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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 289 records · Page 16
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NASA NTRS2020

Comparison of Cloud Detection Algorithms for Sentinel-2 Imagery

Accurate, automated cloud and cloud shadow detection is a key component of the processing needed to prepare optical satellite imagery for scientific analysis. Many existing cloud detection algorithms rely on temperature information to identify clouds, making detection difficult for imagers that lack a thermal band, like Sentinel-2. To get maximum benefit from Sentinel-2 products it is critical to understand which algorithms best identify clouds and their shadows in images. We examined the relative performance of five different cloud-masking algorithms (Sen2Cor, MAJA, LaSRC, Fmask and Tmask) in 6 Sentinel-2 scenes (28 total images) distributed across the Eastern Hemisphere. Expanding on these comparisons, we tested ensemble approaches to improve results. We tested three ensemble approaches to cloud and shadow classification based on the outputs of the five initial algorithms using the cloud masks in: (1) a majority prediction model; (2) a random forests model; and (3) a conditional logic model. Accuracy assessments show a trade-off between omission and commission errors in cloud detection for individual algorithms across all sites, and some algorithms are better at detecting either clouds or cloud shadows. No single algorithm outperforms the others for both clouds and shadows. Aggregating the results from multiple algorithms produces fewer undetected clouds and higher overall accuracy than any single algorithm, with as high as 2.7% improvement over the top-performing algorithm, suggesting an ensemble approach may be the most useful for processing of Sentinel-2 data.

Sentinel-2↗
NASA NTRS1986

Science opportunities from the Topex/Poseidon mission

The U.S. National Aeronautics and Space Administration (NASA) and the French Centre National d'Etudes Spatiales (CNES) propose to conduct a Topex/Poseidon Mission for studying the global ocean circulation from space. The mission will use the techniques of satellite altimetry to make precise and accurate measurements of sea level for several years. The measurements will then be used by Principal Investigators (selected by NASA and CNES) and by the wider oceanographic community working closely with large international programs for observing the Earth, on studies leading to an improved understanding of global ocean dynamics and the interaction of the ocean with other processes influencing life on Earth. The major elements of the mission include a satellite carrrying an altimetric system for measuring the height of the satellite above the sea surface; a precision orbit determination system for referring the altimetric measurements to geodetic coordinates; a data analysis and distribution system for processing the satellite data, verifying their accuracy, and making them available to the scientific community; and a principal investigator program for scientific studies based on the satellite observations. This document describes the satellite, its sensors, its orbit, the data analysis system, and plans for verifying and distributing the data. It then discusses the expected accuracy of the satellite's measurements and their usefulness to oceanographic, geophysical, and other scientific studies. Finally, it outlines the relationship of the Topex/Poseidon mission to other large programs, including the World Climate Research Program, the U.S. Navy's Remote Ocean Sensing System satellite program and the European Space Agency's ERS-1 satellite program.

Stewart, R.↗
NASA NTRS1978

Achievements of ATS-6 beacon experiment over Indian sub-continent

The repositioning of the ATS-6 satellite at 34 deg E enabled the scientific community of India to use the satellite's radio beacon for ionospheric studies. Two scientific projects were undertaken. The objective of the first project was to map ionospheric electron content, range rate errors, traveling ionospheric phenomena, solar flare effect, and magnetic phenomena. The second project was aimed at studying geophysical phenomena associated with the equatorial electrojet. The principal results of these studies are described.

Deshpande, M. R.↗
NASA NTRS1978

Infrared Astronomical Satellite /IRAS/ and Shuttle Infrared Telescope Facility /SIRTF/ - Implications of scientific objectives on focal plane sensitivity requirements

The full potential of infrared astronomy can be realized only through observations made with space-based telescopes cooled to cryogenic temperatures. The paper outlines the scientific mission, system description, and focal plane requirements for two cryogenic telescopes: the Infrared Astronomical Satellite (IRAS) and the Shuttle Infrared Telescope Facility (SIRTF). IRAS, a 60-cm superfluid-helium-cooled telescope system, will perform a one-year 8-120-micron IR sky survey; it will provide results of high reliability and sensitivity, produce the first complete survey data for the 30-120-micron region, and fill in missing portions (spectrally and spatially) of previous surveys short of 30 microns; its focal plane assembly is being designed to approach background-limited performance with an array of 62 discrete detectors. The SIRTF design will allow detailed follow-up studies in the 1-1000-micron range with a 116-160-cm observatory-class instrument. The Shuttle sortie capability introduces the unique SIRTF concept of an easily refurbishable or replaceable focal plane instrument complement in an orbiting cryogenic telescope.

Mccreight, C. R.↗
NASA NTRS1976

Report of the Joint Scientific Mission Definition Team for an infrared astronomical satellite

The joint effort is reported of scientists and engineers from the Netherlands, the United Kingdom, and the United States working as a team for the purpose of exploring the possibility of a cooperative venture. The proposed mission builds upon experience gained from the successful Astronomical Netherlands Satellite (ANS). This satellite will be in a polar orbit at an altitude of 900 km. It will carry an 0.6 m diameter telescope cooled with helium to a temperature near 10K. An array of approximately 100 detectors will be used to measure the infrared flux in four wavelength bands centered at 10, 20, 50, and 100 microns. Sources will be located on the sky with positional accuracy of 1/2 arcminute. The instrument should be able to investigate the structure of extended sources with angular scales up to 1.0 deg. The entire sky will be surveyed and the full lifetime of the mission of about one year will be necessary to complete the survey. Special observational programs will also be incorporated into the mission.

Source record↗
NASA NTRS1997

Re-Flight of the Deployable Retrievable Booms

The Tethered Satellite System (TSS), a scientific payload which was flown on STS-46 and again on STS-75, included two satellite-mounted Deployable Retrievable Booms (DRB's). The system was launched aboard the Space Shuttle Atlantis in July 1992. However, because of the problems which occurred at the original attempted deployment of the Tethered Satellite, the DRBs were never operated on-orbit during the STS-46 mission. In postflight functional tests, both DRB's failed to relatch properly. This paper discusses the troubleshooting of the anomalies, design changes, and DRB operational constraints incorporated for the STS-75 mission

Foster, C. L.↗
NASA NTRS2003

SAO Participation in the GOME and SCIAMACHY Satellite Instrument Programs

This report summarizes the progress on our three-year program of research to refine the measurement capability for satellite-based instruments that monitor ozone and other trace species in the Earth's stratosphere and troposphere, to retrieve global distributions of these and other constituents from the GOME and SCIAMACHY satellite instruments, and to conduct scientific studies for the ILAS instruments. This continues our involvements as a U.S. participant in GOME and SCIAMACHY since their inception, and as a member of the ILAS-II Science Team. These programs have led to the launch of the first satellite instrument specifically designed to measure height-resolved ozone, including the tropospheric component (GOME), and the development of the first satellite instrument that will measure tropospheric ozone simultaneously with NO2, CO, HCHO, N2O, H2O, and CH4 (SCIAMACHY). The GOME program now includes the GOME-2 instruments, to be launched on the Eumetsat Metop satellites, providing long-term continuity in European measurements of global ozone that complement the measurements of the TOMS, SBW, OMI, OMPS instruments. The research primarily focuses on two areas: Data analysis, including algorithm development and validation studies that will improve the quality of retrieved data products, in support for future field campaigns (to complement in situ and airborne campaigns with satellite measurements), and scientific analyses to be interfaced to atmospheric modeling studies.

Chance, Kelly↗
NASA NTRS2004

SAO Participation in the GOME and SCIAMACHY Satellite Instrument Programs

This report summarizes the progress on our three-year program of research to refine the measurement capability for satellite-based instruments that monitor ozone and other trace species in the Earth's stratosphere and troposphere, to retrieve global distributions of these and other constituents h m the GOME and SCIAMACHY satellite instruments, and to conduct scientific studies for the ILAS instruments. This continues our involvements as a U.S. participant in GOME and SCIAMACHY since their inception, and as a member of the ILAS-II Science Team. These programs have led to the launch of the first satellite instrument specifically designed to measure height-resolved ozone, including the tropospheric component (GOME), and the development of the first satellite instrument that will measure tropospheric ozone simultaneously with NO2, CO, HCHO, N2O, H2O, and CH4 (SCIAMACHY). The GOME program now includes the GOME-2 instruments, to be launched on the Eumetsat Metop satellites, providing long-term continuity in European measurements of global ozone that complement the measurements of the TOMS, SBUV, OMI, OMPS instruments. The research primarily focuses on two areas: Data analysis, including algorithm development and validation studies that will improve the quality of retrieved data products, in support for future field campaigns (to complement in situ and airborne campaigns with satellite measurements), and scientific analyses to be interfaced to atmospheric modeling studies.

Hilsenrath, Ernest↗
NASA NTRS1992

Cloud fraction, layer, and direction of movement results from sky cameras during the FIRE IFO, Coffeyville, Kansas, experiment for the period Nov. 12 through Dec. 9, 1991

Tables and figures are presented which show local site observations of cloud fractions, the number of cloud layers, direction of movement, and precipitation data collected during the FIRE (First ISCCP Regional Experiment) Phase 2 Cirrus Intensive Field Observations (IFO) conducted in Coffeyville, Kansas during November and December, 1991. Selected data are also presented at the times of the TIROS Operational Vertical Sounder (TOVS) satellite overpass. Several major scientific projects have used surface-based observations of clouds to compare directly with those being observed from satellites. Characterizing the physical properties of clouds is extremely useful in obtaining a more accurate analysis of the effect of clouds and their movements on weather and climate. It is the purpose of this paper to report data collected during the FIRE Phase 2 IFO experiment and to provide a brief history of such a surface-based system and the technical information required for recording local cloud parameters.

Gerald C Purgold↗
NASA NTRS1983

Preliminary scientific results from the first six months of the infrared astronomy satellite (IRAS)

The Infrared Astronomy Satellite (IRAS) was successfully launched on 25 January 1983. The goals of this joint U.S., Dutch, and British project were twofold. The first, and most important, goal was to perform an unbiased all-sky survey at wavelengths of 12, 25, 60, and 100 microns to establish the importance of infrared emission in the energy balance of the universe, to map the diffuse emission from the Galaxy and the material in the solar system, and to obtain low resolution spectra of the brightest sources identified at 12 and 25 microns. A second mission objective was to study specific known astronomical objects in more detail to gain higher sensitivity or higher spatial resolution than that achievable by normal survey observations. The satellite is now seven months into its one year mission life, and survey operations are exceeding prelaunch expectations. The initial all-sky survey was completed on 26 August 1983. In the last four months of the mission a second all-sky survey will be conducted to enhance the survey completeness. A previous paper in the proceedings of this conference (Low et al., 1983) has described the design and performance of the satellite. In this paper a description is provided of some of the early scientific results from the IRAS mission.

Soifer, B. T.↗
NASA NTRS1972

S-cubed-a spacecraft and experiment description

The launch of the Explorer 45 satellite and the instruments installed in the satellite are discussed. The scientific objectives of the first mission, the orbital parameters, and the capabilities of the data system are examined. The satellite is designed to carry out investigations of specific magnetospheric phenomena in the heart of the magnetosphere. The data handling system is programmable from the ground for greater flexibility.

Longanecker, G. W.↗
NASA NTRS1990

Selecting a model of the neutral atmosphere

The characteristics and applicability of some of the more frequently used atmospheric models covering the thermosphere are discussed from the point of view of selecting the most appropriate model for an engineering or scientific problem. Models based on satellite atmospheric drag are the earliest examples of global models and are still widely used for engineering studies. Later models based on satellite instrumentation and ground based measurements were originally aimed at scientific studies of the atmosphere, but their absolute accuracies for total densities are now similar to those of drag based models while providing better thermospheric temperature, composition, and winds. Theoretical models are now approaching the accuracy of climatological empirical models and may surpass them in the near future. Each new model generation, however, is more complicated and costly to run on a computer.

Hedin, A. E.↗
NASA NTRS1985

Launching rockets and small satellites from the lunar surface

Scientific payloads and their propulsion systems optimized for launch from the lunar surface differ considerably from their counterparts for use on earth. For spin-stabilized payloads, the preferred shape is a large diameter-to-length ratio to provide stability during the thrust phase. The rocket motor required for a 50-kg payload to reach an altitude of one lunar radius would have a mass of about 41 kg. To place spin-stabilized vehicles into low altitude circular orbits, they are first launched into an elliptical orbit with altitude about 840 km at aposelene. When the spacecraft crosses the desired circular orbit, small retro-rockets are fired to attain the appropriate direction and speed. Values of the launch angle, velocity increments, and other parameters for circular orbits of several altitudes are tabulated. To boost a 50-kg payload into a 100-km altitude circular orbit requires a total rocket motor mass of about 90 kg.

Anderson, K. A.↗
NASA NTRS1992

Considerations on formation flying separations for earth observing satellite missions

We assume that scientific requirements (or other mission requirements) call for simultaneous observations from sensors located on different formation-flying spacecraft, and assess how well various kinds of formations of two and three spacecraft can meet these simultaneity requirements. We simulate two types of formation, one where the slave spacecraft moves with respect to the reference spacecraft, and the other where the two spacecraft are kept at a constant time separation. For each type of formation we consider two attitudes: a perfect local vertical local horizontal (LVLH) and an attitude which represents the maximum allowable mission tolerance offset from the mission requirements for attitude determination. We simulate formations of multiple spacecraft and determine how well they can perform simultaneous observations. For each spacecraft we compute the instantaneous ground projection of the center of the imager's fieId of view and plot the movement of the instantaneous ground projection of one spacecraft in the formation relative to the other. The size and shape of this effective ground target parametrize the size and shape of the actual ground target as well as the size and shape of the imager's field of view and the percentage of overlap required.

Folta, David↗
NASA NTRS2016

Capturing Complete Spatial Context in Satellite Observations of Greenhouse Gases

Scientific consensus from a 2015 pre-Decadal Survey workshop highlighted the essential need for a wide-swath (mapping) low earth orbit (LEO) instrument delivering carbon dioxide (CO2), methane (CH4), and carbon monoxide (CO) measurements with global coverage. OCO-2 pioneered space-based CO2 remote sensing, but lacks the CH4, CO and mapping capabilities required for an improved understanding of the global carbon cycle. The Carbon Balance Observatory (CARBO) advances key technologies to enable high-performance, cost-effective solutions for a space-based carbon-climate observing system. CARBO is a compact, modular, 15-30° field of view spectrometer that delivers high-precision CO2, CH4, CO and solar induced chlorophyll fluorescence (SIF) data with weekly global coverage from LEO. CARBO employs innovative immersion grating technologies to achieve diffraction-limited performance with OCO-like spatial (2 x 2 sq.km) and spectral (λ/Δλ≈ 20,000) resolution in a package that is >50% smaller, lighter and more cost-effective. CARBO delivers a 25- to 50-fold increase in spatial coverage compared to OCO-2 with no loss of detection sensitivity. Individual CARBO modules weigh < 20 kg, opening diverse new space-based platform opportunities.

Miller, Charles E.↗
NASA NTRSDate not supplied

Production of Flight Instruments for Multi-Satellite Constellations

Recent National Academy of Science Decadal Surveys in space and Earth-science have called for simultaneous, distributed multi-point measurements in and from space, requiring constellations of small spacecraft. Small satellites have demonstrated their utility for enabling high-quality science measurements and observations. NASA missions have leveraged advances in sensor miniaturization, technology innovations, and new small satellite mission architectures to enable meaningful measurement-based scientific investigations that operate on small satellites and that are responsive to science objectives described in National Academy of Science Decadal Surveys. The advent of high capability small spacecraft enables consideration of science missions involving multiple small spacecraft, constellations of a few or many for simultaneous distributed in situ observations or remote observations from a variety of viewpoints. The central challenge for fielding instrumented space-flight constellations is to provide the required multiple sets of fully verified and calibrated instrument hardware, software, and operational processes from within a one-off project-based scientific space flight culture. Although there are numerous commercial entities providing “off-the shelf” spacecraft and avionics, the challenge lies in the multi-unit production of the uniquely targeted instrumentation necessary to perform the specific measurements required for a particular science investigation. Traditionally, the cost of such instrumentation has represented a significant portion of the hardware cost for a mission and posed the highest risk area for implementation. A shift in paradigm from large science platforms to constellations of smaller satellites drives the challenge to build instruments in a quasi-production environment. This paper describes key aspects of, and challenges encountered in the development program for the successful production of instruments for the Fast-Plasma Investigation (FPI) instrument suite of 64 flight plasma spectrometers and supporting electronics on the NASA Magnetospheric Multiscale (MMS) 4 satellite constellation mission. Although the MMS mission was not composed of small satellites, there are key aspects of the instrument production that apply directly to constellations of small satellites.

Arthur D Jacques↗