1,721,025 research outputs found
NAND Flash Storage Technology for Mission-critical Space Applications
No full textMass memories in space systems are evolving from simple tape-like data recorders to complex intelligent (sub)systems capable of autonomous operations. This evolution is driven by more complex functional requirements coming from complex multi-payload missions and by the availability of ever higher density memory components. In commercial markets, NAND flash memories are widespread as data storage in consumer electronics (e.g., USB flash drives) because of their high storage density, low power, low cost and high data throughput. However, hi-rel electronics is struggling in keeping the pace with the aggressive scaling down of NAND flash technology. As a consequence, the use of NAND flash in space applications is not as established as in the consumer market and is still under research. Furthermore, the full commercial availability of space qualified memories is not an option due to costs, manufacturer's interest, long lead times or performance reasons. Adoption of Commercial Of The Shelves (COTS) NAND flashes is unavoidable. Upscreening of COTS memory chips has demonstrated that most of those components are not able to successfully operate and survive in the demanding space environment. The few candidates that demonstrate promising robustness request additional design effort to meet reliability requirements for space missions. Furthermore, long term reliability and combination of aging and radiation effects over mission and storage lifetimes of decades has not been studied in sufficient breadth. This paper aims to provide an overview of the design challenges to overcome when applying latest generation of terrestrial memory technologies in to high reliability space system
Guest Editorial: IEEE Transactions on Emerging Topics in Computing Special Issue on Advanced Command, Control and On-Board Data Processing for Space Avionic Systems
No full textThe papers in this special issue focus on advanced command, control and on-board data processing for space avionic systems. The domain of space avionic systems is changing extremely rapidly, compared to other technical domains in the spacefaring industry, under the pressure of intense competition, the continuous emergence of new markets and players, the need for cost reduction, as well as an increased obsolescence rate of components and processes due to the relative reduction of hi-rel parts market share with respect to booming volumes of consumer electronics. The emergence of "new space" paradigm, with new (mostly private) players taking the risk of compromising with system's dependability in favour of stripped down cost further contributes to this rapidly changing landscape: new opportunities are opening for the space avionic systems
Total ionizing dose effects on DRAM data retention time
No full textDynamic random access memory (DRAM) data retention time degradation induced by radiation exposure is investigated in this paper. We present the experimental setup and the results of total ionizing dose (TID) test on a COTS SDRAM de- vice. We observed a significant retention time reduction related to the absorbed dose and we assume radiation induced interface trap generation as the origin of the retention time reduction. By measuring individual cells retention time before and after radiation exposures, we found out that the reduction is not homogeneous among cells: the amount of leakage current increase depends on the position and the energy level of the generated trap, leading to a wide distribution of retention time reduction. Of particular interest is the fact that device was unbiased during irradiation and that no post-irradiation recovery was observed
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Characterization of data retention faults in DRAM devices
No full textDynamic random access memory (DRAM) is the most widely used type of memory in the consumer market today, and it is still widely used for mass memories for space application. Even though accurate tests are performed by vendors to ensure high reliability, DRAM errors continue to be a common source of failures in the field. Recent large-scale studies reported how most of the errors experienced by DRAM subsystem are due to faults repeating on the same memory address but occurring only under specific condition. As these failures could be related to the memory cell’s ability to retain its stored charge, an empirical characterization of DRAM data retention time was performed within this study. Retention time information was collected from SDRAM devices from two different vendors to evaluate the impact of four different factors (temperature, data background, previous charge level and variable retention time) on DRAM cells retention time. Gathered results can be useful in defining enhanced test procedures for the early detection of data retention faults
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
An FPGA-based hardware accelerator for CNNs inference on board satellites: Benchmarking with Myriad 2-based solution for the cloudscout case study
No full textIn recent years, research in the space community has shown a growing interest in Artificial Intelligence (AI), mostly driven by systems miniaturization and commercial competition. In particular, the application of Deep Learning (DL) techniques on board Earth Observation (EO) satellites might lead to numerous advantages in terms of mitigation of downlink bandwidth constraints, costs, and increment of the satellite autonomy. In this framework, the CloudScout project, funded by the European Space Agency (ESA), represents the first time in-orbit demonstration of a Convolutional Neural Network (CNN) applied to hyperspectral images for cloud detection. The first instance of this use case has been done with an INTEL Myriad 2 VPU on board a CubeSat optimized for low cost, size, and power efficiency. Nevertheless, this solution introduces multiple drawbacks due to its design not specifically being for the space environment, thus limiting its applicability to short-lifetime Low Earth Orbit (LEO) applications. The current work provides a benchmark between the Myriad 2 and our custom hardware accelerator designed for Field Programmable Gate Arrays (FPGAs). The metrics used for comparison include inference time, power consumption, space qualification, and components. The obtained results show that the FPGA-based solution is characterized by a reduced inference time, and a higher possibility of customization, but at the cost of greater power consumption and a longer Time to Market. As a conclusion, the proposed approach might extend the potential market of DL-based solutions to long-term LEO or interplanetary exploration missions through deployment on space-qualified FPGAs, with a limited cost in energy efficiency
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