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.
There is a significant interest in the Earth Science remote sensing community in substantially increasing the number of observations relative to the current frequency of collection. The obvious reason for such a push is to improve the temporal and surface coverage of measurements. However, there is little analysis available in terms of benefits, costs and optimized set of sensors needed to make these necessary observations. This is a complex problem that should be carefully studied and balanced over many boundaries. For example, the question of technology maturity versus users' desire for obtaining additional measurements is noncongruent. This is further complicated by the limitations of the laws of physics and the economic conditions. With the advent of advanced technology, it is anticipated that developments in spacecraft technology will enable advanced capabilities to become more affordable. However, specialized detector subsystems, and precision flying techniques may still require substantial innovation, development time and cost. Additionally, the space deployment scheme should also be given careful attention because of the high associated expense. Nonetheless, it is important to carefully examine the science priorities and steer the development efforts that can commensurate with the tangible requirements. This paper outlines a possible set of architectural concepts, operational scenarios and potential benefits of one scheme versus another. It further makes some suggestions where one can draw boundary conditions to incrementally solve this predicament.
Proceedings Volume Editor (1)
This will count as one of your downloads.
You will have access to both the presentation and article (if available).