Using Additional Moderator to Control the Footprint of a COSMOS Rover for Soil Moisture Measurement

Badiee, Amir, Wallbank, John R., Pulido Fentanes, Jaime , Trill, Emily, Scarlet, Peter, Zhu, Yongchao, Cielniak, Grzegorz, Cooper, Hollie, Blake, James R., Evans, Jonathan G., Zreda, Marek, Markus, Köhli, Pearson, Simon, , , , and , (2021) Using Additional Moderator to Control the Footprint of a COSMOS Rover for Soil Moisture Measurement. Water Resources Research, 57 (6). e2020WR028478. ISSN 0043-1397

Full content URL: https://doi.org/10.1029/2020WR028478

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Using Additional Moderator to Control the Footprint of a COSMOS Rover for Soil Moisture Measurement
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Abstract

Cosmic Ray Neutron Probes (CRNP) have found application in soil moisture estimation
due to their conveniently large (>100 m) footprints. Here we explore the possibility of using
high density polyethylene (HDPE) moderator to limit the field of view, and hence the footprint,
of a soil moisture sensor formed of 12 CRNP mounted on to a mobile robotic platform
(Thorvald) for better in-field localisation of moisture variation. URANOS neutron scattering
simulations are used to show that 5 cm of additional HDPE moderator (used to shield the upper
surface and sides of the detector) is sufficient to (i), reduce the footprint of the detector
considerably, (ii) approximately double the percentage of neutrons detected from within 5 m
of the detector, and (iii), does not affect the shape of the curve used to convert neutron counts
into soil moisture. Simulation and rover measurements for a transect crossing between grass
and concrete additionally suggest that (iv), soil moisture changes can be sensed over a length
scales of tens of meters or less (roughly an order of magnitude smaller than commonly used
footprint distances), and (v), the additional moderator does not reduce the detected neutron
count rate (and hence increase noise) as much as might be expected given the extent of the
additional moderator. The detector with additional HDPE moderator was also used to conduct
measurements on a stubble field over three weeks to test the rover system in measuring spatial
and temporal soil moisture variation.

Keywords:Cosmic Neutron, Cosmic-ray Soil Moisture Sensor, Neutron Moderator, COSMOS Rover, Footprint
Subjects:H Engineering > H671 Robotics
F Physical Sciences > F330 Environmental Physics
D Veterinary Sciences, Agriculture and related subjects > D443 Water Resource Management
D Veterinary Sciences, Agriculture and related subjects > D400 Agriculture
D Veterinary Sciences, Agriculture and related subjects > D750 Soil as an Agricultural medium
Divisions:College of Science
College of Science > Lincoln Institute for Agri-Food Technology
College of Science > School of Engineering
ID Code:45017
Deposited On:10 Jun 2021 15:22

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