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At least 217 records · Page 12

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NASA NTRS1995

Mars Pathfinder Landing Site Workshop 2: Characteristics of the Ares Vallis Region and Field Trips in the Channeled Scabland, Washington

Mars Pathfinder will place a single lander on the surface of Mars on July 4, 1997, following a December 1996 launch. As a result of the very successful first Mars Pathfinder Landing Site Workshop, the project has selected the Ares Vallis outflow channel in Chryse Planitia as the landing site. This location is where a large catastrophic outflow channel debouches into the northern lowlands. A second workshop and series of field trips, entitled Mars Pathfinder Landing Site Workshop 2: Characteristics of the Ares Vallis Region and Field Trips in the Channeled Scabland, Washington, were held in Spokane and Moses Lake, Washington. The purpose of the workshop was to provide a focus for learning as much as possible about the Ares Vallis region on Mars before landing there. The rationale is that the more that can be learned about the general area prior to landing, the better scientists will be able interpret the observations made by the lander and rover and place them in the proper geologic context. The field trip included overflights and surface investigations of the Channeled Scabland (an Earth analog for the martian catastrophic outflow channels), focusing on areas particularly analogous to Ares Vallis and the landing site. The overflights were essential for placing the enormous erosional and depositional features of the Channeled Scabland into proper three-dimensional context. The field trips were a joint educational outreach activity involving K-12 science educators, Mars Pathfinder scientists and engineers, and interested scientists from the Mars scientific community. Part 1 of the technical report on this workshop includes a description of the Mars Pathfinder mission, abstracts accepted for presentation at the workshop, an introduction to the Channeled Scabland, and field trip guides for the overflight and two field trips. This part, Part 2, includes the program for the workshop, summaries of the workshop technical sessions, a summary of the field trips and ensuing discussions, late abstracts of workshop presentations, reports on the education and public outreach activities carried out by the educators, and a list of the workshop and field trip participants.

Golombek, M. P.↗

NASA NTRS1993

Anabolic Responses of an Adult Cancellous Bone Site to Prostaglandin E2 in the Rat

The objects of this study were to determine: (1) the response of a non-growing cancellous bone site to daily prostaglandin E2 (PGE2) administration; and (2) the differences in the effects of daily PGE2, administration in growing (proximal tibial metaphysis, PTM) and non-growing cancellous bone sites (distal tibial metaphysis, DTM). Seven-month-old male Sprague-Dawley rats were given daily subcutaneous injections of 0, 1, 3 and 6 mg PGE2/kg per day for 60, 120 and 180 days. The static and dynamic histomorphometric analyses were performed on double-fluorescent labeled undecalcified distal tibial metaphyses (DTM). No age-related changes were found in static and dynamic histomorphometry of DTM cancellous bone between 7 and 13 months of age. The DTM of 7-month-old (basal controls) rats consisted of a 24.5 +/- 7.61%-metaphyseal cancellous bone mass, and a thick trabeculae (92 +/- 12 micro-m). It also had a very low tissue-base bone formation rate (3.0 +/- 7.31%/year). Exogenous PGE2 administration produced the following transient changes in a dose-response manner between zero and 60 days: (1) increased trabecular bone mass and improved architecture (increased trabecular bone area, width and number, and decreased trabecular separation); (2) increased trabecular interconnections: (3) increased bone formation parameters; and (4) decreased eroded perimeter. A new steady state with more cancellous bone mass and higher bone turnover was observed from day 60 onward, The elevated bone mass induced by the first 60 days of PGE2 treatment was maintained by another 60 and 120 days with continuous daily PGE2 treatment. When these findings were compared to those previously reported for the PTM, we found that the DTM was much more responsive to PGE2 treatment than the PTM. Percent trabecular bone area and tissue based bone formation rate increased significantly more in DTM as compared to PTM after the 60 days of 6 mg PGE2 treatment. These observations indicate that a non-growing cancellous bone site is more responsive than growing bone site to long-term daily administration of PGE2.

Ito, Hiroshi↗

NASA NTRS1994

Prostaglandin E2 Adds Bone to a Cancellous Bone Site with a Closed Growth Plate and Low Bone Turnover in Ovariectomized Rats

The objects of this study were to determine the responses of a cancellous bone site with a closed growth plate, (the distal tibial metaphysis (DTM), to ovariectomy (OVX) and OVX plus a prostaglandin E(2) treatment, and compare the site's response to previous findings reported for another site, the proximal tibial metaphysis (PTM). Thirty five 3-month old female Sprague-Dawley rats were divided into five groups; basal, sham OVX, and OVX+0, +1, or +6 mg PGE(2)/kg/d injected subcutaneously for 3 months and given double fluorescent labels before sacrifice. Cancellous bone histomorphometric analyses were performed on 20 micrometer thick undecalcified DTM sections. Similar to the PTM, the DTM showed age-related decreases in bone formation and increases in bone resorption, but it differed in that at 3 months POST OVX there was neither bone loss nor changes in formation endpoints. Giving 1 mg PGE(2)/kg/d to OVX rats prevented most age-related changes and maintained the bone formation histomorphometry near basal levels. Treating OVX rats with 6 mg PGE(2)/kd/d prevented age-related bone changes, added extra bone, and improved microanatomical structure by stimulating bone formation, without altering bone resportion. Futhermore, After PGE(2) admimnistration, the DTM, a cancellous bone site with a closed growth plate, increased bone formation more than did the cancellous bone in the PTM.

Ma, Y. F.↗

NASA NTRS1994

Prostaglandin E2 Adds Bone to a Cancellous Bone Site with a Closed Growth Plate and Low Bone Turnover in Ovariectomized Rats

The objects of this study were to determine the responses of a cancellous bone site with a closed growth plate (the distal tibial metaphysis, DTM) to ovariectomy (OVX) and OVX plus a prostaglandin E2 (PGE2) treatment, and compare the site's response to previous findings reported for another site (the proximal tibial metaphysis, PTM). Thirty-five 3-month old female Sprague-Dawley rats were divided into five groups: basal, sham-OVX, and OVX+0, +1, or +6 mg PGE2/kg/d injected subcutaneously for 3 months and given double fluorescent labels before sacrifice. Cancellous bone histomorphometric analyses were performed on 20-micron-thick undecalcified DTM sections. Similar to the PTM, the DTM showed age-related decreases in bone formation and increases in bone resorption, but it differed in that at 3 months post-OVX; there was neither bone loss nor changes in formation endpoints. Giving 1 mg PGE2/kg/d to OVX rats prevented most age-related changes and maintained the bone formation histomorphometry near basal levels. Treating OVX rats with 6 mg PGE2/kg/d prevented age-related bone changes, added extra bone, and improved microanatomical structure by stimulating bone formation without altering bone resorption. Furthermore, after PGE2 administration, the DTM, a cancellous bone site with a closed growth plate, inereased bone formation more than did the cancellous bone in the PTM.

Ma, Y. F.↗

NASA NTRS1995

MagLifter Site Investigation and Implementation Strategies

MagLifter, as defined here, is an advanced, earth-bound catapult system to provide the initial lift for earth orbiting vehicles to reduce or eliminate the need for multistage propulsion, thus reducing the cost of orbital space flight. It is presumed that magnetic levitation will catapult the vehicle to a desired initial velocity sufficient for reaching orbit with the vehicles own engines. Of necessity, the system must be located on and around a mountain with sufficient relief to allow the catapult to accelerate the launch vehicle to a sufficient speed in the desired direction to allow it to reach orbit. Such a mountain site must meet criteria consistent with current and future space launch needs and conditions. It is the purpose of this report to set forth preliminary criteria for choosing a suitable maglifter site. The report is divided into four major sections: (1) Assumed Launch System and Flight Vehicle Characteristics; (2) Task 1.A - Initial Site Selection Criteria; (3) Conclusions; and (4) Appendix - Phases of the Site Selection Process.

Burke, Pamela↗

NASA NTRS1996

Preliminary Work in Obtaining Site-Directed Mutants of Hen Egg White Lysozyme

Protein crystal growth studies are recognized as a critical endeavor in the field of molecular biotechnology. The scientific applications of this field include the understanding of how enzymes function and the accumulation of accurate information of atomic structures, a key factor in the process of rational drug design. NASA has committed substantial investment and resources to the field of protein crystal growth and has conducted many microgravity protein crystal growth experiments aboard shuttle flights. Crystals grown in space tend to be larger, denser and have a more perfect habit and geometry. These improved properties gained in the microgravity environment of space result largely from the reduction of solutal convection, and the elimination of sedimentation at the growing crystal surface. Shuttle experiments have yielded many large, high quality crystals that are suitable for high resolution X-ray diffraction analysis. Examples of biologically important macromolecules which have been successfully crystallized during shuttle missions include: lysozyme, isocitrate lyase, gamma-interferon, insulin, human serum albumin and canavalin. Numerous other examples are also available. In addition to obtaining high quality crystals, investigators are also interested in learning the mechanisms by which the growth events take place. Crystallization experiments indicate that for the enzyme HEWL, measured growth rates do not follow mathematical models for 2D nucleation and dislocation-led growth of tetragonal protein crystals. As has been suggested by the laboratory of Marc L. Pusey, a possible explanation for the disagreement between observation and data is that HEWL tetraconal crystals form by aggregated units of lysozyme in supersaturated solutions. Surface measurement data was shown to fit very well with a model using an octamer unit cell as the growth unit. According to this model, the aggregation pathway and subsequent crystal growth is described by: monomer < ------ > dimer < ------- > tetramer < ------ > octamer < ------ > higher order. It is believed that multimer aggregation of lysozyme occurs by interaction at specific binding sites on the surface of the protein crystals. If the presence of discrete binding sites and the aggregation hypothesis is true, then it follows that the alteration of the binding site(s) should have significant effect on the measurements obtained during growth experiments. Site-directed mutagenesis allows the specific alteration of proteins by replacement, deletion or addition of specific amino acid residues. This report outlines the approach for this strategy and the progress made thus far toward that end.

Holmes, Leonard D.↗

NASA NTRS1998

Modeling of Substitutional Site Preference in Ordered Intermetallic Alloys

We investigate the site substitution scheme of specific alloying elements in ordered compounds and the dependence of site occupancy on compound stoichiometry, alloy concentration. This basic knowledge, and the interactions with other alloying additions are necessary in order to predict and understand the effect of various alloying schemes on the physical properties of a material, its response to various temperature treatments, and the resulting mechanical properties. Many theoretical methods can provide useful but limited insight in this area, since most techniques suffer from constraints in the type of elements and the crystallographic structures that can be modeled. With this in mind, the Bozzolo-Ferrante-Smith (BFS) method for alloys was designed to overcome these limitations, with the intent of providing an useful tool for the theoretical prediction of fundamental properties and structure of complex systems. After a brief description of the BFS method, its use for the determination of site substitution schemes for individual as well as collective alloying additions to intermetallic systems is described, including results for the concentration dependence of the lattice parameter. Focusing on B2 NiAl, FeAl and CoAl alloys, the energetics of Si, Ti, V, Cr, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Hf, Ta and W alloying additions are surveyed. The effect of single additions as well as the result of two simultaneous additions, discussing the interaction between additions and their influence on site preference schemes is considered. Finally, the BFS analysis is extended to ternary L1(sub 2) (Heusler phase) alloys. A comparison between experimental and theoretical results for the limited number of cases for which experimental data is available is also included.

Bozzolo, Guillermo↗

NASA NTRS1998

Geology of Lunar Landing Sites and Origin of Basin Ejecta from a Clementine Perspective

The goals of this research were to examine Clementine multispectral data covering the Apollo landing sites in order to: (1) provide ground truth for the remotely sensed observations, (2) extend our understanding of the Apollo landing sites to the surrounding regions using the empirically calibrated Clementine data, and (3) investigate the composition and distribution of impact-basin ejecta using constraints based upon the remotely sensed data and the Apollo samples. Our initial efforts (in collaboration with P. Lucey and coworkers) to use the Apollo soil compositions to "calibrate" information derived from the remotely sensed data resulted in two extremely useful algorithms for computing estimates of the concentrations of FeO and TiO2 from the UV-VIS 5-band data. In this effort, we used the average surface soil compositions from 37 individual Apollo and 3 Luna sample stations that could be resolved using the Clementine data. We followed this work with a detailed investigation of the Apollo 17 landing site, where the sampling traverses were extensive and the spectral and compositional contrast between different soils covers a wide range. We have begun to investigate the nature and composition of basin ejecta by comparing the thick deposits on the rim of Imbrium in the vicinity of the Apollo 15 site and those occurring southeast of the Serenitatis basin, in the Apollo 17 region. We continue this work under NAG5-6784, "Composition, Lithology, and Heterogeneity of the lunar crust using remote sensing of impact-basin uplift structures and ejecta as probes. The main results of our work are given in the following brief summaries of major tasks. Detailed accounts of these results are given in the attached papers, manuscripts, and extended abstracts.

Jolliff, Bradley L.↗

NASA NTRS2000

Autonomous, Full-Time Cloud Profiling at Arm Sites with Micro Pulse Lidar

Since the early 1990's technology advances permit ground based lidar to operate full time and profile all significant aerosol and cloud structure of the atmosphere up to the limit of signal attenuation. These systems are known as Micro Pulse Lidars (MPL), as referenced by Spinhirne (1993), and were first in operation at DOE Atmospheric Radiation Measurement (ARM) sites. The objective of the ARM program is to improve the predictability of climate change, particularly as it relates to cloud-climate feedback. The fundamental application of the MPL systems is towards the detection of all significant hydrometeor layers, to the limit of signal attenuation. The heating and cooling of the atmosphere are effected by the distribution and characteristics of clouds and aerosol concentration. Aerosol and cloud retrievals in several important areas can only be adequately obtained with active remote sensing by lidar. For cloud cover, the height and related emissivity of thin clouds and the distribution of base height for all clouds are basic parameters for the surface radiation budget, and lidar is essetial for accurate measurements. The ARM MPL observing network represents the first long-term, global lidar study known within the community. MPL systems are now operational at four ARM sites. A six year data set has been obtained at the original Oklahoma site, and there are several years of observations at tropical and artic sites. Observational results include cloud base height distributions and aerosol profiles. These expanding data sets offer a significant new resource for cloud, aerosol and atmospheric radiation analysis. The nature of the data sets, data processing algorithms, derived parameters and application results are presented.

Spinhirne, James D.↗

NASA NTRS2000

Access to Space Interactive Design Web Site

The Access To Space (ATS) Group at NASA's Goddard Space Flight Center (GSFC) supports the science and technology community at GSFC by facilitating frequent and affordable opportunities for access to space. Through partnerships established with access mode suppliers, the ATS Group has developed an interactive Mission Design web site. The ATS web site provides both the information and the tools necessary to assist mission planners in selecting and planning their ride to space. This includes the evaluation of single payloads vs. ride-sharing opportunities to reduce the cost of access to space. Features of this site include the following: (1) Mission Database. Our mission database contains a listing of missions ranging from proposed missions to manifested. Missions can be entered by our user community through data input tools. Data is then accessed by users through various search engines: orbit parameters, ride-share opportunities, spacecraft parameters, other mission notes, launch vehicle, and contact information. (2) Launch Vehicle Toolboxes. The launch vehicle toolboxes provide the user a full range of information on vehicle classes and individual configurations. Topics include: general information, environments, performance, payload interface, available volume, and launch sites.

Leon, John↗

NASA NTRS2000

Active and Passive Supplier Assessment Program (ASAP & PSAP) WWW Sites http://nepp.nasa.gov/imd/asap http://nepp.nasa.gov/imd/psap

The Active and Passive Supplier Assessment Programs (ASAP and PSAP) WWW Sites provide general information to the electronic parts community regarding the availability of electronic parts. They also provide information to NASA regarding modifications to commonly used procurement specifications and test methods. The ASAP and PSAP www sites are ongoing resources produced by Code 562 in support of the NASA HQ funded NASA Electronic Parts and Packaging (NEPP) Program. These WWW sites do not provide information pertaining to patented or proprietary information. All of the information contained in these www sites is available through various other public domain resources such as US Military Qualified Producers Listings (QPLs) and Qualified Manufacturer Listings (QMLs) and industry working groups such as the Electronics Industry Alliance (EIA) and the Space Parts Working Group (SPWG).

Brusse, Jay↗

NASA NTRS2000

Possible Ancient Anthrosols Near Lost City of Ubar Site in Oman

During mapping for the Wadi al Jubal Archaeological Project in Yemen, USGS Geologists Overstreet and Grolier mapped "anthrosols of pre-Islaniic age" east of the Marib dam site (15D 24M N, 45D 18M E). These soils were the result of agriculture supported by irrigation enabled by water impounded by the dam, areas which were abandoned after dam failure. During analysis of Landsat Thematic Mapper satellite images of Yemen and Oman for the Mahra Archaeological Project, we noted that these anthrosols had a distinctive image expression. Based on other remote sensing research and laboratory spectroscopy, we think that the distinctive image signature is due to low reflectivity in Landsat band 7 resulting from relatively high concentrations of gypsum in the anthrosols. Many anthrosol sites were noted, most, but not all, of them previously documented. Undocumented possible anthrosol sites include an area east of Shisr in Oman, the archaeological site discovered by us to be responsible for some features of the "Lost City of Ubar" legends. Included in legendary accounts of the Ubar region are reports of fertile oases, and "areas that have known the plow". Based on demonstrated reliability of aspects of carefully interpreted legendary accounts, we postulate that we may have located the area of desert agriculture that may have existed to support the frankincense caravansary of Ubar. The possible anthrosol area is located at approximately 18D 10M N, 53D 54M E, and will be the subject of study in a future expedition.

Blom, Ronald G.↗

NASA NTRS1998

Apparent Surface Reflectance of the DOE ARM SGP CART Central Site Derived from AVIRIS Spectral Images

The primary objective of the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Program at the Southern Great Plains (SGP) Cloud and Radiation Testbed (CART) is to acquire in situ and remote sensing data to improve cloud and atmospheric radiative models and parameterizations. As a consequence of this program, a large number of atmosphere and surface measurements are being acquired at the ARM SGP CART central site. NASA's Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) overflew this site on August 1, 1997. AVIRIS measures the upwelling spectral solar radiance from 400 to 2500 nm at 10-nm intervals. From 20 km altitude, these calibrated spectra are acquired as images of 11 by up to 800 km with 20-by-20 m spatial resolution. These data were acquired at the ARM SGP CART Central Site to first investigate derivation of atmospheric parameters from the measured spectra, second study the variation of these parameters, and third demonstrate the inversion of the calibrated radiance spectra to apparent surface reflectance. These objectives have been pursued with AVIRIS data at other sites for atmospheric water vapor and derivation of apparent surface reflectance.

Green, Robert O.↗

NASA NTRS1998

Mangala Valles as a Potential Landing Site for the Mars Surveyor 2001 Lander

Mangala Valles is an outflow channel in the Memnonia region of Mars. Although its origin is still under debate, most researchers believe they represent some form of catastrophic flood system which occurred early in the evolutionary history of Mars. The scientific objective of the Mars Surveyor Program 2001 (MSP 01) landed mission is to examine the ancient climatic and geologic history of Mars; to characterized surface materials with respect to elemental and mineral composition of rock and soils; to identify the role water may have played with respect to evolutionary history of the surface; to look for samples which may contain possible evidence of ancient life; and to collect and store unaltered samples which may be eventually returned to Earth during a later mission (MSP 05 - 2005). As with the Mars Pathfinder lander, the landing site will depend on several engineering constraints. Preliminary engineering constraints for MSP 01 landing site is that the landing site lies with 30 N and -15 S of the equator (due to solar power limitations) and below 2 km elevation. Both the scientific objectives and the engineering constraints can be accommodated with a Mangala Valles landing site.

Anderson, R.↗

NASA NTRS1998

Studies of Potential Mars Surveyor 1998 Landing Sites

The 1998 lander payload consists of a descent imager, the Mars Volatiles and Climate Surveyor (MVACS) instruments (lander stereo camera, arm-mounted close-up imager, meteorology package, thermal and evolved gas analyzer), and a LIDAR instrument. The mission focuses on assessment of near-surface water ice in the south polar region, and the volatile and climate history of Mars. In order to achieve these objectives, the landing site must allow access to polar layered deposits by the robotic arm, which may be able to dig as much as 0.5 m below the surface. Hence, the presence of recent aeolian debris at the landing site may adversely affect the ability of the MVACS instruments to gather the samples and acquire data needed to properly address the science objectives. The studies described here include mapping surface units in the landing region (73S - 77S, 140W - 230W) to infer the distribution of aeolian debris and to identify potential landing sites where mantling is minimal. Because the '98 lander will not be able to survive very low temperature conditions, this study also includes mapping of south polar seasonal frost retreat based on Viking Orbiter images. The results of this work, in conjunction with complementary studies by other investigators, will facilitate the selection of the Mars Surveyor 1998 landing site (and backup) by the summer of 1998.

Herkenhoff, K. E.↗

NASA NTRS1999

Landing Site Engineering Constraints

Based upon the lander design, constraints are placed upon the landing site selection process in order to mitigate landing risk and optimize mission performance. Constraints are placed on the landing site latitude, elevation, measured rock abundance and terrain slopes within the landing footprint. Estimated mission lifetime and power availability as a function of landing site latitude will be presented. The dimensions of the landing footprint will be given. Plans for obtaining high resolution MOC images of candidate landing sites will be discussed.

Spencer, D.↗

NASA NTRS2000

Martian Magmatic-Driven Hydrothermal Sites: Potential Sources of Energy, Water, and Life

Magmatic-driven processes and impact events dominate the geologic record of Mars. Such recorded geologic activity coupled with significant evidence of past and present-day water/ice, above and below the martian surface, indicate that hydrothermal environments certainly existed in the past and may exist today. The identification of such environments, especially long-lived magmatic-driven hydrothermal environments, provides NASA with significant target sites for future sample return missions, since they (1) could favor the development and sustenance of life, (2) may comprise a large variety of exotic mineral assemblages, and (3) could potentially contain water/ice reservoirs for future Mars-related human activities. If life developed on Mars, the fossil record would presumably be at its greatest concentration and diversity in environments where long-term energy sources and water coexisted such as at sites where long-lived, magmatic-driven hydrothermal activity occurred. These assertions are supported by terrestrial analogs. Small, single-celled creatures (prokaryotes) are vitally important in the evolution of the Earth; these prokaryotes are environmentally tough and tolerant of environmental extremes of pH, temperature, salinity, and anoxic conditions found around hydrothermal vents. In addition, there is a great ability for bacteria to survive long periods of geologic time in extreme conditions, including high temperature hydrogen sulfide and sulfur erupted from Mount St. Helens volcano. Our team of investigators is conducting a geological investigation using multiple mission-derived datasets (e.g., existing geologic map data, MOC imagery, MOLA, TES image data, geophysical data, etc.) to identify prime target sites of hydrothermal activity for future hydrological, mineralogical, and biological investigations. The identification of these sites will enhance the probability of success for future missions to Mars.

Anderson, R. C.↗

NASA NTRS2001

Measurements of Aerosol, Ocean and Sky Properties at the HOT Site in the Central Pacific

Monthly cruises have been made to the HOT site (approximately 100 km north of Oahu) since October 1988. The goal of these cruises is to make hydrography, chemistry, and biology observations. Measurements are typically made at a near coastal station (Kahe) on the first day to test the equipment and to obtain coastal shallow water (approximately 1500 m) observations. The second and third days are spent at the HOT site. On the morning of the fourth day, measurements are made at the HOT site and noontime measurements are made at the Hale-Aloha station near the mooring before returning to port by early the next morning. The locations of the three stations are Kahe, HOT, and Hale-ALOHA buoy. The routine HOT measurements are available during the summer following the year of the observations. The 1998 measurements will therefore become available during the summer of 1999. The data sets can be obtained at the National Oceanographic Data Center (NODC) or from the HOT web site http://kahana.soest.hawaii.edu/hot/hot_jgofs.html.

Porter, John N.↗