Title: Progress on the 8-40 GHz Wideband Instrument for Snow Measurements
Presenting Author: Timothy Durham
Organization: Harris Corporation
Co-Author(s): Chris Trent, Kerry Speed, Ken Vanhille, Paul Racette, Quenton Bonds, Hans-Peter Marshall, Leung Tsang, Felix Miranda, Kevin Lambert

Abstract:
A 2010 Instrument Incubator Program (IIP) designed, built and tested a wideband instrument (8-40 GHz) that utilizes a unique antenna capable of supporting the complete bandwidth. The Wideband Instrument for Snow Measurement (WISM) was designed to support the Tier III Snow and Cold Land Processes (SCLP) mission as defined by the Decadal Survey. WISM comprises a dual-frequency X- and Ku-band SAR, and dual-frequency Ku- and Ka-band radiometer. The IIP team was led by the Harris Corporation teamed with engineers from Nuvotronics, NASA Goddard/Glenn and scientists from Boise State University and the University of Washington. The capability to perform multiple measurements in a single instrument was achieved by combining a wideband aperture with a software reconfigurable radar/radiometer aircraft payload capable of performing measurements at multiple frequencies for each function. The broad bandwidth of this instrument, particularly in the antenna technology employed, allows flexibility in the number of frequencies used to measure Snow Water Equivalent (SWE). Potential improvements in the estimation of SWE and its spatial/temporal variability have significant implications for hydrologic modeling and water resources management on a global scale. The innovative manufacturing method for the wideband antenna reduces the size and weight of the payload, adds additional functionality, and allows cost/power to remain relatively unchanged. The reflector feed antenna developed for this IIP is based on the innovative current sheet antenna (CSA) technology that has been under development at Harris for over 15 years. The CSA is a wideband phased array technology capable of achieving 10:1 bandwidth with a large scan volume. In collaboration with Nuvotronics, the CSA was engineered to be compatible with Nuvotronics, LLC's PolyStrata manufacturing process which was used to fabricate the antenna and integrated feed network. This process has numerous benefits over traditional manufacturing techniques. Among these are that it allows the fabrication boundary to be moved to well above 18 GHz and the integrated antenna/beamformer greatly reduces SWaP requirements. Two 8-40 GHz antenna feeds were built on this IIP. These will be used to perform flight experiments intended to validate the instrument's utility for measuring SWE on a newly awarded 2013 IIP. Details of the measured performance of these antennas will be presented at the ESTF. Another major part of this effort was the development of a multi-band radar and radiometer instrument. The radiometer was designed and built at Goddard Space Flight Center while the radar was developed at the Harris Corporation. Both instruments have been completed and extensive lab testing performed on all major subsystems. The remaining work to complete the WISM instrument largely involves integrating the two component instruments with the wideband antenna. Considerable preparation for the airborne testing of the integrated instrument consisting of the antenna, radars, and radiometers was also carried out on the 2010 IIP. The goal of successful performance in the airborne environment has been a major consideration in the design of the entire instrument.