Use of multiple-antenna radar systems aboard moving high-altitude platforms has been proposed for measuring rainfall. The platforms contemplated in the proposal would be primarily spacecraft, but, in principle, the proposal could also apply to aircraft. The problem of measuring rainfall velocity from a moving platform is especially challenging because the velocity of the platform (especially in the case of a spacecraft) can be so large that it is difficult to distinguish between the rainfall and platform contributions to Doppler frequency shifts. Furthermore, nonuniform filling of radar beams can lead to biases in Doppler estimates. Although it might be possible to reduce these biases through improved data processing, a potential alternative is to use multiple antennas positioned at suitable alongtrack intervals.
The basic principle of the proposed systems is a variant of that of along-track interferometric synthetic-aperture radar systems used previously to measure ocean waves and currents. The simplest system according to the proposal would include two antennas that would perform crosstrack scans as in a prior rainfall-measuring radar system. The antennas would be located at different along-track positions. The along-track distance between them would be chosen, in conjunction with the along-track velocity of the platform and the radar pulse-repetition frequency (PRF), such that this distance would equal the distance traveled by the platform between two successive pulses. (If necessary, the PRF could be adjusted to enforce this equality.) Thus, in effect, two sets of measurements would be performed at each platform position. Under this condition, extraction of the rainfall Doppler velocity without the platform contribution is substantially simplified and can be done with only minor modification of processing techniques traditionally used for ground-based Doppler radars.
This work was done by Stephen Durden, Simone Tanelli, and Paul Siqueira of Caltech for NASA’s Jet Propulsion Laboratory. For more information, download the Technical Support Package (free white paper) at www.techbriefs. com/tsp under the Electronics/Computers category. NPO-44018
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Multi-Antenna Radar Systems for Doppler Rain Measurements
(reference NPO-44018) is currently available for download from the TSP library.
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Overview
The document is a Technical Support Package from NASA’s Jet Propulsion Laboratory (JPL) focused on Multi-Antenna Radar Systems for Doppler Rain Measurements, identified by NTR Number 44018. It outlines advancements in radar technology aimed at improving precipitation measurement from space, which is crucial for weather forecasting, climate studies, and hydrological modeling.
The primary innovation discussed is the use of multi-antenna radars for spaceborne Doppler precipitation measurements. This technology enhances the ability to measure rainfall rates and storm dynamics by utilizing multiple antennas to capture data from different angles, thereby improving the accuracy and resolution of precipitation observations. The document references a specific paper titled "On the Use of Multiantenna Radars for Spaceborne Doppler Precipitation Measurements," authored by Durden, Siqueira, and Tanelli, published in the IEEE Geoscience and Remote Sensing Letters in January 2007. This paper provides detailed insights into the methodology and benefits of the multi-antenna approach.
The Technical Support Package emphasizes the significance of these radar systems within the broader context of aerospace-related developments, highlighting their potential applications beyond meteorology, including environmental monitoring and disaster management. It is part of NASA's Commercial Technology Program, which aims to disseminate aerospace innovations that can have wider technological, scientific, or commercial implications.
For those seeking further information or assistance regarding this technology, the document provides contact details for the Innovative Technology Assets Management office at JPL, including a mailing address, telephone number, and email. It also includes a disclaimer noting that the U.S. Government does not assume liability for the use of the information contained in the document, nor does it endorse any specific trade names or manufacturers mentioned.
In summary, this Technical Support Package serves as a comprehensive overview of the advancements in multi-antenna radar technology for precipitation measurement, showcasing its importance in enhancing our understanding of weather patterns and its potential applications across various fields.
