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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Evaluating software development by analysis of changes: The data from the software engineering laboratory

An effective data collection methodology for evaluating software development methodologies was applied to four different software development projects. Goals of the data collection included characterizing changes and errors, characterizing projects and programmers, identifying effective error detection and correction techniques, and investigating ripple effects. The data collected consisted of changes (including error corrections) made to the software after code was written and baselined, but before testing began. Data collection and validation were concurrent with software development. Changes reported were verified by interviews with programmers.

Source record↗
NASA NTRS1990

A robust CELP coder with source-dependent channel coding

A CELP coder using Source Dependent Channel Encoding (SDCE) for optimal channel error protection is introduced. With SDCE, each of the CELP parameters are encoded by minimizing a perceptually meaningful error criterion under prevalent channel conditions. Unlike conventional channel coding schemes, SDCE allows for optimal balance between error detection and correction. The experimental results show that the CELP system is robust under various channel bit error rates and displays a graceful degradation in SSNR as the channel error rate increases. This is a desirable property to have in a coder since the exact channel conditions cannot usually be specified a priori.

Sukkar, Rafid A.↗
NASA NTRS2012

Development of Next Generation Memory Test Experiment for Deployment on a Small Satellite

The original Memory Test Experiment successfully flew on the FASTSAT satellite launched in November 2010. It contained a single Ramtron 512K ferroelectric memory. The memory device went through many thousands of read/write cycles and recorded any errors that were encountered. The original mission length was schedule to last 6 months but was extended to 18 months. New opportunities exist to launch a similar satellite and considerations for a new memory test experiment should be examined. The original experiment had to be designed and integrated in less than two months, so the experiment was a simple design using readily available parts. The follow-on experiment needs to be more sophisticated and encompass more technologies. This paper lays out the considerations for the design and development of this follow-on flight memory experiment. It also details the results from the original Memory Test Experiment that flew on board FASTSAT. Some of the design considerations for the new experiment include the number and type of memory devices to be used, the kinds of tests that will be performed, other data needed to analyze the results, and best use of limited resources on a small satellite. The memory technologies that are considered are FRAM, FLASH, SONOS, Resistive Memory, Phase Change Memory, Nano-wire Memory, Magneto-resistive Memory, Standard DRAM, and Standard SRAM. The kinds of tests that could be performed are read/write operations, non-volatile memory retention, write cycle endurance, power measurements, and testing Error Detection and Correction schemes. Other data that may help analyze the results are GPS location of recorded errors, time stamp of all data recorded, radiation measurements, temperature, and other activities being perform by the satellite. The resources of power, volume, mass, temperature, processing power, and telemetry bandwidth are extremely limited on a small satellite. Design considerations must be made to allow the experiment to not interfere with the satellite s primary mission.

MacLeod, Todd↗
NASA NTRS1983

Spacelab high density digital recorders

The design and performance of the high-density digital recorder (HDDR) developed for use at the NASA centers (KSC, JSC, and GSFC) and at the JPL to store and retrieve 50-Mb/s PCM data streams from the Spacelab experiments are reported. The recording reproduction, and transport requirements are reviewed; and the design solutions adopted in the final version of the HDDR are described, incuding three-position-modulation and Y-phase encoding, microprocessor-controlled automatic bit synchronization and equalization, cyclic-redundancy-check error detection and correction, clock regeneration, data and clock variations, tape-speed control, and EEE-488 remote control. Reliable performance, with bit error rates 1 in 10 to the 10th forward and 1 in 10 to the 9th reverse or better and packing density up to 50 percent greater than that obtainable using conventional codes, is reported after 1.5 years of service.

Blais, R. A.↗
NASA NTRS2005

Generic Sensor Modeling Using Pulse Method

Recent development of high spatial resolution satellites such as IKONOS, Quickbird and Orbview enable observation of the Earth's surface with sub-meter resolution. Compared to the 30 meter resolution of Landsat 5 TM, the amount of information in the output image was dramatically increased. In this era of high spatial resolution, the estimation of spatial quality of images is gaining attention. Historically, the Modulation Transfer Function (MTF) concept has been used to estimate an imaging system's spatial quality. Sometimes classified by target shapes, various methods were developed in laboratory environment utilizing sinusoidal inputs, periodic bar patterns and narrow slits. On-orbit sensor MTF estimation was performed on 30-meter GSD Landsat4 Thematic Mapper (TM) data from the bridge pulse target as a pulse input . Because of a high resolution sensor s small Ground Sampling Distance (GSD), reasonably sized man-made edge, pulse, and impulse targets can be deployed on a uniform grassy area with accurate control of ground targets using tarps and convex mirrors. All the previous work cited calculated MTF without testing the MTF estimator's performance. In previous report, a numerical generic sensor model had been developed to simulate and improve the performance of on-orbit MTF estimating techniques. Results from the previous sensor modeling report that have been incorporated into standard MTF estimation work include Fermi edge detection and the newly developed 4th order modified Savitzky-Golay (MSG) interpolation technique. Noise sensitivity had been studied by performing simulations on known noise sources and a sensor model. Extensive investigation was done to characterize multi-resolution ground noise. Finally, angle simulation was tested by using synthetic pulse targets with angles from 2 to 15 degrees, several brightness levels, and different noise levels from both ground targets and imaging system. As a continuing research activity using the developed sensor model, this report was dedicated to MTF estimation via pulse input method characterization using the Fermi edge detection and 4th order MSG interpolation method. The relationship between pulse width and MTF value at Nyquist was studied including error detection and correction schemes. Pulse target angle sensitivity was studied by using synthetic targets angled from 2 to 12 degrees. In this report, from the ground and system noise simulation, a minimum SNR value was suggested for a stable MTF value at Nyquist for the pulse method. Target width error detection and adjustment technique based on a smooth transition of MTF profile is presented, which is specifically applicable only to the pulse method with 3 pixel wide targets.

Helder, Dennis L.↗
NASA NTRS1991

Multiple single event upsets in CMOS static rams

The occurrence of multiple upset errors during ground tests can contaminate the data and lead to error cross sections which are too high. In space, multiple errors may produce higher upsets than predicted and if they occur in single words they can defeat error detection and correction hardware. This investigation involves data which were taken during an experimental study of dose imprint effects in static memories. The results show that multiple errors occurred mainly for heavy ions with high linear energy transfers and with the majority of these in the soft upset sections of the dose-imprinted memory samples. The percentages of the total number of errors which were singles, doubles, and triplets, were determined as a function of LET, dose, and soft or hard section of the devices. The experimental observations are compared to the predictions of simple binomial statistics.

Stassinopoulos, E. G.↗
NASA NTRS1986

Performance analysis of a cascaded coding scheme with interleaved outer code

A cascaded coding scheme for a random error channel with a bit-error rate is analyzed. In this scheme, the inner code C sub 1 is an (n sub 1, m sub 1l) binary linear block code which is designed for simultaneous error correction and detection. The outer code C sub 2 is a linear block code with symbols from the Galois field GF (2 sup l) which is designed for correcting both symbol errors and erasures, and is interleaved with a degree m sub 1. A procedure for computing the probability of a correct decoding is presented and an upper bound on the probability of a decoding error is derived. The bound provides much better results than the previous bound for a cascaded coding scheme with an interleaved outer code. Example schemes with inner codes ranging from high rates to very low rates are evaluated. Several schemes provide extremely high reliability even for very high bit-error rates say 10 to the -1 to 10 to the -2 power.

Lin, S.↗
NASA NTRS1980

The NEEDS Data Base Management and Archival Mass Memory System

A Data Base Management System and an Archival Mass Memory System are being developed that will have a 10 to the 12th bit on-line and a 10 to the 13th off-line storage capacity. The integrated system will accept packetized data from the data staging area at 50 Mbps, create a comprehensive directory, provide for file management, record the data, perform error detection and correction, accept user requests, retrieve the requested data files and provide the data to multiple users at a combined rate of 50 Mbps. Stored and replicated data files will have a bit error rate of less than 10 to the -9th even after ten years of storage. The integrated system will be demonstrated to prove the technology late in 1981.

Bailey, G. A.↗
NASA NTRS2004

Software for Fault-Tolerant Matrix Multiplication

Formal Linear Algebra Recovery Environment is a computer program for high-performance, fault-tolerant matrix multiplication. The program is based on an extension of the prior theory and practice of fault-tolerant matrix matrix multiplication of the form C = AB. This extension provides low-overhead methods for detecting errors, not only in C, but also in A and/or B. These methods enable the detection of all errors as long as, in a given case, only one entry in A, B, or C is corrupted. The program also provides for following a low-overhead rollback approach to correct errors once detected. Results of computational experiments have demonstrated that the methods implemented in this program work well in practice while imposing an acceptably low level of overhead, relative to high-performance matrix-multiplication methods that do not afford fault tolerance.

Katz, Daniel↗
NASA NTRS1990

Performance analysis of a generalized concurrent error detection procedure

A general procedure for error detection in complex systems, called the data block capture and analysis monitoring process, is described and analyzed. It is assumed that, in addition to being exposed to potential external fault sources, a complex system will in general always contain embedded hardware and software fault mechanisms which can cause the system to perform incorrect computations and/or produce incorrect output. Thus, in operation, the system continuously moves back and forth between error and no-error states. These external fault sources or internal fault mechanisms are extremely difficult to detect. The data block capture and analysis monitoring process is concerned with detecting deviations from the normal performance of the system, known as errors, which are symptomatic of fault conditions. The process consists of repeatedly recording a fixed amount of data from a set of predetermined observation lines of the system being monitored (i.e., capturing a block of data) and then analyzing the captured block in an attempt to determine whether the system is functioning correctly. The performances of linear, quadratic, and logarithmic data analysis algorithms are rigorously characterized in terms of the probability of correctly detecting an error, the expectation and variance of the number of false alarms per error, and the expectation and variance of the latency in detection of errors. Insight into the nature of the general problem of error detection is obtained.

Blough, Douglas M.↗
NASA NTRS1978

GCF HSD error control

A selective repeat automatic repeat request (ARQ) system was implemented under software control in the Ground Communications Facility error detection and correction (EDC) assembly at JPL and the comm monitor and formatter (CMF) assembly at the DSSs. The CMF and EDC significantly improved real time data quality and significantly reduced the post-pass time required for replay of blocks originally received in error. Since the remote mission operation centers (RMOCs) do not provide compatible error correction equipment, error correction will not be used on the RMOC-JPL high speed data (HSD) circuits. The real time error correction capability will correct error burst or outage of two loop-times or less for each DSS-JPL HSD circuit.

Hung, C. K.↗
NASA NTRS1970

Self testing and repairing computer - A concept

STAR computer has five redundant modular function units, fixed store, arithmetic, memory, input, and output. Each unit is connected to a diagnostic control unit, each is coded for error detection and error correction. Separation into function units permits assembly of many different systems from the set of units.

Avizienis, A. A.↗
NASA NTRS1971

Development and testing of the infrared interferometer spectrometer for the Mariner Mars 1971 spacecraft

The design, development and testing of the infrared interferometer spectrometer is reported with emphasis on the unique features of the Mariner instrument as compared to previous IRIS instruments flown on the Nimbus meteorological research satellites. The interferometer functions in the spectral range from 50 microns to 6.3 microns. A noise equivalent radiance of 0.5 X 10 to the -7th power W/sq cm/ster/cm has been achieved. Major improvements that were implemented included the cesium iodide beamsplitter and electronic features to suppress the effect of vibration on the Michelson mirror motion and digital filtering through the summation of increased sampling of the infrared signal. A bit error detection and correction scheme was also implemented in order to recover the science data with a higher level of confidence over the telecommunication link.

Hanel, R. H.↗
NASA NTRS1971

A fault-tolerant information processing concept for space vehicles.

A distributed fault-tolerant information processing system is proposed, comprising a central multiprocessor, dedicated local processors, and multiplexed input-output buses connecting them together. The processors in the multiprocessor are duplicated for error detection, which is felt to be less expensive than using coded redundancy of comparable effectiveness. Error recovery is made possible by a triplicated scratchpad memory in each processor. The main multiprocessor memory uses replicated memory for error detection and correction. Local processors use any of three conventional redundancy techniques: voting, duplex pairs with backup, and duplex pairs in independent subsystems.

Hopkins, A. L., Jr.↗
NASA NTRS1968

Shift register generators and applications to coding

The most important properties of shift register generated sequences are exposed. The application of shift registers as multiplication and division circuits leads to the generation of some error correcting and detecting codes.

Morakis, J. C.↗