ALBERT

Description: Rover missions to the surface of Mars after MER 2003, are likely to be centered around focused geologic field mapping. One objective with high priority in selecting landing sites for these missions will be to characterize the nature, spatial distribution, internal structure, composition, and depositional history of exposed sedimentary layered deposits by visiting a number of distributed outcrops identified previously (and with a high degree of certainty) from orbit. These deposits may contain prebiotic material, even fossil organisms, but their primary value will be to enable an assessment of the planet's climate at the time they were emplaced. High resolution imaging from a mobile rover will enable the detailed study of these deposits over a wide area, their internal structure and mineralogy at distributed localities, and could resolve biologically-derived structures (such as stromatolite-like textures) if they are present. With the addition of a spectrometer, it should be possible to ascertain the presence of carbonates, sulfates, organics, water (liquid, frost, and bound water), as well as a variety of silicate minerals in the context of the collected imagery. Such a mission approach is directly relevant to future exploration of Mars, because it provides the geologic context comparable to what a field geologist visiting a site for the first time would acquire. Rover missions after MER will likely have much better targeting and hazard avoidance landing systems, enabling access to planimetrically-challenged sites of high scientific interest. These vehicles will also likely have greater mobility than MER, capable of driving greater distances in a shorter amount of time. Many scientists and mission planners have realized the need to design a rover whose mobility can be comparable to the dimensions of its 3-sigma landing error ellipse.

Description: Using topography collected over one martian year from the Mars Orbiter Laser Altimeter on the Mars Global Surveyor (MGS) spacecraft, we have measured temporal changes in the elevation of the martian surface that correlate with the seasonal cycle of carbon dioxide exchange between the surface and atmosphere. The greatest elevation change (1.5 to 2 meters) occurs at high latitudes ( above 80 degrees ), whereas the bulk of the mass exchange occurs at lower latitudes (below 75 degrees N and below 73 degrees S). An unexpected period of sublimation was observed during northern hemisphere autumn, coincident with dust storms in the southern hemisphere. Analysis of MGS Doppler tracking residuals revealed temporal variations in the flattening of Mars that correlate with elevation changes. The combined changes in gravity and elevation constrain the average density of seasonally deposited carbon dioxide to be 910 +/- 230 kilograms per cubic meter, which is considerably denser than terrestrial snow.

Description: No abstract available

Description: To develop materials for shielding astronauts from the hazards of GCR, natural Martian surface materials are considered for their potential as radiation shielding for manned Mars missions. The modified radiation fluences behind various kinds of Martian rocks and regolith are determined by solving the Boltzmann equation using NASA Langley's HZETRN code along with the 1977 Solar Minimum galactic cosmic ray environmental model. To develop structural shielding composite materials for Martian surface habitats, theoretical predictions of the shielding properties of Martian regolith/polyimide composites has been computed to assess their shielding effectiveness. Adding high-performance polymer binders to Martian regolith to enhance structural properties also enhances the shielding properties of these composites because of the added hydrogenous constituents. Heavy ion beam testing of regolith simulant/polyimide composites is planned to validate this prediction. Characterization and proton beam tests are performed to measure structural properties and to compare the shielding effects on microelectronic devices, respectively.

Description: The western hemisphere of Mars is dominated by the formation of Tharsis, which is an enormous high-standing region (roughly 25% of the surface area of the planet) capped by volcanics, including the solar system's largest shield volcanoes. Tharsis is surrounded by an enormous radiating system of grabens and a circumferential system of wrinkle ridges that extends over the entire western hemisphere of Mars. This region is perhaps the largest and most long lived tectonic and volcanic province of any of the terrestrial planets with a well-preserved history of magmatic-driven activity that began in the Noachian and has lasted throughout Martian geologic time. Tharsis and the surrounding regions comprise numerous components, including volcanic constructs of varying sizes and extensive lava flow fields, large igneous plateaus, fault and ridge systems of varying extent and relative age of formation, gigantic outflow channel systems, vast system of canyons, and local and regional centers of tectonic activity. Many of these centers are interpreted to be the result of magmatic-related activity, including uplift, faulting, dike emplacement, volcanism, and local hydrothermal activity. Below we present a summary of our work for Tharsis focusing primarily on the earliest stage of development, the Noachian period. Here we hone in on the early centers and how they relate to the early development of the Tharsis Magmatic Complex (TMC).

Description: The objective of this project is to expand the capabilities of for the Mars Umbilical Technology Demonstrator (MUTD). The MUTD shall provide electrical power and fiber optic data cable connections between two simulated mars vehicles, 1000 in apart. ne wheeled mobile robot Omnibot is used to provide the mobile base for the system. The mate-to umbilical plate is mounted on a Cartesian robot, which is installed on the Omnibot mobile base. It is desirable to provide the operator controlling the Omnibot, the distance and direction to the target. In this report, an approach for finding the position and orientation of the mobile robot using inertial sensors and beacons is investigated. First phase of the project considered the Omnibot being on the flat surface. To deal with the uneven Mars environment, the orientation as well as position needs to be controlled. During local positioning, the information received from four ultrasonic sensors installed at the four corner of the mate-mi plate is used to identify the position of mate-to plate and mate the umbilical plates autonomously. The work proposed is the continuation of the principal investigator research effort as a participant in the 1999 NASA/ASEE Summer Faculty Fellowship Program.

Description: This paper presents the human exploration of Mars in viewgraph form.

Description: The contents include: 1) Crew Autonomy; 2) Bioastronautics Critical Path Roadmap (CPR); 3) CPR Issues; and 4) Clinical Problems.

Description: A major long term NASA objective is to enable human exploration beyond low Earth orbit. This will take a strange approach, with a concentration on new, enabling technologies and capabilities. Mars robotic missions are logical and necessary steps in the progression toward eventual human missions.

Description: The role of robots and humans in Mars Exploration is presented.

Description: A potential challenge for a human Mars mission is that while humans are by most measures the obvious best way to search for life on Mars, we may also be the most problematic in that we could unduly compromise the search for life by contaminating relevant environments and/or possibly adversely and irreversibly affecting indigenous life. Perhaps more problematic is the fundamental epistemic challenge of the "one data point" limitation which could decrease confidence in applying terrestrially based research to extraterrestrial life issues in general. An informal decision tree is presented as one way to begin thinking about contamination issues. There are many sub-questions and distinctions not shown such as biological vs. nonbiological (but biologically relevant) contamination, viable vs. dead organisms, masking indigenous organisms vs. merely making the search more difficult, and independent origin vs. panspermia distinctions. While it may be unlikely that terrestrial microbes could survive on Mars, let alone reproduce and unduly compromise the search for life, the unpredictable potential for microbial life to survive, grow exponentially, evolve and modify (and sometimes destroy) environments, warrants focusing carefully on biologically relevant contamination as we prepare to send humans to the first planet that may have indigenous life-forms.

Description: This effort supports the Astrobiology Objective 8 the Search for LIFE ON MARS PAST AND PRESENT -(Astrobiology Program Office, 1998, p.7). The essential trade analysis is between returning very small samples to the Earth while protecting them versus in situ analysis on Mars. Developing these explicit parameters encompasses design, instrumentation, system integration, human factors and surface operations for both alternatives. This allocation of capability approach incorporates a "humans and machines in the loop" model that recognizes that every exploration system involves both humans and automated systems. The question is where in the loop they occur whether on Earth, in the Mars Base, in the rover or creeping over the Mars surface.

Description: Mars climatology and its influence on human exploration is presented.

Description: The contents include: 1) Field Exploration Strategy; 2) Analytical Capabilities and Instruments; 3) Crew Skills and Training; and 4) Earth-Mars Communications. This paper is in viewgraph form.

Description: The contents include: 1) Human Contributions; 2) Tasks for Humans (History and Future); 3) Environmental and Physical Limitations; 4) Human and Robotic Implementation Options; 5) Ground Test Experience; 6) Needed Enabling Information and Technology; and 7) Strategic Issues.

Description: This paper presents a comparison of robot and human surface operations on solar system bodies. The topics include: 1) Long Range Vision of Surface Scenarios; 2) Human and Robots Complement Each Other; 3) Respective Human and Robot Strengths; 4) Need More In-Depth Quantitative Analysis; 5) Projected Study Objectives; 6) Analysis Process Summary; 7) Mission Scenarios Decompose into Primitive Tasks; 7) Features of the Projected Analysis Approach; and 8) The "Getting There Effect" is a Major Consideration. This paper is in viewgraph form.

Description: The Mars Environmental Compatibility Assessment (MECA) electrometer is an instrument that was designed jointly by researchers at the Jet Propulsion Laboratory and the Kennedy Space Center, and is intended to fly on a future space exploration mission of the surface of Mars. The electrometer was designed primarily to study (1) the electrostatic interaction between the Martian soil and five different types of insulators, which are attached to the electrometer, as the electrometer is rubbed over the Martian soil. The MECA/Electrometer is also capable of measuring (2) the presence of charged particles in the Martian atmosphere, (3) the local electric field strength, and (4) the local temperature. The goal of the research project described in this report was to test and evaluate the measurement capabilities of the MECA/Electrometer under simulated Martian surface conditions using facilities located in the Labs and Testbeds Division at the Kennedy Space Center. The results of this study indicate that the Martian soil simulant can triboelectrically charge up the insulator surface. However, the maximum charge buildup did not exceed 18% of the electrometer's full-range sensitivity when rubbed vigorously, and is more likely to be as low as 1% of the maximum range when rubbed through soil. This indicates that the overall gain of the MECA/Electrometer could be increased by a factor of 50 if measurements at the 50% level of full-range sensitivity are desired. The ion gauge, which detects the presence of charged particles, was also evaluated over a pressure range from 10 to 400 Torr (13 to 533 mbar). The electric field sensor was also evaluated. Although the temperature sensor was not evaluated due to project time constraints, it was previously reported to work properly.

Description: Interstellar gas and dust constitute the primary material from which the solar system formed. Near the end of the hot early phase of star and planet formation, volatile, less refractory materials were transported into the inner solar system as comets and interplanetary dust particles. Once the inner planets had sufficiently cooled, late accretionary infall seeded them with complex organic compounds [Oro, J. (1961) Nature (London) 190, 389-390; Delsemme, A. H. (1984) Origins Life 14, 51-60; Anders, E. (1989) Nature (London) 342, 255-257; Chyba, C. F. & Sagan, C. (1992) Nature (London) 355, 125-131]. Delivery of such extraterrestrial compounds may have contributed to the organic inventory necessary for the origin of life. Interstellar ices, the building blocks of comets, tie up a large fraction of the biogenic elements available in molecular clouds. In our efforts to understand their synthesis, chemical composition, and physical properties, we report here that a complex mixture of molecules is produced by UV photolysis of realistic, interstellar ice analogs, and that some of the components have properties relevant to the origin of life, including the ability to self-assemble into vesicular structures.

Description: Infrared (IR) studies of laboratory ices can provide information on the evolution of cosmic-type ices as a function of different simulated space environments involving thermal, ultraviolet (UV), or ion processing. Laboratory radiation experiments can lead to the formation of complex organic molecules. However, because of our lack of knowledge about UV photon and ion fluxes, and exposure lifetimes, it is not certain how well our simulations represent space conditions. Appropriate laboratory experiments are also limited by the absence of knowledge about the composition, density, and temperature of ices in different regions of space. Our current understanding of expected doses due to UV photons and cosmic rays is summarized here, along with an inventory of condensed-phase molecules identified on outer solar system surfaces, comets and interstellar grains. Far-IR spectra of thermally cycled H2O are discussed since these results reflect the dramatic difference between the amorphous and crystalline phases of H2O ice, the most dominant condensed-phase molecule in cosmic ices. A comparison of mid-IR spectra of products in proton-irradiated and UV-photolyzed ices shows that few differences are observed for these two forms of processing for the simple binary mixtures studied to date. IR identification of radiation products and experiments to determine production rates of new molecules in ices during processing are discussed. A new technique for measuring intrinsic IR band strengths of several unstable molecules is presented. An example of our laboratory results applied to Europa observations is included.

Description: "Are they worlds, or are they mere masses of matter? Are physical forces alone at work there or has evolution begotten something more complex, something not unakin to what we know on Earth as life? It is in this that lies the peculiar interest of Mars." Percival Lowell (in ref. 1, p. 3).

Description: LaRC(TM)-PETI-5 is a PhenylEthynyl-Terminated Imide resin developed at NASA Langley Research Center (LaRC) during the 1990s. It offers a combination of attractive composite and adhesive properties. IM7/LaRC(TM)-PETI-5 composites exhibit thermal and thermo-oxidative stability typical of polyimides, superior chemical resistance and processability, excellent mechanical properties, toughness and damage tolerance. It was selected for study in the High Speed Research program aimed at developing technologies for a future supersonic aircraft, the High Speed Civil Transport, with a projected life span of 60 000 h at a cruise speed up to Mach 2.4. Robust autoclave processing cycles for LaRC(TM)-PETI-5 composites have been thoroughly designed and demonstrated, which involved hand lay-up of solvent-ladened 'wet' prepregs. However, this type of processing is not only costly but also environmentally unfriendly. Volatile management and shrinkage could become serious problems in the fabrication of large complex airframe structural subcomponents. Robotic tow placement technology utilizing 'dry' material forms represents a new fabrication process which overcomes these deficiencies. This work evaluates and compares mechanical properties of composites fabricated by heated head automated tow placement (dry process) with those obtained by hand lay-up/autoclave fabrication (wet process). Thermal and rheological properties of the robotically as-placed uncured composites were measured. A post-cure cycle was designed due to the requirement of the PETI-5 resin for a 370 C/1 h hold to reach full cure, conditions which cannot be duplicated during heated head robotic placement. Mechanical properties such as 0 degree flexural strength and modulus, open hole tensile and compressive strength and moduli, reduced section compression dogbone compressive strength, and modified zippora-medium small (MZ-MS) tensile and compressive properties were obtained on the post-cured panels. These properties compared favourably with those obtained from the wet process.

Description: The detection of impulsive low-frequency (10 to 80 kHz) radio signals, and separate very-low-frequency (approx. 100 Hz) radio 'whistler' signals provided the first evidence for lightning in the atmosphere of Venus. Later, a small number of impulsive high- frequency (100 kHz to 5.6 MHz) radio signals, possibly due to lightning, were also detected. The existence of lightning at Venus has, however, remained controversial. Here we report the results of a search for high-frequency (0.125 to 16 MHz) radio signals during two close fly-bys of Venus by the Cassini spacecraft. Such signals are characteristic of terrestrial lightning, and are commonly heard on AM (amplitude-modulated) radios during thunderstorms. Although the instrument easily detected signals from terrestrial lightning during a later fly-by of Earth (at a global flash rate estimated to be 70/s, which is consistent with the rate expected for terrestrial lightning), no similar signals were detected from Venus. If lightning exists in the venusian atmosphere, it is either extremely rare, or very different from terrestrial lightning.

Description: The ten-degree tilt of the Jovian magnetic dipole causes the magnetic equator to move back and forth across Jupiter's rotational equator and tile Galileo orbit that lies therein. Beyond about 24 Jovian radii, the equatorial current sheet thins and tile magnetic structure changes from quasi-dipolar into magnetodisk-like with two regions of nearly radial but antiparallel magnetic field separated by a strong current layer. The magnetic field at the center of the current sheet is very weak in this region. Herein we examine tile current sheet at radial distances from 24 55 Jovian radii. We find that the magnetic structure very much resembles tile structure seen at planetary magnetopause and tail current sheet crossings. Tile magnetic field variation is mainly linear with little rotation of the field direction, At times there is almost no small-scale structure present and the normal component of the magnetic field is almost constant through the current sheet. At other times there are strong small-scale structures present in both the southward and northward directions. This small-scale structure appears to grow with radial distance and may provide the seeds for tile explosive reconnection observed at even greater radial distances oil tile nightside. Beyond about 40 Jovian radii, the thin current sheet also appears to be almost constantly in oscillatory motion with periods of about 10 min. The amplitude of these oscillations also appears to grow with radial distance. The source of these fluctuations may be dynamical events in tile more distant magnetodisk.

Description: One major obstacle to human space exploration is the possible limitations imposed by the adverse effects of long-term exposure to the space environment. Even before human spaceflight began, the potentially brief exposure of astronauts to the very intense random solar energetic particle (SEP) events was of great concern. A new challenge appears in deep space exploration from exposure to the low-intensity heavy-ion flux of the galactic cosmic rays (GCR) since the missions are of long duration and the accumulated exposures can be high. Since aluminum (traditionally used in spacecraft to avoid potential radiation risks) leads to prohibitively expensive mission launch costs, alternative materials need to be explored. An overview of the materials related issues and their impact on human space exploration will be given.

Description: Radiation is a primary concern in the planning of a manned mission to Mars. Recent studies using NASA Langley Research Center's HZETRN space radiation transport code show that the low energy neutron fluence on the Martian surface is larger than previously expected. The upper atmosphere of Mars is exposed to a background radiation field made up of a large number of protons during a solar particle event and mixture of light and heavy ions caused by galactic cosmic rays at other times. In either case, these charged ions interact with the carbon and oxygen atoms of the Martian atmosphere through ionization and nuclear collisions producing secondary ions and neutrons which then interact with the atmospheric atoms in a similar manner. In the past, only these downward moving particles have been counted in evaluating the neutron energy spectrum on the surface. Recent enhancements in the HZETRN code allow for the additional evaluation of those neutrons created within the Martian regolith through the same types of nuclear reactions, which rise to the surface. New calculations using this improved HZETRN code show that these upward moving neutrons contribute significantly to the overall neutron spectrum for energies less than 10 MeV.

Description: We use a time dependent, microphysical cloud model to study the formation of carbon dioxide clouds in the Martian atmosphere. Laboratory studies by Glandor et al. show that high critical supersaturations are required for cloud particle nucleation and that surface kinetic growth is not limited. These conditions, which are similar to those for cirrus clouds on Earth, lead to the formation of carbon dioxide ice particles with radii greater than 500 micrometers and concentrations of less than 0.1 cm(exp -3) for typical atmospheric conditions. Within the current Martian atmosphere, CO2 cloud formation is possible at the poles during winter and at high altitudes in the tropics during periods of increased atmospheric dust loading. In both cases, temperature perturbations of several degrees below the CO2 saturation temperature are required to nucleate new cloud particles suggesting that dynamical processes are the most common initiators of carbon dioxide clouds rather than diabatic cooling. The microphysical cloud model, coupled to a two-stream radiative transfer model, is used to reexamine the impact of CO2 clouds on the surface temperature within a dense CO2 atmosphere. The formation of carbon dioxide clouds leads to a warmer surface than what would be expected for clear sky conditions. The amount of warming is sensitive to the presence of dust and water vapor in the atmosphere, both of which act to dampen cloud effects. The radiative warming associated with cloud formation, as well as latent heating, work to dissipate the clouds when present. Thus, clouds never last for periods much longer than several days, limiting their overall effectiveness for warming the surface. The time average cloud optical depth is approximately unity leading to a 5-10 K warming, depending on the surface pressure. However, the surface temperature does not rise about the freezing point of liquid water even for pressures as high as 5 bars, at a solar luminosity of 75% the current value.

Description: The state-of-the-art development of several Metal Matrix Composites (MMC) for NASA's advanced propulsion systems will be presented. The goal is to provide an overview of NASA-Marshall Space Flight Center's on-going activities in MMC components for advanced liquid rocket engines such as the X-33 vehicle's Aerospike engine and X-34's Fastrac engine. The focus will be on lightweight, low cost, and environmental compatibility with oxygen and hydrogen of key MMC materials, within each of NASA's new propulsion application, that will provide a high payoff for NASA's Reusable Launch Vehicles and space access vehicles. In order to fabricate structures from MMC, effective joining methods must be developed to join MMC to the same or to different monolithic alloys. Therefore, a qualitative assessment of MMC's welding and joining techniques will be outlined.

Description: A viewgraph presentation gives an overview of the materials selection for the TransHab, the habitation module on the International Space Station (ISS). Details are given on the location of TransHab on the ISS, the multilayer inflatable shell that surrounds the module, the materials requirements (including information on the expected thermal environment), the materials selection challenges, the bladder materials requirements and testing, and meteoroid/debris shielding material.

Description: Significant efforts have been devoted to establishing the technology foundation to enable the progression to large scale composite structures fabrication. We are not capable today of fabricating many of the composite structures envisioned for the second generation reusable launch vehicle (RLV). Conventional 'aerospace' manufacturing and processing methodologies (fiber placement, autoclave, tooling) will require substantial investment and lead time to scale-up. Out-of-autoclave process techniques will require aggressive efforts to mature the selected technologies and to scale up. Focused composite processing technology development and demonstration programs utilizing the building block approach are required to enable envisioned second generation RLV large composite structures applications. Government/industry partnerships have demonstrated success in this area and represent best combination of skills and capabilities to achieve this goal.

Description: The objective of the Composite, Cryogenic, Conformal, Common Bulkhead, Aerogel-insulated Tank (CBAT) Program is to evaluate the potential for using various new technologies in next generation Reusable Launch Vehicles (RLVs) through design, fabrication, and testing of a subscale system. The new technologies include polymer matrix composites (PMCs), conformal propellant storage, common bulkhead packaging, and aerogel insulation. The National Aeronautics and Space Administration (NASA) and Thiokol Propulsion from Cordant Technologies are working together to develop a design and the processing methodologies which will allow integration of these technologies into a single structural component assembly. Such integration will significantly decrease subsystem weight and reduce shape, volume, and placement restrictions, thereby enhancing overall launch system performance. This paper/presentation focuses on the challenges related to materials and processes that were encountered and overcome during this program to date.

Description: An idea is put forth for a nondestructive characterization (NDC) generated algorithm-N curve to replace a S-N curve. A scenario for NDC life determination has been proposed. There are many challenges for the NDC life determination and prediction, but it could yield a grand payoff. The justification for NDC life determination and prediction is documented.

Description: During the manufacture of the X-33 liquid hydrogen (LH2) Tank 2, a total of 36 reinforcing caps were inspected thermographically. The cured reinforcing sheets of graphite/epoxy were bonded to the tank using a wet cobond process with vacuum bagging and low temperature curing. A foam filler material wedge separated the reinforcing caps from the outer skin of the tank. Manufacturing difficulties caused by a combination of the size of the reinforcing caps and their complex geometry lead to a potential for trapping air in the bond line. An inspection process was desired to ensure that the bond line was free of voids before it had cured so that measures could be taken to rub out the entrapped air or remove the cap and perform additional surface matching. Infrared thermography was used to perform the procure 'wet bond' inspection as well a to document the final 'cured' condition of the caps. The thermal map of the bond line was acquired by heating the cap with either a flash lamp or a set of high intensity quartz lamps and then viewing it during cool down. The inspections were performed through the vacuum bag and voids were characterized by localized hot spots. In order to ensure that the cap had bonded to the tank properly, a post cure 'flash heating' thermographic investigation was performed with the vacuum bag removed. Any regions that had opened up after the preliminary inspection or that were hidden during the bagging operation were marked and filled by drilling small holes in the cap and injecting resin. This process was repeated until all critical sized voids were filled.

Description: Today's modern machining projects are composed more and more of complicated and intricate structure due to a variety of reasons including the ability to computer model complex surfaces and forms. The cost of producing these forms can be extremely high not only in dollars but in time to complete. Changes are even more difficult to incorporate. The subject blade shown is an excellent example. Its complex form would have required hundreds of hours in fabrication for just a simple prototype. The procurement would have taken in the neighborhood of six weeks to complete. The actual fabrication would have been an equal amount of time to complete. An alternative to this process would have been a wood model. Although cheaper than a metal fabrication, it would be extremely time intensive and require in the neighborhood of a month to produce in-house.

Description: Infrared spectra returned by the Thermal Emission Spectrometer (TES) are well suited for retrieval of the thermal structure and the distribution of aerosols in the Martian atmosphere. Combined nadir- and limb-viewing spectra allow global monitoring of the atmosphere up to 0.01 mbar (65 km). We report here on the atmospheric thermal structure and the distribution of aerosols as observed thus far during the mapping phase of the Mars Global Surveyor mission. Zonal and temporal mean cross sections are used to examine the seasonal evolution of atmospheric temperatures and zonal winds during a period extending from northern hemisphere mid-summer through vernal equinox (L(sub s) = 104-360 deg). Temperature maps at selected pressure levels provide a characterization of planetary-scale waves. Retrieved atmospheric infrared dust opacity maps show the formation and evolution of regional dust storms during southern hemisphere summer. Response of the atmospheric thermal structure to the changing dust loading is observed. Maps of water-ice clouds as viewed in the thermal infrared are presented along with seasonal trends of infrared water-ice opacity. Uses of these observations for diagnostic studies of the dynamics of the atmosphere are discussed.

Description: Interplanetary dust particles (IDPs) interact with all planetary atmospheres and leave their imprint as perturbations of the background atmospheric chemistry and structure. They lead to layers of metal ions that can become the dominant positively charged species in lower ionospheric regions. Theoretical models and radio occultation measurements provide compelling evidence that such layers exist in all planetary atmospheres. In addition IDP ablation products can affect neutral atmospheric chemistry, particularly at the outer planets where the IDPs supply oxygen compounds like water and carbon dioxide to the upper atmospheres. Aerosol or smoke particles from incomplete ablation or recondensation of ablated IDP vapors may also have a significant impact on atmospheric properties.

Description: Spectra taken by the Mars Global Surveyor Thermal Emission Spectrometer (TES) have been used to monitor the latitude, longitude, and seasonal dependence of water vapor for over one full Martian year (March 1999-March 2001). A maximum in water vapor abundance is observed at high latitudes during mid-summer in both hemispheres, reaching a maximum value of approximately 100 pr-micrometer in the north and approximately 50 pr-micrometer in the south. Low water vapor abundance (〈5 pr-micrometer) is observed at middle and high latitudes in the fall and winter of both hemispheres. There are large differences in the hemispheric (north versus south) and seasonal (perihelion versus aphelion) behavior of water vapor. The latitudinal and seasonal dependence of the decay of the northern summer water vapor maximum implies cross-equatorial transport of water to the southern hemisphere, while there is little or no corresponding transport during the decay of the southern hemisphere summer maximum. The latitude-longitude dependence of annually-averaged water vapor (corrected for topography) has a significant positive correlation with albedo and significant negative correlations with thermal inertia and surface pressure. Comparison of TES results with those retrieved from the Viking Orbiter Mars Atmospheric Water Detectors (MAWD) experiments shows some similar features, but also many significant differences. The southern hemisphere maximum observed by TES was not observed by MAWD and the large latitudinal gradient in annually-averaged water vapor observed by MAWD does not appear in the TES results.

Description: Solar system debris, in the form of meteoroids, impacts every planet. The flux, relative composition and speed of the debris at each planet depends on the planet's size and location in the solar system. Ablation in the atmosphere evaporates the meteoric material and leaves behind metal atoms. During the ablation process metallic ions are formed by impact ionization. For small inner solar system planets, including Earth, this source of ionization is typically small compared to either photoionization or charge exchange with ambient molecular ions. For Earth, the atmosphere above the main deposition region absorbs the spectral lines capable of ionizing the major metallic atoms (Fe and Mg) so that charge exchange with ambient ions is the dominant source. Within the carbon dioxide atmosphere of Mars (and possibly Venus), photoionization is important in determining the ion density. For a heavy planet like Jupiter, far from the sun, impact ionization of ablated neutral atoms by impacts with molecules becomes a prominent source of ionization due to the gravitational acceleration to high incident speeds. We will describe the processes and location and extent of metal ion layers for Mars, Earth and Jupiter, concentrating on flagging the uncertainties in the models at the present time. This is an important problem, because low altitude ionosphere layers for the planets, particularly at night, probably consist predominantly of metallic ions. Comparisons with Earth will be used to illustrate the differing processes in the three planetary atmospheres.

Description: Future human missions to Mars will require effective communications supporting exploration activities and scientific field data collection. Constraints on cost, size, weight and power consumption for all communications equipment make optimization of these systems very important. These information and communication systems connect people and systems together into coherent teams performing the difficult and hazardous tasks inherent in planetary exploration. The communication network supporting vehicle telemetry data, mission operations, and scientific collaboration must have excellent reliability, and flexibility.

Description: Extraterrestrial material is the source of metal ions in the Earth's atmosphere, Each year approx. 10(exp 8) kg of material is intercepted by the Earth. The origin of this material is predominantly solar orbiting interplanetary debris from comets or asteroids that crosses the Earth's orbit. It contains a very small amount of interstellar material. On occasion the Earth passes through enhanced amounts of debris associated with the orbit of a decaying comet. This leads to enhanced meteor shower displays for up to several days. The number flux of shower material is typically several times the average sporadic background influx of material. Meteoric material is some of the earliest material formed in the solar system. By studying the relative elemental abundances of atmospheric metal ions, information can be gained on the chemical composition of cometary debris and the chemical makeup of the early solar system. Using in situ sampling with rocket-borne ion mass spectrometers; there have been approximately 50 flights that made measurements of the metal ion abundances at attitudes between 80 and 130 km. It is this altitude range where incoming meteoric particles am ablated, the larger ones giving rise to visible meteor. displays. In several rocket measurements isotopic ratios of different atomic ion mass components and metal molecular ion concentrations have been determined and used to identify unambiguously the measured species and to investigate the processes controlling the metal ion distributions The composition of the Earth's ionosphere was first sampled by an ion mass spectrometer flown an a rocket in 1956. In 1958 a rocket-borne ion spectrometer identified, fbr the first time, a layer of metal ions near 95 km. These data were interpreted as evidence of an extraterrestrial rather than a terrestrial source. Istomin predicted: "It seems probable that with some improvement in the method that analysis of the ion composition in the E-region may be used for determining the chemical composition of those meteors which do not reach the ground. Particularly, we hope to get information about the composition difference between particles of different meteor showers and also sporadic and shower meteoroids". These visions categorized the aims of many subsequent rocket-borne ion mass spectrometer experiments in the lower ionosphere, Although the use such measurements to deduce the composition of different classes of meteoroids has not been successful, the past four decades of rocket observations have provided po%erful sets of data for advancing our understanding of meteor ablation, meteoric composition, metal neutral and ion chemistry as well as ionospheric dynamics.

Description: Knowledge gained from measurements and models is used to study the high-speed plasmas interacting with the atmospheres and ionospheres of Titan and Venus. Considering the similarities of the interactions, comparative analysis is used to support the interpretations of observations made at each body. Ionospheric flow inferred to exist by analysis of measurements made from the Pioneer Venus Orbiter supports the interpretation of similar flow in the ionosphere of Titan. The concept that cold ions escape from the ionosphere of Venus is supported by the Voyager I observation that cold ions escape down the magnetic tail of Titan. Pickup O+ ion energy distributions observed at their source in the ionosheath of Venus are shown to be influenced by finite gyroradius effects. The signatures of such effects are expected to be retained as the ions move into the wakes of Titan and Venus.

Description: During the week of March 26, 2001, I was asked by Rich Katz, NASA-GSFC, to participate on the Mars Odyssey Independent Assessment Team (IAT) that would investigate the implications of the failure of an Actel RP 1280 Field Programmable Gate Array (FPGA), which occurred on the Space Infrared Telescope Facility (SIRTF) spacecraft, on the Mars Odyssey spacecraft that was set to launch on April 7, 2001. We were provided with review materials from JPL and Lockheed Martin (LMA) that would be discussed at a meeting on April 2, 2001.

Description: A {1,2}-order theory for laminated composite and sandwich plates is extended to include thermoelastic effects. The theory incorporates all three-dimensional strains and stresses. Mixed-field assumptions are introduced which include linear in-plane displacements, parabolic transverse displacement and shear strains, and a cubic distribution of the transverse normal stress. Least squares strain compatibility conditions and exact traction boundary conditions are enforced to yield higher polynomial degree distributions for the transverse shear strains and transverse normal stress through the plate thickness. The principle of virtual work is used to derive a 10th-order system of equilibrium equations and associated Poisson boundary conditions. The predictive capability of the theory is demonstrated using a closed-form analytic solution for a simply-supported rectangular plate subjected to a linearly varying temperature field across the thickness. Several thin and moderately thick laminated composite and sandwich plates are analyzed. Numerical comparisons are made with corresponding solutions of the first-order shear deformation theory and three-dimensional elasticity theory. These results, which closely approximate the three-dimensional elasticity solutions, demonstrate that through - the - thickness deformations even in relatively thin and, especially in thick. composite and sandwich laminates can be significant under severe thermal gradients. The {1,2}-order kinematic assumptions insure an overall accurate theory that is in general superior and, in some cases, equivalent to the first-order theory.

Description: In this paper we describe the software aspects of the overall Athena SDM rover mobility system in three parts: the control electronics, the software architecture and development environment, and surface navigation software. The Athena SDM architecture has been shown to be capable of meeting mission navigation requirements by being able to safely drive 100 meters using allowable resources within three hours.

Description: Talks of how asteroid 1998 SF36 (25143) is the target of the Japanese/NASA MUSES-C sample return mission.

Description: In this paper the concept for a mobile vehicle system which performs an in situ science mission to Mars is described. This rover mission with its requirements for driving, positioning at science selected targets, and remote and in situ measurement will utilize the technologies for hazard avoidance and autonomous navigation supported by ground operation tools which use rover-based imagery for position estimation and motion planning.

Description: Effective midleware can improve the capability of business and science applications in several ways, e.g., by hiding platform heterogeneity or by providing standard shared services which reduce the complexity or increase the capability of every application. Recent successes in midleware, such as multi-tier client/server and web-based architectures, have fueled phenomenal growth in enterprise level applications, which provide better integration and more rapid adaptability of business in many fields.

Description: This paper talks about planetary exploration spacecraft design.

Description: The Saturn in your kitchen program is a series of hands-on activities that seeks to introduce students to one of the science or engineering concepts relating to the Cassini mission.

Description: A new curing method using automated tape placement (ATP) with electron beam (EB), or e-beam, produces a combination known as in situ e-beam curing. Through a Small Business Innovation Research (SBIR) contract from NASA's Marshall Space Flight Center, Science Research Laboratory, Inc., created the in situ e-beam curing technique, which uses a low-energy electron beam gun to cure various composite materials. One important benefit is the technique's utilization of room temperature curing, which lessens the chance of mismatching the thermal expansion coefficients of different materials. For instance, metals and composites will expand at different rates when heated, but the low-energy e-beam gun reduces the expansion differential. Using a low-energy gun also results in less x-ray shielding, significantly reduced capital costs, reduced facility space, and increased processing capabilities for larger parts. However, using a low-energy gun also means that each tape layer is treated individually because the gun can penetrate only one layer at a time. The e-beam gun emits lower energy x-rays, which are more easily shielded than those emitted by previous guns. The low-energy system is relatively portable due to its light weight and small size. The gun weighs about 70 pounds and can be easily mounted on a robotic arm or an ATP head.

Description: A study in which several surface samples, retrieved from both the Mars Odyssey Spacecraft and the Kennedy Space Center (KSC) Spacecraft Assembly and Encapsulation Facility II (SAEF-II), were prcesed and evaluated by both molecular and traditional culture-based methods for the microbial diversity.

Description: We have constructed a computer model to simulate synchrotron emission from relativistic electrons trapped in Jupiter's magnetic field.

Description: This paper will show the unique features of navigation and mission design related to orbiting an asteroid and to designing a robust navigation system for the NEAR spacecraft.

Description: This is part three of a development program to evaluate candidate nonablative aeroshell designs.

Description: Talks about ways to help make a human trip to Mars more feasible.

Description: This article explains how one would go about building a human habitat on Mars.

Description: The Mars program institutes the Mars Scout Missions in order to address science goals in the program not otherwise covered in the baseline Mars plan. Mars Scout Missions will be Principle-Investigator (PI) led science missions. Analogous to the Discovery Program, PI led investigations optimize the use of limited resources to accomplish the best focused science and allow the flexibility to quickly respond to discoveries at Mars. Scout missions also require unique investments in technology and reliance upon Mars-based infrastructure such as telecom relay orbiters.

Description: Developing cost efficient individual flight projects that perform both orbital and surface exploraton will likely require intelligent infrastructure elements for critical functions such as navigation.

Description: Observations of europa suggest that the jovian satellite may have a liquid ocean underneth its icy surface.

Description: Site construction operations by autonomous robotic systems are essential for a sustained robotic presence and human habitation on mars.

Description: Functionally graded materials (FGM's) are a new generation of engineered materials wherein the microstructural details are spatially varied through nonuniform distribution of the reinforcement phase(s). Engineers accomplish this by using reinforcements with different properties, sizes, and shapes, as well as by interchanging the roles of the reinforcement and matrix phases in a continuous manner (ref. 1). The result is a microstructure that produces continuously or discretely changing thermal and mechanical properties at the macroscopic or continuum scale. This new concept of engineering the material's microstructure marks the beginning of a revolution both in the materials science and mechanics of materials areas since it allows one, for the first time, to fully integrate the material and structural considerations into the final design of structural components. Functionally graded materials are ideal candidates for applications involving severe thermal gradients, ranging from thermal structures in advanced aircraft and aerospace engines to computer circuit boards. Owing to the many variables that control the design of functionally graded microstructures, full exploitation of the FGM's potential requires the development of appropriate modeling strategies for their response to combined thermomechanical loads. Previously, most computational strategies for the response of FGM's did not explicitly couple the material's heterogeneous microstructure with the structural global analysis. Rather, local effective or macroscopic properties at a given point within the FGM were first obtained through homogenization based on a chosen micromechanics scheme and then subsequently used in a global thermomechanical analysis.

Description: Actively cooled ceramic matrix composite (CMC) components are enabling or enhancing for a broad range of hypersonic and reusable launch vehicle propulsion systems. Teaming with other NASA centers, the Air Force, and industry, the Glenn Ceramics Branch has successfully tested multiple cooled CMC panel concepts in high-heat-flux, high-pressure, flowing rocket engine combustion gas environments. Sub-element components survived multiple cycles and the severe thermal gradients imposed by combustion gas temperatures in excess of 5500 F and cryogenic hydrogen or ambient temperature water internal coolants. These demonstrations are critical for the continued development of this class of materials, and the research is expected to continue with additional concepts and increasingly larger and more complex geometries being fabricated and tested in a broad range of engine operating conditions.

Description: Solar arrays will be the power supply for future missions to the planet Mars, including landers, rovers, and eventually human missions to explore the Martian surface. Until Mars Pathfinder landed in July 1997, no solar array had been used on the surface. The MATE package is intended to measure the solar energy reaching the surface, characterize the Martian environment to gather the baseline information required for designing power systems for long-duration missions, and to quantify the performance and degradation of advanced solar cells on the Martian surface. To measure the properties of sunlight reaching the Martian surface, MATE incorporates two radiometers and a visible/NIR spectrometer. The radiometers consist of multiple thermocouple junctions using thin-film technology. These devices generate a voltage proportional to the solar intensity. One radiometer measures the global broadband solar intensity, including both the direct and scattered sunlight, with a field of view of approximately 130. The second radiometer incorporates a slit to measure the direct (unscattered) intensity radiation. The direct radiometer can only be read once per day, with the Sun passing over the slit. The spectrometer measures the global solar spectrum with two 256-element photodiode arrays, one Si sensitive in the visible range (300 to 1100 nm), and a second InGaAs sensitive to the near infrared (900 to 1700 nm). This range covers 86 percent of the total energy from the Sun, with approximately 5-nm resolution. Each photodiode array has its own fiber-optic feed and grating. Although the purpose of the MATE is to gather data useful in designing solar arrays for Mars surface power systems, the radiometer and spectrometer measurements are expected to also provide important scientific data for characterizing the properties of suspended atmospheric dust. In addition to measuring the solar environment of Mars, MATE will measure the performance of five different individual solar cell types and two different solar cell strings, to qualify advanced solar cell types for future Mars missions. The MATE instrument, designed for the Mars-2001 Surveyor Lander mission, contains a capable suite of sensors that will provide both scientific information as well as important engineering data on the operation of solar power systems on Mars. MATE will characterize the intensity and spectrum of the solar radiation on Mars and measure the performance of solar arrays in the Mars environment. MATE flight hardware was built and tested at the NASA Glenn Research Center and is ready for flight.

Description: The plane-stress equations of linear elasticity are used in conjunction with those of the boundary element method to develop a novel curved, quadratic boundary element applicable to structures composed of anisotropic materials in a state of plane stress or plane strain. The curved boundary element is developed to solve two-dimensional, elastostatic problems of arbitrary shape, connectivity, and material type. As a result of the anisotropy, complex variables are employed in the fundamental solution derivations for a concentrated unit-magnitude force in an infinite elastic anisotropic medium. Once known, the fundamental solutions are evaluated numerically by using the known displacement and traction boundary values in an integral formulation with Gaussian quadrature. All the integral equations of the boundary element method are evaluated using one of two methods: either regular Gaussian quadrature or a combination of regular and logarithmic Gaussian quadrature. The regular Gaussian quadrature is used to evaluate most of the integrals along the boundary, and the combined scheme is employed for integrals that are singular. Individual element contributions are assembled into the global matrices of the standard boundary element method, manipulated to form a system of linear equations, and the resulting system is solved. The interior displacements and stresses are found through a separate set of auxiliary equations that are derived using an Airy-type stress function in terms of complex variables. The capabilities and accuracy of this method are demonstrated for a laminated-composite plate with a central, elliptical cutout that is subjected to uniform tension along one of the straight edges of the plate. Comparison of the boundary element results for this problem with corresponding results from an analytical model show a difference of less than 1%.

Description: The nanoscale reinforcement of polymers is becoming an attractive means of improving the properties and stability of polymers. Polymer-silicate nanocomposites are a relatively new class of materials with phase dimensions typically on the order of a few nanometers. Because of their nanometer-size features, nanocomposites possess unique properties typically not shared by more conventional composites. Polymer-layered silicate nanocomposites can attain a certain degree of stiffness, strength, and barrier properties with far less ceramic content than comparable glass- or mineral-reinforced polymers. Reinforcement of existing and new polyimides by this method offers an opportunity to greatly improve existing polymer properties without altering current synthetic or processing procedures.

Description: Particle-reinforced composites are candidate materials for a wide variety of aerospace and nonaerospace applications. The high costs and technical difficulties involved with the use of many fiber-reinforced composites often limit their use in many applications. Consequently, particulate composites have emerged as viable alternatives to conventional fiber-reinforced composites. Particulate composites can be processed to near net shapepotentially reducing the manufacturing costs. They are candidate materials where shock or impact properties are important. For example, particle-reinforced metal matrix composites have shown great potential for many automotive applications. Typically, these materials are aluminum matrix reinforced with SiC or TiC particles. Reinforced concrete can also be thought of as a particle-reinforced composite. In situ ceramics can be modeled as particulate composites and are candidate materials for many high-temperature applications. The characterization of these materials is fundamental to their reliable use. It has been observed that the overall properties of these composites exhibit scatter because of the uncertainty in the constituent material properties, and fabrication-related parameters.

Description: Since the dawn of human civilization, there has always been a delicate balance between expanding human frontiers and coexisting with the ecosystem. In the new millennium, it will be extremely important to develop various materials, products, and processes to sustain a healthy life in harmony with nature that allow us to minimize any harmful effects. Environment-conscious ceramics (ecoceramics) are a new class of materials that can be produced with renewable resources (wood) and wood wastes (wood sawdust). Wood is one of the best and most intricate engineering materials created by nature. Natural woods of various types are available throughout the world. In addition, wood sawdusts are generated in abundant quantities by sawmills. Environment-conscious ceramic materials, fabricated via the pyrolysis and infiltration of natural wood-derived preforms with silicon have tailorable properties with numerous potential applications.

Description: Polymer matrix composites (PMC's) are being increasingly used in applications where they are exposed for long durations to harsh environments such as elevated temperatures, moisture, oils and solvents, and thermal cycling. The exposure to these environments leads to the degradation of structures made from these materials. This also affects the useful lifetimes of these structures. Some of the more prominent aerospace applications of polymer matrix composites include engine supports and cowlings, reusable launch vehicle parts, radomes, thrust-vectoring flaps, and the thermal insulation of rocket motors. This demand has led to efforts to develop lightweight, high-strength, high-modulus materials that have upper-use temperatures over 316 C. A cooperative program involving two grants to the Massachusetts Institute of Technology and in-house work at the NASA Glenn Research Center was conducted to identify the mechanisms and the measurement of mechanical and physical properties that are necessary to formulate a mechanism-based model for predicting the lifetime of high-temperature polymer matrix composites. The polymer that was studied was PMR-15 polyimide, a leading matrix resin for use in high-temperature-resistant aerospace composite structures such as propulsion systems. The temperature range that was studied was from 125 to 316 C. The diffusion behavior of PMR-15 neat resin was characterized and modeled. Thermogravimetric analysis (TGA) was also conducted in nitrogen, oxygen, and air to provide quantitative information on thermal and oxidative degradation reactions. A new low-cost technique was developed to collect chemical degradation data for isothermal tests lasting up to 4000 hr in duration. In the temperature range studied, results indicate complex behavior that was not observed by previous TGA tests, including the presence of weight-gain reactions. These were found to be significant in the initial periods of aging from 125 to 225 C. Two types of weight loss reactions dominated at aging temperatures above 225 C. One was concentrated at the surface of the polymer and was very active at temperatures above 225 C. The second was observed to dominate in the latter stages of aging at temperatures below 260 C. This three-reaction model satisfactorily explains past findings that the degradation mechanism of PMR-15 appears to change around 316 C. It also indicates that the second weight gain mechanism is a significant factor at temperatures below 204 C. On the basis of these results, a predictive model was developed for the thermal degradation of PMR-15 at 316 C. A comparison of data generated by this model with actual experimental data is shown in the following figure.

Description: PMR polyimides, in particular PMR-15, are well known for their excellent high-temperature stability and performance, and solvent resistance. However, the processing of these materials is limited, for the most part, to prepreg-based methods, such as compression or autoclave processing. These methods involve substantial amounts of hand labor, and as a result, manufacturing costs for components made from PMR polyimides can be high. In cost-sensitive applications, these high manufacturing costs can make the use of PMR polyimide-based components cost prohibitive. Lower cost manufacturing methods, such as resin transfer molding (RTM) and resin film infusion, have been demonstrated to reduce manufacturing costs by as much as 50 percent over prepreg-based methods. However, these processes are only amenable to materials with melt viscosities below 30 poise. Most PMR polyimides have melt viscosities on the order of 100 poise or higher. Recent efforts at the NASA Glenn Research Center have focused on chemical modifications to PMR polyimides to reduce their melt viscosity to the point where they could be processed by these low-cost manufacturing methods without adversely affecting their high-temperature properties and performance. These efforts have led to a new family of PMR polyimides that have melt viscosities significantly lower than that of PMR-15. Reductions in melt viscosity are brought about through the introduction of molecular twists in the polymer backbone. Carbon fiber (T650- 35) composites were prepared from one of these polyimides, designated PMR-Flex, by compression molding. The properties of these composites are presented below and compared with comparable composites made from PMR-15 and PETI-RTM, a new low-melt-viscosity polyimide.

Description: This paper describes the evolution of our concept of hopping robot for planetary exploration, that combines coarse long range mobility achieved by hopping, with short range wheeled mobility for precision target acquisition.

Description: The ESA Mars Express Orbiter will be nearly polar and have an initial orbital period of 7.6 hours for the first 440 days and then will reduce its period to 6.7 hours. As periapsis of the elliptical orbit walks around Mars every 2 years, the ascending and descending nodes of the Mars Express orbit on the Mars equatorial plane will have the same radius as the orbit of Phobos and close encounters of Phobos will occur when Phobos is near the node as Mars Express passes.

Description: The ESA Mars Express Orbiter will be nearly polar and have an initial orbital period of 7.6 hours for the first 440 days and then will reduce its period to 6.7 hours. As periapsis of the elliptical orbit walks around Mars every 2 years, the ascending and descending nodes of the Mars Express orbit on the Mars equatorial plane will have the same radius as the orbit of Phobos and close encounters of Phobos will occur when Phobos is near the node as Mars Express passes.

Description: The global digital topography and elevation models of Mars produced by the Mars Global Surveyor (MGS) Mars Orbiter Laser Altimeter (MOLA) and of Mars derived from Viking Orbiter stereo imaging have many uses for geodesy, geophysics, morphology and cartography studies of these two planetary bodies.

Description: This paper describes the science driven requirements for a robotic vehicle, which utilizes gravity, and both passive and active heating systems to drive ice to a liquid phase change state, in order to facilitate mobility.

Description: Analyses of Lunar Laser ranges Shaw a displacement in direction of the Moon's pole of rotation which indicates that strong dissipation is acting on the rotation.

Description: Composite particles containing internal scatterers have been proposed as an explanation for the fact that most photometric studies of planetary surfaces based on Hapke's bidirectional reflectance model have found the planetary particles to exhibit moderately backscattering phase functions.

Description: The lunar gravity field is determined from the tracking data of previous missions to the Moon with the 1998-1999 Lunar Prospector (LP) mission being the major contributor.