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  • Other Sources  (1,873)
  • ASTROPHYSICS  (778)
  • LUNAR AND PLANETARY EXPLORATION  (555)
  • Lunar and Planetary Science and Exploration  (372)
  • COMMUNICATIONS AND RADAR  (168)
  • Analytical Chemistry and Spectroscopy
  • Electronic structure and strongly correlated systems
  • Humans
  • Life and Medical Sciences
  • 2015-2019  (367)
  • 1985-1989  (1,506)
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  • 1
    Publication Date: 2019-08-14
    Description: Establishing the abundance and physical properties of regolith and boulders on asteroids is crucial for understanding the formation and degradation mechanisms at work on their surfaces. Using images and thermal data from NASA's Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) spacecraft, we show that asteroid (101955) Bennu's surface is globally rough, dense with boulders, and low in albedo. The number of boulders is surprising given Bennu's moderate thermal inertia, suggesting that simple models linking thermal inertia to particle size do not adequately capture the complexity relating these properties. At the same time, we find evidence for a wide range of particle sizes with distinct albedo characteristics. Our findings imply that ages of Bennu's surface particles span from the disruption of the asteroid's parent body (boulders) to recent in situ production (micrometre-scale particles).
    Keywords: Lunar and Planetary Science and Exploration
    Type: GSFC-E-DAA-TN67770 , Nature Astronomy (e-ISSN 2397-3366); 3; 341–351
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  • 2
    Publication Date: 2019-08-13
    Description: OSIRIS-REx will return pristine samples of carbonaceous asteroid Bennu. This manuscript describes how pristine was defined based on expectations of Bennu and on a realistic understanding of what is achievable with a constrained schedule and budget, and how that definition flowed to requirements and implementation. To return a pristine sample, the OSIRIS-REx spacecraft sampling hardware was maintained at Level 100 A/2 and less than 180 nanograms per square centimeter of amino acids and hydrazine on the sampler head through precision cleaning, control of materials, and vigilance. Contamination is further characterized via witness material exposed to the spacecraft assembly and testing environment as well as in space. This characterization provided knowledge of the expected background and will be used in conjunction with archived spacecraft components for comparison with the samples when they are delivered to Earth for analysis. Most of all, the cleanliness of the OSIRIS-REx spacecraft was achieved through communication between scientists, engineers, managers, and technicians.
    Keywords: Lunar and Planetary Science and Exploration
    Type: GSFC-E-DAA-TN41800 , International Conference on the Origin of Life; Jul 16, 2018 - Jul 21, 2018; San Diego, CA; United States
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  • 3
    Publication Date: 2019-08-26
    Description: OSIRIS-REx will return pristine samples of carbonaceous asteroid Bennu. This article describes how pristine was defined based on expectations of Bennu and on a realistic understanding of what is achievable with a constrained schedule and budget, and how that definition flowed to requirements and implementation. To return a pristine sample, the OSIRIS-REx spacecraft sampling hardware was maintained at level 100 A/2 and less than 180 ng/cm(exp 2) of amino acids and hydrazine on the sampler head through precision cleaning, control of materials, and vigilance. Contamination is further characterized via witness material exposed to the spacecraft assembly and testing environment as well as in space. This characterization provided knowledge of the expected background and will be used in conjunction with archived spacecraft components for comparison with the samples when they are delivered to Earth for analysis. Most of all, the cleanliness of the OSIRIS-REx spacecraft was achieved through communication among scientists, engineers, managers, and technicians.
    Keywords: Lunar and Planetary Science and Exploration
    Type: GSFC-E-DAA-TN50790 , Space Science Review (ISSN 0038-6308) (e-ISSN 1572-9672); 214; 1; 19
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  • 4
    Publication Date: 2011-08-19
    Description: The results of Voyager 2 photopolarimetry (PPS) surveys of Uranus, the ring system, occultation experiments and observations of the Uranian moons are reported. Dual-channel photometry and polarimetry data obtained of the atmosphere at various emission and phase angles are delineated and compared with characteristics of the Saturn and Jupiter atmospheres. The results of temperature, UV absorption and density profile calculations are also discussed. Extensive ring dimensional data, based on two occultation experiments, are provided in tabular form noting that the rings contain no dust. Finally, the geometric albedos of the five major moons and the phase curve of the moon Titania are presented. The latter data indicate that Titanian surface features are not the result of recent events such as volcanism or ice slurry outflows.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science (ISSN 0036-8075); 233; 65-70
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  • 5
    Publication Date: 2020-01-04
    Description: Active asteroids are those that show evidence of ongoing mass loss. We report repeated instances of particle ejection from the surface of (101955) Bennu, demonstrating that it is an active asteroid. The ejection events were imaged by the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and SecurityRegolith Explorer) spacecraft. For the three largest observed events, we estimated the ejected particle velocities and sizes, event times, source regions, and energies. We also determined the trajectories and photometric properties of several gravitationally bound particles that orbited temporarily in the Bennu environment. We consider multiple hypotheses for the mechanisms that lead to particle ejection for the largest events, including rotational disruption, electrostatic lofting, ice sublimation, phyllosilicate dehydration, meteoroid impacts, thermal stress fracturing, and secondary impacts.
    Keywords: Lunar and Planetary Science and Exploration
    Type: GSFC-E-DAA-TN76455 , Science (ISSN 0036-8075) (e-ISSN 1095-9203); 366; 6470; eaay3544
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  • 6
    Publication Date: 2019-07-13
    Description: NASA's Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission successfully launched on September 8th, 2016. During its rendezvous with near-Earth asteroid (101955) Bennu beginning in 2018, OSIRIS-REx will characterize the asteroid's physical, mineralogical, and chemical properties in an effort to globally map the properties of Bennu, a primitive carbonaceous asteroid, and choose a sampling location [e.g. 1]. In preparation for these observations, we spectrally characterized a suite of analog samples across visible, near- and thermal-infrared wavelengths and used these in initial tests of phase detection and abundance determination software algorithms. Here we present the thermal infrared laboratory measurements of the analog sample suite measured under asteroidlike conditions, which are relevant to the interpretation of spectroscopic observations by the OSIRIS-REx Thermal Emission Spectrometer (OTES) [2, 3]. This suite of laboratory measurements of asteroid analogs under asteroid-like conditions is the first of their kind.
    Keywords: Lunar and Planetary Science and Exploration
    Type: JSC-CN-38849 , Lunar and Planetary Science Conference; Mar 20, 2017 - Mar 24, 2017; The Woodlands, TX; United States
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  • 7
    Publication Date: 2006-02-14
    Description: Narrowband CCD profiles of C2 and grains in several comets (including P/Halley and P/Giacobini-Zinner) were performed. Rotational light curves were made of Comet P/Arend-Rigaux (visible and infrared) yielding the size, shape, albedo, and rotation period of the nucleus. Production rates were measured as a function of heliocentric distance for OH, CN, and C2 in P/Giacobini-Zinner and for OH, NH, CN, C3, and C2 in P/Halley. Detection and measurement was made of forbidden (O I) lines near 6300 and 5577 A in P/Halley, permitting the production rate of oxygen from CO to be distinguished from that from H2O. Identification of C-12C-13 lines in cometary spectra indicating a possible enrichment of C-13 over the telluric value was made. An assessment of techniques for detecting (determining the existence of) a trans-Neptunian comet belt is included.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Reports of Planetary Astronomy, 1985; p 68-70
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  • 8
    Publication Date: 2006-02-14
    Description: Determination of the size, shape, mean density, and albedo of Ceres was made. Predictions for 133 occultations of bright stars occurring in 1986 and 1987 were completed and published, as have predictions of occultations of stars by Comet Halley. Twenty-nine mutual events involving Galilean satellites were observed at Flagstaff in 1985.
    Keywords: ASTROPHYSICS
    Type: NASA, Washington Reports of Planetary Astronomy, 1985; p 108-109
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  • 9
    Publication Date: 2014-10-08
    Description: Spacecraft images revealed that extremely long lava flows (more than 200 km long) exist on the surface of Mars and Io. Compared to terrestial volcanic eruptions, the occurrence of these long flows is very unusual, and may hint at a different style of either magma production or eruption. Attempts to model the emplacement of the long flows on other planets, using a Bingham rheological model, were only partially successful. The objective is to conduct field measurements on long lava flows in Hawaii (where individual flows such as those of 1859 and 1881 exceed 40 km in length) in order to document and interpret their flow characteristics. In this way, a better understanding of the formation of long lava flows is sought as well as a determination of whether the Mauna Loa flows are terrestrial analogs to the long flows seen on Mars and Io.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Repts. of Planetary Geol. and Geophys. Program; p 248-250
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  • 10
    Publication Date: 2013-08-31
    Description: The future possibility of actively testing the current understanding of how energetic particles may be accelerated in space or dumped from the radiation belts using intense electromagnetic energy from ground based antennas is discussed. The ground source of radiation is merely a convenience. A space station source for radiation that does not have to pass through the atmosphere and lower ionosphere, is an attractive alternative. The text is divided into two main sections addressing the possibilities of: (1) accelerating electrons to fill selected flux tubes above the Kennel-Petscheck limit for stably trapped fluxes, and (2) using an Alfven maser to cause rapid depletion of energetic protons or electrons from the radiation belts.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL, Space Technology Plasma Issues in 2001; p 213-224
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