Novel sensor technology for monitoring and control of critical plant nutrient parameters.

A novel dielectric sensor technology has been developed for monitoring and control of plant nutrient delivery systems as part of NASA's Controlled Ecological Life Support System (CELSS) program. A unique measurement phenomenon was discovered in which the electrostatic field is shunted to a third terminal of the sensor, resulting in a much greater sensitivity to changes in the complex dielectric properties of the nutrient solution. Based on this phenomenon, a small, flexible, thin-film shunting dielectric sensor (SDS) was designed to provide low-frequency, non-invasive measurement of both the thickness and nutrient concentration of the layer of solution on a plant growth surface. Test results indicate a sensitivity of +/- 0.05mm in layer thickness while characterization of the ability to measure nutrient concentration continues. The development plan for this sensor is presented and other applications are discussed.     

Avionics cost of ownership

The cost of ownership of avionics includes not only the development and acquisition cost, but also the yearly operating and support (O and S) (maintenance) cost of hardware, software, and support equipment. This paper presents an avionics cost of ownership methodology developed for USAF, its data sources, and business metrics computed for USAF decision makers as we move toward operating avionics as a business. The business model is used to determine which existing avionics are candidates for replacement with new technology and to prioritize the replacements. These avionics are often used on multiple aircraft types which necessitates analysis of the causes of the high cost of ownership on each type. Databases are used to document the processing functions, data flow, and constraints of the item being analyzed. These constraints include physical, environmental, electrical, and data interfaces. Databases containing alternatives are evaluated against standard mission scenarios for aircraft utilizing these high cost avionics to determine their impact on performance, O and S costs, and mission effectiveness. The results of the foregoing analyses steps are then used in life cycle cost analyses which consider different retrofit scenarios for each alternative for each aircraft type against the avionics being analyzed for replacement. The alternatives are prioritized and a risk analysis performed considering technical, schedule, and cost growth risks. The avionics cost of ownership methodology described in this paper processes data from USAF maintenance organizations. This has revealed the very large expenditures being made to support highly unreliable avionics. These methods can be applied to all military and commercial aircraft systems to determine not only the cost of ownership of existing systems, but also the cost of ownership of new systems when they are retrofit     

GNSS receiver for GLONASS signal reception

This paper deals with the latest version of Experimental GNSS receiver built at the Czech Technical University and describes integration of GLONASS signal processing to the receiver. The new FPGA platform Virtex-D Pro by Xilinx is used and enables integration of whole digital signal processing of GNSS receiver into the single chip. The RE unit of the receiver is capable of processing all GLONASS frequency of the Li and L2 bands in two independent RE channels; each channel can process one band. The frequency selection of the appropriate satellite is accomplished in a digital correlator. The development flow of the GLONASS correlator is discussed herein. The complexity of the GLONASS correlator with complexity of GPS correlator is compared. The developed GLONASS correlator was tested in Simuelink tool during development. The next test was carried out using GLONASS simulator and real GLONASS satellite signal.     

Radiation biodosimetry: applications for spaceflight.

The multiparametric dosimetry system that we are developing for medical radiological defense applications could be adapted for spaceflight environments. The system complements the internationally accepted personnel dosimeters and cytogenetic analysis of chromosome aberrations, considered the best means of documenting radiation doses for health records. Our system consists of a portable hematology analyzer, molecular biodosimetry using nucleic acid and antigen-based diagnostic equipment, and a dose assessment management software application. A dry-capillary tube reagent-based centrifuge blood cell counter (QBC Autoread Plus, Becton [correction of Beckon] Dickinson Bioscience) measures peripheral blood lymphocytes and monocytes, which could determine radiation dose based on the kinetics of blood cell depletion. Molecular biomarkers for ionizing radiation exposure (gene expression changes, blood proteins) can be measured in real time using such diagnostic detection technologies as miniaturized nucleic acid sequences and antigen-based biosensors, but they require validation of dose-dependent targets and development of optimized protocols and analysis systems. The Biodosimetry Assessment Tool, a software application, calculates radiation dose based on a patient's physical signs and symptoms and blood cell count analysis. It also annotates location of personnel dosimeters, displays a summary of a patient's dosimetric information to healthcare professionals, and archives the data for further use. These radiation assessment diagnostic technologies can have dual-use applications supporting general medical-related care.     

Development of a Digital Array Radar (DAR)

Twenty-first century littoral and open-sea missions present US Navy (USN) shipboard-radar systems with the challenge of detecting small targets in severe clutter and against multiple sources of interference. In Fiscal Year 2000 (FY00), the Office of Naval Research (ONR) sponsored a program to develop an active array radar that includes a digital beamforming (DBF) architecture. The DBF radar system has the potential for improved time-energy management, improved signal-to-clutter (S/C) ratios, improved reliability and reduced life-cycle costs. This paper summarizes the latest developments of the program during FY00     

Asynchronous router specification

We describe the application of three formal design tools to a case study in the design of a distributed system. The case study in question involves the specification of an asynchronous message router; the three design tools are process algebra (specifically Milner's Calculus of Communicating Systems CCS), the modal μ-calculus and the Edinburgh Concurrency Workbench (CWB). We demonstrate how an informally-presented specification can be formalised within the language of the modal μ-calculus, allowing for a rigorous mathematical analysis of the correctness of our proposed implementation. For modest-sized versions of the router, this correctness proof has been carried out using the CWB     

Development of an advanced rocket propellant handler's suit.

Most launch vehicles and satellites in the US inventory rely upon the use of hypergolic rocket propellants, many of which are toxic to humans. These fuels and oxidizers, such as hydrazine and nitrogen tetroxide have threshold limit values as low as 0.01 PPM. It is essential to provide space workers handling these agents whole body protection as they are universally hazardous not only to the respiratory system, but the skin as well. This paper describes a new method for powering a whole body protective garment to assure the safety of ground servicing crews. A new technology has been developed through the small business innovative research program at the Kennedy Space Center. Currently, liquid air is used in the environmental control unit (ECU) that powers the propellant handlers suit (PHE). However, liquid air exhibits problems with attitude dependence, oxygen enrichment, and difficulty with reliable quantity measurement. The new technology employs the storage of the supply air as a supercritical gas. This method of air storage overcomes all of three problems above while maintaining high density storage at relatively low vessel pressures (<7000 kPa or approximately 1000 psi). A one hour prototype ECU was developed and tested to prove the feasibility of this concept. This was upgraded by the design of a larger supercritical dewar capable of holding 7 Kg of air, a supply which provides a 2 hour duration to the PHE. A third version is being developed to test the feasibility of replacing existing air cooling methodology with a liquid cooled garment for relief of heat stress in this warm Florida environment. Testing of the first one hour prototype yielded data comparable to the liquid air powered predecessor, but enjoyed advantages of attitude independence and oxygen level stability. Thermal data revealed heat stress relief at least as good as liquid air supplied units. The application of supercritical air technology to this whole body protective ensemble marked an advancement in the state-of-the-art in personal protective equipment. Not only was long duration environmental control provided, but it was done without a high pressure vessel. The unit met human performance needs for attitude independence, oxygen stability and relief of heat stress. This supercritical air (and oxygen) technology is suggested for microgravity applications in life support such as the Extravehicular Mobility Unit.     

Energy storage at 77 K in multilayer ceramic capacitors

A ceramic material having a large dielectric constant at 77 K, ε=8000-12000, has been developed for capacitive energy storage at this temperature. A large matrix of multilayer ceramic capacitors were fabricated using conventional tape-casting methods to optimize the dielectric breakdown strength at 77 K, and measured energy storage values on these capacitors range up to 6 J/cm³ at 77 K. An unfused bank of these capacitors was voltage-cycled 10⁵ times at 77 K without failure, and the heating effects during cycling were immeasurably small (i.e., nitrogen boiloff was monitored). An electrocaloric effect on discharge (ΔT~1 K) contributes to the thermal stability. Measurements of the frequency dependence of the dielectric properties of the ceramic at 77 K indicate a fundamental limit of about 8 μs for the switching repetition rate. Improved capacitor-manufacturing methods are discussed which can increase the energy density to the 20-30 J/cm³ range     

Factors influencing the heating of the auroral electrojet by high power radio waves

Results are presented from recent ionospheric modification experiments in which the EISCAT UHF radar measured the E-region temperature and density response to high power RF heating above Tromsø. A variety of electrojet conditions were encountered during these experiments. In particular, the electron drift velocity varied considerably allowing the heating efficiency of the RF heater to be investigated as a function of electron flow velocity. These observations constitute the first direct investigation of electrojet temperature modifications by high power radio waves and provide a test of a recent theoretical model in which the combined effects of RF heating and of natural plasma turbulence associated with the Farley-Buneman instability have been considered.