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NASA NTRS1987

The case for planetary sample return missions. I - Origin of the solar system

The scientific aims and proposed scenarios of sample-return missions (SRMs) to Mars, Venus, comets, and asteroids are reviewed. SRMs are currently being evaluated as natural follow-ons to the NASA remote-sensing orbiter missions of the 1990s. The technological advantages of ground laboratory analysis of returned samples are discussed; and it is argued that SRMs to large evolved bodies can provide a record of (1) the composition of the solar system at different heliocentric distances and (2) the nature of the processes that led to the accretion of small objects (preserved as comets and asteroids) into large planetary bodies. Also considered are NASA research and analysis programs needed to support studies of solar-system origin. It is recommended that planning of SRMs be begun immediately, although they may not be feasible before the year 2000.

Drake, Michael J.↗

NASA NTRS1986

Sequential estimation and satellite data assimilation in meteorology and oceanography

The role of dynamics in estimating the state of the atmosphere and ocean from incomplete and noisy data is discussed and the classical applications of four-dimensional data assimilation to large-scale atmospheric dynamics are presented. It is concluded that sequential updating of a forecast model with continuously incoming conventional and remote-sensing data is the most natural way of extracting the maximum amount of information from the imperfectly known dynamics, on the one hand, and the inaccurate and incomplete observations, on the other.

Ghil, M.↗

NASA NTRS1987

Introduction to the physics and techniques of remote sensing

This book presents a comprehensive overview of the basics behind remote-sensing physics, techniques, and technology. The physics of wave/matter interactions, techniques of remote sensing across the electromagnetic spectrum, and the concepts behind remote sensing techniques now established and future ones under development are discussed. Applications of remote sensing are described for a wide variety of earth and planetary atmosphere and surface sciences. Solid surface sensing across the electromagnetic spectrum, ocean surface sensing, basic principles of atmospheric sensing and radiative transfer, and atmospheric remote sensing in the microwave, millimeter, submillimeter, and infrared regions are examined.

Elachi, Charles↗

NASA NTRS1987

Effects of charged particles on the surfaces of the satellites of Uranus

Measurements of the ion and electron fluxes in the Uranian magnetosphere made by the low-energy charged-particle (LECP) instrument on the Voyager 2 spacecraft are used to discuss possible particle-induced modifications of the moons and rings of Uranus. The energy spectra of the orbit-integrated particle dosages expected on the major moons are derived from the LECP measurements of particle intensities and pitch-angle distributions. Laboratory-derived results on charged-particle-induced chemical and physical modifications of H2O, CH4, CO, and CO2 ions are used. The erosion rates of water ice and the darkening of organic ices on the surfaces of the moons are estimated from the orbit-integrated fluxes. Significant darkening of fresh organic ices to depths of the order of 1 micron is expected to occur for times as short as a few thousand years. Darkening at deeper depths will occur at increasingly longer times. The implications of these results for the interpretation of remote-sensing data are discussed.

Lanzerotti, L. J.↗

NASA NTRS1988

Far-infrared measurement of stratospheric carbon monoxide

The stratospheric vertical distribution of CO is obtained from balloon-based FIR limb thermal emission spectra by analyzing several limb sequences of the R8 and R1 spectral lines at 34.588 and 49.932/cm, respectively. This constitutes the first determination of the stratospheric CO profile from IR thermal emission spectra. The results, indicating 24.6 + or - 7.6 ppbv at 21 km and 34.4 + or - 10.1 ppbv at 37 km, are compared with the remote-sensing and in situ measurements by other groups and with photochemical-dynamical model calculations.

Abbas, M. M.↗

NASA NTRS1988

The temperature structure, mass, and energy flow in the corona and inner solar wind

Remote-sensing and in situ data are used to constrain a radiative energy balance model in order to study the radial variations of coronal temperatures, densities, and outflow speeds in several types of coronal holes and in an unstructured quiet region of the corona. A one-fluid solar wind model is used which takes into account the effects of radiative and inward conductive losses in the low corona and the chromospheric-coronal transition region. The results show that the total nonradiative energy input in magnetically open coronal regions is 5 + or - 10 to the 5th ergs/sq cm, and that most of the energy heating the coronal plasma is dissipated within 2 solar radii of the solar surface.

Withbroe, George L.↗

NASA NTRS1987

Development of the imaging spectrometer - Technical challenges and solutions

The imaging spectrometer (IS) is capable of performing direct identification of surface materials through their spectral signatures. This paper describes some of the system design and technology tradeoffs associated with the development of ISs; particular attention is given to optics, spectral dispersion, focal plane, and data handling,. Design examples for both earth and planetary remote-sensing applications are described, including AVIRIS, HIRIS, and VIMS.

Herring, Mark↗

NASA NTRS1988

The earth observing system - A mission for lidar remote sensing technology

NASA plans an earth observing system (EOS) to address low earth orbit remote sensing satellite requirements. EOS will incorporate three active remote-sensing instruments employing some form of lidar: (1) the Lidar Atmospheric Sounder and Altimeter (LASA), the Laser Atmospheric Wind Sounder (LAWS), and the Geodynamics Laser Ranging System (GLRS). LASA will deepen understanding of atmospheric composition and structure; LAWS will measure winds using Doppler lidar technology; GLRS will be used to ascertain the position of strategically placed retroreflectors to an accuracy of several cm.

Sokoloski, Martin M.↗

NASA NTRS1988

Observations of marine stratocumulus clouds during FIRE

The First International Satellite Cloud Climatology Project Regional Experiment (FIRE) to study extensive fields of stratocumulus clouds off the coast of California is presented. Measurements on the regional and detailed local scales were taken, allowing for a wide interpretation of the mean, turbulent, microphysical, radiative, and chemical characteristics of stratocumulus. Multiple aircraft and ground-based remote-sensing systems were used to study the time evolution of the boundary layer structure over a three-week period, and probes from tethered balloons were used to measure turbulence and to collect cloud-microphysical and cloud-radiative data. The observations provide a base for studying the generation maintenance and dissipation of stratocumulus clouds, and could aid in developing numerical models and improved methods for retrieving cloud properties by satellite.

Albrecht, Bruce A.↗

NASA NTRS1989

Integrated-Circuit Broadband Infrared Sources

Microscopic devices consume less power, run hotter, and are more reliable. Simple, compact, lightweight, rapidly-responding reference sources of broadband infrared radiation made available by integrated-circuit technology. Intended primarily for use in calibration of remote-sensing infrared instruments, devices eventually replace conventional infrared sources. New devices also replace present generation of miniature infrared sources. Self-passivating nature of poly-crystalline silicon adds to reliability of devices. Maximum operating temperature is 1,000 K, and power dissipation is only one-fourth that of prior devices.

Lamb, G.↗

NASA NTRS1988

Gossans on Mars

The appearance of rusty iron-rich oxidized cappings over sulfide-bearing rocks on earth indicates that similar gossans may have formed on the surface of Mars. Electrochemical processes and thermodynamic relationships linking acidity to oxidation-reduction reactions between primary sulfide minerals and their oxidative weathering products present in the regolith of Mars are discussed. Remote-sensed visible spectra of the Martian surface are in keeping with the presence of poorly-crystalline FeOOH, jarosite, silica, and clay silicates found in gossans, while incompletely weathered pyrrhotite may represent the magnetic material observed in Martian regolith.

Burns, Roger G.↗

NASA NTRS1988

The role of GPS in precise earth observation

The potential of the Global Positioning System (GPS) for precise earth observation is evaluated. It is projected that soon GPS will be utilized to track remote-sensing satellites with subdecimeter accuracy. The first will be Topex/Poseidon, a US/French ocean altimetry mission to be launched in 1991. In addition, it is suggested that developments planned for future platforms may push orbit accuracy near 1 cm within a decade. GPS receivers on some platforms will track the signals down to the earth limb to observe occultation by intervening media. This will provide comprehensive information on global temperature and climate and help detect the possible onset of a greenhouse effect. It is also projected that dual-frequency observations will be used to trace the flow of energy across earth systems through detection of ionospheric gravity waves, and to map the structure of the ionosphere by computer tomography.

Yunck, Thomas P.↗

NASA NTRS1988

Geological applications of the Space Station core platform

The manned core platform of the Space Station will repeatedly provide observations of the tropical and subtropical parts of earth from about 500 km altitude in a 28.5 degree orbit. This orbit covers most of the landmasses in the Southern Hemisphere, half of the world ocean, and more than 120 nations. The platform can provide remote-sensing activities by means of: (1) sensors attached to structural members of the platform; (2) sensors deployed on one or more pointable platforms attached to structural members, or man-tended in separate orbits; (3) sensors operated from the resource nodes; (4) sensors operated through earth-viewing, optical-quality windows; and (5) hand-held cameras operated by crew members throughout the facility. Major applications of observations from the core platform in the exploration for and production of resources are discussed.

Amsbury, David L.↗

NASA NTRS1989

A model for depolarized radar echoes from Mars

The depolarized radar echoes from Mars are modeled using a combination of remote-sensing observations. The model reproduces the variations of the total radar cross-sections with longitude observed by Goldstone (1986) along 7 S, yields larger magnitudes of total radar cross-sections along 22 N than those along 7 S, and produces depolarized echo spectra that broadly match those observed by the Arecibo radar in 1980 and 1982. The model indicates that volcanoes and lava plains of the Tharsis-Alba Patera, Elysium, and Amazonia regions have the strongest depolarized echoes from the entire planet. Rock populations for the moon and Mars are estimated assuming depolarized radar echoes result from rocks with radii between 1.3 and three times the wavelength.

Thompson, T. W.↗

NASA NTRS1988

The current status of and future outlook for the NASA space program

A brief general overview of NASA programs and planning is presented. Topics discussed include long-term policy goals (creating commercial opportunities, construction of the International Space Station, and manned planetary missions), the scientific and technological projects planned for the Space Station, the key role of the Space Station in solar-system exploration, the pathfinder-technologies concept, and the comprehensive remote-sensing program Mission to Planet Earth.

Myers, D. D.↗

NASA NTRS1989

Mineralogical clues to the origins of asteroid dynamical families

Remote-sensing data are the bases of the present tabulation of the mineralogical composition of the asteroid dynamical families' parent bodies, in which correlations are presented between Tholen's (1984) taxonomic types and the family-membership lists of Hirayama (1933), Brouwer (1951), Arnold (1969), Carusi and Massaro (1978), Kozai (1979), and Williams (1979). In conjunction with recently obtained IR and radar data, these tables suggest that most of the smaller proposed families cannot share the origin of the larger, well-defined families as fragments of collisionally disrupted parent bodies.

Bell, Jeffrey F.↗

NASA NTRS1989

LIMEX '87 ice surface characteristics - Implications for C-band SAR backscatter signatures

Ice surface characterization data collected in 1987, during the Labrador Sea Ice Margin Experiment, are analyzed to estimate the changes in snow and ice properties at the onset of melt. Surface measurements were made from an ice research vessel on several days (some of which had coincident remote-sensing flights) at a number of locations in the marginal ice zone. These data are used as input parameters in a simple scattering model to simulate the effects of variations in material properties upon C-band scattering signatures. Snow moisture and large-scale surface roughness are demonstrated to have the largest effect upon HH polarization scattering cross-section sigma(HH)(O) and large differences are predicted between undeformed floe surfaces and deformed or undulating rough ice surfaces. Using a parametric approach, an approximate picture of rough and smooth ice signatures and their relative contrast are provided. The models reproduce a trend observed in synthetic aperture radar (SAR) images of increasing backscatter contrast between deformed and underformed ice over an early period of warning: such observations are consistent with the results of analysis of SAR images to date. The model also reproduces a calibrated SAR-derived signature with a reasonable degree of accuracy.

Drinkwater, Mark R.↗

NASA NTRS1989

The Earth Observing System (EOS) SAR ground data system

NASA, in association with ESA and NASDA, will launch the Space Station Freedom in 1993. As a complement to the Space Station, several unmanned Polar-Orbit Platforms (POPs) will be developed, built and launched with suites of instruments devoted to remote-sensing for earth surface and atmosphere observations or to planetary and deep-space studies. Attention is presently given to the POPs-associated Earth Observing System SAR Ground Data System, which encompasses a SAR processor, a postprocessing subsystem, a geophysical processor, and a data management and control subsystem.

Curlander, John C.↗