Abstract
Some outcomes of a feasibility analysis of a spaceborne bistatic radar mission for soil moisture retrieval are presented in this paper. The study starts from the orbital design of the configuration suitable for soil moisture estimation identified in a previous study. This configuration is refined according to the results of an analysis of the spatial resolution. The paper focuses on the assessment of the spatial coverage i.e., on the verification that an adequate overlap between the footprints of the antennas is ensured and on the duty cycle, that is the fraction of orbital period during which the bistatic data are acquired. A non-cooperating system is considered, in which the transmitter is the C-band Advanced Synthetic Aperture Radar aboard Envisat. The best performances in terms of duty cycle are achieved if the transmitter operates in Wide Swath Mode. The higher resolution Image Swath Modes that comply with the selected configuration have a duty cycle that is never less than 12% and can exceed 21%. When Envisat operates in Wide Swath Mode, the bistatic system covers a wide latitude range across the equator, while in some of the Image Swath Modes, the bistatic measurements, collected from the same orbit, cover mid-latitude areas. In the latter case, it might be possible to achieve full coverage in an Envisat orbit repeat cycle, while, for a very large latitude range such as that covered in Wide Swath Mode, bistatic acquisitions could be obtained over about 65% of the area.
Highlights
A spaceborne bistatic radar system is defined when antennas for reception and transmission are physically separated and located aboard two spacecraft
In a previous work [2], we reported on a theoretical investigation aiming at identifying the best bistatic measurement configuration, in terms of incidence angle, observation direction, polarization, and frequency band, for soil moisture content (SMC) retrieval
The study has started from the identification of the bistatic configurations suitable for SMC retrieval, in terms of frequency and ideal transmitter-target-receiver relative geometry accomplished in a previous study
Summary
A spaceborne bistatic radar system is defined when antennas for reception and transmission are physically separated and located aboard two spacecraft. While in [2] we did not tackle the problem of verifying the identified radar configurations from a technical point of view, this work deals with spatial resolution, spatial coverage and duty cycle (i.e., the fraction of the orbit in which suitable bistatic data collection is ensured). It aims at evaluating whether an adequate overlap between the footprints of the transmitting and receiving antennas is ensured for the bistatic observation geometry that guarantees both an improvement of the quality of the SMC retrieval and a quite good spatial resolution.
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