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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Flight performance of SEASAT-1 attitude control system

The paper describes the attitude control flight performance of SEASAT-A, (launched in June 1978), until failure of the power subsystem terminated the mission in Oct. 1978. Information provided by the satellite pertained to surface winds and coastal storm activity, currents and wave heights, ocean topography and temperature. The ACS used three-axis momentum exchange and magnetic momentum containment and was set in a nose-down configuration. Attitude control sensing was via horizon sensors and attitude anomalies, resulting from solar interference with the sensors, is covered in detail. Remedial action was taken by reconfiguring the IR scanners, but failure resulted nevertheless. Recommendations for similar future missions include consideration of the effect of light sources and circuit time constants and scan rates. A block diagram of the ACS is included.

Beach, S. W.↗
NASA NTRS1988

Detection of a buried horizon with a high thermal diffusivity using thermal remote sensing

A field investigation using thermal remote sensing was performed to test the feasibility of detecting the surface topography of granite bedrock beneath a thin cover of alluvium. Imagery of a region of the Mojave Desert were taken with an airborne multispectral scanner with thermal spectral bandwidths of 10.4 and 12.5 microns an instantaneous field of view of 2.5 mrad. It is suggested that a buried high thermal diffusivity horizon measurably lowers the surface temperature of the overlying lower diffusivity material during the peak of the annual heating cycle.

Nash, David B.↗
NASA NTRS2021

Satellites for long-term monitoring of inland U.S. lakes: The MERIS time series and application for chlorophyll-a

Lakes and other surface fresh waterbodies provide drinking water, recreational and economic opportunities, food, and other critical support for humans, aquatic life, and ecosystem health. Lakes are also productive ecosystems that provide habitats and influence global cycles. Chlorophyll concentration provides a common metric of water quality, and is frequently used as a proxy for lake trophic state. Here, we document the generation and distribution of the complete MEdium Resolution Imaging Spectrometer (MERIS; Appendix A provides a complete list of abbreviations) radiometric time series for over 2300 satellite resolvable inland bodies of water across the contiguous United States (CONUS) and more than 5,000 in Alaska. This contribution greatly increases the ease of use of satellite remote sensing data for inland water quality monitoring, as well as highlights new horizons in inland water remote sensing algorithm development. We evaluate the performance of satellite remote sensing Cyanobacteria Index (CI)-based chlorophyll algorithms, the retrievals for which provide surrogate estimates of phytoplankton concentrations in cyanobacteria dominated lakes. Our analysis quantifies the algorithms' abilities to assess lake trophic state across the CONUS. As a case study, we apply a bootstrapping approach to derive a new CI-to-chlorophyll relationship, ChlBS, which performs relatively well with a multiplicative bias of 1.11 (11%) and mean absolute error of 1.60 (60%). While the primary contribution of this work is the distribution of the MERIS radiometric timeseries, we provide this case study as a roadmap for future stakeholders' algorithm development activities, as well as a tool to assess the strengths and weaknesses of applying a single algorithm across CONUS.

MERIS timeseries↗
NASA NTRS1976

The solar occultation technique for remote sensing of particulates in the earth's atmosphere. I - The inversion of horizon radiances from space

The aerosol scattering coefficient as a function of height can be recovered from a direct inversion of the single-scattering horizon radiance provided the sun is above the horizon and an independent measurement of extinction as a function of height is made. Aerosol detection is effected by means of spacecraft measurements of the horizon radiance made during periods of spacecraft twilight. A solar occultation technique which allows the twilight measurements to be made when the sun is still above the horizon greatly reduces the complexity of the inversion problem. The second part of the paper reports on the use of a coronograph aboard Skylab to photograph the horizon just before spacecraft twilight in order to monitor the aerosol component above the tropopause. The coronograph picture, centered on 26.5 degrees E longitude and 63.0 degrees S latitude, shows that the aerosol layer peaks at a height of 48 plus or minus 1 km.

Schuerman, D. W.↗
NASA NTRS1962

Study of a Proposed Infrared Horizon Scanner for Use in Space-Orientation Control Systems

An attitude-sensing device for space vehicles which detects the thermal radiation discontinuity at opposite horizons of a planetary body to produce an attitude error signal is described. The planetary body may be the Earth, its Moon, Mars, or Venus. The sensor is expected to have an accuracy of 0.25 degrees for the Earth, a long continuous operating lifetime, a wide altitude range, a wide capture capability, and an inherent ability to produce signals indicating vehicle altitude. An experimental model incorporating many of the features of the proposed sensor indicates that the proposed sensor will be low in weight, volume, and power consumption. The sensor's altitude range, accuracy, lifetime, and sensitivity to radiation from the Moon and planets are discussed.

INFRARED HORIZON SCANNER↗
NASA NTRS1993

Antennas and Propagation; Proceedings of the International Conference, 8th, Heriot-Watt Univeristy, Edinburgh, UK, Mar. 30 - Apr. 2, 1993. Vols. 1 & 2

Conference papers from sessions on the following topics are presented: satellite antennas; modal analysis of transmission line structures; fading and scintillation; microcellular; numerical analysis; Olympus; indoor mobile; mechanical aspects of satellite antennas; flat plate and printed antennas; fade counter measures; electromagnetic theory; feeds for satellites; antennas for personal communications; frequency selected surfaces; remote sensing; active patch antennas; antenna measurements; clear air/trans horizon; high frequency system and noise; rain attenuation and rain scatter; and high frequency direction finding.

Source record↗
NASA NTRS2001

Technology Thrusts for Future Earth Science Applications

This paper presents NASA's recent direction to invest in the critical science instrument and platform technologies in order to realize more reliable, frequent and versatile missions for future Earth Science measurements. Historically, NASA's Earth Science Enterprise has developed and flown science missions that have been large in size, mass and volume. These missions have taken much longer to implement due to technology development time, and have carried a large suite of instruments on a large spacecraft. NASA is now facing an era where the budget for the future years is more or less flat and the possibility for any major new start does not vividly appear on the horizon. Unfortunately, the scientific measurement needs for remote sensing have not shrunk to commensurate with the budget constraints. In fact, the challenges and scientific appetite in search of answers to a score of outstanding questions have been gradually expanding. With these factors in mind, for the last three years NASA has been changing its focus to concentrate on how to take advantage of smaller missions by relying on industry, and minimizing the overall mission life cycle by developing technologies that are independent of the mission implementation cycle. The major redirection of early investment in the critical technologies should eventually have its rewards and significantly reduce the mission development period. Needless to say, in the long run this approach should save money, minimize risk, promote or encourage partnering, allow for a rapid response to measurement needs, and enable frequent missions making a wider variety of earth science measurements. This paper gives an overview of some of the identified crucial technologies and their intended applications for meeting the future Earth Science challenges.

Habib, Shahid↗
NASA NTRS1984

Stimulus factors in motion perception and spatial orientation

The Malcolm horizon utilizes a large projected light stimulus Peripheral Vision Horizon Device (PVHD) as an attitude indicator in order to achieve a more compelling sense of roll than is obtained with smaller devices. The basic principle is that the larger stimulus is more similar to visibility of a real horizon during roll, and does not require fixation and attention to the degree that smaller displays do. Successful implementation of such a device requires adjustment of the parameters of the visual stimulus so that its effects on motion perception and spatial orientation are optimized. With this purpose in mind, the effects of relevant image variables on the perception of object motion, self motion and spatial orientation are reviewed.

Post, R. B.↗
NASA NTRS2016

An Efficient Ray-Tracing Method for Determining Terrain Intercepts in EDL Simulations

The calculation of a ray's intercept from an arbitrary point in space to a prescribed surface is a common task in computer simulations. The arbitrary point often represents an object that is moving according to the simulation, while the prescribed surface is fixed in a defined frame. For detailed simulations, this surface becomes complex, taking the form of real-world objects such as mountains, craters or valleys which require more advanced methods to accurately calculate a ray's intercept location. Incorporation of these complex surfaces has commonly been implemented in graphics systems that utilize highly optimized graphics processing units to analyze such features. This paper proposes a simplified method that does not require computationally intensive graphics solutions, but rather an optimized ray-tracing method for an assumed terrain dataset. This approach was developed for the Mars Science Laboratory mission which landed on the complex terrain of Gale Crater. First, this paper begins with a discussion of the simulation used to implement the model and the applicability of finding surface intercepts with respect to atmosphere modeling, altitude determination, radar modeling, and contact forces influencing vehicle dynamics. Next, the derivation and assumptions of the intercept finding method are presented. Key assumptions are noted making the routines specific to only certain types of surface data sets that are equidistantly spaced in longitude and latitude. The derivation of the method relies on ray-tracing, requiring discussion on the formulation of the ray with respect to the terrain datasets. Further discussion includes techniques for ray initialization in order to optimize the intercept search. Then, the model implementation for various new applications in the simulation are demonstrated. Finally, a validation of the accuracy is presented along with the corresponding data sets used in the validation. A performance summary of the method will be shown using the analysis from the Mars Science Laboratory's terminal descent sensing model. Alternate uses will also be shown for determining horizon maps and orbiter set times.

Shidner, Jeremy D.↗
DOE OSTI2022

Evaluation of Horizon of Viability Optimization Engine for Sustained Power to Critical Infrastructure: Preprint

In the aftermath of increasingly frequent catastrophic events, a typical scenario is Critical Infrastructure (CI) units being supported by available backup sources with a weak power grid that can be intermittent or absent. Such a scenario is significantly challenging in the sense of reliable supply of power to CI units. In this article, an intelligent optimization scheme termed as Horizon of Viability (HoV) engine is developed to guarantee the viability of a sustained reliable supply of power to the CI units over a time-horizon. The proposed HoV engine generates a cost-optimal portfolio of the locally available generation sources and the loads over a time horizon using a mixed-integer convex programming problem. A Controller hardware-in-the-loop (CHIL) platform is developed to evaluate the control performance of the HoV engine. The experimental results corroborates the efficacy in maintaining the viability of the CI units after a grid interruption event. Further, the proposed HoV optimization scheme performs better compared to existing net-load management schemes in the literature.

disaster resiliency↗
NASA NTRS2013

Airborne Remote Sensing for Earth Science Applications

Topics covered include: Passive Remote Sensing Methods, Imaging Spectroscopy Approach, Remote Measurement via Spectral Fitting, Imaging Spectroscopy Mapping Wetland Dominants 2010 LA (AVIRIS), Deepwater Horizon Response I, Deepwater Horizon Response II, AVIRIS Ocean Color Studies.

AVIRIS: Airborne Imaging Spectrometer↗
NASA NTRS2003

Future Applications of Remote Sensing to Archeological Research

Archeology was one of the first disciplines to use aerial photography in its investigations at the turn of the 20th century. However, the low resolution of satellite technology that became available in the 1970 s limited their application to regional studies. That has recently changed. The arrival of the high resolution, multi-spectral capabilities of the IKONOS and QUICKBIRD satellites and the scheduled launch of new satellites in the next few years provides an unlimited horizon for future archeological research. In addition, affordable aerial and ground-based remote sensing instrumentation are providing archeologists with information that is not available through traditional methodologies. Although many archeologists are not yet comfortable with remote sensing technology a new generation has embraced it and is accumulating a wealth of new evidence. They have discovered that through the use of remote sensing it is possible to gather information without disturbing the site and that those cultural resources can be monitored and protected for the future.

Sever, Thomas L.↗
NASA NTRS2021

Revisiting Topographic Horizons in the Era of Big Data and Parallel Computing

Widely used to calculate illumination geometry forestimates of solar and emitted longwave radiation, and forcorrecting remotely sensed data for topographic effects, digitalelevation models (DEMs) are now extensive globally at 10–30-mspatial resolution and locally at spatial resolutions down to afew centimeters. Globally, regionally, or locally, elevation datasetshave many grid points. Many software packages calculate gradi-ents over every grid cell or point, but in the mountains, shadingby nearby terrain must also be assessed. Terrain may obscure aslope that would otherwise face the Sun. Four decadesago, a fastmethod to calculate topographic horizons at every point in anelevation grid required computations related only linearly to thesize of the grid, but grids now have so many points that parallelcomputing still provides an advantage. Exploiting parallelismover terrain grids can use alternative strategies: among columnsof a rotated grid, or simultaneously at multiple rotation angles,or on different tiles of a grid. On a multi-processor machine, theimprovement in computing time approaches 2/3 the number ofprocessors deployed,

Jeff Dozier↗
NASA NTRS2014

Preserved Flora and Organics in Impact Melt Breccias

At least seven glass-bearing strata of varying ages occur at different horizons in the Pampean sediments of Argentina dating back to the Miocene. In a strict sense, these impact glasses are melt-matrix breccias composed of partially digested minerals clasts and basement fragments indicative of crater excavation. Ar-40/Ar-39 dating yield ages (+/- 2 sigma) of 6 +/- 2 Ka, 114 +/- 26 Ka, 230 +/- 30 Ka, 445 +/- 21 Ka, 3.27 +/- 0.08 Ma (near Mar del Plata = MdP), 5.28 +/- 0.04 Ma, and 9.21 +/- 0.08 Ma (near Chasico = CH) Where found in place (not reworked), these ages are consistent with the local stratigraphy and faunal assemblages. A striking property of some of these impact glasses is the encapsulation of preserved fragments of floral (and even soft-tissue faunal remains). Here we identify retained organics and describe a likely process of encapsulation and preservation.

Schultz, P. H.↗
NASA NTRS2001

Spacecraft Formation Flying Maneuvers Using Linear-Quadratic Regulation with No Radial Axis Inputs

Regarding multiple spacecraft formation flying, the observation has been made that control thrust need only be applied coplanar to the local horizon to achieve complete controllability of a two-satellite (leader-follower) formation. A formulation of orbital dynamics using the state of one satellite relative to another is used. Without the need for thrust along the radial (zenith-nadir) axis of the relative reference frame ' propulsion system simplifications and weight reduction may be accomplished. Several linear-quadratic regulators (LQR) are explored and compared based on performance measures likely to be important to many missions, but not directly optimized in the LQR designs. Maneuver simulations are performed using commercial ODE solvers to propagate the Keplerian dynamics of a controlled satellite relative to an uncontrolled leader. These short maneuver simulations demonstrate the capacity of the controller to perform changes from one formation geometry to another. This work focusses on formations in which the controlled satellite has a relative trajectory which projects onto the local horizon of the uncontrolled satellite as a circle. This formation has potential uses for distributed remote sensing systems.

Starin, Scott R.↗
NASA NTRS1989

Remote sensing of the atmospheric aerosols and noctilucent clouds from space

The method for the determination of the optical density of tropospheric and mesospheric aerosols and for the estimation of the scattering phase function in the forward directions (0 to 30 deg) is proposed. The method is based on measurements of the brightness of the twilight horizon with the high resolution limb camera having five separated fields of view. In some detail the features of the camera are described and the mathematical aspects of remote sensing data inversion are discussed.

Avaste, O.↗