ABORT-like detectors: a Bayesian approach

In this paper, we deal with the problem of adaptive radar detection of point-like targets in presence of noise with unknown spectral properties. As customary, we assume that a set of data sharing the same properties of the noise in the cell under test is available. To cope with a limited number of training data, a Bayesian framework is adopted at the design stage. In order to come up with detectors with good rejection capabilities, the possible presence of a fictitious signal under the null hypothesis is modeled probabilistically, as opposite to the conventional ABORT-like approach. Several detectors are devised for the problem at hand, with different complexities. The performance assessment, conducted by means of Monte Carlo simulations, reveals that a good trade-off between detection power and selectivity can be achieved, even assuming a limited number of training data

NASA Capability Roadmaps Executive Summary

This document is the result of eight months of hard work and dedication from NASA, industry, other government agencies, and academic experts from across the nation. It provides a summary of the capabilities necessary to execute the Vision for Space Exploration and the key architecture decisions that drive the direction for those capabilities. This report is being provided to the Exploration Systems Architecture Study (ESAS) team for consideration in development of an architecture approach and investment strategy to support NASA future mission, programs and budget requests. In addition, it will be an excellent reference for NASA's strategic planning. A more detailed set of roadmaps at the technology and sub-capability levels are available on CD. These detailed products include key driving assumptions, capability maturation assessments, and technology and capability development roadmaps

Environmental Control and Life Support (ECLS) Integrated Roadmap Development

This white paper documents a roadmap for development of Environmental Control and Life Support (ECLS) Systems (ECLSS) capabilities required to enable beyond-Low Earth Orbit (LEO) Exploration missions. In many cases, the execution of this Exploration-based roadmap will directly benefit International Space Station (ISS) operational capability by resolving known issues and/or improving overall system reliability. In addition, many of the resulting products will be applicable across multiple Exploration elements such as Multi-Purpose Crew Vehicle (MPCV), Multi-Mission Space Exploration Vehicle (MMSEV), Deep Space Habitat (DSH), and Landers. Within the ECLS community, this white paper will be a unifying tool that will improve coordination of resources, common hardware, and technologies. It will help to align efforts to focus on the highest priority needs that will produce life support systems for future human exploration missions that will simply run in the background, requiring minimal crew interaction

Methods to improve the reliability and resiliency of near/sub-threshold digital circuits

Energy consumption is one of the primary bottlenecks to both large and small scale modern compute platforms. Reducing the operating voltage of digital circuits to voltages where the supply voltage is near or below the threshold of the transistors has recently gained attention as a method to reduce the energy required for computations by as much as 6 times. However, when operating at near/sub-threshold voltages (where the supply voltage is near or below the threshold of the transistors), imperfections in transistor manufacturing, changes in temperature, and other difficult-to-predict factors cause wide variations in the timing of Complementary Metal-Oxide Semiconductor (CMOS) circuits due to an increased sensitivity at lower voltages. These increased variations result in poor aggregate performance and cause increased rates of error occurrence in computation. This work introduces several new methods to improve the reliability of near/sub-threshold circuits. The first is a design automation technique that is used to aid in low-voltage digital standard cell synthesis. Second, two circuit-level techniques are also introduced that aim to improve the reliability and resiliency of digital circuits by means of completion/error detection. These techniques are shown to improve speed and lower energy consumption at low overheads compared to previous methods. Most importantly, these circuit-level methods are specifically designed to operate at low voltages and can themselves tolerate variations and operation in harsh environments. Finally, a test-chip prototype designed in 65nm-CMOS demonstrates the practicality and feasibility of a proposed current sensing error detector

ESMD Space Grant Faculty Report

The strength of the Exploration Systems Mission Directorate ESMD Faculty Project lies in its ability to meet National Aeronautics Space Administration NASA's Strategic Educational Outcome 1 by developing a sustainable and long-term integration of student involvement at academic institutions with all NASA Centers. This outcome is achieved by a three-fold approach: 1) by collecting Senior Design projects pertaining to Constellation work performed at each of the ten NASA Centers, 2) by engaging students at Minority Serving Institutions in the art of systems engineering and systems design of technologies required for space exploration, and 3) by identifying potential internships at each Center relative to exploration that provide students who are supported by their institutional Space Grant to engage in on-going mission-level and explorative systems designs. The objectives of the ESMD Faculty Project are to: 1. Aid the Centers (both Education Offices and associated technical organizations) in providing relevant opportunities for the ESMD Space Grant Program to support student and faculty in Senior Design projects 2. Enable better matches between the ESMD work required and what the Space Grant Consortia can do to effectively contribute to NASA programs 3. Provide the Space Grant Consortia an opportunity to strengthen relations with the NASA Centers 4. Develop better collective understanding of the U.S. Space Exploration Policy by the Center, Space Grant, faculty, Education Office, and students 5. Enable Space Grant institution faculty to better prepare their students to meet current and future NASA needs 6. Enable the Center Education Offices to strengthen their ties to their technical organizations and Space Grant Consortia 7. Aid KSC in gaining a greater and more detailed understanding of each of the Center activities Senior Design projects are intended to stimulate undergraduate students on current NASA activities related to lunar, Mars, and other planetary missions and to bring out innovative and novel ideas that can be used to complement those currently under development at respective NASA Centers. Additionally, such academic involvement would better the prospects for graduating seniors to pursue graduate studies and to seek careers in the space industry with a strong sense for systems engineering and understanding of design concepts. Internships, on the other hand, are intended to provide hands-on experience to students by engaging them in diverse state-of-the-art technology development, prototype bread-boarding, computer modeling and simulations, hardware and software testing, and other activities that provide students a strong perspective of NASA's vision and mission in enhancing the knowledge of Earth and space planetary sciences. Ten faculty members, each from a Space Grant Consortium-affiliated university, worked at ten NASA Centers for five weeks between June 2 and July 3, 2008. The project objectives listed above were achieved. In addition to collecting data on Senior Design ideas and identifying possible internships that would benefit NASA/ESMD, the faculty fellows promoted and collected data when required for other ESMD-funded programs and helped the Center's Education Office, as,needed.

Phase Shaping In The Infrared By Planar Quasi-periodic Surfaces Comprised Of Sub-wavelength Elements

Reflectarrays are passive quasi-periodic sub-wavelength antenna arrays designed for discrete reflected phase manipulation at each individual antenna element making up the array. By spatially varying the phase response of the antenna array, reflectarrays allow a planar surface to impress a non-planar phasefront upon re-radiation. Such devices have become commonplace at radio frequencies. In this dissertation, they are demonstrated in the infrared for the first time--at frequencies as high as 194 THz. Relevant aspects of computational electromagnetic modeling are explored, to yield design procedures optimized for these high frequencies. Modeling is also utilized to demonstrate the phase response of a generalized metallic patch resonator in terms of its dependence on element dimensions, surrounding materials, angle of incidence, and frequency. The impact of realistic dispersion of the real and imaginary parts of the metallic permittivity on the magnitude and bandwidth of the resonance behavior is thoroughly investigated. Several single-phase reflectarrays are fabricated and measurement techniques are developed for evaluating these surfaces. In all of these cases, there is excellent agreement between the computational model results and the measured device characteristics. With accurate modeling and measurement, it is possible to proceed to explore some specific device architectures appropriate for focusing reflectarrays, including binary-phase and phase-incremental approaches. Image quality aspects of these focusing reflectarrays are considered from geometrical and chromatic-aberration perspectives. The dissertation concludes by briefly considering two additional analogous devices--the transmitarray for tailoring transmissive phase response, and the emitarray for angular control of thermally emitted radiation

WDM/TDM PON bidirectional networks single-fiber/wavelength RSOA-based ONUs layer 1/2 optimization

This Thesis proposes the design and the optimization of a hybrid WDM/TDM PON at the L1 (PHY) and L2 (MAC) layers, in terms of minimum deployment cost and enhanced performance for Greenfield NGPON. The particular case of RSOA-based ONUs and ODN using a single-fibre/single-wavelength is deeply analysed. In this WDM/TDM PON relevant parameters are optimized. Special attention has been given at the main noise impairment in this type of networks: the Rayleigh Backscattering effect, which cannot be prevented. To understand its behaviour and mitigate its effects, a novel mathematical model for the Rayleigh Backscattering in burst mode transmission is presented for the first time, and it has been used to optimize the WDM/TDM RSOA based PON. Also, a cost-effective, simple design SCM WDM/TDM PON with rSOA-based ONU, was optimized and implemented. This prototype was successfully tested showing high performance, robustness, versatility and reliability. So, the system is able to give coverage up to 1280 users at 2.5 Gb/s / 1.25 Gb/s downstream/upstream, over 20 Km, and being compatible with the GPON ITU-T recommendation. This precedent has enabled the SARDANA network to extend the design, architecture and capabilities of a WDM/TDM PON for a long reach metro-access network (100 km). A proposal for an agile Transmission Convergence sub-layer is presented as another relevant contribution of this work. It is based on the optimization of the standards GPON and XG-PON (for compatibility), but applied to a long reach metro-access TDM/WDM PON rSOA-based network with higher client count. Finally, a proposal of physical implementation for the SARDANA layer 2 and possible configurations for SARDANA internetworking, with the metro network and core transport network, are presented