Design Options For Low Cost, Low Power Microsatellite Based SAR.

This research aims at providing a system design that reduces the mass and cost of spaceborne Synthetic Aperture Radar (SAR) missions by a factor of two compared to current (TecSAR - 300 kg, ~ £ 127 M) or planned (NovaSAR-S — 400 kg, ~ £ 50 M) mission. This would enable the cost of a SAR constellation to approach that of the current optical constellation such as Disaster Monitoring Constellation (DMC). This research has identified that the mission cost can be reduced significantly by: focusing on a narrow range of applications (forestry and disasters monitoring); ensuring the final design has a compact stowage volume, which facilitates a shared launch; and building the payload around available platforms, rather than the platform around the payload. The central idea of the research has been to operate the SAR at a low instantaneous power level—a practical proposition for a micro-satellite based SAR. The use of a simple parabolic reflector with a single horn at L-band means that a single, reliable and efficient Solid State Power Amplifier (SSPA) can be used to lower the overall system cost, and to minimise the impact on the spacecraft power system. A detailed analysis of basic pulsed (~ 5 - 10 % duty cycle) and Continuous Wave (CW) SAR (100 % duty cycle) payloads has shown their inability to fit directly into existing microsatellite buses without involving major changes, or employing more than one platform. To circumvent the problems of pulsed and CW techniques, two approaches have been formulated. The first shows that a CW SAR can be implemented in a mono-static way with a single antenna on a single platform. In this technique, the SAR works in an Interrupted CW (ICW) mode, but these interruptions introduce periodic gaps in the raw data. On processing, these gapped data result in artefacts in the reconstructed images. By applying data based statistical estimation techniques to “fill in the gaps” in the simulated raw SAR data, this research has shown the possibility of minimising the effects of these artefacts. However, once the same techniques are applied to the real SAR data (in this case derived from RADARSAT-1), the artefacts are shown to be problematic. Because of this the ICW SAR design technique it is—set aside. The second shows that an extended chirp mode pulsed (ECMP) SAR (~ 20 - 54 % duty cycle) can be designed with a lowered peak power level which enables a single SSPA to feed a parabolic Cassegrain antenna. The detailed analysis shows the feasibility of developing a microsatellite based SAR design at a comparable price to those of optical missions

Antenna Modeller for Synthetic Aperture Radar Applications. Electromagnetic and Radiometric Considerations

The objective of the present Master Thesis is designing an optimizer of the excitation coefficients of a phased array antenna

Dual-polarization (HH/HV) RADARSAT-2 ScanSAR Observations of New, Young and First-year Sea Ice

Observations of sea ice from space are routinely used to monitor sea ice extent, concentration and type to support human marine activity and climate change studies. In this study, eight dual-polarization (dual-pol) (HH/HV) RADARSAT-2 ScanSAR images acquired over the Gulf of St. Lawrence during the winter of 2009 are analysed to determine what new or improved sea ice information is provided by dual-pol C-band synthetic aperture radar (SAR) data at wide swath widths, relative to single co-pol data. The objective of this study is to assess how dual-pol RADARSAT-2 ScanSAR data might improve operational ice charts and derived sea ice climate data records. In order to evaluate the dual-pol data, ice thickness and surface roughness measurements and optical remote sensing data were compared to backscatter signatures observed in the SAR data. The study found that: i) dual-pol data provide improved separation of ice and open water, particularly at steep incidence angles and high wind speeds; ii) the contrast between new, young and first-year (FY) ice types is reduced in the cross-pol channel; and iii) large areas of heavily deformed ice can reliably be separated from level ice in the dual-pol data, but areas of light and moderately ridged ice cannot be resolved and the thickness of heavily deformed ice cannot be determined. These results are limited to observations of new, young and FY ice types in winter conditions. From an operational perspective, the improved separation of ice and open water will increase the accuracy of ice edge and total ice concentration estimates while reducing the time required to produce image analysis charts. Further work is needed to determine if areas of heavily ridged ice can be separated from areas of heavily rafted ice based on knowledge of ice conditions in the days preceding the formation of high backscatter deformed ice. If rafted and ridged ice can be separated, tactical ridged ice information should be included on image analysis charts. The dual-pol data can also provide small improvements to ice extent and concentration data in derived climate data records. Further analysis of dual-pol RADARSAT-2 ScanSAR data over additional ice regimes and seasons is required

Proceedings of the Third Spaceborne Imaging Radar Symposium

This publication contains summaries of the papers presented at the Third Spaceborne Imaging Radar Symposium held at the Jet Propulsion Laboratory (JPL), California Institute of Technology, in Pasadena, California, on 18-21 Jan. 1993. The purpose of the symposium was to present an overview of recent developments in the different scientific and technological fields related to spaceborne imaging radars and to present future international plans. This symposium is the third in a series of 'Spaceborne Imaging Radar' symposia held at JPL. The first symposium was held in Jan. 1983 and the second in 1986

High-resolution mapping of Bora winds in the northern Adriatic Sea using synthetic aperture radar

Author Posting. © American Geophysical Union, 2010. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 115 (2010): C04020, doi:10.1029/2009JC005524.The Adriatic Sea is regularly subjected to strong Bora wind events from the northeast during winter. The events have a strong effect on the oceanography in the Adriatic, driving basin-scale gyres that determine the transport of biogeochemical material and extracting large amounts of heat. The Bora is known to have multiple surface wind jets linked to the surrounding orography and have been the focus of many studies, but it has not been possible to describe the detailed spatial structure of these jets by in situ observations. Using high-resolution spaceborne RADARSAT-1 synthetic aperture radar (SAR) images collected during an active Bora period (23 January–16 February 2003), we created a series of high-resolution (300 m) maps of the wind field. The obtained winds show reasonable agreement with several in situ wind observations, with an RMS wind speed error of 3.6 m/s, slightly higher than the 2–3 m/s errors reported in previous studies. These SAR images reveal the spatial structure of the Bora wind in unprecedented detail, showing several new features. In the Senj region of Croatia, several images show rhythmic structure with wavelengths of 2–3 km that may reflect Bora pulsation seen at fixed locations by previous investigators. Along the Italian coast, several images show a wide (20–30 km) band of northwesterly winds that abruptly change to the northeasterly Bora winds further offshore. Meteorological model results suggest that these northwesterly winds are consistent with those of a barrier jet forming along the Italian Apennine mountain chain

Wavelet Analysis for Wind Fields Estimation

Wind field analysis from synthetic aperture radar images allows the estimation of wind direction and speed based on image descriptors. In this paper, we propose a framework to automate wind direction retrieval based on wavelet decomposition associated with spectral processing. We extend existing undecimated wavelet transform approaches, by including à trous with B3 spline scaling function, in addition to other wavelet bases as Gabor and Mexican-hat. The purpose is to extract more reliable directional information, when wind speed values range from 5 to 10 ms−1. Using C-band empirical models, associated with the estimated directional information, we calculate local wind speed values and compare our results with QuikSCAT scatterometer data. The proposed approach has potential application in the evaluation of oil spills and wind farms

Ocean Remote Sensing with Synthetic Aperture Radar

The ocean covers approximately 71% of the Earth’s surface, 90% of the biosphere and contains 97% of Earth’s water. The Synthetic Aperture Radar (SAR) can image the ocean surface in all weather conditions and day or night. SAR remote sensing on ocean and coastal monitoring has become a research hotspot in geoscience and remote sensing. This book—Progress in SAR Oceanography—provides an update of the current state of the science on ocean remote sensing with SAR. Overall, the book presents a variety of marine applications, such as, oceanic surface and internal waves, wind, bathymetry, oil spill, coastline and intertidal zone classification, ship and other man-made objects’ detection, as well as remotely sensed data assimilation. The book is aimed at a wide audience, ranging from graduate students, university teachers and working scientists to policy makers and managers. Efforts have been made to highlight general principles as well as the state-of-the-art technologies in the field of SAR Oceanography

Antenna Modeller for Synthetic Aperture Radar Applications. Electromagnetic and Radiometric Considerations

The objective of the present Master Thesis is designing an optimizer of the excitation coefficients of a phased array antenna

Potential of Spaceborne X & L-Band SAR-Data for Soil Moisture Mapping Using GIS and its Application to Hydrological Modelling: the Example of Gottleuba Catchment, Saxony / Germany

Hydrological modelling is a powerful tool for hydrologists and engineers involved in the planning and development of integrated approach for the management of water resources. With the recent advent of computational power and the growing availability of spatial data, RS and GIS technologies can augment to a great extent the conventional methods used in rainfall runoff studies; it is possible to accurately describe watershed characteristics in particularly when determining runoff response to rainfall input. The main objective of this study is to apply the potential of spaceborne SAR data for soil moisture retrieval in order to improve the spatial input parameters required for hydrological modelling. For the spatial database creation, high resolution 2 m aerial laser scanning Digital Terrain Model (DTM), soil map, and landuse map were used. Rainfall records were transformed into a runoff through hydrological parameterisation of the watershed and the river network using HEC-HMS software for rainfall runoff simulation. The Soil Conservation Services Curve Number (SCS-CN) and Soil Moisture Accounting (SMA) loss methods were selected to calculate the infiltration losses. In microwave remote sensing, the study of how the microwave interacts with the earth terrain has always been interesting in interpreting the satellite SAR images. In this research soil moisture was derived from two different types of Spaceborne SAR data; TerraSAR-X and ALOS PALSAR (L band). The developed integrated hydrological model was applied to the test site of the Gottleuba Catchment area which covers approximately 400 sqkm, located south of Pirna (Saxony, Germany). To validate the model historical precipitation data of the past ten years were performed. The validated model was further optimized using the extracted soil moisture from SAR data. The simulation results showed a reasonable match between the simulated and the observed hydrographs. Quantitatively the study concluded that based on SAR data, the model could be used as an expeditious tool of soil moisture mapping which required for hydrological modelling