) synchronisation is precise, low-cost, passive and covert, and appears well-suited to synchronise networked radar. However, very few published examples exist. An imperfectly synchronised bistatic transmitter-receiver is modelled. Measures and plots are developed enabling the rapid selection of appropriate synchronisation technologies. Three low-cost, open, versatile, and extensible, quartz-based GPSDOs are designed and calibrated at zero-baselines. These GPSDOs are uniquely capable of acquiring phase-lock four times faster than conventional phase-locked loops (PLLs) and a new time synchronisation mechanism enables low-jitter sub-10 ns oneway GPS time synchronisation. In collaboration with University College London, UK, the 2.4 GHz coherent pulsed-Doppler networked radar, called NetRAD, is synchronised using the University of Cape Town developed GPSDOs. This resulted in the first published example of pulsed-Doppler phase synchronisation using GPS. A tri-static experiment is set up in Simon’s Bay, South Africa, with a maximum baseline of 2.3 km. The Roman Rock lighthouse was used as a static target to simultaneously assess the range, frequency, phase, and Doppler performance of the monostatic, bistatic, and LOS phase corrected bistatic returns. The real-world results compare well to that predicted by the earlier developed bistatic model and zero-baseline calibrations. GPS timing limits the radar bandwidth to less than 37.5 MHz when it is required to synchronise to within the range resolution. Low-cost quartz GPSDOs offer adequate frequency synchronisation to ensure a target radial velocity accuracy of better than 1 km/h and frequency drift of less than the Doppler resolution over integration periods of one second or less. LOS phase compensation, when used in combination with low-cost GPSDOs, results in near monostatic pulsed-Doppler performance with a subclutter visibility improvement of about 30 dB

Space Security 2008

Provides data and analysis on space activities in 2007 and their cumulative impact on security issues, including space laws, policies, and doctrines; civil space programs and global utilities; commercial uses; and environmental and military issues