Low-cost, flexible spaceborne radar architectures are needed to provide critical data for Earth and science applications. An instrument concept was developed for an advanced spaceborne radar system that can measure terrestrial biomass (woody mass per unit area), ecosystem structure (height and density), and extent on a global scale. The PNTB band polarimetric radar architecture employs advanced techniques to increase the science value of the measurements while achieving it at a lower cost. The spaceborne radar concept leverages the existing airborne L-band digital beamforming synthetic aperture radar (DBSAR) and the new P-band digital beamforming (DBF) polarimetric and interferometric EcoSAR (ESTO IIP) architectures that employ DBF and reconfigurable hardware to provide advanced radar capabilities not possible with conventional radar instruments.

DBF enables implementation of multi-mode radar techniques in a single platform without slewing the antenna. This capability allows for smart data collection, where a single radar system can provide different data types (e.g., high- or low-resolution polarimetric imaging, interferometry, altimetry, or scatterometry), depending on the science requirements defined for each surface target.

The DBF spaceborne SAR concept enables multiple antenna beams that can be synthesized simultaneously, permitting the implementation of nonconventional imaging, and overcoming fundamental limitations of conventional radar systems. Some of the benefits of these techniques include an increase in the measurement swath without reducing the received antenna gain, and the suppression of ambiguities or localized interference in the receiver signal by appropriate null-steering of the antenna pattern. Beams can be synthesized on both sides of the aircraft flight-track using a single nadir-looking antenna, thus increasing the coverage area.

The ability to rapidly image large areas of the surface using the simultaneous left/right imaging with no degradation in resolution allows for a faster primary mission that would still produce full coverage mapping. Alternatively, it can allow for a more efficient use of time as the radar instrument trades off operations with other selected instruments. This capability reduces mission cost and allows for increased spatial coverage. The concept also includes the onboard processing capabilities of DBSAR and EcoSAR, which provide a significant advancement over other radars, and can reduce the amount of data transmitted to Earth while maximizing the overall science payoff.

This work was done by Rafael Rincon and Temioloa Fatoyinbo of Goddard Space Flight Center. GSC-16838-1

NASA Tech Briefs Magazine

This article first appeared in the October, 2014 issue of NASA Tech Briefs Magazine.

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