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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

KBase Narrative - Viral Analysis End-to-End

This pipeline processes a single metagenomic dataset (downloaded from NCBI SRA) from the Global Ocean Viromes dataset, identifies the viral sequences using VirSorter, and subsequently classifies them with vConTACT2. Along the way there are several intermediary steps to convert files from one KBase object to another - and though some of these can be skipped for this particular dataset - we're explicitly doing them here as to be more easily generalized to other datasets.

Bolduc, Benjamin↗
DOE OSTI2023

From Images to Dark Matter: End-to-end Inference of Substructure from Hundreds of Strong Gravitational Lenses

Abstract Constraining the distribution of small-scale structure in our universe allows us to probe alternatives to the cold dark matter paradigm. Strong gravitational lensing offers a unique window into small dark matter halos (<10 10 M ⊙ ) because these halos impart a gravitational lensing signal even if they do not host luminous galaxies. We create large data sets of strong lensing images with realistic low-mass halos, Hubble Space Telescope (HST) observational effects, and galaxy light from HST’s COSMOS field. Using a simulation-based inference pipeline, we train a neural posterior estimator of the subhalo mass function (SHMF) and place constraints on populations of lenses generated using a separate set of galaxy sources. We find that by combining our network with a hierarchical inference framework, we can both reliably infer the SHMF across a variety of configurations and scale efficiently to populations with hundreds of lenses. By conducting precise inference on large and complex simulated data sets, our method lays a foundation for extracting dark matter constraints from the next generation of wide-field optical imaging surveys.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1978

Potential end-to-end imaging information rate advantages of various alternative communication systems

Various communication systems were considered which are required to transmit both imaging and a typically error sensitive, class of data called general science/engineering (gse) over a Gaussian channel. The approach jointly treats the imaging and gse transmission problems, allowing comparisons of systems which include various channel coding and data compression alternatives. Actual system comparisons include an Advanced Imaging Communication System (AICS) which exhibits the rather significant potential advantages of sophisticated data compression coupled with powerful yet practical channel coding.

Rice, R. F.↗
NASA NTRS1981

Science and Applications Space Platform (SASP) End-to-End Data System Study

The capability of present technology and the Tracking and Data Relay Satellite System (TDRSS) to accommodate Science and Applications Space Platforms (SASP) payload user's requirements, maximum service to the user through optimization of the SASP Onboard Command and Data Management System, and the ability and availability of new technology to accommodate the evolution of SASP payloads were assessed. Key technology items identified to accommodate payloads on a SASP were onboard storage devices, multiplexers, and onboard data processors. The primary driver is the limited access to TDRSS for single access channels due to sharing with all the low Earth orbit spacecraft plus shuttle. Advantages of onboard data processing include long term storage of processed data until TRDSS is accessible, thus reducing the loss of data, eliminating large data processing tasks at the ground stations, and providing a more timely access to the data.

Crawford, P. R.↗
NASA NTRS1981

End-to-end quality measure for transmission of compressed imagery over a noisy coded channel

For the transmission of imagery at high data rates over large distances with limited power and system gain, it is usually necessary to compress the data before transmitting it over a noisy channel that uses channel coding to reduce the effect of noise introduced errors. Both compression and channel noise introduce distortion into the imagery. In order to design a communication link that provides adequate quality of received images, it is necessary first to define some suitable distortion measure that accounts for both these kinds of distortion and then to perform various tradeoffs to arrive at system parameter values that will provide a sufficiently low level of received image distortion. The overall mean square error is used as the distortion measure and a description of how to perform these tradeoffs are included.

Korwar, V. N.↗
NASA NTRS1982

End-to-end imaging information rate advantages of various alternative communication systems

The efficiency of various deep space communication systems which are required to transmit both imaging and a typically error sensitive class of data called general science and engineering (gse) are compared. The approach jointly treats the imaging and gse transmission problems, allowing comparisons of systems which include various channel coding and data compression alternatives. Actual system comparisons include an advanced imaging communication system (AICS) which exhibits the rather significant advantages of sophisticated data compression coupled with powerful yet practical channel coding. For example, under certain conditions the improved AICS efficiency could provide as much as two orders of magnitude increase in imaging information rate compared to a single channel uncoded, uncompressed system while maintaining the same gse data rate in both systems. Additional details describing AICS compression and coding concepts as well as efforts to apply them are provided in support of the system analysis.

Rice, R. F.↗
NASA NTRS1983

An end-to-end data system for the Gamma-Ray Observatory

A data system, which includes parts in the orbiting Gamma-Ray Observatory and in its associated ground system, has been designed to rapidly deliver autonomous, packeted data to the science users. Data autonomy means all of the data, including auxiliary data, necessary for processing is included in the data packet that leaves the spacecraft. The data packets leaving the spacecraft remain unopened until they reach the user. Handling the data on a packet rather than a byte level allows simpler and generic software. The data goes through the system more quickly. This in turn reduces cost.

Hrastar, J.↗
NASA NTRS1988

Wiener restoration of sampled image data - End-to-end analysis

The Wiener filter is formulated as a function of the basic image-gathering and image-reconstruction constraints, thereby providing a method for minimizing the mean-squared error between the (continuous-input) radiance field and its restored (continuous-output) representation. This formulation of the Wiener filter is further extended to the Wiener-characteristic filter, which provides a method for explicitly specifying the desired representation. Two specific examples of Wiener filters are presented.

Fales, Carl L.↗
NASA NTRS1991

Data compression: The end-to-end information systems perspective for NASA space science missions

The unique characteristics of compressed data have important implications to the design of space science data systems, science applications, and data compression techniques. The sequential nature or data dependence between each of the sample values within a block of compressed data introduces an error multiplication or propagation factor which compounds the effects of communication errors. The data communication characteristics of the onboard data acquisition, storage, and telecommunication channels may influence the size of the compressed blocks and the frequency of included re-initialization points. The organization of the compressed data are continually changing depending on the entropy of the input data. This also results in a variable output rate from the instrument which may require buffering to interface with the spacecraft data system. On the ground, there exist key tradeoff issues associated with the distribution and management of the science data products when data compression techniques are applied in order to alleviate the constraints imposed by ground communication bandwidth and data storage capacity.

Tai, Wallace↗
NASA NTRS1992

End-to-end modelling of He II flow systems

A practical computer code has been developed which uses the accepted two-fluid model to simulate He II flow in complicated systems. The full set of equations are used, retaining the coupling between the pressure, temperature and velocity fields. This permits modeling He II flow over the full range of conditions, from strongly or weakly driven flow through large pipes, narrow channels and porous media. The system may include most of the components used in modern superfluid flow systems: non-ideal thermomechanical pumps, tapered sections, constrictions, lines with heated side walls and heat exchangers. The model is validated by comparison with published experimental data. It is applied to a complex system to show some of the non-intuitive feedback effects that can occur. This code is ready to be used as a design tool for practical applications of He II. It can also be used for the design of He II experiments and as a tool for comparison of experimental data with the standard two-fluid model.

Mord, A. J.↗
NASA NTRS1993

An end-to-end pointing budget approach to planetary observing systems with application to EOS

Previously published error budgets have focused on spacecraft error sources for pointing error and have tended to include only spacecraft pointing rather than the ultimate geolocation of each pixel of dam onto a well-defined spot on the surface of the Earth. A systematic approach to geolocation error budgeting, including all contributors in the geolocation process is presented. Its structure allows simultaneous expression of the needs of instrument teams as well as spacecraft design teams. It allows explicit acknowledgement of approximations made for on-board control as well as the ultimate geolocation accuracy achievable after ground processing and exploits the commonality inherent in the on-board and post-processing error budgets. It also includes the uncontrolled and unmeasured spacecraft jitter. This approach can be used to investigate the mission-wide benefit of a variety of design choices, (such as on-board sensing and ground correction of measurements contrasted with on-board correction of measurements). Additionally, in light of increasing accuracy requirements as sensor resolution improves, numerous non-spacecraft contributors to geolocation error are quantified.

Throckmorton, A.↗