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Remote Sens. 2015, 7(11), 15269-15294; doi:10.3390/rs71115269

An Autonomous System to Take Angular Thermal-Infrared Measurements for Validating Satellite Products

1
Earth Physics and Thermodynamics Department, University of Valencia, 50 Dr. Moliner, E-46100 Burjassot-Valencia, Spain
2
Instituto Universitario Centro de Estudios Ambientales del Mediterráneo–CEAM-UMH, 14 Charles Darwin, E-46980 Paterna-Valencia, Spain
*
Author to whom correspondence should be addressed.
Academic Editors: Janet Nichol and Prasad S. Thenkabail
Received: 30 July 2015 / Revised: 22 October 2015 / Accepted: 10 November 2015 / Published: 13 November 2015
View Full-Text   |   Download PDF [1157 KB, uploaded 13 November 2015]   |  

Abstract

An autonomous system for field land surface temperature (LST) measurements taken at different observation angles was developed to be deployed easily at any conventional meteorological tower station. The system permits ground-truth data to be acquired on a continuous basis, and angularly scans land and sky hemispheres with a single thermal-infrared (TIR) radiometer. This paper describes the autonomous angular system and the methodology to assess ground-truth LST and relative-to-nadir emissivity data from system measurements. Ground-truth LSTs were used to validate satellite-retrieved LST products at two experimental sites (rice crop and shrubland areas). The relative-to-nadir emissivity values were used to analyze the anisotropy of surface emissive properties over thermally-homogeneous covers. The EOS-MODIS MOD11_L2/MYD11_L2 LST product was evaluated and shown to work within expected uncertainties (<2.0 K) when tested against the system data. A slight underestimation of around −0.15 K was observed, which became greater for the off-nadir observation angles at the shrubland site. The system took angular measurements for the different seasonal homogeneous covers at the rice crop site. These measurements showed emissivity angular anisotropies, which were in good agreement with previously published data. The dual-view ENVISAT-AATSR data reproduced them, and revealed that the system data collected for thermally-homogeneous surfaces could be used to test future satellite TIR sensors with multi-angular or bi-angular capabilities, like the forthcoming SLSTR on board Copernicus Sentinel-3A. View Full-Text
Keywords: thermal-infrared; land surface temperature; angular system; emissivity; satellite product Validation; emissivity anisotropy thermal-infrared; land surface temperature; angular system; emissivity; satellite product Validation; emissivity anisotropy
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Niclòs, R.; Valiente, J.A.; Barberà, M.J.; Coll, C. An Autonomous System to Take Angular Thermal-Infrared Measurements for Validating Satellite Products. Remote Sens. 2015, 7, 15269-15294.

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