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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 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
NASA NTRS2017

Multi-Beam Laser Beacon Propagation Over Lunar Distance: Comparison of Predictions and Measurements

A multi-beam beacon was transmitted from the Optical Communication Telescope Laboratory (OCTL) located at Table Mountain, CA to the Lunar Laser Space Terminal (LLST), on-board the Lunar Atmospheric Dust and Environment Explorer (LADEE) spacecraft, during NASA’s recent Lunar Laser Communication Demonstration (LLCD). The laser beacon (1568?0.1 nm) was square wave modulated and sensed by a LLST quadrant sensor to enable link acquisition and tracking. LLST computed the mean received beacon power and returned 5 kHz sampled power time series over the downlink. Post-processing of the decoded downlink received at OCTL retrieved the uplink power recorded at LLST. The predicted mean irradiance delivered to LLST consistently agreed with the variable beam divergence transmitted from OCTL to within < 1 decibel (dB). Irradiance fluctuations detected at LLST were reconciled with an uplink wave-propagation model derived using independently monitored atmospheric parameters. We report good agreement of the scintillation index and atmospheric coherence time.

Biswas, A↗
NASA NTRS2004

A distance of 133-137 parsecs to the Pleiades star cluster

Nearby open clusters of stars (those that are not gravitationally bound)have played a crucial role in the development of steller astronomy because, as a consequence of the stars having a common age, they provide excellent natural laboratories to test theoretical stellar models.

Theoretical↗
NASA NTRS2021

Prospective Futures of Distance Education

Society is in the midst of IT, Bio, Nano, Quantum and Energetics Technology Revolutions, which have changed and are changing econometrics, national security, health, transportation, shopping, travel, cost of living, socialization, commerce, employment, and education. We are now beyond the Industrial Age, are in the IT Age and heading rapidly into the Virtual Age.In that process we are changing from physical activities to virtual activities, developing and embracing tele-everything including tele-commuting, tele-work, tele-travel, tele-education, tele-shopping, tele-medicine, tele-commerce, tele-socialization, tele-politics and with on-site printing manufacture, tele-manufacturing. The gig economy, largely on the web and operated virtually, is a large and increasing portion of the national economy. Tele-everything took a great leap forward during the COVID pandemic response

Dennis M. Bushnell↗
NASA NTRS2021

Dendroarchaeological Analysis of the Terminal Warehouse in New York City Reveals A History of Long-Distance Timber Transport During the Gilded Age

The Gilded Age of the late 19th century marked a period of rapid development and urbanization in New York City, U.S. To accommodate the high demand in wood products during that time, the timbers used for development of the city were increasingly sourced from locations distant from the northeastern United States. The Terminal Warehouse in the Chelsea neighborhood of New York City was one of many large buildings erected during this period of city expansion, and is an important symbol of New York City commerce during the late 1800s. To determine the history and provenance of timbers used in the construction of the Terminal Warehouse, we used tree-ring analysis on longleaf pine (Pinus palustris Mill.) joists that were original to the building. The ring-width patterns on the joists cross dated well internally, suggesting a common origin of the sampled lumber. Further, our Terminal Warehouse tree-ring chronology (1512–1891 C.E.) correlated strongly with existing tree-ring chronologies from western/central Georgia and eastern Alabama, indicating that the timbers were extracted from this region of the southeastern United States. The provenancing and dating of the Terminal Warehouse timbers underscores the important role that southern pines played in the expansion and development of New York City during the Gilded Age.

Dendroprovenance↗
NASA NTRS2020

Feasibility of “Weak GPS” Real-Time Positioning/Timing at Lunar Distance

There are multiple Global Navigation Satellite Systems (GNSS’s), comprising over 100 navigation satellites in the Earth’s medium and high orbits. Most of these satellites have antennas that point Nadir to earth, and transmit navigation signals so vehicles on Earth’s surface and in its vicinity can perform trilateration and estimate its 3-dimenional (3D) positioning. The sidelobes of these antennas can occasionally point to the Moon. It is postulated that a lunar vehicle carrying a large enough receiving antenna can occasionally detects and receives four or more sidelobes of these weak GNSS signals, thus enabling the vehicle to perform 3D positioning using an onboard GNSS receiver. We propagate the orbits of the GNSS satellites from United States’ Global Positioning Satellite (GPS) constellation, the Europe’s Galileo constellation, and the Russia’s GLONASS constellation, a total of 81 satellites. We simulate the visibility of these satellites by a lunar vehicle in a Near Rectilinear Halo Orbit (NRHO), based on the assumption that the lunar vehicle is “in-view” of a GNSS satellite as long as it falls within the 40- degree beam-width of the satellite. We also simulate the 3D positioning performance as a function of satellites’ ephemeris errors and pseudo-range errors. The preliminary results show that the lunar vehicle can “see” 5 – 13 satellites, and achieve a 3D positioning error (one-sigma) of 200 – 300 meters based on reasonable ephemeris and pseudo- range error assumptions. We also consider the case of using relative positioning to mitigate the GNSS satellites’ ephemeris biases. That is, by assuming a reference receiver with accurately known positioning that is close to the lunar vehicle, and computing the relative position of the lunar vehicle relative to the reference.

Cheung, Kar-Ming↗
NASA NTRSDate not supplied

Intense High-Energy ESP Events and Self-Excited Waves at Inner Heliospheric Distances

Energetic Storm Particle (ESP) events are particle intensity increases associated with the passage of interplanetary (IP) shocks. Although ESP events at 1 AU are usually a low-energy phenomenon (i.e., at proton energies <10 MeV), occasionally they may reach energies of >100 MeV. An analysis of the ESP events observed at proton energies >40 MeV over the last four solar cycles shows that these high-energy particle intensity increases tend to occur when unrelated IP structures such as intervening coronal mass ejections and other unlinked shocks are present in the solar wind through which the IP shock generating the ESP event propagates. The acceleration of particles by IP shocks becomes more efficient when particles repeatedly interact with the traveling shocks. These multiple interactions may be favored by either the effects that these unrelated IP structures produce in the particle transport, or by amplified magnetic field fluctuations excited by the accelerated particles. However, the search for these self-excited waves at IP shocks at 1 AU has been often unsuccessful, with just a handful of events showing enhanced field fluctuations that can resonate with the energetic particles. Modeling results indicate that particle acceleration to the highest energies by the shocks occurs close to the Sun, resulting in large intensities of self-excited waves. We have initiated a search for ESP events in the inner heliosphere with evidence for self-excited waves and few cases observed by Parker Solar Probe will be shown.

David Lario↗