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SCoBi-Veg stands for Signals of opportunity Coherent Bistatic scattering model for Vegetated terrains. It simulates polarimetric reflectometry of vegetation canopy over a flat ground using a Monte Carlo scheme. The model is aimed at assessing the value of navigation and communication satellite Signals of Opportunity in a range of frequencies from P- to S-bands for remote sensing of a number of geophysical land parameters such as soil moisture and biomass. A fully polarimetric expression for bistatic scattering from a vegetation canopy is first formulated for a general case and is then specialized to the practical case of ground-based/low-altitude platforms with passive receivers overlooking vegetation using the signals transmitted from large distances. Using analytical wave theory in conjunction with distorted Born approximation, the transmit and receive antenna effects (i.e., polarization crosstalk/mismatch, orientation, and altitude) are explicitly accounted for. The forward model developed here enables the understanding of the effect of different geophysical parameters and system configurations on the coherent and incoherent components of the reflected signatures. It can thus help developing robust inverse algorithm for extraction of soil moisture and biomass. The model is applied to P-band signals of geostationary communication satellites to describe polarimetric reflections from tree canopies as observed from down-looking platforms at various altitudes. The relative contributions of diffuse and specular scattering on total reflected power and reflectivity are quantified for various observing scenarios.

It is critically important for the existence of life on Earth to understand and reliably predict how our planet is changing on a long-term basis. Over the past few decades, NASA, and other space agencies, have developed technologies and methodologies to measure Earth science parameters on a global scale with high spatial and temporal resolutions. NASA’s Goddard Space Flight Center (GSFC) has significantly contributed to this cause. In this report, we plan to review the microwave, millimeter wave and optical sensors technology developed, validated, and patented at GSFC for Earth monitoring and analyzing data to create more accurate predictive models. Since its foundation, GSFC has been in the business of launching many spacecraft to explore Earth and the solar system. A number of novel technologies developed at GSFC have been embedded into sensor instruments on these exploring missions. This report will explore some of these innovations, many of which have been patented. GSFC is interested in licensing these patented technologies to U.S. industries and participating in collaborating discussions with global entities.

A coherent bistatic vegetation scattering model, based on a Monte Carlo simulation, is being developed to simulate polarimetric bi-static reflectometry at VHF/UHF-bands (240–270 MHz). The model is aimed to assess the value of geostationary satellite signals of opportunity to enable estimation of the Earth's biomass and root-zone soil moisture. An expression for bistatic scattering from a vegetation canopy is derived for the practical case of a ground-based/low altitude platforms with passive receivers overlooking vegetation. Using analytical wave theory in conjunction with distorted Born approximation (DBA), the transmit and receive antennas effects (i.e., polarization, orientation, height, etc.) are explicitly accounted for. Both the coherency nature of the model (joint phase and amplitude information) and the explicit account of system parameters (antenna, altitude, polarization, etc) enable one to perform various beamforming techniques to evaluate realistic deployment configurations. In this paper, several test scenarios will be presented and the results will be evaluated for feasibility for future biomass and root-zone soil moisture application using geostationary communication satellite signals of opportunity at low frequencies.

Flying qubit designs have emerged as a new approach for adding dynamic control to solid-state qubit implementations including heterostructure-based electron gas implementations. The flying qubit approach utilizes the potential minimum of a SAW wave for the capture and transport of a single or few electron(s) from a reduced dimensionality electron pool. Many details of the interactions between the dynamic potential well induced by propagating SAW wave with the reduced dimensionality electron pool are unknown. In the present work, we investigate the effect of the SAW wave longitudinal component modelled as perturbation to the k-space momentum in the transport direction for a heterostructure-based finite width 1D channel. A new quadratic expression for the k-space momentum and a new expression for the number density are reported for the first time. A major effect of positive or negative longitudinal perturbations on electron transport is the introduction of shifts that can affect both quantum channel accessibility and number density allowed occupations.

Advanced Digital Beamforming (DBF) Synthetic Aperture Radar (SAR) technology is an area of research and development pursued at the NASA Goddard Space Flight Center (GSFC). Advanced SAR architectures enhances radar performance and opens a new set of capabilities in radar remote sensing. DBSAR-2 and EcoSAR are two state-of-the-art radar systems recently developed and tested. These new instruments employ multiple input-multiple output (MIMO) architectures characterized by multi-mode operation, software defined waveform generation, digital beamforming, and configurable radar parameters. The instruments have been developed to support several disciplines in Earth and Planetary sciences. This paper describes the radars advanced features and report on the latest SAR processing and calibration efforts.

The main goal of this research is to design, fabricate, and test deployable VHF antennas for 6U Cubesat platforms to enable validation of root zone soil moisture (RZSM) estimation algorithms for signal of opportunity (SoOp) remote sensing over the 240–270MHz frequency band. The proposed work provides a strong foundation for establishing a technology development path for maturing a truly global direct surface soil moisture (SM) and RZSM measurement system (Figure 1) over a variety of land covers with limited density restrictions. In SoOp methodology, signals transmitted by already existing transmitters (known as transmitters of opportunity, in this case the Military Satellite Communication (MilSatCom) System's UHF Follow-On program) are utilized to measure properties of reflecting targets by recording reflected signals using a simple passive microwave receiver.

This paper reports on a recent field campaign that aims to collect time-series multi-frequency microwave data over winter wheat during the entire growth cycle. The data are being collected to characterize vegetation dynamics and to quantify its effects on soil moisture retrievals. A C-band radar was recently incorporated within the existing L-band radar/radiometer system called ComRAD (SMAP's ground based simulator) and an additional VHF receiver is being constructed as well. With C-band's ability to sense vegetation details and VHF's root-zone soil moisture within ComRAD's footprint, we will have an opportunity to test our ‘discrete scatterer’ vegetation models and parameters at various surface conditions. The purpose of this investigation is to determine optical depth and effective scattering albedo of vegetation of a given type (i.e. winter wheat) at various stages of growth that are needed to refine soil moisture retrieval algorithms for the SMAP mission.

The instrument is currently under development with science flights planned aboard a Beechcraft Super King Air B200 aircraft. The flights will include NASA's SLAP L-Band radar and radiometer to provide coincident measurements. The instrument comprises two dual-polarization antennas (one each for sky and Earth views), a four-channel RF receiver with internal calibration network, and a digital receiver to correlated signal pairs. Brass boards of the P-band receivers have been fabricated and have been used to monitor P-Band satellite transmissions to develop spectrum population statistics and survey unwanted RFI. These results have led to requirements for channel processing and RFI mitigation in both the RF and digital portions of the system. The instrument will store complex correlation coefficients for all pairs of elements formed by the two dual-polarization antennas. These coefficients will be averaged in ground processing to reduce noise prior to estimating reflectivity and retrieving soil moisture. A “Smart Antenna” approach will be used in ground processing to steer an antenna pattern null towards the unwanted reflected signal as seen by the sky-view antenna. The background and status of the SoOp-AD instrument will be discussed along with sources of error and mitigation strategies.

This paper presents an integrating of highly transparent X band reflectarray on the cover glass of solar panels. Two types of element geometries are studied, and optimal unit cell element, effect of the solar cell on the antenna, feed consideration, and final design data are presented. The overall transparency and aperture efficiency of the design are more than 90% and 40% respectively, making it a promising solution as a high gain conformal satellite antenna.

In this study, we present an improved genetic algorithm (GA) to design user-specified filters housed in a waveguide of arbitrary cross-sectional dimensions. An edge-based finite element method (FEM) is employed as the forward solver for the problem. Additionally, the structures generated via the GA are easily constructed using standard printed circuit board fabrication techniques. Two of the major improvements to the GA are: (1) a technique for enhancing the GA's ability to avoid local minima and (2) a fine-tuning mechanism which allows the GA to more efficiently seek out a minimum once a low error has been obtained. Using the aforementioned techniques, numerical/experimental results are presented for notch, low pass, high pass, and bandpass filters. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.

This paper describes objectives and recent progress on the development of the EcoSAR, a new P-band airborne radar instrument being developed at the NASA/ Goddard Space Flight Center (GSFC) for the polarimetric and interferometric measurements of ecosystem structure and biomass. These measurements support science requirements for the study of the carbon cycle and its relationship to climate change. The instrument is scheduled to be completed and flight tested in 2013.

This paper discusses Innovative wavelet-based filter banks designed to enhance the analysis of super resolution Synthetic Aperture Radar (SAR) images using parametric spectral methods and signal classification algorithms, SAR finds applications In many of NASA's earth science fields such as deformation, ecosystem structure, and dynamics of Ice, snow and cold land processes, and surface water and ocean topography. Traditionally, standard methods such as Fast-Fourier Transform (FFT) and Inverse Fast-Fourier Transform (IFFT) have been used to extract Images from SAR radar data, Due to non-parametric features of these methods and their resolution limitations and observation time dependence, use of spectral estimation and signal pre- and post-processing techniques based on wavelets to process SAR radar data has been proposed. Multi-resolution wavelet transforms and advanced spectral estimation techniques have proven to offer efficient solutions to this problem.

In this paper the Finite Element Method (FEM) is presented for mass/volume gauging of a fluid in a tank subjected to zero or microgravity conditions. In this approach first mutual capacitances between electrodes embedded inside the tank are measured. Assuming the medium properties the mutual capacitances are also estimated using FEM approach. Using proper non-linear optimization the assumed properties are updated by minimizing the mean square error between estimated and measured capacitances values. Numerical results are presented to validate the present approach.

NASA's mission to Moon, Mars, and Beyond envisions landing of a light weight measurement platform on the planetary surface. The Multi-Wavelength Dielectrometer (MWD) on-board consists of essential electronics and metallic plates acting as electrodes attached to the body of such platform. An electric signal applied to one of the electrodes acting as a cathode sets up electric field pattern (in the soil medium) between the cathode and other electrodes acting as anodes. The electrodes are swept through multiple wavelengths (1Hz-1MHz) and the electric current drawn by the electrodes is measured at each frequency. The measured current whose amplitude and phase depend upon electrode spacing, dielectric constant of the subsurface soil, and the frequency is then used to estimate electrical properties of the soil. In this paper the MWD sensor that will measure the dielectric properties of Moon/Mars s soil is presented. A procedure to process the MWD measured data for extracting the soil properties is also described. Assuming the subsurface soil structure as multilayer strata having varying electric properties, an electric equivalent circuit of the multiple electrodes configuration placed on a multi-layer soil sample is obtained. The current drawn by the equivalent circuit from the low frequency signal generator is then calculated. By minimizing the difference between the model s estimated current and measured MWD data the electric properties of soil samples are extracted. Experimental and simulated results will be presented to validate the proposed procedure for extracting soil properties.

A general optimization scheme for the autonomous design of transverse waveguide filters has been presented. By employing a novel genetic algorithm in conjunction with a commercial FEM software package, the technique demonstrated here is readily applicable to a wide variety of waveguide filter problems. Specifically, the method was shown to yield excellent results for notch and bandpass filter responses when comparing ideal, simulated, and measured |S/sub 21/| responses.