Geosynchronous Synthetic Aperture Radar: concept design, properties and possible applications
- Paper number
IAC-05-B1.2.08
- Author
Mr. Davide Bruno, Cranfield University, United Kingdom
- Coauthor
Dr. Stephen Hobbs, Cranfield University, United Kingdom
- Coauthor
Mr. Giuseppe Ottavianelli, University of Cranfield, United Kingdom
- Year
2005
- Abstract
Geosynchronous orbits have the unique characteristic that their orbital period is equal to one sidereal day. A synthetic aperture radar (SAR) placed in a geosynchronous orbit can provide daily coverage for approximately 1/3 of the globe with a very short revisit time (up to 12 hours). This paper investigates both active and passive configurations, highlighting their different features and advantages. The proposed active configuration is an L-band SAR with a 30 meter diameter antenna in a 60° inclined orbit. It provides an azimuth ground resolution of about 2 meters with an integration time of 20 minutes. The passive concept overcomes the technological limit imposed by the antenna aperture as it requires a relatively small (10 m diameter) receiver-only antenna. The orbit required to achieve a reasonable SNR is only slightly inclined. The azimuth resolution attainable is about 40 m (integration time 8 hours) while the coverage is limited to continental scale. The passive system may reuse the signal transmitted by other geostationary illuminators such as Digital Broadcasting satellites (L-band). The proposal includes the analysis of a possible multistatic configuration that increases flexibility and improves azimuth resolution. A SAR simulator has been developed to study the influence of integration time on SAR processing in both LEO and GEO cases. Different scenarios with targets affected by noise sources with various correlation lengths have been simulated in order to test the system response. Simulations show that in a geosynchronous SAR the long integration time averages out non-stationary signals in the resolution cell converting their influence to background clutter. Indeed, noise rejection is effective even if noise amplitude is one order of magnitude larger than the signal itself. In presence of correlated noise the azimuth resolution is reduced by a factor proportional to the noise correlation time. The response of the LEO SAR (integration time 1 second) is different as it does not show any effective noise rejection and, in presence of uncorrelated noise superimposed to a coherent target, the SNR is about 10 dB lower than in the geosynchronous case. The features that have been demonstrated via numerical simulations could be exploited in new SAR applications. SAR interferometry can benefit of the increased temporal correlation as all the high frequency components of interferometric phase noise have been previously filtered out. Fine temporal sampling is a characteristic that might be exploited for disaster management and might lead to major advances in the understanding of rapidly evolving phenomena on the ground surface. Future applications can be foreseen also in the area of atmospheric monitoring. For the purpose the passive configuration is particularly promising as, reducing azimuth resolution to 1 km, a 20 minute temporal sampling can be achieved to monitor atmosphere on a continental scale.
- Abstract document
- Manuscript document
IAC-05-B1.2.08.pdf (🔒 authorized access only).
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