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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 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Small Explorers - Small is beautiful

NASA's Small Explorer Program aims to achieve a flight rate of one mission per year in a program of small scientific satellites launched from small expendable launch vehicles. The Program is developing 3 missions for launch in the early 1990's: the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX), the Submillimeter Wave Astronomy Satellite (SWAS), and the Fast Auroral Snapshot Explorer (FAST). This paper gives an overview of the program, a description of the selected missions, the approach to developing the missions and the plans for the next Announcement of Opportunity.

Gilman, David↗
NASA NTRS2006

Complex Organic Materials on Planetary Satellites and Other Small Bodies of the Solar System

The search for organic materials on small bodies of the Solar System is conducted spectroscopically from Earth-based telescopes and from spacecraft. Although the carbonaceous meteorites carry a significant inventory of complex organic solids, the sources of these meteorites have not been identified. Infrared spectra of a sample of the suspected sources, the C- and D-class asteroids, including new data from the Spitzer Space Telescope, show signatures of silicates, but none diagnostic of organic compounds. In the absence of discrete spectral features, the low albedos and colors in the visible and near-IR spectral regions are the principal links between the organic-bearing meteorites and the asteroids. While Pluto and a few trans-neptunian objects show spectral signatures of frozen CH4. Solid CH3OH has been identified on two Centaur objects in the outer Solar System. In some cases the red colors of those objects suggest the presence of tholins. The VIMS instrument aboard the Cassini spacecraft in orbit around Saturn has detected near-IR spectral features on at least three of Saturn's satellites that are indicative or suggestive of organic molecules. One entire hemisphere of the satellite Iapetus is covered with low-albedo material that shows a spectral signature of aromatic hydrocarbons (3.3 microns) and the -CH2 stretching mode bands of an aliphatic component. Organics absorbing at 3.44 microns are suspected in the region of the south pole of Enceladus, and also on the surface of Phoebe. Organic material may originate on icy bodies in the current epoch by various processes of energy deposition into native material, or they may fall to the surface from an external (probably cometary) source. Some organic material may be pre-solar, having originated in the interstellar medium before the formation of the Solar System. Using the techniques of remote sensing, its detection and analysis are slow and difficult.

Cruikshank, Dale P.↗
NASA NTRS1972

Definition of multipath/RFI experiments for orbital testing with a small applications technology satellite

An investigation was made to define experiments for collection of RFI and multipath data for application to a synchronous relay satellite/low orbiting satellite configuration. A survey of analytical models of the multipath signal was conducted. Data has been gathered concerning the existing RFI and other noise sources in various bands at VHF and UHF. Additionally, designs are presented for equipment to combat the effects of RFI and multipath: an adaptive delta mod voice system, a forward error control coder/decoder, a PN transmission system, and a wideband FM system. The performance of these systems was then evaluated. Techniques are discussed for measuring multipath and RFI. Finally, recommended data collection experiments are presented. An extensive tabulation is included of theoretical predictions of the amount of signal reflected from a rough, spherical earth.

Birch, J. N.↗
NASA NTRS1974

Small astronomy satellite-A, Uhuru data analysis

Objectives were to conduct observations with the first satellite entirely devoted to X-ray astronomy and to analyze the results obtained. A catalog of X-ray sources was generated, and results of discoveries and further detailed observations of sources were presented in scientific journals and meetings. A list of how objectives were met, a brief description of the instrument, significant results, the X-ray catalog, and a complete bibliography of results are included.

Koch, D.↗
NASA NTRS1992

Satellite communications application to Pacific countries above Ku band

An application of satellite communications above the Ku band to the Pacific region is described, focusing on: (1) Lightsat system and (2) a high capacity satellite system. A small geostationary satellite system using Ku band for the Federated States of Micronesia is shown as an example. A concept of multi-gigabits/second high capacity communications system using two satellites in the Ka band is described. The onboard bit-by-bit processing is very useful in the low link margin environment due to rain attenuation. These topics were obtained by the Asia Pacific Telecommunications Study granted by NASA conducted by the University of Colorado at Boulder.

Iida, Takashi↗
NASA NTRS1992

Sealed aerospace metal-hydride batteries

Nickel metal hydride and silver metal hydride batteries are being developed for aerospace applications. There is a growing market for smaller, lower cost satellites which require higher energy density power sources than aerospace nickel-cadmium at a lower cost than space nickel-hydrogen. These include small LEO satellites, tactical military satellites and satellite constellation programs such as Iridium and Brilliant Pebbles. Small satellites typically do not have the spacecraft volume or the budget required for nickel-hydrogen batteries. NiCd's do not have adequate energy density as well as other problems such as overcharge capability and memory effort. Metal hydride batteries provide the ideal solution for these applications. Metal hydride batteries offer a number of advantages over other aerospace battery systems.

Coates, Dwaine↗
NASA NTRS1982

TOPEX satellite concept. TOPEX option study report

Candidate bus equipment from the Viking, Applications Explorer Mission, and Small Scientific Satellite programs for application to the TOPEX mission options is assessed. Propulsion module equipment and subsystem candidates from the Applications Explorer Mission satellites and the Small Scientific Satellite spacecraft are evaluated for those TOPEX options. Several subsystem concepts appropriate to the TOPEX options are described. These descriptions consider performance characteristics of the subsystems. Cost and availability information on the candidate equipment and subsystems are also provided.

Meyer, D. P.↗
NASA NTRS1989

Electrodynamics of the Getaway Tether Experiment

An electrodynamic circuit model of the interaction of a pair of small tethered satellites and the ionosphere is developed and analyzed. The system under study, the Getaway Tether Experiment (GATE), is composed of two small satellites and 1 km of insulated conducting tether. The nonlinear model has elements representing the emission, collection, and resistive flow of charge through an electrically conductive tether, plasma contactors, and the ionosphere. The circuit model is incorporated into a dynamic orbital simulation to predict mission performance. Simulation results show the feasibility to bilaterally transfer energy between stored electrical energy and orbital momentum. A transient model is also developed using the circuit model and a string of N lumped-parameter modules, each consisting of resistance, capacitance, and induced potential for the tether. Transients are shown via simulation to occur over millisecond intervals.

Greene, Michael↗
NASA NTRS1974

Geomagnetic background events observed by Uhuru

Problems due to sporadic background events observed by Uhuru (Small Astronomy Satellite - A) do not compromise the study of discrete X-ray sources. Nevertheless, direct particle effects and auroral type X-ray events in the atmosphere may occasionally occur. Therefore, even on the geomagnetic equator, an experiment must be prepared to recognize and eliminate such events when the ultimate level of sensitivity is desired. The test equipment contained in the satellite and the orbital mechanics of Small Astronomy Satellite - A are described. The sporadic events which were observed by the satellite are analyzed.

Schwartz, D. A.↗
NASA NTRS2015

Satellite Radar Altimetry for Monitoring Small Rivers and Lakes in Indonesia

Remote sensing and satellite geodetic observations are capable of hydrologic monitoring of freshwater resources. Although satellite radar altimetry has been used in monitoring water level or discharge, its use is often limited to monitoring large rivers ( >1 km) with longer interval periods (>1 week) because of its low temporal and spatial resolutions (i.e., satellite revisit period). Several studies have reported successful retrieval of water levels for small rivers as narrow as 40m. However, processing current satellite altimetry signals for such small water bodies to retrieve water levels accurately remains challenging. Physically, the radar signal returned by water bodies smaller than the satellite footprint is most likely contaminated by non-water surfaces, which may degrade the measurement quality. In order to address this scientific challenge, we carefully selected the waveform shapes corresponding to the range measurement resulting from standard retrackers for the European Space Agency's (ESA's) Envisat (Environmental Satellite) radar altimetry. We applied this approach to small (40-200m in width) and medium-sized (200-800m in width) rivers and small lakes (extent<1000 sq km) in the humid tropics of Southeast Asia, specifically in Indonesia. This is the first study that explored the ability of satellite altimetry to monitor small water bodies in Indonesia.

Satellite↗
DOE OSTI2020

Constraining the Milky Way Mass Profile with Phase-space Distribution of Satellite Galaxies

We estimate the Milky Way (MW) halo properties using satellite kinematic data including the latest measurements from Gaia DR2. With a simulation-based 6D phase-space distribution function (DF) of satellite kinematics, we can infer halo properties efficiently and without bias, and handle the selection function and measurement errors rigorously in the Bayesian framework. Applying our DF from the EAGLE simulation to 28 satellites, we obtain an MW halo mass of $M={1.23}_{-0.18}^{+0.21}\times {10}^{12}{M}_{\odot }$ and a concentration of $c={9.4}_{-2.1}^{+2.8}$ with the prior based on the M–c relation. The inferred mass profile is consistent with previous measurements but with better precision and reliability due to the improved methodology and data. Potential improvement is illustrated by combining satellite data and stellar rotation curves. Using our EAGLE DF and best-fit MW potential, we provide much more precise estimates of the kinematics for those satellites with uncertain measurements. Compared to the EAGLE DF, which matches the observed satellite kinematics very well, the DF from the semi-analytical model based on the dark-matter-only simulation Millennium II (SAM-MII) over-represents satellites with small radii and velocities. We attribute this difference to less disruption of satellites with small pericenter distances in the SAM-MII simulation. Finally, by varying the disruption rate of such satellites in this simulation, we estimate a ~5% scatter in the inferred MW halo mass among hydrodynamics-based simulations.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2008

Small-Body Extensions for the Satellite Orbit Analysis Program (SOAP)

An extension to the SOAP software allows users to work with tri-axial ellipsoid-based representations of planetary bodies, primarily for working with small, natural satellites, asteroids, and comets. SOAP is a widely used tool for the visualization and analysis of space missions. The small body extension provides the same visualization and analysis constructs for use with small bodies. These constructs allow the user to characterize satellite path and instrument cover information for small bodies in both 3D display and numerical output formats. Tri-axial ellipsoids are geometric shapes the diameters of which are different in each of three principal x, y, and z dimensions. This construct provides a better approximation than using spheres or oblate spheroids (ellipsoids comprising two common equatorial diameters as a distinct polar diameter). However, the tri-axial ellipsoid is considerably more difficult to work with from a modeling perspective. In addition, the SOAP small-body extensions allow the user to actually employ a plate model for highly irregular surfaces. Both tri-axial ellipsoids and plate models can be assigned to coordinate frames, thus allowing for the modeling of arbitrary changes to body orientation. A variety of features have been extended to support tri-axial ellipsoids, including the computation and display of the spacecraft sub-orbital point, ground trace, instrument footprints, and swathes. Displays of 3D instrument volumes can be shown interacting with the ellipsoids. Longitude/latitude grids, contour plots, and texture maps can be displayed on the ellipsoids using a variety of projections. The distance along an arbitrary line of sight can be computed between the spacecraft and the ellipsoid, and the coordinates of that intersection can be plotted as a function of time. The small-body extension supports the same visual and analytical constructs that are supported for spheres and oblate spheroids in SOAP making the implementation of the more complex algorithms largely transparent to the user.

Carnright, Robert↗
DOE OSTI2020

Fast Data Processing for Hyperspectral Sensors on Small Platforms

Hyperspectral imaging is a very promising technology for nuclear proliferation detection. However, due to size and weight restrictions, small hyperspectral platforms such as satellites and small drones lack the on-board computing resources for accurate, real-time analysis of the enormous flow of data that a continuously operating hyperspectral sensor generates. This severely limits satellite systems, which can collect far more data than what they can telemeter, and hinders the ability of all platforms to adapt their missions on the fly in response to observations. This program addresses the hyperspectral data processing challenge through development of new, fast and accurate algorithms that produce data products in real time. The algorithms circumvent the major computational bottlenecks in existing processing streams, and would be incorporated in lightweight, power-efficient single-board computer systems. The toolkit of fast algorithms will be immediately useful in current and future hyperspectral systems being built by the Government and by private industry, including drone-based systems and satellite constellations that acquire timely global imagery.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
NASA NTRS1983

Planetary rings - 2-2/3 centuries of nearly total ignorance, 4 years of information explosion

Saturn lies at nearly twice Jupiter's distance from the sun and nearly all parts of its system are characterized by much smaller scales than those which are important in the case of Jupiter. This appears in the structures of the planet's atmosphere, in the sizes of classical satellites other than Titan vis-a-vis those of the Galilean satellites, in the plethora of small Saturnian satellites, especially Lagrangian co-orbiters, in the structure of Saturn's F-Ring as contrasted with that of Jupiter's Ring and finally in the highly structured detail in Saturn's Rings, much finer than seriously considered in past theoretical discussions. Uranus' Rings were unknown until five years ago. The discovery and observation of these rings have revived contributions to theory originally intended for application to Saturn's Rings. Models have also been generated for eccentric rings for application to Uranus' Rings which also apply to those of Saturn. These two classes of model are reviewed in the present paper along with the first tentative steps made down the road to unravelling the complexity of Saturn's Rings.

Cook, A. F.↗