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NASA NTRS2011

Simultaneous Ka-Band Site Characterization: Goldstone, CA, White Sands, NM, and Guam, USA

To statistically characterize atmospheric effects on Ka-band links at NASA operational sites, NASA has constructed site test interferometers (STI s) which directly measure the tropospheric phase stability and rain attenuation. These instruments observe an unmodulated beacon signal broadcast from a geostationary satellite (e.g., Anik F2) and measure the phase difference between the signals received by the two antennas and its signal attenuation. Three STI s have been deployed so far: the first one at the NASA Deep Space Network Tracking Complex in Goldstone, California (May 2007); the second at the NASA White Sands Complex, in Las Cruses, New Mexico (February 2009); and the third at the NASA Tracking and Data Relay Satellite (TDRS) Remote Ground Terminal (GRGT) complex in Guam (May 2010). Two station-years of simultaneous atmospheric phase fluctuation data have been collected at Goldstone and White Sands, while one year of data has been collected in Guam. With identical instruments operating simultaneously, we can directly compare the phase stability and rain attenuation at the three sites. Phase stability is analyzed statistically in terms of the root-mean-square (rms) of the tropospheric induced time delay fluctuations over 10 minute blocks. For two years, the time delay fluctuations at the DSN site in Goldstone, CA, have been better than 2.5 picoseconds (ps) for 90% of the time (with reference to zenith), meanwhile at the White Sands, New Mexico site, the time delay fluctuations have been better than 2.2 ps with reference to zenith) for 90% of time. For Guam, the time delay fluctuations have been better than 12 ps (reference to zenith) at 90% of the time, the higher fluctuations are as expected from a high humidity tropical rain zone. This type of data analysis, as well as many other site quality characteristics (e.g., rain attenuation, infrastructure, etc.) will be used to determine the suitability of all the sites for NASA s future communication services at Ka-band.

Acosta, Roberto↗

NASA NTRS2012

Refinement of a Method for Identifying Probable Archaeological Sites from Remotely Sensed Data

To facilitate locating archaeological sites before they are compromised or destroyed, we are developing approaches for generating maps of probable archaeological sites, through detecting subtle anomalies in vegetative cover, soil chemistry, and soil moisture by analyzing remotely sensed data from multiple sources. We previously reported some success in this effort with a statistical analysis of slope, radar, and Ikonos data (including tasseled cap and NDVI transforms) with Student's t-test. We report here on new developments in our work, performing an analysis of 8-band multispectral Worldview-2 data. The Worldview-2 analysis begins by computing medians and median absolute deviations for the pixels in various annuli around each site of interest on the 28 band difference ratios. We then use principle components analysis followed by linear discriminant analysis to train a classifier which assigns a posterior probability that a location is an archaeological site. We tested the procedure using leave-one-out cross validation with a second leave-one-out step to choose parameters on a 9,859x23,000 subset of the WorldView-2 data over the western portion of Ft. Irwin, CA, USA. We used 100 known non-sites and trained one classifier for lithic sites (n=33) and one classifier for habitation sites (n=16). We then analyzed convex combinations of scores from the Archaeological Predictive Model (APM) and our scores. We found that that the combined scores had a higher area under the ROC curve than either individual method, indicating that including WorldView-2 data in analysis improved the predictive power of the provided APM.

Tilton, James C.↗

NASA NTRS2012

Urban Climate Station Site Selection Through Combined Digital Surface Model and Sun Angle Calculations

Meteorological measurements within urban areas are becoming increasingly important due to the accentuating effects of climate change upon the Urban Heat Island (UHI). However, ensuring that such measurements are representative of the local area is often difficult due to the diversity of the urban environment. The evaluation of sites is important for both new sites and for the relocation of established sites to ensure that long term changes in the meteorological and climatological conditions continue to be faithfully recorded. Site selection is traditionally carried out in the field using both local knowledge and visual inspection. This paper exploits and assesses the use of lidar-derived digital surface models (DSMs) to quantitatively aid the site selection process. This is acheived by combining the DSM with a solar model, first to generate spatial maps of sky view factors and sun-hour potential and second, to generate site-specific views of the horizon. The results show that such a technique is a useful first-step approach to identify key sites that may be further evaluated for the location of meteorological stations within urban areas.

digital surface model↗

NASA NTRSDate not supplied

Mars Entry, Descent, Landing, and Ascent Systems Sensitivities to Landing Site and Atmospheric Dust

Plans for human missions to Mars continue to go through several architectural changes, dating all the way back to the 1950s [1]. The continuous study, reformulation, and refinement of Mars architectures and system concepts is necessary in order to incorporate evolving mission objectives, technology advancements, and growth in the body of knowledge regarding human factors and the various environments of human space travel. This evolution has continued into the 21st century, with architectures concepts such as NASA’s Design Reference Architecture 5.0 in 2009 [2], The Evolvable Mars Campaign in 2016 [3], and as recently as 2020, an architecture focused on a crewed mission as early as the 2030s that aims to minimizing crewed duration and infrastructure investment for the first mission [4]. Within these architectures, numerous studies around the current concept designs for Mars entry, descent, landing, and ascent (EDLA) systems have been performed over the last half a decade [[5], [6], [7], [8], [9], [10]]. Despite the breadth and depth of these studies, landing site, a key design parameter relevant to the design of EDLA systems, has remained nebulous over the years, largely due to the ever evolving mission objectives and architecture concept over the decades. However, the specific landing site has direct impact on the altitude and atmospheric conditions, which subsequently impact the design of EDLA systems. To accommodate the lack of a specific landing site, a baseline reference altitude of 0 km relative to the Mars Orbiter Laser Altimeter (MOLA), which is similar to an Earth sea level reference, has typically been selected and fixed for these past studies. Similarly, a baseline reference atmosphere has typically been utilized in these studies, either the Mars Global Reference Atmospheric Model [11], or a general 1982 standard warm, high pressure atmosphere model derived from Viking lander data [12]. Fig. 1 shows the range of elevations across the surface of Mars. Current architectures are focused on latitudes greater than 30 degrees north in an effort to ensure access to frozen water ice. From the figure, it is quickly evident that elevations over the range of longitudes at or above this latitude are significantly varied between roughly -4 to +4 km MOLA. Based on these observations, initial qualitative assessments of the impacts of landing site elevation on EDLA systems were performed. Fig. 2 depicts the expected trends in EDLA system mass for variations in both land site latitude and elevation. The background coloring is a qualitative evaluation of the current knowledge on ice water availability at the latitudes. Further modeling and simulation was performed to obtain numerical predictions of sensitivities to these parameters. Results indicate up to +2% to -4% mass variation from the current baseline Mars Ascent Vehicle concept, with the potential for greater than 6% mass variation at latitudes greater than 70 degrees north. However, variations in the descent system due to landing site were much more significant with mass variations in the range of -15% to +30% around the current baseline Mars Descent System concept. Additionally, Fig. 3 provides a depiction of potential Mars atmospheric density variations with both dust and Martian season. Though the Martian atmosphere is relatively thin compared to Earth’s atmosphere, it still poses significant impact on the design of EDLA systems. Variations in atmospheric density indicated by this slice of data would have significant impact on the design of EDLA systems. However, due to the highly complex nature of atmospheric flight, a qualitative assessment could not be performed. Rather, sensitivity results relied on modeling and simulation to provide numerical results for sensitivities on the current EDLA design concepts under consideration. Understanding these sensitivities is vital to the overall systems design of a Mars architecture. The resulting mass impacts on EDLA systems, driven by landing site elevation and dust level variations, has rippling impacts throughout the architecture that, ultimately, impact the viability of the architecture. Results showed fairly minor mass impacts to the current Mars Ascent Vehicle baseline configuration, roughly -0.6% to + 0.4% mass variations, while the Mars Descent System say greater variations due to dust, roughly -4% to +6% around the baseline concept.

EDLA↗

NASA NTRSDate not supplied

Volcanic Field Sites for Artemis Testing and Training

The Artemis Program will reestablish human presence on the Moon and lead to a new era of scientific discovery and exploration. Led by the National Aeronautics and Space Administration (NASA), the Artemis Program is a collaboration of space agencies and companies around the world. An integrated effort between various disciplines of science, engineering, and mission operations is currently developing methods, facilities, and analog field locations to train astronauts and test hardware and concepts of operations. These efforts aim to best prepare for the next steps of human exploration on the lunar surface and beyond. Numerous terrestrial volcanic field sites were evaluated and selected for their unique roles in helping to prepare for the lunar surface mission phases. This effort heavily leveraged the comprehensive academic research conducted at these field sites, as well as the tremendous Apollo heritage. The currently selected volcanic field sites include the San Francisco Volcanic Field in Northern Arizona, the Potrillo Volcanic Field in southern New Mexico, the highlands of Iceland, and the Southwestern Nevada Volcanic Field. Within each of these volcanic field sites numerous specific testing and training locations are being further developed utilizing the analogous terrain and unique features in these regions. Recent Artemis testing and training events have been conducted at a number of these volcanic field sites by both a dedicated Artemis Geology Training Team and a Joint Extra Vehicular Activity (EVA) Testing Team. This presentation will highlight the selected sites as well as the objectives and accomplishments of some of the recent field-testing events and training courses. Additionally, we continually strive to pursue additional sites, locations, data sets, collaborations, and partnerships in this endeavor and welcome knowledge transfer and community input.

Trevor Graff↗

NASA NTRS2019

Biomarker and Geochemical Assay Validation in Mars Analog Sites: Lessons from the FELDSPAR (Field Exploration and Life Detection Sampling for Planetary Analog Research) Project

Missions looking for signs of life on other worlds can often only take a few samples once they arrive. Making sense of these "few and far between" observations is easier if we know what a "normal" level of variation for that kind of planet is. Recent eruption sites in Iceland are good places to learn about this, because they have very little life present and the same types of rocks as many places on Mars. We have visited several of these sites in Iceland and tested many different kinds of measurements: the energy available for life, the amount of DNA (an important biological molecule) present, the relative amounts of different kinds of micro-organisms, and the specific minerals that make up the rocks and ground. In addition to recommendations for future expeditions, we have also shown that using early on-site measurements to choose later on-site sample sites is very helpful in reducing the number of sample sites needed.

Geochemical Assay Validation↗

NASA NTRS2019

Planetary Mapping for Landing Sites Selection: The Mars Case Study

The selection of a landing site on a planetary body is a multistep process that involves both the fulfillment of several engineering constraints and the accomplishment of scientific requirements. In this chapter, we will show how the simultaneous production and exploitation of different GIS maps depicting these criteria are pivotal in the landing site selection. Indeed, all of such constraints are presently evaluated through the use of GIS-based software. To show this, we will focus on the Martian site identification outline, providing multiple real examples taken from two ongoing study cases, i.e., the Simud Vallis landing site proposed by Pajola et al. (Icarus 268:355–381, 2016a) for the ESA ExoMars rover and the Eridania landing site proposed by Pajola et al. (Icarus 275:163–182, 2016b) for the NASA Mars 2020 landing site selection.

Planetary mapping↗

NASA NTRS2018

WRF Hindcasts of Cold Front Passages over the ARM Eastern North Atlantic Site: A Sensitivity Study

The present study explores the ability of the Weather Research and Forecasting (WRF) Model to accurately reproduce the passage of extratropical cold fronts at the DOE-ARM Eastern North Atlantic (ENA) observation site on the Azores Islands. An analysis of three case studies is performed in which the impact of the WRF domain size, position of the model boundary relative to the ENA site, grid spacing, and spectral nudging conditions are explored. The results from these case studies indicate that model biases in the timing and duration of cold front passages change with the distance between the model domain boundary and the ENA site. For these three cases, if the western model boundary is further than 1500 km from the site, the front becomes too meridional and fails to reach the site, making 1000 km or 1500 km the optimal distances. In contrast, integrations with small distances (e.g., 500 km) between the site and domain boundaries have inadequate spatial spin-up, i.e. the domain is too small for the model to properly stabilize. For all 3 cases, regardless of domain size, the model has biases in its upper-level circulation that impact the position and timing of the front. However, this issue is most serious for 4000 km2 domains and larger. For these domains, prolonged spectral nudging can correct cold front biases. As such, this analysis provides a framework to optimize the WRF model configuration necessary for a realistic hindcast of a cold front passage at a fixed location centered in a domain as large as computationally possible.

Faycal Lamraoui↗

NASA NTRS1976

Search for the Viking 2 landing site

The search for the landing site of Viking 2 is reviewed, emphasizing the characteristics of the various candidate sites and reasons for rejecting unsuitable sites. It is shown that the B3 site in Utopia Planitia was selected because the B latitude band (40 to 50 deg N) was of the highest scientific interest, the site appeared to be smoothed by uniform mantling, and the additional data analysis and acquisition required to land at any other site could have resulted in a landing delay and significant additional operational complexity. It is tentatively concluded that the Viking 2 lander rests in a deflation hollow.

Masursky, H.↗

NASA NTRS1978

Siting Issues for Solar Thermal Power Plants with Small Community Applications

Technologies for solar thermal plants are being developed to provide energy alternatives for the future. Implementation of these plants requires consideration of siting issues as well as power system technology. While many conventional siting considerations are applicable, there is also a set of unique siting issues for solar thermal plants. Early experimental plants will have special siting considerations. The siting issues associated with small, dispersed solar thermal power plants in the 1 to 10 MWe power range for utility/small community applications are considered. Some specific requirements refer to the first 1 MWe engineering experiment for the Small Power Systems Applications (SPSA) Project. The siting issues themselves are discussed in three categories: (1) system resource requirements, (2) environmental effects on the system, and (3) potential impact of the plant on the environment. Within these categories, specific issues are discussed in a qualitative manner. Examples of limiting factors for some issues are taken from studies of other solar systems.

Holbeck, J. J.↗

NASA NTRS1982

Assessing the representativeness of wind data for wind turbine site evaluation

Once potential wind turbine sites (either for single installations or clusters) are identified through siting procedures, actual evaluation of the sites must commence. This evaluation is needed to obtain estimates of wind turbine performance and to identify hazards to the machine from the turbulence component of the atmosphere. These estimates allow for more detailed project planning and for preliminary financing arrangements to be secured. The site evaluation process can occur in two stages: (1) utilizing existing nearby data, and (2) establishing and monitoring an onsite measurement program. Since step (2) requires a period of at least 1 yr or more from the time a potential site has been identified, step (1) is often an essential stage in the preliminary evaluation process. Both the methods that have been developed and the unknowns that still exist in assessing the representativeness of available data to a nearby wind turbine site are discussed. How the assessment of the representativeness of available data can be used to develop a more effective onsite meteorological measurement program is also discussed.

Renne, D. S.↗

NASA NTRS1982

Two Mars years of surface changes seen at the Viking Landing sites

An analysis of the spectrophotometric properties of the new dust deposited at the Viking Lander 1 site indicates that the new deposits are the same as the bright red material that only partially covered the site at the beginning of the mission. Certain areas of the Viking 1 site also showed an increase in contrast during the second year. The contrast increase is thought to be due to the partial removal of the recently deposited dust cover by high-velocity winds. What is more, a small soil slump occurred near the base of a boulder lying about 25 m from the lander. It is noted that whereas no obvious erosion has been detected at the Viking 2 site, periodic removal of the dust cover at this site is implied by the abundance of rocks at the site.

Guinness, E. A.↗

NASA NTRS1992

Geology of the Apollo 17 site

The Apollo 17 landing site was unique in several aspects: (1) it was the only site that was not selected from telescopic-based geologic interpretation--interest in the site was generated by the visual observations of Al Worden, Apollo 15 Command Module pilot, who interpreted dark-haloed craters as possible cinder cones; (2) instead of 20-m-resolution photographs, as was the norm for all earlier missions, this site had Apollo 15 panoramic camera photography coverage that had 2-m resolution; and (3) it had a geologist-astronaut aboard who was intimately involved in all stages of planning and mission operation, and was also instrumental in the design of a long-handled sample bag holder that eliminated the need for crew to dismount before collecting a sample, which then permitted sampling between major stations. Details of site geology, sample description, and geologic synthesis of the site as viewed from studies through 1976 are summarized.

Muehlberger, W. R.↗

NASA NTRS1992

Testing the Li-Strahler four-component canopy reflectance model in the HAPEX-Sahel shrub savanna sites using ground reflectance data

The rate at which a light field decays in water is characterized by the diffuse attenuation coefficient k. The Li-Strahler discrete-object canopy reflectance model was tested in two sites, a shrub grass savanna and a degraded shrub savanna on bare soil, in the proposed HAPEX (Hydrologic Atmospheric Pilot Experiment) II/Sahel study area in Niger, West Africa. Average site reflectance was predicted for each site from the reflectances and cover proportions of four components: shrub canopy, background (soil or grass and soil), shaded canopy, and shaded background. Component reflectances were sampled in the SPOT wavebands using a hand-held radiometer. Predicted reflectance was compared to average site reflectance measured using the same radiometer mounted on a backpack with measurements recorded every 5 m along two 1-km transects, also in the SPOT (Systeme Probatoire d'Observation de la Terre) bands. Measurements and predictions were made for each of the three days during the summer growing season, approximately two weeks apart. Red, near infrared reflectance, and the NDVI (normalized difference vegetation index) were all predicted with a high degree of accuracy for the shrub/grass site and with reasonable accuracy for the degraded shrub site.

Franklin, J.↗

NASA NTRS1992

Spectral bidirectional and hemispherical reflectance characteristics of selected sites in the Streletskaya steppe

Measurements of plant canopy bidirectional reflectance made by the PARABOLA (portable apparatus for rapid acquisition of bidirectional observations of the land and atmosphere) instrument in three spectral bands are analyzed for steppe grassland sites of differing productivity levels. The variation of spectral reflectance and the normalized difference vegetation index in the solar principal plane is presented. Comparisons are made with PARABOLA measurements from selected first ISLSCP field experiment (FIFE) grassland sites in the Konza prairie, Kansas. The Streletskaya steppe sites showed no strong hot spot reflectance, while this effect was present in some FIFE sites but absent in others. The hot spot effect seems to be dependent on canopy geometry and background reflectance characteristics of these sites. Spectral hemispherical reflectance was computed from the angular integration of the bidirectional measurements for the steppe sites. Total shortwave albedo was estimated from these hemispherical reflectance measurements and compared to albedo measured by pyranometers. The albedo estimates from PARABOLA were found to be approximately 12-17 percent higher than the pyranometer measurements.

Eck, Thomas F.↗

NASA NTRS1993

Site diversity for satellite earth terminals and measurements at 28 GHz

This paper reviews site diversity concepts and models and presents the results of a site diversity experiment, in which radiometers were used to measure attenuation on earth-space paths, performed at Columbus, Ohio, for a period of one year. Attenuation statistics are presented first in the form of the joint probability density function of attenuation at the two sites. From these are derived the cumulative two-dimensional distribution of attenuation at both sites, the cumulative distribution of attenuation at each site, the effective cumulative distribution of attenuation for a diversity system that always switches to the better of two signals, and the effective cumulative distribution of attenuation for a system with maximal-ratio signal combining. The switched-system diversity gain is compared with Hodge's predictive model, and the diversity improvement is compared with Boithias' model. Fade-duration and interfade-interval statistics are also presented for each site and for systems that employ switching and maximal-ratio combining. Rain-rate and interrainfall interval statistics are also included.

Lin, Kuan-Ting↗

NASA NTRS1991

GIS modeling of archaeological site locations: A low-tech approach

A Geographic Information System (GIS)-type analysis of archaeological site locations using a dBase III plus program and a desk top computer is presented. A previously developed model of site locations in the Sequatchie Valley of northeastern Alabama is tested against known site locations in another large survey area there. The model fails to account for site locations in the test area. A model is developed for the test area and indicates the site locations are indeed different. Whether this is due to differences in site locations on a sub-regional level, or to sample error in the original model is unknown.

Futato, Eugene M.↗

NASA NTRS1993

Highland crust at the Apollo 14 site: A review

Recent petrologic studies of pristine nonmare samples from the Apollo 14 site have demonstrated the unique character of the western highlands crust. Many of the lithologies which occur here are not found at other highland sites or represent unique variations of more common lithologies. Rare highland samples found at the Apollo 12 site have petrologic and geochemical affinities with the Apollo 14 highland suite and the two sites taken together constitute what can be called the Western Highland Province. Rocks of the Western Highland Province are geochemically distinct from similar lithologies found at eastern highland sites (Apollo 15, Apollo 16, Apollo 17, and the Luna sites) -- a fact which adds further complications to current petrogenetic models for the lunar crust. Nonetheless, an understanding of how the Western Highlands Province formed and why it differs from highland crust in the east is crucial to our overall understanding of primordial lunar differentiation and petrogenesis.

Shervais, John W.↗