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Reflectometry and Occultation Sounding Using GNSS and Other Opportunity Signals

A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Remote Sensors".

Deadline for manuscript submissions: closed (31 March 2018) | Viewed by 11291

Special Issue Editors


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Guest Editor
NASA - Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91125, USA
Interests: remote sensing of atmospheric, ionospheric, and geomagnetic perturbations; GNSS signal processing; radio science remote sensing for the earth and planetary science; wavelet-based pattern classifications
Signal Theory and Communications Department, Universitat Politècnica de Catalunya, Campus Nord UPC, D4-016, C/Jordi Girona, 1-3, 08034 Barcelona, Spain
Interests: remote sensing; passive microwave remote sensing, modeling, and simulation; image processing; GNSS reflectometry; small satellite systems

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Guest Editor
Department of Physical and Environmental Sciences, Texas A and M University - Corpus Christi, Corpus Christi, TX 78412, USA
Interests: spaceborne and airborne GNSS radio occultation sounding for neutral atmosphere studies

Special Issue Information

Dear Colleagues,

Global Navigation Satellite System reflectometry (GNSS-R) and GNSS radio occultation (GNSS-RO) were originally proposed about two decades ago, and significant advances have been made since then. The use of Global Positioning System (GPS) signals as signals of opportunity to perform ocean scatterometry was originally proposed in 1988, and then in 1993 for mesoscale altimetry. The first evidence that GPS navigation signals could be collected and tracked after being scattered on the sea surface dates back to 1991, when a French aircraft was testing a GPS receiver. In 1996, it was proposed to use the reflection of the GPS signals from the oceans to extend ionospheric measurements in satellites carrying single-frequency radar altimeters.

On the other hand, since the GPS/MET satellite mission in 1995, GNSS radio occultation technique has emerged as a powerful approach for sounding the global atmosphere with high resolution and precision in all weather conditions. Various RO space missions have proved successful in addressing a broad range of scientific questions on climate monitoring, operational weather prediction, ionospheric research, space weather forecasting, calibrating other observing systems, and geodesy.

With the advent of other Global or Regional Navigation Satellite Systems (GNSS or RNSS) such as GLONASS, Galileo, Beidou, IRNSS, and QZSS, and satellite-based augmentation systems including WAAS, EGNOS, MSAS, etc., the number of transmitting satellites is dramatically increasing, thus providing potentially even more simultaneous observations.

Since the early days of GNSS Reflectometry, different techniques have been developed to make better use of the signal properties. Besides the originally proposed applications (wind speed and altimetry), many new applications have been developed, including wind speed and direction, ice altimetry, soil moisture, vegetation height and biomass, snow depth, etc. The NASA CYGNSS mission, launched in December 2016, measures the ocean surface wind field with unprecedented temporal resolution and spatial coverage, and also opens new applications for wetlands and soil moisture monitoring, etc.

In the past years, the use of other opportunity signals away from L-band has also taken off, such as P- and X-band, using satellite radio and TV signals, but also ground transmitters. This opens even more new applications given the larger bandwidth and higher signal-to-noise ratio, and/or the longer wavelength signal capable of deeper penetration into the ground. Correspondingly, the sensor technologies for various opportunity signals are developed including the experimental setup.

This special issue seeks to publish original contributions in theory, methodology, sensors, instrumentation, experiments, retrieval techniques, and scientific applications in both the reflectometry and occultation from ground-based, drone-based, airborne, or space-borne platforms.

Dr. Yu-Ming Yang
Dr. Hyuk Park
Dr. Feiqin Xie
Guest Editors

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Keywords

  • GNSS-R
  • reflectometry, signals of opportunity
  • sensors
  • instrumentation, interferometric
  • antenna arrays
  • ocean winds
  • ocean altimetry
  • soil moisture
  • biomass
  • wetlands
  • GNSS-RO
  • radio occultation, climate, weather, spaceborne, airborne
  • ground-based, ionosphere, space weather

Published Papers (2 papers)

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Research

16 pages, 7796 KiB  
Article
Analysis of Key Issues on GNSS-R Soil Moisture Retrieval Based on Different Antenna Patterns
by Fei Li, Xuefeng Peng, Xiuwan Chen, Maolin Liu and Liwen Xu
Sensors 2018, 18(8), 2498; https://doi.org/10.3390/s18082498 - 1 Aug 2018
Cited by 12 | Viewed by 3176
Abstract
GNSS-R (Global Navigation Satellite System-Reflectometry) has been demonstrated to be a new and powerful tool to sense soil moisture in recent years. Multi-antenna pattern and single-antenna pattern have been proposed regarding how to receive and process reflected signals. Great efforts have been made [...] Read more.
GNSS-R (Global Navigation Satellite System-Reflectometry) has been demonstrated to be a new and powerful tool to sense soil moisture in recent years. Multi-antenna pattern and single-antenna pattern have been proposed regarding how to receive and process reflected signals. Great efforts have been made concerning ground-based and air-borne observations. Meanwhile, a number of satellite-based missions have also been implemented. For the in-depth study of soil moisture remote sensing by the technique of GNSS-R, regardless of the extraction methods of the reflected signals or the types of the observation platform, three key issues have to be determined: The specular reflection point, the spatial resolution and the detection depth in the soil. However, in current literatures, there are no comprehensive explanations of the above three key issues. This paper conducts theoretical analysis and formula derivation, aiming to systematically and quantitatively determine the extent of soil moisture being detected in three dimensions from the above-mentioned aspects. To further explain how the three factors behave in the specific application, the results of two application scenarios are shown: (1) a ground-based GPS measurement in Marshall, Colorado, US from the Plate Boundary Observatory, corresponding to single-antenna pattern. The relative location of the specular reflection points, the average area of the First Fresnel Ellipse Clusters and the sensing depth of the time-series soil moisture are analyzed, and (2) an aviation experiment conducted in Zhengzhou to retrieve soil moisture content, corresponding to the multi-antenna pattern. The spatial distribution of soil moisture estimation with a certain resolution based on the flight tracks and the relevant sensing depth are manifested. For remote sensing using GNSS reflected signals, BeiDou is different from GPS mainly in the carrier frequency. Therefore, the results of this study can provide references for China’s future development of the BeiDou-R technique. Full article
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18 pages, 3952 KiB  
Article
3Cat-3/MOTS Nanosatellite Mission for Optical Multispectral and GNSS-R Earth Observation: Concept and Analysis
by Jordi Castellví, Adriano Camps, Jordi Corbera and Ramon Alamús
Sensors 2018, 18(1), 140; https://doi.org/10.3390/s18010140 - 6 Jan 2018
Cited by 8 | Viewed by 7415
Abstract
The 3Cat-3/MOTS (3: Cube, Cat: Catalunya, 3: 3rd CubeSat mission/Missió Observació Terra Satèl·lit) mission is a joint initiative between the Institut Cartogràfic i Geològic de Catalunya (ICGC) and the Universitat Politècnica de Catalunya-BarcelonaTech (UPC) to foster innovative Earth Observation (EO) techniques based [...] Read more.
The 3Cat-3/MOTS (3: Cube, Cat: Catalunya, 3: 3rd CubeSat mission/Missió Observació Terra Satèl·lit) mission is a joint initiative between the Institut Cartogràfic i Geològic de Catalunya (ICGC) and the Universitat Politècnica de Catalunya-BarcelonaTech (UPC) to foster innovative Earth Observation (EO) techniques based on data fusion of Global Navigation Satellite Systems Reflectometry (GNSS-R) and optical payloads. It is based on a 6U CubeSat platform, roughly a 10 cm × 20 cm × 30 cm parallelepiped. Since 2012, there has been a fast growing trend to use small satellites, especially nanosatellites, and in particular those following the CubeSat form factor. Small satellites possess intrinsic advantages over larger platforms in terms of cost, flexibility, and scalability, and may also enable constellations, trains, federations, or fractionated satellites or payloads based on a large number of individual satellites at an affordable cost. This work summarizes the mission analysis of 3Cat-3/MOTS, including its payload results, power budget (PB), thermal budget (TB), and data budget (DB). This mission analysis is addressed to transform EO data into territorial climate variables (soil moisture and land cover change) at the best possible achievable spatio-temporal resolution. Full article
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