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At least 919 records · Page 51
All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

A Conceptual Design For A Spaceborne 3D Imaging Lidar

First generation spaceborne altimetric approaches are not well-suited to generating the few meter level horizontal resolution and decimeter accuracy vertical (range) resolution on the global scale desired by many in the Earth and planetary science communities. The present paper discusses the major technological impediments to achieving few meter transverse resolutions globally using conventional approaches and offers a feasible conceptual design which utilizes modest power kHz rate lasers, array detectors, photon-counting multi-channel timing receivers, and dual wedge optical scanners with transmitter point-ahead correction.

Degnan, John J.↗
NASA NTRS2001

Venus Multiprobe Mission

A summary of the proposal for the Discovery Program Venus Multiprobe Mission (VMPM) which was submitted in 1994 will be presented. The major goal of the mission was to provide sufficient observations of winds and thermal structure in the Venus atmosphere that the mechanism producing the atmospheric superrotation could be identified. The superrotation has been a major unsolved problem of planetary science for over 30 years. In spite of many theoretical efforts and many spacecraft missions to Venus, the principal driving mechanism(s) remain undetermined. Sixteen small probes, modeled after the Pioneer Venus small probes, would enter the Venus atmosphere, and measure winds, temperatures, and pressures from 60 km to the surface. Towards the bottom of the atmosphere, measurements would be made at 10 meter intervals. Temperature and pressure measurements are similar to those used on Pioneer Venus, but are four times more sensitive. Winds would be obtained by dual-frequency, differential. long-baseline interferometry, using S- and X-band transmitters on the probes, and four receiving telescopes round the Pacific rim. The precision of wind measurements is 0.05 ms- 1 or better, at least twenty times more precise than for Pioneer Venus. Ground based observations occurring in conjunction with the multiprobe entries would provide a temporal context for the upper boundary to the probe observations. UV and near IR features would be tracked for periods of hours to weeks to obtain cloud level zonal mean and transient eddy circulations with accuracies of 10 /ms or better. The data would be processed into wind and opacity maps. A hierarchy of atmospheric numerical models would be used to distinguish different dynamical elements existing in the data. Primary among the models was the development of a Venus general circulation model containing all known physical processes.

Young, Richard E.↗
NASA NTRS1997

Review of Galileo Probe Entry Technology

This talk is a review of the Galileo entry mission with a focus on entry technology, not planetary science. A general description of the mission, entry parameters, and entry vehicle are provided, followed by a more detailed description of the vehicle heatshield shape, size, materials, and instrumentation. The heat shield design tools and process are discussed wish emphasis on the issues and challenges which were faced and the role of ground test facilities. Flight data are compared with the preflight predictions. What have we learned?

Milos, Frank S.↗
NASA NTRS2001

New Concepts and Perspectives on Micro-Rotorcraft and Small Autonomous Rotary-Wing Vehicles

A key part of the strategic vision for rotorcraft research as identified by senior technologists within the Army/NASA Rotorcraft Division at NASA Ames Research Center is the development and use of small autonomous rotorcraft. Small autonomous rotorcraft are defined for the purposes of this paper to be a class of vehicles that range in size from rotary-wing micro air vehicles (MAVs) to larger, more conventionally sized, rotorcraft uninhabited aerial vehicles (UAVs) - i.e. vehicle gross weights ranging from hundreds of grams to thousands of kilograms. The development of small autonomous rotorcraft represents both a technology challenge and a potential new vehicle class that will have substantial societal impact for: national security, personal transport, planetary science, and public service.

Young, Larry A.↗
NASA NTRS2002

Optical Scattering Characterization for the Glennan Microsystems Microscale Particulate Classifier

Small sensors that are tolerant to mechanically and thermally harsh environments present the possibility for in-situ particle characterization in propulsion, industrial, and planetary science applications. Under a continuing grant from the Glennan Microsystems Initiative to the Microgravity Fluids Physics Branch of the NASA-Glenn Research Center, a Microscale Particle Classifier (MiPAC) instrument is being developed. The MiPAC instrument will be capable of determining the size distribution of airborne particles from about 1 nm to 30 micrometers, and will provide partial information as to the concentration, charge state, shape, and structure of the particles, while being an order of magnitude smaller in size and lighter in weight than presently commercially available instruments. The portion of the instrument that will characterize the nm-range particles will employ electrical mobility techniques and is being developed under a separate grant to Prof. David Pui of the University of Minnesota. The portion of the instrument that will characterize the micrometer-size particles such as dirt, pollens, spores, molds, soot, and combustion aerosols will use light scattering techniques. The development of data analysis techniques to be employed in the light scattering portion of the instrument is covered by this grant.

Lock, James A.↗
NASA NTRS2002

Toward an Improved Single-Particle Model for Large Irregular Grains

To interpret remote spectral observations, scattering and absorption in a particulate surface are simulated via radiative transfer models. The standard model for this purpose among the planetary science community is the Hapke model. This model (like many others) uses two parameters to characterize the optical behavior of individual grains in a particulate surface, the single-scattering albedo omega and phase function p(g). These terms describe, respectively, the quantity and the angular distribution of light scattered by an individual grain. Unfortunately, these parameters are strictly optical. They can be rather difficult to interpret in terms of more interesting particle properties such as grain sizes, shapes, and compositions, that a remote sensing experiment might seek to discover. An equivalent slab approximation is typically used to relate omega to the grain size and optical constants of the material. This approach can mimic the wavelength-dependent absorption behavior of irregular grains, as long as the imaginary index kappa is much less than 1, the shape is equant, and the grain size D is much larger than the wavelength lambda. Unfortunately, the equivalent slab approach provides no information about p(g), which also has a strong dependence on optical constants and particle form.

Grundy, W. M.↗
NASA NTRS2002

The Opposition Effect: A Very Unusual Case

The reflection of electromagnetic radiation from a planetary regolith involves a combination of geometric and physical optics processes which contribute to the signal returned to the remote observer. The geometric optics effects are the product of singly and multiply scattered radiation from the surfaces of the regolith particles, combined with radiation which has undergone various combinations of transmission through one or more regolith grains followed by one or more scatterings from other particles. The physical optics effects include diffraction of radiation around the edges of large irregular particles and cooperative coherent scattering between particles which are small when compared to the wavelength of the incident radiation. These effects produce measurable changes in the intensity and polarization of reflected light as a function of illumination and viewing geometry. In particular, as phase angle becomes small, the reflectance of a particulate material will increase non-linearly and exhibit the 'opposition effect'. In the planetary science context, the phase curve, and in particular the size of the opposition surge and the width of the phase curve near zero degrees, have been attributed to two processes commonly called 'shadow hiding' (SHOE) and 'coherent backscattering' (CBOE).

Nelson, R. M.↗
NASA NTRS1993

Project Hyreus: Mars Sample Return Mission Utilizing in Situ Propellant Production

Project Hyreus is an unmanned Mars sample return mission that utilizes propellants manufactured in situ from the Martian atmosphere for the return voyage. A key goal of the mission is to demonstrate the considerable benefits of using indigenous resources and to test the viability of this approach as a precursor to manned Mars missions. The techniques, materials, and equipment used in Project Hyreus represent those that are currently available or that could be developed and readied in time for the proposed launch date in 2003. Project Hyreus includes such features as a Mars-orbiting satellite equipped with ground-penetrating radar, a large rover capable of sample gathering and detailed surface investigations, and a planetary science array to perform on-site research before samples are returned to Earth. Project Hyreus calls for the Mars Landing Vehicle to land in the Mangala Valles region of Mars, where it will remain for approximately 1.5 years. Methane and oxygen propellant for the Earth return voyage will be produced using carbon dioxide from the Martian atmosphere and a small supply of hydrogen brought from Earth. This process is key to returning a large Martian sample to Earth with a single Earth launch.

Bruckner, A. P.↗
NASA NTRS2003

Outer Solar System Nomenclature

This grant has supported work by T. Owen and B. A. Smith on planetary and satellite nomenclature, carried out under the general auspices of the International Astronomical Union (IAU). The IAU maintains a Working Group on Planetary and Satellite Nomenclature (WGPSN) whose current chair is Prof.Kaare Aksnes of the Rosseland Institute for Theoretical Astrophysics in Oslo, Norway. Both Owen and Smith are members of the WGPSN; Owen as chair of the Outer Solar System Task Group, and Smith as chair of the Mars Task Group. The major activity during the last grant period (2002) was the approval of several new names for features on Mars by Smith's group and features on Jovian satellites plus new names for satellites of Jupiter, Saturn and Uranus by Owen's group. Much of this work was accomplished by e-mail exchanges, but the new nomenclature was formally discussed and approved at a meeting of the WGPSN held in conjunction with the Division for Planetary Sciences meeting in Birmingham, Alabama in October 2002.

Owen, Tobias C.↗
NASA NTRS2003

Mars Exploration Rover Landing Site Selection

Selection of the landing sites for the Mars Exploration Rovers has involved over 2 years of research and analysis effort that has included the participation of broad sections of the planetary sciences community through a series of open landing site workshops. The effort has included the definition of the engineering constraints based on the landing system, mapping those engineering constraints into acceptable regions and prospective sites, the acquisition of new information from Mars Global Surveyor and Mars Odyssey orbiters, the evaluation of science and safety criteria for the sites, and the downselection and final site selection based on the sites science potential and safety. The final landing sites (Meridiani Planum and Gusev crater) were selected by NASA Headquarters on April 11, 2003, prior to launch in June. This paper presents engineering requirements, and potential landing sites for Mars Exploration Rovers.

M Golombek↗
NASA NTRS2003

A New Time-dependent Model for the Martian Radiation Environment

Manned space activities have been until present time limited to the near-Earth environment, most of them to low Earth orbit (LEO) scenarios, with only some of the Apollo missions targeted to the Moon. In current times most human exploration and development of space (HEDS) activities are related to the development of the International Space Station (ISS), and therefore take place in the LEO environment. A natural extension of HEDS activities will be going beyond LEO, and reach asteroids, Mars, Jupiter, Saturn, the Kuiper belt and the outskirts of the Solar System. Such long journeys onboard spacecraft outside the protective umbrella of the geomagnetic field will require higher levels of protection from the radiation environment found in the deep space for both astronauts and equipment. So, it is important to have available a tool for radiation shielding which takes into account the radiation environments found all along the interplanetary space and at the different bodies encountered in the Solar System. Moreover, the radiation protection is one of the two NASA highest concerns and priorities. A tool integrating different radiation environments with shielding computation techniques especially tailored for deep space mission scenario is instrumental in view of this exigency. In view of manned missions targeted to Mars, for which radiation exposure is one of the greatest problems and challenges to be tackled, it is of fundamental importance to have available a tool which allows to know which are the particle flux and spectra at any time at any point of the Martian surface. With this goal in mind, a new model for the radiation environment to be found on the planet Mars due to Galactic Cosmic Rays (GCR) has been developed. Solar modulated primary particles rescaled for Mars conditions are transported within the Martian atmosphere, with temporal properties modeled with variable timescales, down to the surface, with altitude and backscattering patterns taken into account. The tool allows analysis for manned Mars landing missions, as well as planetary science studies, e.g. subsurface water and volatile inventory studies. This Mars environmental model is available through the SIREST website, a project of NASA Langley Research Center.

G De Angelis↗
NASA NTRS2003

Lunar and Planetary Information Bulletin

The articles in this issue cover the end of the Galileo mission to Jupiter, educational outreach programs, and news on planetary science, including discoveries and updates on Mars missions. This issue also features brief book reviews, and a calender listing conferences for 2003.

Schenk, Paul M.↗
NASA NTRS2003

Expanded Citations Database in the NASA ADS Abstract Service

The NASA-ADS Abstract Service provides a sophisticated search capability for the literature in Astronomy, Planetary Sciences, Physics/Geophysics, and Space Instrumentation. The ADS is funded by NASA and access to the ADS services is free to anybody worldwide without restrictions. It allows the user to search the literature by author, title, and abstract text.

Eichhorn, G.↗
NASA NTRS2003

The Laboratory for Terrestrial Physics

The Laboratory for Terrestrial Physics is dedicated to the advancement of knowledge in Earth and planetary science, by conducting innovative research using space technology. The Laboratory's mission and activities support the work and new initiatives at NASA's Goddard Space Flight Center (GSFC). The Laboratory's success contributes to the Earth Science Directorate as a national resource for studies of Earth from Space. The Laboratory is part of the Earth Science Directorate based at the GSFC in Greenbelt, MD. The Directorate itself is comprised of the Global Change Data Center (GCDC), the Space Data and Computing Division (SDCD), and four science Laboratories, including Laboratory for Terrestrial Physics, Laboratory for Atmospheres, and Laboratory for Hydrospheric Processes all in Greenbelt, MD. The fourth research organization, Goddard Institute for Space Studies (GISS), is in New York, NY. Relevant to NASA's Strategic Plan, the Laboratory ensures that all work undertaken and completed is within the vision of GSFC. The philosophy of the Laboratory is to balance the completion of near term goals, while building on the Laboratory's achievements as a foundation for the scientific challenges in the future.

Source record↗
NASA NTRS2003

The Moon Beyond 2002

Over a hundred lunar scientists met in the clear mountain air of the Taos Ski Valley, September 12-14, 2002, to share their discoveries and, most importantly, their questions about the composition, geological evolution, and future exploration of the Moon. The wealth of data from the Clementine and Lunar Prospector missions, coupled with continued study of lunar samples, has led lunar scientists to pose sophisticated questions about the Moon. Because of the Moon's central role in planetary science, answers to these questions will help us understand the other rocky bodies in the Solar System. A fascinating array of missions is planned, including orbiting spacecraft and sample-return missions. Human habitation of the Moon may not be far beyond.

Taylor, G. Jeffrey↗
NASA NTRS2004

Identification of Aqueous Alteration Products on Low-Albedo Asteroids

The following accomplishments were funded by this grant: 1) Partially supported the writing and publication of "Hydrated Minerals on Asteroids". 2) Partially supported the writing and publication of "Near-Infrared Spectrophotometry of Phobos and Deimos". 3) Partially supported the writing and publication of "Hydrogen concentrations on C-class asteroids derived from remote sensing". 4) Travel to 2002 Lunar and Planetary Sciences Conferences and presentation of "Calculated Water Concentrations on C-Class Asteroids". 5) Reduction of asteroidal spectroscopic data including corrections for thermal flux, as described in the grant proposal and descoping document. These data appeared in the publications listed in items 1, 3 and 4.

Rivkin, Andrew↗
NASA NTRS1998

Resuspension of Particles by Aerodynamic Deagglomeration

A deagglomerator system was developed, characterized by laboratory tests and flown under low gravity (low-g) microgravity conditions. Requirements for a dry powder deagglomeration system were generated by university and National Aeronautics and Space Administration (NASA) scientists from diverse fields of interest including exobiology, planetary sciences, and atmospheric sciences. Existing deagglomeration methods and devices are reviewed. An aerosol generation method suitable for dry powders over a large range of particles sizes and types at high concentrations with consistent deagglomeration efficiency was evaluated. Development of a pulsed-flow laboratory device and experimental approaches to meet the requirements without being g- dependent are described. Results of laboratory one-g quantitative characterization on one type of dry powder particle generator is discussed. Data from NASA low-g tests are summarized.

Fonda, Mark↗