Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Surface coverage”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

Infrared and Passive Microwave Radiometric Sea Surface Temperatures and Their Relationships to Atmospheric Forcing

The current generation of infrared (IR) and passive microwave (MW) satellite sensors provides highly complementary information for monitoring sea surface temperature (SST). On the one hand, infrared sensors provide high resolution and high accuracy but are obscured by clouds. Microwave sensors on the other hand, provide coverage through non-precipitating clouds but have coarser resolution and generally poorer accuracy. Assuming that the satellite SST measurements do not have spatially variable biases, they can be blended combining the merits of both SST products. These factors have motivated recent work in blending the MW and IR data in an attempt to produce high-accuracy SST products with improved coverage in regions with persistent clouds. The primary sources of retrieval uncertainty are, however, different for the two sensors. The main uncertainty in the MW retrievals lies in the effects of wind-induced surface roughness and foam on emissivity, whereas the IR retrievals are more sensitive to the atmospheric water vapor and aerosol content. Average nighttime differences between the products for the month periods of January 1999 and June 2000 are shown. These maps show complex spatial and temporal differences as indicated by the strong spatially coherent features in the product differences and the changes between seasons. Clearly such differences need to be understood and accounted for if the products are to be combined. The overall goals of this project are threefold: (1) To understand the sources of uncertainty in the IR and MW SST retrievals and to characterize the errors affecting the two types of retrieval as a fiction of atmospheric forcing; (2) To demonstrate how representative the temperature difference between the two satellite products is of Delta T; (3) To apply bias adjustments and to device a comprehensive treatment of the behavior of the temperature difference across the oceanic skin layer to determine the best method for blending thermal infrared and passive microwave measurements of SSTs.

Castro, Sandra L.↗
NASA NTRS1985

Mars - Dual-polarization radar observations with extended coverage

Arecibo Observatory radar observations of Mars at 13 cm wavelength have yielded accurate measurements of the full backscatter spectrum in two orthogonal polarizations, and constitute the first global view of the small scale surface roughness distribution on Mars. Areas of maximum depolarization correlate well with the volcanic regions Tharsis and Elysium. Comparisons between the moon and Mars using radar data, ground truth, and simple scattering models, suggest that Mars possesses a relatively high average coverage by decimeter-scale rocks. Attention is also given to quasi-specular scattering results, of which the most unusual were obtained over the Olympus Mons aureole region.

Harmon, J. K.↗
NASA NTRS2017

The Mars Reconnaissance Orbiter Mission: Continuing a Record of Exploration from Mars Orbit

The Mars Reconnaissance Orbiter (MRO) has been on station in its low altitude, sun-synchronous, primary science orbit since September 2006 performing both scientific and Mars programmatic support functions. The spacecraft is a very capable remote sensing science platform carrying six science payloads supporting seven investigations and a UHF telecommunications radio (Electra) for surface relay. Developed to support a mix of nadir mapping and targeted, highresolution surface observations, the spacecraft’s powerful telecommunications and command & data handling (C&DH) subsystems communicate an average of 16 hours a day with the Deep Space Network (DSN). To date, more than 300 TB of scientific data has been returned to Earth. All of the original science payloads are active with standard and new observing modes contributing to the advancement of Mars science through peer-reviewed paper publications and the timely dissemination of their data to the science community as a whole. Results from the science teams have revealed an amazing diversity of ancient aqueous environments and ongoing surface change is evident through gully formation, avalanches, and cratering. Extending the MRO-MGS climate record to a decade of Mars years is contributing to a better understanding of current atmospheric and polar processes. In addition to its fundamental scientific objectives, MRO is a critical element of NASA’s Mars Exploration Program (MEP) providing needed infrastructure support for landed and future missions. Using its Electra telecommunications payload, MRO provides landers and rovers critical event coverage during their entry, descent, and landing (EDL) phases and UHF relay support once they are on the Martian surface. MRO’s high-resolution imagers are used to scout potential landing sites and certify safe zones for landing. As MRO begins its Fourth Extended Mission, the spacecraft remains fully capable of carrying out an ambitious science observing plan and the programmatic tasks assigned to it. In addition to highlighting recent discoveries of the mission, this paper describes recent challenges the spacecraft engineers have faced in flight and the plans for extending spacecraft life well into the 2020’s.

Tamppari, Leslie K.↗
NASA NTRS2014

Worldwide Weather Radar Imagery May Allow Substantial Increase in Meteorite Fall Recovery

Weather radar imagery is a valuable new technique for the rapid recovery of meteorite falls, to include falls which would not otherwise be recovered (e.g. Battle Mountain). Weather radar imagery reveals about one new meteorite fall per year (18 falls since 1998), using weather radars in the United States alone. However, an additional ~75 other nations operate weather radar networks according to the UN World Meteorological Organization (WMO). If the imagery of those radars were analyzed, the current rate of meteorite falls could be improved considerably, to as much as ~3.6 times the current recovery rate based on comparison of total radar areal coverage. Recently, the addition of weather radar imagery, seismometry and internet-based aggregation of eyewitness reports has improved the speed and accuracy of fresh meteorite fall recovery [e.g. 1,2]. This was demonstrated recently with the radar-enabled recovery of the Sutter's Mill fall [3]. Arguably, the meteorites recovered via these methods are of special scientific value as they are relatively unweathered, fresh falls. To illustrate this, a recent SAO/NASA ADS search using the keyword "meteorite" shows that all 50 of the top search results included at least one named meteorite recovered from a meteorite fall. This is true even though only ~1260 named meteorite falls are recorded among the >49,000 individual falls recorded in the Meteoritical Society online database. The US NEXRAD system used thus far to locate meteorite falls covers most of the United States' surface area. Using a WMO map of the world's weather radars, we estimate that the total coverage of the other ~75 national weather radar networks equals about 3.6x NEXRAD's coverage area. There are two findings to draw from this calculation: 1) For the past 16 years during which 18 falls are seen in US radar data, there should be an additional ~65 meteorite falls recorded in worldwide radar imagery. Also: 2) if all of the world's radar data could be analyzed, the rate of recovery of fresh meteorite falls can increase by as much as ~3.6x the current rate. The authors' experience to date indicates that the most effective course of action would be to have local meteorite research groups (outside of the US) form research consortia and develop a working relationship with their nation's weather bureau for access to data. These research consortia could utilize the same, proven methods used for US NEXRAD imagery, internet eyewitness report aggregation, seismometry analysis, etc. to locate meteorite falls. The consortia could then recover and analyze meteorite falls and enrich their own research efforts. It would be beneficial to conduct a global program to coordinate the development of methods and data tools, as well as to coordinate meteorite sample sharing and research. Perhaps an institution such as the Meteoritical Society could lead such an effort.

Fries, Marc↗
NASA NTRS2000

Estimating Long Term Surface Soil Moisture in the GCIP Area From Satellite Microwave Observations

Soil moisture is an important component of the water and energy balances of the Earth's surface. Furthermore, it has been identified as a parameter of significant potential for improving the accuracy of large-scale land surface-atmosphere interaction models. However, accurate estimates of surface soil moisture are often difficult to make, especially at large spatial scales. Soil moisture is a highly variable land surface parameter, and while point measurements are usually accurate, they are representative only of the immediate site which was sampled. Simple averaging of point values to obtain spatial means often leads to substantial errors. Since remotely sensed observations are already a spatially averaged or areally integrated value, they are ideally suited for measuring land surface parameters, and as such, are a logical input to regional or larger scale land process models. A nine-year database of surface soil moisture is being developed for the Central United States from satellite microwave observations. This region forms much of the GCIP study area, and contains most of the Mississippi, Rio Grande, and Red River drainages. Daytime and nighttime microwave brightness temperatures were observed at a frequency of 6.6 GHz, by the Scanning Multichannel Microwave Radiometer (SMMR), onboard the Nimbus 7 satellite. The life of the SMMR instrument spanned from Nov. 1978 to Aug. 1987. At 6.6 GHz, the instrument provided a spatial resolution of approximately 150 km, and an orbital frequency over any pixel-sized area of about 2 daytime and 2 nighttime passes per week. Ground measurements of surface soil moisture from various locations throughout the study area are used to calibrate the microwave observations. Because ground measurements are usually only single point values, and since the time of satellite coverage does not always coincide with the ground measurements, the soil moisture data were used to calibrate a regional water balance for the top 1, 5, and 10 cm surface layers in order to interpolate daily surface moisture values. Such a climate-based approach is often more appropriate for estimating large-area spatially averaged soil moisture because meteorological data are generally more spatially representative than isolated point measurements of soil moisture. Vegetation radiative transfer characteristics, such as the canopy transmissivity, were estimated from vegetation indices such as the Normalized Difference Vegetation Index (NDVI) and the 37 GHz Microwave Polarization Difference Index (MPDI). Passive microwave remote sensing presents the greatest potential for providing regular spatially representative estimates of surface soil moisture at global scales. Real time estimates should improve weather and climate modelling efforts, while the development of historical data sets will provide necessary information for simulation and validation of long-term climate and global change studies.

Owe, Manfred↗
NASA NTRS2011

Physical Validation of GPM Retrieval Algorithms Over Land: An Overview of the Mid-Latitude Continental Convective Clouds Experiment (MC3E)

The joint NASA Global Precipitation Measurement (GPM) -- DOE Atmospheric Radiation Measurement (ARM) Midlatitude Continental Convective Clouds Experiment (MC3E) was conducted from April 22-June 6, 2011, centered on the DOE-ARM Southern Great Plains Central Facility site in northern Oklahoma. GPM field campaign objectives focused on the collection of airborne and ground-based measurements of warm-season continental precipitation processes to support refinement of GPM retrieval algorithm physics over land, and to improve the fidelity of coupled cloud resolving and land-surface satellite simulator models. DOE ARM objectives were synergistically focused on relating observations of cloud microphysics and the surrounding environment to feedbacks on convective system dynamics, an effort driven by the need to better represent those interactions in numerical modeling frameworks. More specific topics addressed by MC3E include ice processes and ice characteristics as coupled to precipitation at the surface and radiometer signals measured in space, the correlation properties of rainfall and drop size distributions and impacts on dual-frequency radar retrieval algorithms, the transition of cloud water to rain water (e.g., autoconversion processes) and the vertical distribution of cloud water in precipitating clouds, and vertical draft structure statistics in cumulus convection. The MC3E observational strategy relied on NASA ER-2 high-altitude airborne multi-frequency radar (HIWRAP Ka-Ku band) and radiometer (AMPR, CoSMIR; 10-183 GHz) sampling (a GPM "proxy") over an atmospheric column being simultaneously profiled in situ by the University of North Dakota Citation microphysics aircraft, an array of ground-based multi-frequency scanning polarimetric radars (DOE Ka-W, X and C-band; NASA D3R Ka-Ku and NPOL S-bands) and wind-profilers (S/UHF bands), supported by a dense network of over 20 disdrometers and rain gauges, all nested in the coverage of a six-station mesoscale rawinsonde network. As an exploratory effort to examine land-surface emissivity impacts on retrieval algorithms, and to demonstrate airborne soil moisture retrieval capabilities, the University of Tennessee Space Institute Piper aircraft carrying the MAPIR L-band radiometer was also flown during the latter half of the experiment in coordination with the ER-2. The observational strategy provided a means to sample the atmospheric column in a redundant framework that enables inter-calibration and constraint of measured and retrieved precipitation characteristics such as particle size distributions, or water contents- all within the umbrella of "proxy" satellite measurements (i.e., the ER-2). Complimenting the precipitation sampling framework, frequent and coincident launches of atmospheric soundings (e.g., 4-8/day) then provided a much larger mesoscale view of the thermodynamic and winds environment, a data set useful for initializing cloud models. The datasets collected represent a variety cloud and precipitation types including isolated cumulus clouds, severe thunderstorms, mesoscale convective systems, and widespread regions of light to moderate stratiform precipitation. We will present the MC3E experiment design, an overview of operations, and a summary of preliminary results.

Petersen, Walter A.↗
NASA NTRS2023

Lunar Dust Mitigation: A Guide and Reference: First Edition (2021)

On the surface of the Moon, lunar dust specifically presents unique challenges to operations long-term due to regolith particles’ ubiquitous presence in the lunar environment, potential to electrostatically charge and possible chemical reactivity. Whether to avoid exposure, try to remove or simply to tolerate lunar dust infiltrating a system becomes a complex question involving length of required service life, dust effects and critical risks, mass and complexity trades for the entire system. This publication provides a snapshot of advice from topical experts for specific areas of concern to systems targeted for deployment on the lunar surface. Following introductory overview commentary, dust mitigation approaches appropriate to the lunar surface are first addressed for typically static structures such as optical surfaces, radiators, and other thermal control surfaces, followed by regolith exposure concerns for communications equipment and non-optical sensors. The broad topic of mechanisms and mechanical assemblies is broken down to address relevant component level concerns, such as for bearings and for seals. “Soft goods” components of space suits (fabric) specific concerns are discussed, followed finally by brief coverage of human health issues and concerns, though the emphasis of this publication remains with components directly exposed to the harsh lunar surface environment. A description of some lunar surface hazard details, in particular characteristics of lunar surface dust, follows in Appendix A, and more detailed explanations of quantification issues for particulates are in Appendix B. The simple inertial removal of particles from a surface is discussed in Appendix C, followed by a summary of terrestrial best practices for dust mitigation recommended within select industries in Appendix D. The aggregated bibliography of references, while extensive and very useful, should not be construed to be exhaustive and can serve as a constructive start.

dust↗
NASA NTRS2023

Modulation of the Seasonal Cycle of the Antarctic Sea Ice Extent By Sea Ice Processes and Feedbacks With the Ocean and the Atmosphere

The seasonal cycle of the Antarctic sea ice extent is strongly asymmetric, with a relatively slow increase after the summer minimum followed by a more rapid decrease after the winter maximum. This cycle is intimately linked to the seasonal cycle of the insolation received at the top of the atmosphere, but sea ice processes as well as the exchanges with the atmosphere and ocean may also play a role. To quantify these contributions, a series of idealized sensitivity experiments have been performed with an eddy-permitting (∘) NEMO-LIM3 (Nucleus for European Modelling of the Ocean–Louvain-la-Neuve sea ice model version 3) Southern Ocean configuration, including a representation of ice shelf cavities, in which the model was either driven by an atmospheric reanalysis or coupled to the COSMO-CLM2 regional atmospheric model. In those experiments, sea ice thermodynamics and dynamics as well as the exchanges with the ocean and atmosphere are strongly perturbed. This perturbation is achieved by modifying snow and ice thermal conductivities, the vertical mixing in the ocean top layers, the effect of freshwater uptake and release upon sea ice growth and melt, ice dynamics, and surface albedo. We find that the evolution of sea ice extent during the ice advance season is largely independent of the direct effect of the perturbation and appears thus mainly controlled by initial state in summer and subsequent insolation changes. In contrast, the melting rate varies strongly between the experiments during the retreat, in particular if the surface albedo or sea ice transport are modified, demonstrating a strong contribution of those elements to the evolution of ice coverage through spring and summer. As with the advance phase, the retreat is also influenced by conditions at the beginning of the melt season in September. Atmospheric feedbacks enhance the model winter ice extent response to any of the perturbed processes, and the enhancement is strongest when the albedo is modified. The response of sea ice volume and extent to changes in entrainment of subsurface warm waters to the ocean surface is also greatly amplified by the coupling with the atmosphere.

regional atmosphere ocean sea ice model↗
NASA NTRS2010

Effect of Simulant Type on the Absorptance and Emittance of Dusted Thermal Control Surfaces in a Simulated Lunar Environment

During the Apollo program the effects of lunar dust on thermal control surfaces was found to be more significant than anticipated, with several systems overheating due to deposition of dust on them. In an effort to reduce risk to future missions, a series of tests has been initiated to characterize the effects of dust on these surfaces, and then to develop technologies to mitigate that risk. Given the variations in albedo across the lunar surface, one variable that may be important is the darkness of the lunar dust, and this study was undertaken to address that concern. Three thermal control surfaces, AZ-93 white paint and AgFEP and AlFEP second surface mirrors were dusted with three different lunar dust simulants in a simulated lunar environment, and their solar absorptivity and thermal emissivity values determined experimentally. The three simulants included JSC 1AF, a darker mare simulant, NU-LHT-1D, a light highlands simulant, and 1:1 mixture of the two. The response of AZ-93 was found to be slightly more pronounced than that of AgFEP. The increased with fractional dust coverage in both types of samples by a factor of 1.7 to 3.3, depending on the type of thermal control surface and the type of dust. The of the AZ-93 decreased by about 10 percent when fully covered by dust, while that of AgFEP increased by about 10 percent. It was found that alpha/epsilon varied by more than a factor of two depending on the thermal control surface and the darkness of the dust. Given that the darkest simulant used in this study may be significantly lighter than the darkest dust that could be encountered on the lunar surface, it becomes apparent that the performance degradation of thermal control surfaces due to dust on the moon will be strongly dependent on the and of the dust in the specific locality.

Gaier, James R.↗
NASA NTRS2010

Effect of Simulant Type on the Absorptance and Emittance of Dusted Thermal Control Surfaces in a Simulated Lunar Environment

During the Apollo program the effects of lunar dust on thermal control surfaces was found to be more significant than anticipated, with several systems overheating due to deposition of dust on them. In an effort to reduce risk to future missions, a series of tests has been initiated to characterize the effects of dust on these surfaces, and then to develop technologies to mitigate that risk. Given the variations in albedo across the lunar surface, one variable that may be important is the darkness of the lunar dust, and this study was undertaken to address that concern. Three thermal control surfaces, AZ-93 white paint and AgFEP and AlFEP second surface mirrors were dusted with three different lunar dust simulants in a simulated lunar environment, and their integrated solar absorptance ( ) and thermal emittance ( ) values determined experimentally. The three simulants included JSC-1AF, a darker mare simulant, NU-LHT-1D, a light highlands simulant, and 1:1 mixture of the two. The response of AZ-93 was found to be slightly more pronounced than that of AgFEP. The increased with fractional dust coverage in both types of samples by a factor of 1.7 to 3.3, depending on the type of thermal control surface and the type of dust. The of the AZ-93 decreased by about 10 percent when fully covered by dust, while that of AgFEP increased by about 10 percent. It was found that / varied by more than a factor of two depending on the thermal control surface and the darkness of the dust. Given that the darkest simulant used in this study may be lighter than the darkest dust that could be encountered on the lunar surface, it becomes apparent that the performance degradation of thermal control surfaces due to dust on the Moon will be strongly dependent on the and of the dust in the specific locality

Gaier, James R.↗
NASA NTRS1998

Gaseous Etching for Characterization of Structural Defects in Silicon Carbide Single Crystals

Single crystal SiC substrates were subjected to high-temperature H2/C3H8 gaseous etches. The etches resulted in a variety of surface features on 4H-SiC substrates that included elongated hillocks from 10 to more than 100 microns in length by a few microns in width. In some 4H- and 6H-SiC substrates, the etches resulted in a continuous coverage of macrosteps. We conclude that the morphology observed after the etching process is influenced by the local Si-C bilayer stacking sequence on the surface of off-(0001)oriented substrates. A model is presented for the formation of the hillocks, based on localized transformations of the 4H substrates during the high temperature etch process.

Powell, J. A.↗
NASA NTRS2011

A Study of an Optical Lunar Surface Communications Network with High Bandwidth Direct to Earth Link

A lunar surface systems study explores the application of optical communications to support a high bandwidth data link from a lunar relay satellite and from fixed lunar assets. The results show that existing 1-m ground stations could provide more than 99% coverage of the lunar terminal at 100Mb/s data rates from a lunar relay satellite and in excess of 200Mb/s from a fixed terminal on the lunar surface. We have looked at the effects of the lunar regolith and its removal on optical samples. Our results indicate that under repeated dust removal episodes sapphire rather than fused silica would be a more durable material for optical surfaces. Disruption tolerant network protocols can minimize the data loss due to link dropouts. We report on the preliminary results of the DTN protocol implemented over the optical carrier.

lunar optical communications↗
NASA NTRSDate not supplied

Generation of Land Surface Reflectance with Combined Geo-KOMPSAT-2A AMI and Himawari 8 AHI Observations

The latest generation of geostationary satellites has opened a new era of Earth observations with unprecedented spatiotemporal resolution and spectral range. Together with GOES 16/17 ABI, FY4-A AGRI, and Himawari-8 AHI, a new Korean geostationary satellite (Geo-KOMPSAT-2A AMI) has operationally collected a full-disk image in 16 channels every ten minutes since July 2019, allowing diurnal land surface monitoring over a large proportion of Asia and all of Oceania. Retrieving accurate surface reflectance (SR) over land from GK-2A/AMI is a challenging but high priority objective. One of the challenges is the absence of a spectral band in the 2.2 m SWIR range from AMI, which is required by many atmospheric correction algorithms to retrieve atmospheric aerosol properties. To remedy this issue, we adopt a strategy that combines concurrent GK-2A/AMI and Himawari 8/AHI observations in order to derive AMI SR. We have adapted the NASA Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm to process the data stream from Himawari 8/AHI. The advantages of the MAIAC algorithm is its capability to exploit the high temporal frequency and varying illumination geometry of the geostationary data for advanced cloud/snow detection, aerosol retrieval, and characterization of surface bidirectional reflectance properties. Leveraging the similarities of spectral bands and the sun-target-sensor geometry between AMI and AHI, we are able to create denser time series of observations and enhanced BRDF samples over most of the spatial coverage of AMI (and AHI). The combined stereo-type observations not only help derive SR for AMI but also enhance retrievals of the corresponding AHI surface products. We evaluate the resulting AMI SR using ground (AERONET) observations and corresponding MODIS products. Further, we discuss potential challenges in utilizing the geostationary satellite data for land surface monitoring.

geostationary satellite↗
NASA NTRS1995

Ice surface temperature retrieval from AVHRR, ATSR, and passive microwave satellite data: Algorithm development and application

During the second phase project year we have made progress in the development and refinement of surface temperature retrieval algorithms and in product generation. More specifically, we have accomplished the following: (1) acquired a new advanced very high resolution radiometer (AVHRR) data set for the Beaufort Sea area spanning an entire year; (2) acquired additional along-track scanning radiometer(ATSR) data for the Arctic and Antarctic now totalling over eight months; (3) refined our AVHRR Arctic and Antarctic ice surface temperature (IST) retrieval algorithm, including work specific to Greenland; (4) developed ATSR retrieval algorithms for the Arctic and Antarctic, including work specific to Greenland; (5) developed cloud masking procedures for both AVHRR and ATSR; (6) generated a two-week bi-polar global area coverage (GAC) set of composite images from which IST is being estimated; (7) investigated the effects of clouds and the atmosphere on passive microwave 'surface' temperature retrieval algorithms; and (8) generated surface temperatures for the Beaufort Sea data set, both from AVHRR and special sensor microwave imager (SSM/I).

Key, Jeff↗
NASA NTRS2010

Sea Surface Salinity Variability from Simulations and Observations: Preparing for Aquarius

Oceanic fresh water transport has been shown to play an important role in the global hydrological cycle. Sea surface salinity (SSS) is representative of the surface fresh water fluxes and the upcoming Aquarius mission scheduled to be launched in December 2010 will provide excellent spatial and temporal SSS coverage to better estimate the net exchange. In most ocean general circulation models, SSS is relaxed to climatology to prevent model drift. While SST remains a well observed variable, relaxing to SST reduces the range of SSS variability in the simulations (Fig.1). The main objective of the present study is to simulate surface tracers using a primitive equation ocean model for multiple forcing data sets to identify and establish a baseline SSS variability. The simulated variability scales are compared to those from near-surface argo salinity measurements.

Jacob, S. Daniel↗
NASA NTRS1975

Illumination of Saturn's ring by the ball. I - Preliminary results

Indirect solar illumination of Saturn's ring via scattering from the ball of the planet provides a new ground-based observational technique for studying the single scattering albedo and phase function of the individual particles. Information concerning optical thickness may also be obtained. Essentially complete phase angle coverage can be achieved by studying the variation with azimuth of the indirect contribution to the surface brightness of the ring. Initial application of the technique is reported. The indirect contribution to the radiation scattered from the ring has been marginally detected by electronographic areal photometry. The results have been interpreted using simple scattering models. The photometric accuracy was insufficient to permit investigation of departures from isotropic scattering. But high single scattering albedos, and an essentially opaque ring, are indicated.

Price, M. J.↗
NASA NTRS1977

Where do we locate the moon base

Because the lunar polar regions permit continuous solar energy collection and adjacent cryogenic temperature, they may be the preferred sites for early human occupation and use of the moon. If permafrost exists in the polar shaded regions, this preference will become dominant. Though not ideal from the point of view of all-sky coverage for astronomical observations, and also possibly subject to terminator-plane particle hazes near the surface, polar sites (especially the south polar region) may offer enough advantages (e.g., constant cryogenic telescope environments and unlimited tracking time) to be preferred sites for the first lunar observatories.

Burke, J. D.↗
NASA NTRS1979

The study of 'microsurfaces' using thermal desorption spectroscopy

The use of a newly combined ultrahigh vacuum technique for studying continuous and particulate evaporated thin films using thermal desorption spectroscopy (TDS), transmission electron microscopy (TEM), and transmission electron diffraction (TED) is discussed. It is shown that (1) CO thermal desorption energies of epitaxially deposited (111) Ni and (111) Pd surfaces agree perfectly with previously published data on bulk (111) single crystal, (2) contamination and surface structural differences can be detected using TDS as a surface probe and TEM as a complementary technique, and (3) CO desorption signals from deposited metal coverages of one-thousandth of a monolayer should be detectable. These results indicate that the chemisorption properties of supported 'microsurfaces' of metals can now be investigated with very high sensitivity. The combined use of TDS and TEM-TED experimental methods is a very powerful technique for fundamental studies in basic thin film physics and in catalysis.

Thomas, M. E.↗