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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

The Galileo Solid-State Imaging experiment

The Galileo Orbiter's Solid-State Imaging (SSI) experiment uses a 1.5-m focal length TV camera with 800 x 800 pixel, virtual-phase CCD detector in order to obtain images of Jupiter and its satellites which possess a combination of sensitivity levels, spatial resolutions, geometric fidelity, and spectral range that are unmatched by earlier imaging data. After describing the performance of this equipment on the basis of ground calibrations, attention is given to the SSI experiment's Jupiter system observation objectives; these encompass atmospheric science, satellite surfaces, ring structure, and 'darkside' experiments.

Belton, Michael J. S.↗
NASA NTRS1993

Data analysis for GOPEX image frames

The data analysis based on the image frames received at the Solid State Imaging (SSI) camera of the Galileo Optical Experiment (GOPEX) demonstration conducted between 9-16 Dec. 1992 is described. Laser uplink was successfully established between the ground and the Galileo spacecraft during its second Earth-gravity-assist phase in December 1992. SSI camera frames were acquired which contained images of detected laser pulses transmitted from the Table Mountain Facility (TMF), Wrightwood, California, and the Starfire Optical Range (SOR), Albuquerque, New Mexico. Laser pulse data were processed using standard image-processing techniques at the Multimission Image Processing Laboratory (MIPL) for preliminary pulse identification and to produce public release images. Subsequent image analysis corrected for background noise to measure received pulse intensities. Data were plotted to obtain histograms on a daily basis and were then compared with theoretical results derived from applicable weak-turbulence and strong-turbulence considerations. Processing steps are described and the theories are compared with the experimental results. Quantitative agreement was found in both turbulence regimes, and better agreement would have been found, given more received laser pulses. Future experiments should consider methods to reliably measure low-intensity pulses, and through experimental planning to geometrically locate pulse positions with greater certainty.

Levine, B. M.↗
NASA NTRS1993

Earth imaging results from Galileo's second encounter

The recent flyby of the Galileo spacecraft en route to Jupiter contributes a unique perspective to our view of our home planet. Imaging activities conducted during the second Earth encounter provide an important opportunity to assess new methods and approaches on familiar territory. These include unique multispectral observations, low light-level imaging (searches for aurorae, lightning and artificial lights on the nightside) and experiments with multiple exposure times to extend the effective radiometric resolution and dynamic range of the camera system. Galileo imaging data has the potential to make important contributions to terrestrial remote sensing. This is because the particular set of filters included in the Solid State Imaging system are not presently incorporated in any currently operating Earth-orbiting sensor system. The visible/near-infrared bandpasses of the SSI filters are well suited to remote sensing of geological, glaciological, botanical, and meteorological phenomena. Data from this and the previous Earth encounter may provide an extremely valuable reference point in time for comparison with similar data expected from EOS or other systems in the future, contributing directly to our knowledge of global change. The highest resolution imaging (0.2 km/pixel) during the December, 1992 encounter occurred over the central Andes; a five filter mosaic of visible and near infrared bands displays the remarkable spectral heterogeneity of this geologically diverse region. As Galileo departed the Earth, cooperative imaging with the Near Infrared Mapping Spectrometer (NIMS) instrument targeted Antarctica, Australia, and Indonesia at 1.0 to 2.5 km/pixel resolutions in the early morning local times near the terminator. The Antarctic data are of particular interest, potentially allowing ice grain size mapping using the 889 and 968 nm filters and providing an important means of calibrating the technique for application to the Galilean satellites. As the spacecraft receded further, regional scale imaging provided data which, along with data from the previous encounter, will enable the production of global multispectral mosaics of Earth in each of the SSI filters.

Greenberg, R.↗
NASA NTRS1994

An image assessment study of image acceptability of the Galileo low gain antenna mission

This paper describes a study conducted by NASA Ames Research Center (ARC) in collaboration with the Jet Propulsion Laboratory (JPL), Pasadena, California on the image acceptability of the Galileo Low Gain Antenna mission. The primary objective of the study is to determine the impact of the Integer Cosine Transform (ICT) compression algorithm on Galilean images of atmospheric bodies, moons, asteroids and Jupiter's rings. The approach involved fifteen volunteer subjects representing twelve institutions involved with the Galileo Solid State Imaging (SSI) experiment. Four different experiment specific quantization tables (q-table) and various compression stepsizes (q-factor) to achieve different compression ratios were used. It then determined the acceptability of the compressed monochromatic astronomical images as evaluated by Galileo SSI mission scientists. Fourteen different images were evaluated. Each observer viewed two versions of the same image side by side on a high resolution monitor, each was compressed using a different quantization stepsize. They were requested to select which image had the highest overall quality to support them in carrying out their visual evaluations of image content. Then they rated both images using a scale from one to five on its judged degree of usefulness. Up to four pre-selected types of images were presented with and without noise to each subject based upon results of a previously administered survey of their image preferences. Fourteen different images in seven image groups were studied. The results showed that: (1) acceptable compression ratios vary widely with the type of images; (2) noisy images detract greatly from image acceptability and acceptable compression ratios; and (3) atmospheric images of Jupiter seem to have higher compression ratios of 4 to 5 times that of some clear surface satellite images.

Chuang, S. L.↗
NASA NTRS1994

Subjective evaluations of integer cosine transform compressed Galileo solid state imagery

This paper describes a study conducted for the Jet Propulsion Laboratory, Pasadena, California, using 15 evaluators from 12 institutions involved in the Galileo Solid State Imaging (SSI) experiment. The objective of the study was to determine the impact of integer cosine transform (ICT) compression using specially formulated quantization (q) tables and compression ratios on acceptability of the 800 x 800 x 8 monochromatic astronomical images as evaluated visually by Galileo SSI mission scientists. Fourteen different images in seven image groups were evaluated. Each evaluator viewed two versions of the same image side by side on a high-resolution monitor; each was compressed using a different q level. First the evaluators selected the image with the highest overall quality to support them in their visual evaluations of image content. Next they rated each image using a scale from one to five indicating its judged degree of usefulness. Up to four preselected types of images with and without noise were presented to each evaluator.

Haines, Richard F.↗
NASA NTRS1999

Studies for the Loss of Atomic and Molecular Species from Io

A summary discussion of research undertaken in this project is presented and is related to six published papers attached in the appendix. The discussion is divided into six sections describing a variety of studies for the loss of atomic and molecular species from Io. They include studies for: (1) atomic sodium, (2) SO2, (3) O and S, (4) spectacular high-spatial resolution ultraviolet image observations of O, S, and possibly H in Io's atmosphere and/or corona acquired by the Space Telescope Imaging Spectrometer (STIS) of the Hubble Space Telescope (HST), (5) spectacular high-spatial resolution visible Io eclipse image observations acquired by the Solid State Imager (SSI) of Galileo spacecraft, (6) ground-based observations acquired by the Solid State Imager (SSI) of Galileo spacecraft, and (7) ground-based observations of Io's neutral cloud in [OI] 6300 angstrom emission. New source rates at Io's exobase for SO2, O, and H are given and a variety of interesting implications for Io's atmosphere and for the Io plasma torus are discussed. Appendices that are comprised of articles published during the contract are also presented.

Smyth, William H.↗
NASA NTRS2001

HST/STIS Visible Images of Io in Eclipse

On 1999 August 27, Io was observed with HST STIS/CCD using a 2"x 2" aperture soon after it entered into eclipse (CML = 342 to 346). Two G750M/I spectral images, covering 5815 Angstroms to 6380 Angstroms and starting 3 and 17 minutes after 2nd contact, recorded emissions of Na I 5890,5896 Angstroms and [O I] 6300,6364 Angstroms. The oxygen and sodium emissions show several similar features. (1) Downstream wake emission that correlates in location with jovian magnetic field orientation; (2) Enhanced emissions near the sub-jovian region, albeit a relatively weak enhancement for sodium; and (3) Limb glow that is brighter in the hemisphere facing the jovian magnetic equator. These features are qualitatively similar to [O I] 6300 Angstrom images obtained with HST WFPC2 and to the UV STIS results of Roesler et al. 1999 (Science, 283, 353), as well as broadband images taken by the Galileo SSI (Geissler et al. JGR submitted) and more recent Cassini images. The integrated oxygen (6300 Angstrom + 6364 Angstrom) emission intensity (10.5 k Rayleighs (kR) disk averaged) did not change between the two exposures while the integrated disk averaged sodium D emission intensity decreased by 19% from 5.7 kR to 4.6 kR. Also, in contrast to the oxygen emission, sodium showed relatively enhanced emission in the northern polar regions. Likewise, on 1999 August 23, Io eclipse STIS observations were made in the near-UV and blue regions to try to identify the Galileo SSI violet filter emissions. Preliminary analysis reveals a residual signal after subtraction of a dominant scattered light background that is suggestive of a SO2 band structure. In addition, the largest individual emission at about 4075 Angstrom could be the S(+) doublet.

Oliversen, Ron J.↗
NASA NTRS2002

Satellite Observations of Solar Irradiance and Sun-Climate Impacts

Solar activity is now near its maximum, with events such as the 2001 "Bastille Day Event", a Coronal Mass Ejection which merited a full session at AGO'S annual meeting - and two major sunspot groupings earlier this year, with associated variations in TSI (Total Solar Irradiance). We discuss recent satellite measurements of TSI by ACRIM 2 and 3 And Virgo, and new precision observations of TSI and SSI (Solar Spectral Irradiance) expected from the SORCE mission, planned to launch in fall 2002. SSG has been added to TSI as a required EOS and NPOESS measurement because different spectral components provide energy inputs to different components of the climate system - UV into upper atmosphere and ozone, IR into lower atmosphere and clouds, and Visible into the biosphere. Succeeding satellite missions being planned for 2006 and 2010 will continue to monitor both TSI and SSI. We summarize current ideas about the potential impact of solar variability on Earth's climate on time scales from days to decades to centuries.

Cahalan, R.↗
NASA NTRS2003

Future Satellite Observations of Solar Irradiance

Required solar irradiance measurements for climate studies include those now being made by the Total Irradiance Monitor (TIM) and the Spectral Irradiance Monitor (SIM) onboard the SORCE satellite, part of the Earth Observing System fleet of NASA satellites. Equivalent or better measures of Total Solar Irradiance (TSI) and Spectral Solar Irradiance (SSI, 200 to 2000 nm) are planned for the post-2010 satellites of the National Polar-orbiting Operational Environmental Satellite System ("OESS). The design life of SORCE is 5 years, so a "Solar Irradiance Gap Filler" EOS mission is being planned for launch in the 2007 time frame, to include the same TSI and SSI measurements. Besides avoiding any gap, overlap of the data sources is also necessary for determination of possible multi-decadal trends in solar irradiance. We discuss these requirements and the impacts of data gaps, and data overlaps, that may occur in the monitoring of the critical solar radiative forcing.

Cahalan, R. F.↗
NASA NTRS2002

Reliability and Productivity Modeling for the Optimization of Separated Spacecraft Interferometers

As technological systems grow in capability, they also grow in complexity. Due to this complexity, it is no longer possible for a designer to use engineering judgement to identify the components that have the largest impact on system life cycle metrics, such as reliability, productivity, cost, and cost effectiveness. One way of identifying these key components is to build quantitative models and analysis tools that can be used to aid the designer in making high level architecture decisions. Once these key components have been identified, two main approaches to improving a system using these components exist: add redundancy or improve the reliability of the component. In reality, the most effective approach to almost any system will be some combination of these two approaches, in varying orders of magnitude for each component. Therefore, this research tries to answer the question of how to divide funds, between adding redundancy and improving the reliability of components, to most cost effectively improve the life cycle metrics of a system. While this question is relevant to any complex system, this research focuses on one type of system in particular: Separate Spacecraft Interferometers (SSI). Quantitative models are developed to analyze the key life cycle metrics of different SSI system architectures. Next, tools are developed to compare a given set of architectures in terms of total performance, by coupling different life cycle metrics together into one performance metric. Optimization tools, such as simulated annealing and genetic algorithms, are then used to search the entire design space to find the "optimal" architecture design. Sensitivity analysis tools have been developed to determine how sensitive the results of these analyses are to uncertain user defined parameters. Finally, several possibilities for the future work that could be done in this area of research are presented.

Kenny, Sean↗
NASA NTRS2004

Solar Activity and its Impact on Earth's Climate

The Sun's activity is now approaching an expected 2006 minimum, following the dramatic maximum of Solar Cycle 23, that included events such as the 2001 "Bastille Day" Coronal Mass Ejection, and the record-setting Oct-Nov 2003 solar flares, with their associated sunspots and variations in Total Solar Irradiance, or TSI. On Nov 4,2003 the largest X-ray flare ever detected (X-28) was observed in detail. We discuss recent satellite measurements of TSI by ACRIM 2 and 3 and Virgo, and new precision observations of TSI and SSI (Solar Spectral Irradiance) from the SORCE mission, that launched on January 25,2003. TSI variations recorded during the June 8,2004 transit of Venus show the unprecedented precision of the SORCE Total Irradiance Monitor (TIM) instrument, the first of its kind to employ phase-sensitive detection. The SORCE spectral instruments, XPS, Solstice, and SIM, record the Sun's changes over a wide range of wavelengths, from 1 to more than 2000 nanometers, for the first time covering the peak of the solar spectrum, including spectral components that provide energy inputs to key components of the climate system - ultraviolet (UV) into the upper atmospheric ozone layer, infrared (IR) into the lower atmosphere and clouds, and Visible into the Oceans and biosphere. Succeeding satellite missions are planned to monitor both TSI and SSI through Cycle 24. We summarize current ideas about decadal and longer solar variability, and associated potential impacts on Earth's climate on time scales from decades to centuries, especially highlighting the role of feedbacks in the climate system.

Cahalan, Robert F.↗
NASA NTRS2009

PrimeSupplier Cross-Program Impact Analysis and Supplier Stability Indicator Simulation Model

PrimeSupplier, a supplier cross-program and element-impact simulation model, with supplier solvency indicator (SSI), has been developed so that the shuttle program can see early indicators of supplier and product line stability, while identifying the various elements and/or programs that have a particular supplier or product designed into the system. The model calculates two categories of benchmarks to determine the SSI, with one category focusing on agency programmatic data and the other focusing on a supplier's financial liquidity. PrimeSupplier was developed to help NASA smoothly transition design, manufacturing, and repair operations from the Shuttle program to the Constellation program, without disruption in the industrial supply base.

Calluzzi, Michael↗
NASA NTRS2009

Primesupplier Podcast

PrimeSupplier, s supplier cross program and element impact simulation model with supplier solvency indicator (SSI), has been developed so that the Shuttle Program can see an early indicator of supplier and product line stability while identifying the various elements and/or programs that have a particular supplier of product designed into the system. The model calculates two categories of benchmarks to determine the SSI with one category focusing on Agency programmatic and the other being a supplier financial liquidity.

Galluzzi, Michael↗
NASA NTRS2013

Phoenix Telemetry Processor

Phxtelemproc is a C/C++ based telemetry processing program that processes SFDU telemetry packets from the Telemetry Data System (TDS). It generates Experiment Data Records (EDRs) for several instruments including surface stereo imager (SSI); robotic arm camera (RAC); robotic arm (RA); microscopy, electrochemistry, and conductivity analyzer (MECA); and the optical microscope (OM). It processes both uncompressed and compressed telemetry, and incorporates unique subroutines for the following compression algorithms: JPEG Arithmetic, JPEG Huffman, Rice, LUT3, RA, and SX4. This program was in the critical path for the daily command cycle of the Phoenix mission. The products generated by this program were part of the RA commanding process, as well as the SSI, RAC, OM, and MECA image and science analysis process. Its output products were used to advance science of the near polar regions of Mars, and were used to prove that water is found in abundance there. Phxtelemproc is part of the MIPL (Multi-mission Image Processing Laboratory) system. This software produced Level 1 products used to analyze images returned by in situ spacecraft. It ultimately assisted in operations, planning, commanding, science, and outreach.

Stanboli, Alice↗
NASA NTRS2015

UAS Integration in the NAS Project: Fast-Time Simulation Studies

NASA is working on the project for Unmanned Aircraft System (UAS) integration into the National Airspace System (NAS) and helping the RTCA's Special Committee 228 (RTCA SC-228) to develop the minimum operational performance standards (MOPS) for detect-and avoid (DAA) systems. The Ames' Separation Assurance-Sense and Avoid Interoperability (SSI) team for the project is supporting this effort through fast-time simulation studies using the Airspace Concept Evaluation System (ACES) simulation platform. This presentation introduces the Ames SSI team's tasks and shows some results from accomplished fast-time simulation studies. It is a part of overall presentations for NASA's efforts for the UAS integration into the NAS project.

fast time simulation↗
NASA NTRS2022

A Survey of Mathematical Structures for Lunar Networks

To sustain the current and increasing accessibility of space, a scalable communications infrastructure (i.e. the Solar System Internet, SSI) is necessary. The goal of this paper is to begin the discovery of the fundamental underlying mathematical structure of space networks to help the research community harness these structures for algorithm development and optimization. To ensure the applicability of the research, the approaches are considered through the lens of simulated scenarios inspired by the Artemis Back-to-the-Moon mission set for 2024. We note that any approach to an SSI must fit under the umbrella of Delay Tolerant Networking (DTN), due to celestial mobility, high link latencies, high variance in link latencies, disconnections, lack of end-to-end paths, and so on. These difficulties are exacerbated by the fact that the underlying structure of a space network is a time-evolving network and may experience multiple discontinuities in its topology. In this paper we propose several novel approaches to a mathematical foundation for Delay Tolerant Networking Theory that fall outside the traditional scope of temporal network theory. These techniques include methods from Topological Data Analysis, Dynamic Graph Analysis, Applied Algebraic Geometry, Probability Theory, and Game Theory. Some of these methods include tools adapted to the study of dynamic metric spaces, such as zigzag persistent homology and their higher parameter analogs. We find that several of these methods target desired engineering outcomes such as discovery and automatic sub-netting. While each approach is theoretical, they are also algorithmic in nature and offer immediate practical applications. The paper concludes with comparisons of the various methods along with suggestions for future work.

Delay tolerant networking↗
NASA NTRS2022

Solar Temperature Variations Computed from SORCE SIM Irradiances Observed During 2003-2020

NASA’s Solar Radiation and Climate Experiment (SORCE) Spectral Irradiance Monitor (SIM) instrument produced about 17 years of daily average Spectral Solar Irradiance ( SSI ) data for wavelengths 240 nm – 2416 nm. We choose a day of minimal solar activity, 2008-08-24, during the 2008 − 2009 minimum between cycles 23 and 24, and compute the brightness temperature (𝑇 o ) from that day’s solar spectral irradiance (𝑆𝑆𝐼 o ). We consider small variations of T and SSI about these reference values, and derive linear and quadratic analytic approximations by Taylor expansion about the reference day values. To determine approximation accuracy, we compare to exact brightness temperatures T computed from the Planck spectrum, by solving analytically for T , or equivalent root-finding in Wolfram Mathematica. We find that the linear analytic approximation overestimates, while the quadratic underestimates the exact result. This motivates search for statistical “fit” models “in between” the two analytic models, with minimum root-mean-square-error RMSE. We make this search using open-source statistical R software, determine coefficients for linear and quadratic fit models, and compare statistical with analytic RMSE’s. When only linear analytic and fit models are compared, the fit model is superior at ultraviolet, visible, and near infrared wavelengths. This again holds true when comparing only quadratic models. Quadratic is superior to linear for both analytic and statistical models, and statistical fits give smallest RMSE’s. Lastly, we use linear analytic and fit models to find an interpolating function in wavelength, useful in case the SIM results need adjustment to another choices of wavelengths, to compare or extend to any other instrument.

SORCE↗