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Center Independent Research & Development: GSFC IRAD

Beam Steering and Synthetizing on a Single-Dish Radiometer (SLPR)

Active Technology Project

Project Introduction

The primary objective of this work is to define the next generation sensor: a sensor that will continue the measurement of ocean salinity demonstrated by Aquarius and will address issues identified in current observations, such as:

       a.  The need to reduce uncertainty in cold water;

       b.  The need for improved spatial resolution to address applications in the coastal zone and near the ice edge where effects of climate change are most likely to be important.

The general approach is to examine options for improved spatial resolution (e.g. better antennas and/or interferometry) and frequencies in addition to the primary L-band to improve accuracy of the science product.  Specifically, this work will:

       1) Define  the science requirements and associated instrument performance requirements;

        2) Conduct a science/engineering study to identify risks and benefits in the choice of observing frequencies (P-band, L-band, S-band, C-band);

       3)  Conduct a trade study to inform the choice between a single, multi-octave feed and optimized, single-frequency ones;

       4)  Review technology to define options among pushbroom and conical scanning conventional radiometers and interferometric radiometers [Martin-Neira et al., 2014];

       5) Assuming a conventional radiometer, identify a preliminary design for the primary reflector antenna and the illuminating feed(s);

       6) Determine the need for a passive (radiometer) and active (radar) combination and if so, at which frequencies.

This study will cover the early stages of instrument development, outlining a reasonable approach to a future mission with the aim of enhancing Goddard’s competiveness in the competition for a future flight implementation. It will also assess the present-day TRL of key technologies, to help identify areas where development funds could be more fruitfully invested.

At the end of this project we will have gained a better understanding of the design requirements and technology challenges for the next-generation sea salinity instrument.

The goals of the FY2018 research are to:

  • Demonstrate that the wide beams of a multi-feed antenna can be combined via a correlator to synthetize a single narrow footprint and that the resulting instrument can be made frequency-agile over 5-10% of the central frequency at least at L- and P-bands.
  • Develop the algorithms needed to produce one (or multiple) high-resolution beams from a multi-beam coarser-resolution instrument.
  • Analyze, design and possibly assemble a scale model for a P-band 12 meter single-dish, N-feed interferometer (where N is a yet-to-be-determined number between 3 and 8). Assemble N wideband radiometers from commercially available components
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