A theoretical model that describes the power of a scattered Global Positioning System (GPS) signal as function geometrical and environmental parameters has been developed. This is based on bistatic radar equation derived using geometric optics limit Kirchhoff approximation. The waveform (i.e., time-delayed obtained in delay-mapping technique) depends wave-slope probability density function, which turn wind. Waveforms for aircraft altitudes velocities indicate within interval 5-15 km are best...

In traditional GNSS applications, signals arriving at a receiver's antenna from nearby reflecting surfaces (multipath) interfere with the received directly satellites which can often result in reduction of positioning accuracy. About two decades ago researchers produced an idea to use reflected for remote-sensing applications. this new concept transmitter together receiver capable processing scattered opportunity becomes bistatic radar. By properly signal, system be configured either as...

Measurements of soil moisture, both its global distribution and temporal variations, are required to study the water carbon cycles. A network in situ moisture stations is needed supplement datasets from satellite sensors. We demonstrate that signals routinely recorded by Global Positioning System (GPS) receivers for precise positioning applications can also be related surface variations. Over a three month interval, GPS‐derived estimates 300 m 2 area closely match fluctuations top 5 cm...

Snow is an important component of the climate system and a critical storage in hydrologic cycle. However, situ observations snow distribution are sparse, remotely sensed products imprecise only available at coarse spatial scale. GPS geodesists have long recognized that can affect signal, but it has not been shown receiver placed standard geodetic orientation be used to measure depth. In this paper, changes depth clearly tracked corresponding multipath modulation signal. Results for two...

Abstract The Cyclone Global Navigation Satellite System (CYGNSS) is a new NASA earth science mission scheduled to be launched in 2016 that focuses on tropical cyclones (TCs) and convection. mission’s two primary objectives are the measurement of ocean surface wind speed with sufficient temporal resolution resolve short-time-scale processes such as rapid intensification phase TC development ability measurements penetrate through extremely high precipitation rates typically encountered inner...

Measurements of soil moisture at various spatial and temporal scales are needed to study the water carbon cycles. While satellite missions have been planned measure global scales, these also need ground-based data validate their observations retrieval algorithms. Here, we demonstrate that signals routinely recorded by Global Positioning System (GPS) receivers installed crustal deformation for geophysical studies could be used provide a network sensors. The sensitivity is seen in reflected...

Instrumentation and retrieval algorithms are described which use the forward scattered range-coded signals from global positioning system (GPS) radio navigation for measurement of sea surface roughness. This roughness has long been known to be dependent upon wind speed. Experiments were conducted aircraft along TOPEX ground track over experimental truth buoys. These flights used a receiver capable recording cross-correlation power in reflected signal. The shape this distribution was then...

Abstract A small-slope approximation (SSA) is used for numerical calculations of a radar backscattering cross section the ocean surface both K u - and C-bands various wind speeds incident angles. Both lowest order SSA one that includes next-order correction to it are considered. The were made by assuming surface-height spectrum Elfouhaily et al fully developed seas. Empirical scattering models CMOD2-I3 SASS-II comparison. Theoretical in good overall agreement with experimental data...

Reflected Global Positioning System (GPS) signals can be used to infer information about soil moisture in the vicinity of GPS antenna. Interference direct and reflected causes composite signal, observed using signal-to-noise ratio (SNR) data, undulate with time while satellite ascends or descends at relatively low elevation angles. The change affects both phase SNR modulation pattern its magnitude. In order more thoroughly understand mechanism how leads a modulation, we built an...

Global Positioning System (GPS) multipath signals can be used to infer volumetric soil moisture around a GPS antenna. While most users concentrate on the signal that travels directly from satellite antenna, is reflected by nearby surfaces contains information about environment surrounding The interference between direct and produces modulation observed in temporal variations of signal-to-noise ratio (SNR) data recorded receiver. Changes dielectric constant soil, which are associated with...

The Cyclone Global Navigation Satellite System (CYGNSS) is a spaceborne mission concept focused on tropical cyclone (TC) inner core process studies. CYGNSS attempts to resolve the principle deficiencies with current TC intensity forecasts, which lies in inadequate observations and modeling of core. consists 8 GPS bistatic radar receivers deployed separate nanosatellites. primary science driver rapid sampling ocean surface winds cyclones.

A sea ice detection algorithm developed using the U.K. TechDemoSat-1 (U.K. TDS-1) global navigation satellite systems (GNSSs)-reflectometry data over Arctic and Antarctic regions is presented. It based on measuring similarity of received GNSS reflected waveform or delay Doppler map (DDM) to coherent reflection model waveform. Over open ocean, scattered signal has a diffusive, incoherent nature; it described by rough surface scattering geometric optics Gaussian statistics for ocean slopes....

The bistatic radar equation currently used for simulating surface-reflected waveforms or delay-Doppler maps (DDMs), produced by signals of opportunity from global navigation satellites system (GNSS) communication satellites, was previously derived under some limiting assumptions. One them the use Kirchhoff approximation in a geometric optics limit that assumes strong diffuse (noncoherent) scattering typical very rough surfaces. This would produce an incorrect result case weak scattering,...

Fully polarimetric radars have advantages compared to more conventional single-polarization when measuring ocean wave characteristics. However, the theoretical analysis of full-polarization radar scattering frequently presents a challenge. For example, classical composite model fails correctly predict cross-polarization components normalized cross section (NRCS). The new version numerical implementation small slope approximation second order, SSA2, is presented in this paper. SSA2 predicts...

Abstract Snow is a critical storage component in the hydrologic cycle, but current measurement networks are sparse. In addition, heterogeneity of snow requires surveying larger areas to measure areal average. We presented measurements using GPS interferometric reflectometry (GPS‐IR). GPS‐IR measures large area (~100 m 2 ), and existing installations around world have potential expand networks. uses standard, geodetic installation surface via reflected signal. reported depth made at Niwot...

Global navigation satellite system (GNSS) reflectometry has emerged recently as a promising remote sensing tool to retrieve various geophysical parameters of the Earth's surface. GNSS-reflected signals, after being received and processed by airborne or spaceborne receiver, are available delay correlation waveforms delay-Doppler maps (DDMs). In case rough ocean surface, those characteristics can be related rms L-band limited slopes surface waves and, from there, wind speed. The raw signal...

The potential to use GPS signal-to-noise ratio (SNR) data estimate changes in vegetation surrounding a ground-based antenna is evaluated. A 1-D plane-stratified model that simulates the response of SNR both soil moisture and presented. validated against observations from four field sites with varying cover. Validation shows average correlation between modeled observed higher than concurrent different satellite tracks at site. also reproduces variations metrics amplitude, phase, effective...

Global positioning system (GPS) signals reflected from the ocean surface can be used for various remote sensing purposes. Some possibilities include measurements of roughness characteristics which rms wave slopes, wind speed, and direction could determined. In this paper, GPS that were collected using aircraft with a delay mapping receiver are to explore possibility determining speed during flights Hurricanes Michael Keith in October 2000. To interpret data, theoretical model is describe...

Stemming from research using GPS bistatically scattered signals to remotely sense ocean surface wind speeds, the authors provide proof-of-concept results for determining soil moisture reflected signatures. They present land-reflected power measurements an aircraft-mounted, modified receiver and recorded in different environments. The estimated peak signal is shown correlate with land features. As a first attempt moisture, mean compared situ moisture. Recommendations further analysis retrieve...

This paper describes a new research effort to extend the application of Global Positioning System (GPS) signal reflections, received by airborne instruments, cryospheric remote sensing. Their experimental results indicate that reflected GPS signals have potential provide information on presence and condition sea fresh-water ice as well freeze/thaw state frozen ground. They show from aircraft experiments over pack near Barrow, Alaska indicating correlation between forward-scattered returns...

Reflectometry of signals opportunity such as those emitted by a global navigation satellite system, known GNSS-R, has been developed over the past years technique with great potential for ocean scatterometry, among other applications. Different approaches have proposed to use GNSS-R remote sensing surface roughness. One them is based on deriving some descriptor/metric from measured delay-Doppler map (DDM) and directly relating it geophysical property scattering surface. For instance,...

Many of the currently used models scattering from a rough ocean surface are designed for regime strong diffuse that takes place at large Rayleigh parameter Ra. Using them case weak, or even moderate is characterized by Rα≲ 1 would lead to an incorrect result. At same time, practical applications, it important describe transition partially coherent completely noncoherent, in terms bistatic radar cross section σ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML"...