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At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS2007

Radiation-Tolerant Dual Data Bus

An architecture, and a method of utilizing the architecture, have been proposed to enable error-free operation of a data bus that includes, and is connected to, commercial off-the-shelf (COTS) circuits and components that are inherently susceptible to singleevent upsets [SEUs (bit flips caused by impinging high-energy particles and photons)]. The architecture and method are applicable, more specifically, to data-bus circuitry based on the Institute for Electrical and Electronics Engineers (IEEE) 1394b standard for a high-speed serial bus.

Kinstler, Gary A.↗
NASA NTRS2009

Integrated System Health Management: Foundational Concepts, Approach, and Implementation

A sound basis to guide the community in the conception and implementation of ISHM (Integrated System Health Management) capability in operational systems was provided. The concept of "ISHM Model of a System" and a related architecture defined as a unique Data, Information, and Knowledge (DIaK) architecture were described. The ISHM architecture is independent of the typical system architecture, which is based on grouping physical elements that are assembled to make up a subsystem, and subsystems combine to form systems, etc. It was emphasized that ISHM capability needs to be implemented first at a low functional capability level (FCL), or limited ability to detect anomalies, diagnose, determine consequences, etc. As algorithms and tools to augment or improve the FCL are identified, they should be incorporated into the system. This means that the architecture, DIaK management, and software, must be modular and standards-based, in order to enable systematic augmentation of FCL (no ad-hoc modifications). A set of technologies (and tools) needed to implement ISHM were described. One essential tool is a software environment to create the ISHM Model. The software environment encapsulates DIaK, and an infrastructure to focus DIaK on determining health (detect anomalies, determine causes, determine effects, and provide integrated awareness of the system to the operator). The environment includes gateways to communicate in accordance to standards, specially the IEEE 1451.1 Standard for Smart Sensors and Actuators.

Figueroa, Fernando↗
NASA NTRS2010

Advances in Spatial Data Infrastructure, Acquisition, Analysis, Archiving and Dissemination

The authors review recent contributions to the state-of-thescience and benign proliferation of satellite remote sensing, spatial data infrastructure, near-real-time data acquisition, analysis on high performance computing platforms, sapient archiving, multi-modal dissemination and utilization for a wide array of scientific applications. The authors also address advances in Geoinformatics and its growing ubiquity, as evidenced by its inclusion as a focus area within the American Geophysical Union (AGU), European Geosciences Union (EGU), as well as by the evolution of the IEEE Geoscience and Remote Sensing Society's (GRSS) Data Archiving and Distribution Technical Committee (DAD TC).

Ramapriyan, Hampapuran K.↗
NASA NTRS2010

C-Band Airport Surface Communications System Standards Development, Phase I

This document is being provided as part of ITT's NASA Glenn Research Center Aerospace Communication Systems Technical Support (ACSTS) contract NNC05CA85C, Task 7: "New ATM Requirements--Future Communications, C-Band and L-Band Communications Standard Development." The proposed future C-band (5091- to 5150-MHz) airport surface communication system, referred to as the Aeronautical Mobile Airport Communications System (AeroMACS), is anticipated to increase overall air-to-ground data communications systems capacity by using a new spectrum (i.e., not very high frequency (VHF)). Although some critical services could be supported, AeroMACS will also target noncritical services, such as weather advisory and aeronautical information services as part of an airborne System Wide Information Management (SWIM) program. AeroMACS is to be designed and implemented in a manner that will not disrupt other services operating in the C-band. This report defines the AeroMACS concepts of use, high-level system requirements, and architecture; the performance of supporting system analyses; the development of AeroMACS test and demonstration plans; and the establishment of an operational AeroMACS capability in support of C-band aeronautical data communications standards to be advanced in both international (International Civil Aviation Organization, ICAO) and national (RTCA) forums. This includes the development of system parameter profile recommendations for AeroMACS based on existing Institute of Electrical and Electronics Engineering (IEEE) 802.16e- 2009 standards

Hall, Edward↗
NASA NTRS2010

Constellation Program Electrical Ground Support Equipment Research and Development

At the Kennedy Space Center, I engaged in the research and development of electrical ground support equipment for NASA's Constellation Program. Timing characteristics playa crucial role in ground support communications. Latency and jitter are two problems that must be understood so that communications are timely and consistent within the Kennedy Ground Control System (KGCS). I conducted latency and jitter tests using Alien-Bradley programmable logic controllers (PLCs) so that these two intrinsic network properties can be reduced. Time stamping and clock synchronization also play significant roles in launch processing and operations. Using RSLogix 5000 project files and Wireshark network protocol analyzing software, I verified master/slave PLC Ethernet module clock synchronization, master/slave IEEE 1588 communications, and time stamping capabilities. All of the timing and synchronization test results are useful in assessing the current KGCS operational level and determining improvements for the future.

McCoy, Keegan S.↗
NASA NTRS2010

Interference Analysis for an Aeronautical Mobile Airport Communications System

The next generation of aeronautical communications for airport surface applications has been identified through a NASA research program and an international collaborative future communications study. The result, endorsed by both the United States and European regulatory agencies is called AeroMACS (Aeronautical Mobile Airport Communications System) and is based upon the IEEE 802.16e mobile wireless standard. Coordinated efforts to develop appropriate aviation standards for the AeroMACS system are now underway within RTCA (United States) and Eurocae (Europe). AeroMACS will be implemented in a recently allocated frequency band, 5091- 5150 MHz. As this band is also occupied by fixed satellite service uplinks, AeroMACS must be designed to avoid interference with this incumbent service. The aspects of AeroMACS operation that present potential interference to the fixed satellite service are under analysis in order to enable the definition of standards that assure that such interference will be avoided. The NASA Glenn Research Center has been involved in this analysis, and the first results of modeling and simulation efforts directed at this analysis are the subject of this paper.12

Wilson, Jeffrey D.↗
NASA NTRS2011

Interference Analysis for an Aeronautical Mobile Airport Communications System

The next generation of aeronautical communications for airport surface applications has been identified through a NASA research program and an international collaborative future communications study. The result, endorsed by both the United States and European regulatory agencies is called AeroMACS (Aeronautical Mobile Airport Communications System) and is based upon the IEEE 802.16e mobile wireless standard. Coordinated efforts to develop appropriate aviation standards for the AeroMACS system are now underway within RTCA (United States) and Eurocae (Europe). AeroMACS will be implemented in a recently allocated frequency band, 5091-5150 MHz. As this band is also occupied by fixed satellite service uplinks, AeroMACS must be designed to avoid interference with this incumbent service. The aspects of AeroMACS operation that present potential interference to the fixed satellite service are under analysis in order to enable the definition of standards that assure that such interference will be avoided. The NASA Glenn Research Center has been involved in this analysis, and the first results of modeling and simulation efforts directed at this analysis are the subject of this presentation.

Wilson, Jeffrey D.↗
NASA NTRS2011

Virtual Sensor Test Instrumentation

Virtual Sensor Test Instrumentation is based on the concept of smart sensor technology for testing with intelligence needed to perform sell-diagnosis of health, and to participate in a hierarchy of health determination at sensor, process, and system levels. A virtual sensor test instrumentation consists of five elements: (1) a common sensor interface, (2) microprocessor, (3) wireless interface, (4) signal conditioning and ADC/DAC (analog-to-digital conversion/ digital-to-analog conversion), and (5) onboard EEPROM (electrically erasable programmable read-only memory) for metadata storage and executable software to create powerful, scalable, reconfigurable, and reliable embedded and distributed test instruments. In order to maximize the efficient data conversion through the smart sensor node, plug-and-play functionality is required to interface with traditional sensors to enhance their identity and capabilities for data processing and communications. Virtual sensor test instrumentation can be accessible wirelessly via a Network Capable Application Processor (NCAP) or a Smart Transducer Interlace Module (STIM) that may be managed under real-time rule engines for mission-critical applications. The transducer senses the physical quantity being measured and converts it into an electrical signal. The signal is fed to an A/D converter, and is ready for use by the processor to execute functional transformation based on the sensor characteristics stored in a Transducer Electronic Data Sheet (TEDS). Virtual sensor test instrumentation is built upon an open-system architecture with standardized protocol modules/stacks to interface with industry standards and commonly used software. One major benefit for deploying the virtual sensor test instrumentation is the ability, through a plug-and-play common interface, to convert raw sensor data in either analog or digital form, to an IEEE 1451 standard-based smart sensor, which has instructions to program sensors for a wide variety of functions. The sensor data is processed in a distributed fashion across the network, providing a large pool of resources in real time to meet stringent latency requirements.

Wang, Roy↗
NASA NTRS2011

Fault Tolerance in ZigBee Wireless Sensor Networks

Wireless sensor networks (WSN) based on the IEEE 802.15.4 Personal Area Network standard are finding increasing use in the home automation and emerging smart energy markets. The network and application layers, based on the ZigBee 2007 PRO Standard, provide a convenient framework for component-based software that supports customer solutions from multiple vendors. This technology is supported by System-on-a-Chip solutions, resulting in extremely small and low-power nodes. The Wireless Connections in Space Project addresses the aerospace flight domain for both flight-critical and non-critical avionics. WSNs provide the inherent fault tolerance required for aerospace applications utilizing such technology. The team from Ames Research Center has developed techniques for assessing the fault tolerance of ZigBee WSNs challenged by radio frequency (RF) interference or WSN node failure.

Alena, Richard↗
NASA NTRS2011

Performance Comparison of Wireless Sensor Network Standard Protocols in an Aerospace Environment: ISA100.11a and ZigBee

Wireless Sensor Networks (WSNs) can provide a substantial benefit in spacecraft systems, reducing launch weight and providing unprecedented flexibility by allowing instrumentation capabilities to grow and change over time. Achieving data transport reliability on par with that of wired systems, however, can prove extremely challenging in practice. Fortunately, much progress has been made in developing standard WSN radio protocols for applications from non-critical home automation to mission-critical industrial process control. The relative performances of candidate protocols must be compared in representative aerospace environments, however, to determine their suitability for spaceflight applications. In this paper, we will present the results of a rigorous laboratory analysis of the performance of two standards-based, low power, low data rate WSN protocols: ZigBee Pro and ISA100.11a. Both are based on IEEE 802.15.4 and augment that standard's specifications to build complete, multi-hop networking stacks. ZigBee Pro targets primarily the home and office automation markets, providing an ad-hoc protocol that is computationally lightweight and easy to implement in inexpensive system-on-a-chip components. As a result of this simplicity, however, ZigBee Pro can be susceptible to radio frequency (RF) interference. ISA100.11a, on the other hand, targets the industrial process control market, providing a robust, centrally-managed protocol capable of tolerating a significant amount of RF interference. To achieve these gains, a coordinated channel hopping mechanism is employed, which entails a greater computational complexity than ZigBee and requires more sophisticated and costly hardware. To guide future aerospace deployments, we must understand how well these standards relatively perform in analog environments under expected operating conditions. Specifically, we are interested in evaluating goodput -- application level throughput -- in a representative crewed environment in the presence of varying levels of 802.11g Wi-Fi traffic. To do so, we use the NASA Johnson Space Center Wireless Habitat Testbed (WHT), a metallic, habitation-sized module designed for co-existence testing of wireless systems. In its quiescent state, the sealed WHT provides an RF-quiet environment to which we can selectively add interfering systems; it also provides a realistic level of multi-path self-interference for systems under investigation. In our test, we deploy two representative five node networks, configured in a star topology with all nodes reporting directly to a WSN gateway. Each ZigBee network WSN node is built using a Texas Instruments (TI) CC2530 system-on-a-chip radio running TI's ZigBee Pro Z-stack. Each ISA100.11a network node is built using a Nivis VersaNode 210 system-on-a-chip radio. In both cases, radios interface with TI MSP430-F5438 microcontroller implementing a common test application. Interference is provided by a D-link 802.11g Wi-Fi router transporting traffic generated using the Iperf network testing tool. For the single-channel ZigBee network, effects of both direct and indirect Wi-Fi interference are evaluated. For the channel-hopping ISA100.11a network, effects of interference from multiple Wi-Fi routers configured in non-overlapping 802.11g channels are evaluated. Our results show that, in general, the more lightweight ZigBee network performs well at low interference levels, but performance degrades as interference increases. Conversely, the more complex and costly ISA100.11a network continues to perform well as Wi-Fi interference levels increase.

Wagner, Raymond S.↗
NASA NTRS2011

Attitude Control and Orbital Dynamics Challenges of Removing the First 3-Axis Stabilized Tracking and Data Relay Satellite from the Geosynchronous ARC

Launched on April 4, 1983 onboard STS 6 (Space Shuttle Challenger), the First Tracking and Data Relay Satellite (TDRS 1) was retired above the Geosynchronous Orbit (GEO) on June 27, 2010 after having provided real-time communications with a variety of low-orbiting spacecraft over a 26-year period. To meet NASA requirements limiting orbital debris 1, a team of experts was assembled to conduct an End-Of-Mission (EOM) procedure to raise the satellite 350 km above the GEO orbit. Following the orbit raising via conventional station change maneuvers, the team was confronted with having to deplete the remaining propellant and passivate all energy storage or generation sources. To accomplish these tasks within the time window, communications (telemetry and control links), electrical power, propulsion, and thermal constraints, a spacecraft originally designed as a three-axis stabilized satellite was turned into a spinner. This paper (a companion paper to Innovative Approach Enabled the Retirement of TDRS 1, paper # 1699, IEEE 2011 Aerospace Conference, March 5-12, 2011 sup 2) focuses on the challenges of maintaining an acceptable spinning dynamics, while repetitively firing thrusters. Also addressed are the effects of thruster firings on the orbit characteristics and how they were mitigated by a careful scheduling of the fuel depletion operations. Periodic thruster firings for spin rate adjustment, nutation damping, and precession of the momentum vector were also required in order to maintain effective communications with the satellite. All operations were thoroughly rehearsed and supported by simulations thus lending a high level of confidence in meeting the NASA EOM goals.

Benet, Charles A.↗
NASA NTRS2005

LabVIEW Interface for PCI-SpaceWire Interface Card

This software provides a LabView interface to the NT drivers for the PCISpaceWire card, which is a peripheral component interface (PCI) bus interface that conforms to the IEEE-1355/ SpaceWire standard. As SpaceWire grows in popularity, the ability to use SpaceWire links within LabVIEW will be important to electronic ground support equipment vendors. In addition, there is a need for a high-level LabVIEW interface to the low-level device- driver software supplied with the card. The LabVIEW virtual instrument (VI) provides graphical interfaces to support all (1) SpaceWire link functions, including message handling and routing; (2) monitoring as a passive tap using specialized hardware; and (3) low-level access to satellite mission-control subsystem functions. The software is supplied in a zip file that contains LabVIEW VI files, which provide various functions of the PCI-SpaceWire card, as well as higher-link-level functions. The VIs are suitably named according to the matching function names in the driver manual. A number of test programs also are provided to exercise various functions.

Lux, James↗
NASA NTRS2011

The Habitat Demonstration Unit Project: A Modular Instrumentation System for a Deep Space Habitat

NASA is focused on developing human exploration capabilities in low Earth orbit (LEO), expanding to near Earth asteroids (NEA), and finally to Mars. Habitation is a crucial aspect of human exploration, and a current focus of NASA activities. The Habitation Demonstration Unit (HDU) is a project focused on developing an autonomous habitation system that enables human exploration of space by providing engineers and scientists with a test bed to develop, integrate, test, and evaluate habitation systems. A critical feature of the HDU is the instrumentation system, which monitors key subsystems within the habitat. The following paper will discuss the HDU instrumentation system performance and lessons learned during the 2010 Desert Research and Technology Studies (D-RaTS). In addition, this paper will discuss the evolution of the instrumentation system to support the 2011 Deep Space Habitat configuration, the challenges, and the lessons learned of implementing this configuration. In 2010, the HDU was implemented as a pressurized excursion module (PEM) and was tested at NASA s D-RaTS in Arizona [1]. For this initial configuration, the instrumentation system design used features that were successful in previous habitat instrumentation projects, while also considering challenges, and implementing lessons learned [2]. The main feature of the PEM instrumentation system was the use of a standards-based wireless sensor node (WSN), implementing an IEEE 802.15.4 protocol. Many of the instruments were connected to several WSNs, which wirelessly transmitted data to the command and data handling system via a mesh network. The PEM instrumentation system monitored the HDU during field tests at D-RaTS, and the WSN data was later analyzed to understand the performance of this system. In addition, several lessons learned were gained from the field test experience, which fed into the instrumentation design of the next generation of the HDU.

Rojdev, Kristina↗
NASA NTRS2011

Aeronautical Mobile Airport Communications System (AeroMACS)

To help increase the capacity and efficiency of the nation s airports, a secure wideband wireless communications system is proposed for use on the airport surface. This paper provides an overview of the research and development process for the Aeronautical Mobile Airport Communications System (AeroMACS). AeroMACS is based on a specific commercial profile of the Institute of Electrical and Electronics Engineers (IEEE) 802.16 standard known as Wireless Worldwide Interoperability for Microwave Access or WiMAX (WiMax Forum). The paper includes background on the need for global interoperability in air/ground data communications, describes potential AeroMACS applications, addresses allocated frequency spectrum constraints, summarizes the international standardization process, and provides findings and recommendations from the world s first AeroMACS prototype implemented in Cleveland, Ohio, USA.

Budinger, James M.↗
NASA NTRS2003

SpaceWire Driver Software for Special DSPs

A computer program provides a high-level C-language interface to electronics circuitry that controls a SpaceWire interface in a system based on a space qualified version of the ADSP-21020 digital signal processor (DSP). SpaceWire is a spacecraft-oriented standard for packet-switching data-communication networks that comprise nodes connected through bidirectional digital serial links that utilize low-voltage differential signaling (LVDS). The software is tailored to the SMCS-332 application-specific integrated circuit (ASIC) (also available as the TSS901E), which provides three highspeed (150 Mbps) serial point-to-point links compliant with the proposed Institute of Electrical and Electronics Engineers (IEEE) Standard 1355.2 and equivalent European Space Agency (ESA) Standard ECSS-E-50-12. In the specific application of this software, the SpaceWire ASIC was combined with the DSP processor, memory, and control logic in a Multi-Chip Module DSP (MCM-DSP). The software is a collection of low-level driver routines that provide a simple message-passing application programming interface (API) for software running on the DSP. Routines are provided for interrupt-driven access to the two styles of interface provided by the SMCS: (1) the "word at a time" conventional host interface (HOCI); and (2) a higher performance "dual port memory" style interface (COMI).

Clark, Douglas↗
NASA NTRS2012

Health-Enabled Smart Sensor Fusion Technology

A process was designed to fuse data from multiple sensors in order to make a more accurate estimation of the environment and overall health in an intelligent rocket test facility (IRTF), to provide reliable, high-confidence measurements for a variety of propulsion test articles. The object of the technology is to provide sensor fusion based on a distributed architecture. Specifically, the fusion technology is intended to succeed in providing health condition monitoring capability at the intelligent transceiver, such as RF signal strength, battery reading, computing resource monitoring, and sensor data reading. The technology also provides analytic and diagnostic intelligence at the intelligent transceiver, enhancing the IEEE 1451.x-based standard for sensor data management and distributions, as well as providing appropriate communications protocols to enable complex interactions to support timely and high-quality flow of information among the system elements.

Wang, Ray↗
NASA NTRS2012

Detection Thresholds of Falling Snow from Satellite-Borne Active and Passive Sensors

Precipitation, including rain and snow, is a critical part of the Earth's energy and hydrology cycles. In order to collect information on the complete global precipitation cycle and to understand the energy budget in terms of precipitation, uniform global estimates of both liquid and frozen precipitation must be collected. Active observations of falling snow are somewhat easier to estimate since the radar will detect the precipitation particles and one only needs to know surface temperature to determine if it is liquid rain or snow. The challenges of estimating falling snow from passive spaceborne observations still exist though progress is being made. While these challenges are still being addressed, knowledge of their impact on expected retrieval results is an important key for understanding falling snow retrieval estimations. Important information to assess falling snow retrievals includes knowing thresholds of detection for active and passive sensors, various sensor channel configurations, snow event system characteristics, snowflake particle assumptions, and surface types. For example, can a lake effect snow system with low (~2.5 km) cloud tops having an ice water content (Iwe) at the surface of 0.25 g m-3 and dendrite snowflakes be detected? If this information is known, we can focus retrieval efforts on detectable storms and concentrate advances on achievable results. Here, the focus is to determine thresholds of detection for falling snow for various snow conditions over land and lake surfaces. The analysis relies on simulated Weather Research Forecasting (WRF) simulations of falling snow cases since simulations provide all the information to determine the measurements from space and the ground truth. Results are presented for active radar at Ku, Ka, and W-band and for passive radiometer channels from 10 to 183 GHz (Skofronick-Jackson, et al. submitted to IEEE TGRS, April 2012). The notable results show: (1) the W-Band radar has detection thresholds more than an order of magnitude lower than the future GPM sensors, (2) the cloud structure macrophysics influences the thresholds of detection for passive channels, (3) the snowflake microphysics plays a large role in the detection threshold for active and passive instruments, (4) with reasonable assumptions, the passive 166 GHz channel has detection threshold values comparable to the GPM DPR Ku and Ka band radars with ~0.05 g m-3 detected at the surface, or an ~0.5-1 mm hr-l melted snow rate (equivalent to 0.5-2 cm hr-l solid fluffy snowflake rate).

Jackson, Gail↗
NASA NTRS2012

Dependence of AeroMACS Interference on Airport Radiation Pattern Characteristics

AeroMACS (Aeronautical Mobile Airport Communications System), which is based upon the IEEE 802.16e mobile wireless standard, is expected to be implemented in the 5091 to 5150 MHz frequency band. As this band is also occupied by Mobile Satellite Service (MSS) feeder uplinks, AeroMACS must be designed to avoid interference with this incumbent service. The aspects of AeroMACS operation that present potential interference are under analysis in order to enable the definition of standards that assure that such interference will be avoided. In this study, the cumulative interference power distribution at low earth orbit from AeroMACS transmitters at the 497 major airports in the contiguous United States was simulated with the Visualyse Professional software. The dependence of the interference power on the number of antenna beams per airport, gain patterns, and beam direction orientations was simulated. As a function of these parameters, the simulation results are presented in terms of the limitations on transmitter power required to maintain the cumulative interference power under the established threshold.

Wilson, Jeffrey D.↗