The NASA Earth Observing System Simulators Suite (NEOS<sup>3</sup>) is a modular framework of forward simulations tools for remote sensing of Earth’s Atmosphere from space. It was initiated as the Instrument Simulator Suite for Atmospheric
Remote Sensing (ISSARS) under the NASA Advanced Information Systems Technology (AIST) program of the Earth
Science Technology Office (ESTO) to enable science users to perform simulations based on advanced atmospheric and
simple land surface models, and to rapidly integrate in a broad framework any experimental or innovative tools that they
may have developed in this context. The name was changed to NEOS<sup>3</sup> when the project was expanded to include more advanced modeling tools for the surface contributions, accounting for scattering and emission properties of layered
surface (e.g., soil moisture, vegetation, snow and ice, subsurface layers). NEOS<sup>3</sup> relies on a web-based graphic user
interface, and a three-stage processing strategy to generate simulated measurements. The user has full control over a
wide range of customizations both in terms of a priori assumptions and in terms of specific solvers or models used to
calculate the measured signals.This presentation will demonstrate the general architecture, the configuration procedures
and illustrate some sample products and the fundamental interface requirements for modules candidate for integration.
The thickness of Arctic sea ice plays a critical role in Earth's climate and ocean circulation. An accurate measurement of this parameter on synoptic scales at regular intervals would enable characterization of this important component for the understanding of ocean circulation and the global heat balance. Presented in this paper is a low frequency VHF interferometer technique and associated radar instrument design to measure sea ice thickness based on the use of backscatter correlation functions. The sea ice medium is represented as a multi-layered medium consisting of snow, sea-ice and sea water, with the interfaces between layers characterized as rough surfaces. This technique utilizes the correlation of two radar waves of different frequencies and incident and observation angles, scattered from the sea ice medium. The correlation functions relate information about the sea ice thickness. Inversion techniques such as the genetic algorithm, gradient descent, and least square methods, are used to derive sea ice thickness from the phase information related by the correlation functions. The radar instrument is designed to be implemented on a spacecraft and the initial test-bed will be on a Twin Otter aircraft. Radar system and instrument design and development parameters as well as some measurement requirements are reviewed. The ability to obtain reliable phase information for successful ice thickness retrieval for various thickness and surface interface geometries is examined.
Imaging through random media is an important problem with many applications including optical remote sensing and bio-optics. As the optical depth gets larger, the imaging resolution and contrast deteriorates because of the effect of scattering. In this paper, we present the solution to the vector radiative transfer equation (VRTE) and its application to the optical imaging problem. Since the incoherent component created by the scattering in random media is responsible for the deterioration of the quality of images, several techniques are proposed to improve the imaging by reducing the incoherent component. The Off-Axis Intensity Subtraction (OAIS) and Cross-Polarization Intensity Subtraction (CPIS) imaging techniques are based on the fact that off-axis and cross polarization contains most of the incoherent component. Photon Density Waves (PDW) is a frequency-domain method which exhibits less effect of multiple scattering from the random media. We investigate the techniques mentioned above using numerical solution of VRTE and show the effectiveness, the limitations and the conditions of these techniques. Because we consider the polarized pulse wave case, we also discuss the time-domain behavior and the application of time-gating to the imaging problem. The time-gating method is investigated in both position and duration. Since in practice an array of detectors are often used, we also include the effect of Field Of View of a detector (pixel FOV) in our calculations. We quantitatively measure the performance of imaging techniques by contrast. Also, we apply these techniques to numerical simulations of cross images and show the improvement of the quality of the images.
We have studied the polarization characteristics of light scattered from randomly distributed spherical particles using the 4x4 Mueller matrix. The experimental system consists of a Helium-Neon laser, polarizers (vertical, horizontal, 45-degree linear, left-hand circular) and six analyzers (vertical, horizontal, 45-degree linear, 135-degree linear, right-hand circular, left-hand circular). If the six polarized states of the scattered light for a given incident polarization are measured with analyzers, we can calculate the Stokes vector. By repeating this measurement for four independent incident polarizations, we can obtain the complete Mueller matrix. Random media consist of spherical particles of different concentrations suspended in water. The numerical study is based on the complete solution of the radiative transfer equation. Using the discrete ordinate method and matrix solver, we obtain the Stokes vector for a given incident polarization. By calculating Stokes vector for four independent polarizations, we can obtain a full Mueller matrix. The experimental results are compared with the numerical analysis.
Using radiative transfer, we investigate linear and circular polarized light normally impinging a plane-parallel medium containing a random distribution of identically sized latex spheres in water. The focus of this study is to understand fundamental properties of polarized light scattering. In particular, we analyze backscattered and transmitted flux responses computed form direct numerical simulations. Form these numerical computations, we observe that circular polarized light depolarizes at a slower rate than linear polarized light. In addition, circular polarized light shows a more noticeable dependence on the size of the scatterers than linear polarized light. Furthermore, the helicity flip observed in circular polarized backscattered light is a fundamental phenomenon manifested by low order scattering.