A KU-BAND GEOSYNCHRONOUS SYNTHETIC APERTURE RADAR MISSION ANALYSIS WITH MEDIUM TRANSMITTED POWER AND MEDIUM-SIZED ANTENNA Josep Ruiz Rodon, Antoni Broquetas, Andrea Monti Guarnieri, Fabio Rocca 07/27/2011 IGARSS’11 Vancouver

Outline Introduction to GEOSAR System description: synthetic aperture formation. GEOSAR constraints and system features. Image reconstruction for simulated GEOSAR raw data. The APS correction for long term acquisitions. Conclusions. 07/27/2011 IGARSS’11 Vancouver

Introduction to GEOSAR (I) What?: Ku-Band monostatic SAR mission to get high resolution images from a radar system placed in a geosynchronous satellite. How?: relative motion achieved by the slight perturbations (eccentricity and/or inclination) of the non-perfect geostationary orbit → Synthetic Aperture formation. Why?: constant monitoring of a wide Earth’s area (revisit time limited only by the synthetic aperture integration time). North-South illumination. 07/27/2011 IGARSS’11 Vancouver

Introduction to GEOSAR (II) Drawbacks: low power echo → increase integration time and/or the resolution cell (degrade resolution). Possible Atmospheric Phase Screen artefacts and target coherence loss due to long integration time. Configurations: Monostatic: transceiver on a communications satellite or dedicated geosynchronous satellite. Bistatic: illuminator of opportunity + receiver tuned to one of the downlink channels or receiver on ground station. 07/27/2011 IGARSS’11 Vancouver

System description (I): Synthetic Aperture Formation Satellite motion with respect to the Earth’s surface governed by eccentricity and inclination of the orbit. Longitude and latitude histories with respect to an Earth’s centered rotating reference system: Typically, elliptical tracks are obtained by tuning the orbital parameters. (1) (2) 07/27/2011 IGARSS’11 Vancouver

System description (II): Obit design parameters Orbit design flexibility: 07/27/2011 IGARSS’11 Vancouver

GEOSAR constraints and system features (I): timing and PRF selection PRF selection: avoid transmission interferences and nadir eclipses. Dartboard diagram PRF=30Hz Dartboard diagram PRF=100Hz 07/27/2011 IGARSS’11 Vancouver

GEOSAR constraints and system features (II): SNR requirements SNR after SAR processing (pulse compression and integration): (3) @12GHz Compressed 07/27/2011 IGARSS’11 Vancouver

GEOSAR constraints and system features (III): APS retrieval Meteorological applications of GEOSAR: Atmospheric Phase Screen (APS) monitoring. Fast temporal evolution (~minuntes) but high spatial correlation (~Km). @12GHz Compressed 07/27/2011 IGARSS’11 Vancouver

GEOSAR image reconstruction (I): Doppler behavior Non-perfect circular orbit → variable Doppler centroid during the acquisition. Doppler centroid track/compensation from the information of a reference position. 07/27/2011 IGARSS’11 Vancouver

GEOSAR image reconstruction (II): Doppler behavior Example: e=0.0004 and inc.: 0.046º Scene: 1 x 1 Km. Reference target: central scene point. 07/27/2011 IGARSS’11 Vancouver

GEOSAR image reconstruction (III): TDBP focusing Raw data simulation: 1 x 1 Km scene with centered point target during 1 hour. No atmospheric artifacts and noise considered. Perfect reconstruction via TDBP algorithm: 50 x 50 meters resolution. 07/27/2011 IGARSS’11 Vancouver

APS correction for long term acquisitions (I) Short term GBSAR acquisitions for long integration time synthetic aperture assessment. 07/27/2011 IGARSS’11 Vancouver

APS correction for long term acquisitions (II) APS correction from phase information of a stable point target (corner reflector). 07/27/2011 IGARSS’11 Vancouver

Conclusions Monostatic GEOSAR configuration with typical LEOSAR parameters with long integration. Synthetic Aperture formation, timing analysis and SNR requirements shows the feasibility of geosynchronous satellites for SAR applications. TDBP algorithm to focus simulated raw data from a GEOSAR configuration with Doppler centroid compensation. Atmospheric phase stability in long term acquisition as well as target coherence loss have to be deeply studied in further analysis. 07/27/2011 IGARSS’11 Vancouver

Thank you Josep Ruiz Rodon e-mail: josep.ruiz@tsc.upc.edu Phone:+34 93 401 74 26 http://www.tsc.upc.edu/rs 07/27/2011 IGARSS’11 Vancouver