Digital Beamforming has gained significant importance in radar applications in the past years. It helps improve radar performance while reducing mass and power. Improving these figures becomes even more important for space applications. The Space Exploration Synthetic Aperture Radar (SESAR) is a novel P-band (70 cm wavelength) radar instrument developed for planetary applications that will enable surface and near-subsurface measurements of Solar System planetary bodies. The radar will measure full polarimetry at meter-scale resolution, and perform beam steering through programmable digital beamforming architecture. The data obtained with SESAR will provide key information on buried ice and water signatures that can facilitate the design of future human and robotic exploration missions. In this paper we describe SESAR’s large antenna array, the sub-systems integration process, and the different environmental testing activities performed to the overall system in order to raise the Technology Readiness Level (TRL) for its future inclusion in a space-proven system.
The NASA RADSTAR instrument is a compact scatterometer-radiometer system designed for airborne and space
remote sensing of Earth surface properties such as soil moisture and sea surface salinity. In this paper we describe the
active portion of RADSTAR, the L-band Imaging Scatterometer (LIS). The system employs electronic steering and
digital beamforming techniques to generate multiple, low-sidelobe beams over a scan range of +/-50 degrees below an
aircraft. We discuss the design and testing of LIS, and the planned merging of the scatterometer with the radiometric
components of the final instrument. In its final configuration, RadSTAR will employ a single broadband antenna to
efficiently support simultaneous scatterometer (LIS) and radiometer measurements in airborne and spaceborne
applications. LIS is currently being flown along with the ESTAR synthetic aperture radiometer aboard the NASA P-3
aircraft in order to prove the concept of coregistered data, setting the path for future spaceborne, single aperture,
electronically scanned, radar/radiometer systems.
This paper discusses the concept and design of a real-time Digital Beamforming Synthetic Aperture Radar (DBSAR) for
airborne applications which can achieve fine spatial resolutions and wide swaths. The development of the DBSAR
enhances important scientific measurements in Earth science, and serves as a prove-of-concept for planetary exploration
missions. A unique aspect of DBSAR is that it achieves fine resolutions over large swaths by synthesizing multiple
cross-track beams simultaneously using digital beamforming techniques. Each beam is processed using SAR algorithms
to obtain the fine ground resolution without compromising fine range and azimuth resolutions. The processor uses an
FPGA-based architecture to implement digital in-phase and quadrature (I/Q) demodulation, beamforming, and range
and azimuth compression. The DBSAR concept will be implemented using the airborne L-Band Imaging Scatterometer
(LIS) on board the NASA P3 aircraft. The system will achieve ground resolutions of less than 30 m and swaths of 10
km from an altitude of 8 km.
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