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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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292 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Lunar Phase Function at 1064 Nm from Lunar Orbiter Laser Altimeter Passive and Active Radiometry

We present initial calibration and results of passive radiometry collected by the Lunar Orbiter Laser Al- timeter onboard the Lunar Reconnaissance Orbiter over the course of 12 months. After correcting for time- and temperature-dependent dark noise and detector responsivity variations, the LOLA passive radiometry measurements are brought onto the absolute radiance scale of the SELENE Spectral Profiler. The resulting photometric precision is estimated to be approximately 5%. We leverage the unique ability of LOLA to measure normal albedo to explore the 1064 nm phase function's dependence on various geologic parameters. On a global scale, we find that iron abundance and optical maturity (quantified by FeO and OMAT) are the dominant controlling parameters. Titanium abundance (TiO2 ), surface roughness on decimeter to decameter scales, and soil thermophysical properties have a smaller effect, but the latter two are correlated with OMAT, indicating that exposure age is the driving force behind their effects in a globally-averaged sense. The phase function also exhibits a dependence on surface slope at approximately 300 m baselines, possibly the result of mass wasting exposing immature material and/or less space weathering due to reduced sky visibility. Modeling the photometric function in the Hapke framework, we find that, relative to the highlands, the maria exhibit decreased backscattering, a smaller opposition effect (OE) width, and a smaller OE amplitude. Immature highlands regolith has a higher backscattering fraction and a larger OE width compared to mature highlands regolith. Within the maria, the backscattering fraction and OE width show little dependence on TiO2 and OMAT. Variations in the phase function shape at large phase angles are observed in and around the Copernican-aged Jackson crater, including its dark halo, a putative impact melt deposit. Finally, the phase function of the Reiner Gamma Formation behaves more optically immature than is typical for its composition and OMAT, suggesting the visible-to-near-infrared spectrum and phase function respond differently to the unusual regolith evolution and properties at this location.

LOLA↗
NASA NTRSDate not supplied

Exploring de Gerlache Crater

The campaign of Artemis missions will result in the first crewed missions to the surface of the Moon in the 21stCentury. As outlined by the Lunar Exploration Analysis Group (LEAG) United States Lunar Exploration Roadmap (US-LER), human missions to the Moon will result in significant advances across a wide variety of scientific and engineering disciplines[1]contributing significantly to scientific discovery, economic prosperity, and world security. A significant focus is exploring lunar Permanently Shadowed Regions (PSRs). PSRs can contain volatiles, including water ice, which makes them high priority for scientific investigation and economic activity.

Moon↗
NASA NTRSDate not supplied

An Observational Approach to Low Lunar Frozen Orbit Design

Low lunar frozen orbits can be used to enable long-duration missions at the Moon while also minimizing the fuel usage necessary for orbit maintenance. There is no analytical expression for determining these frozen orbits, so a high-fidelity simulation approach is required. A differential correction targeting approach was used to find initial conditions that zeroed out argument of periapsis and eccentricity growth. This approach was used during the Lunar Reconnaissance Orbiter extended mission period for four different frozen orbit instances. Observations of the evolution of key orbit elements (e.g. periapsis altitude and the eccentricity vector) led to an understanding of the orbit dynamics and helped to formulate a simple observational approach to finding frozen or quasi-frozen low lunar orbits that looks at minimizing the spread in the periselene altitude evolution.

Moon Frozen Orbit LRO↗
NASA NTRSDate not supplied

An Observational Approach to Low Lunar Frozen Orbit Design

Low lunar frozen orbits can be used to enable long-duration missions at the Moon while also minimizing the fuel usage necessary for orbit maintenance. There is no analytical expression for determining these frozen orbits, so a high-fidelity simulation approach is required. A differential correction targeting approach was used to find initial conditions that zeroed out argument of periapsis and eccentricity growth. This approach was used during the Lunar Reconnaissance Orbiter extended mission period for four different frozen orbit instances. Observations of the evolution of key orbit elements (e.g. periapsis altitude and the eccentricity vector) led to an understanding of the orbit dynamics and helped to formulate a simple observational approach to finding frozen or quasi-frozen low lunar orbits that looks at minimizing the spread in the periselene altitude evolution.

Moon Frozen Orbit LRO↗