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  • 1
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    Detecting Thin Cirrus in Multiangle Imaging Spectroradiometer Aerosol Retrievals (2010)
    In:  Other Sources
    Details
    Publication Date: 2018-06-06
    Description: Thin cirrus clouds (optical depth (OD) 〈 03) are often undetected by standard cloud masking in satellite aerosol retrieval algorithms. However, the Mu]tiangle Imaging Spectroradiometer (MISR) aerosol retrieval has the potential to discriminate between the scattering phase functions of cirrus and aerosols, thus separating these components. Theoretical tests show that MISR is sensitive to cirrus OD within Max{0.05 1 20%l, similar to MISR's sensitivity to aerosol OD, and MISR can distinguish between small and large crystals, even at low latitudes, where the range of scattering angles observed by MISR is smallest. Including just two cirrus components in the aerosol retrieval algorithm would capture typical MISR sensitivity to the natural range of cinus properties; in situations where cirrus is present but the retrieval comparison space lacks these components, the retrieval tends to underestimate OD. Generally, MISR can also distinguish between cirrus and common aerosol types when the proper cirrus and aerosol optical models are included in the retrieval comparison space and total column OD is 〉-0.2. However, in some cases, especially at low latitudes, cirrus can be mistaken for some combinations of dust and large nonabsorbing spherical aerosols, raising a caution about retrievals in dusty marine regions when cirrus is present. Comparisons of MISR with lidar and Aerosol Robotic Network show good agreement in a majority of the cases, but situations where cirrus clouds have optical depths 〉0.15 and are horizontally inhomogeneous on spatial scales shorter than 50 km pose difficulties for cirrus retrieval using the MISR standard aerosol algorithm..
    Keywords: Geophysics
    Type: Journal of Geophysical Research - Atmospheres (ISSN 0148-0227); Volume 115
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  • 2
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    Construction and Resource Utilization Explorer: Regolith Characterization Using a Modular Instrument Suite and Analysis Tools (2005)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The Construction Resource Utilization Explorer (CRUX) is a technology maturation project for the U.S. National Aeronautics and Space Administration to provide enabling technology for lunar and planetary surface operations (LPSO). The CRUX will have 10 instruments, a data handling function (Mapper - with features of data subscription, fusion, interpretation, and publication through geographical information system [GIs] displays), and a decision support system DSS) to provide information needed to plan and conduct LPSO. Six CRUX instruments are associated with an instrumented drill to directly measure regolith properties (thermal, electrical, mechanical, and textural) and to determine the presence of water and other hydrogen sources to a depth of about 2 m (Prospector). CRUX surface and geophysical instruments (Surveyor) are designed to determine the presence of hydrogen, delineate near subsurface properties, stratigraphy, and buried objects over a broad area through the use of neutron and seismic probes, and ground penetrating radar. Techniques to receive data from existing space qualified stereo pair cameras to determine surface topography will also be part of the CRUX. The Mapper will ingest information from CRUX instruments and other lunar and planetary data sources, and provide data handling and display features for DSS output. CRUX operation will be semi-autonomous and near real-time to allow its use for either planning or operations purposes.
    Keywords: Geophysics
    Type: ILC 2005 - 7th ILEWG International Conference on Exploration and Utilization of the Moon; Sep 18, 2005 - Sep 23, 2005; Toronto; Canada
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  • 3
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    Drilling Automation Demonstrations in Subsurface Exploration for Astrobiology (2006)
    In:  Other Sources
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    Publication Date: 2019-07-18
    Description: This project proposes to study subsurface permafrost microbial habitats at a relevant Arctic Mars-analog site (Haughton Crater, Devon Island, Canada) while developing and maturing the subsurface drilling and drilling automation technologies that will be required by post-2010 missions. It builds on earlier drilling technology projects to add permafrost and ice-drilling capabilities to 5m with a lightweight drill that will be automatically monitored and controlled in-situ. Frozen cores obtained with this drill under sterilized protocols will be used in testing three hypotheses pertaining to near-surface physical geology and ground H2O ice distribution, viewed as a habitat for microbial life in subsurface ice and ice-consolidated sediments. Automation technologies employed will demonstrate hands-off diagnostics and drill control, using novel vibrational dynamical analysis methods and model-based reasoning to monitor and identify drilling fault states before and during faults. Three field deployments, to a Mars-analog site with frozen impact crater fallback breccia, will support science goals, provide a rigorous test of drilling automation and lightweight permafrost drilling, and leverage past experience with the field site s particular logistics.
    Keywords: Geophysics
    Type: Astrobiology Science Conference; Mar 26, 2006 - Mar 30, 2006; Washington, DC; United States
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  • 4
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    Constraining the Origin of Impact Craters on Al Foils from the Stardust Interstellar Dust Collector (2012)
    In:  CASI
    Details
    Publication Date: 2019-08-26
    Description: Preliminary examination (PE) of the aerogel tiles and Al foils from the Stardust Interstellar Dust Collector has revealed multiple impact features. Some are most likely due to primary impacts of interstellar dust (ISD) grains, and others are associated with secondary impacts of spacecraft debris, and possibly primary impacts of interplanetary dust particles (IDPs) [1, 2]. The current focus of the PE effort is on constraining the origin of the individual impact features so that definitive results from the first direct laboratory analysis of contemporary ISD can be reported. Because crater morphology depends on impacting particle shape and composition, in addition to the angle and direction of impact, unique particle trajectories are not easily determined. However, elemental analysis of the crater residues can distinguish real cosmic dust from the spacecraft debris, due to the low cosmic abundance of many of the elements in the spacecraft materials. We present here results from the elemental analysis of 24 craters and discuss the possible origins of 4 that are identified as candidate ISD impacts
    Keywords: Geophysics
    Type: JSC-CN-25744 , 43rd Lunar and Planetary Science Conference; Mar 19, 2012 - Mar 23, 2012; The Woodlands, TX; United States
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  • 5
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    Accuracy of High-Rate GPS for Seismology (2006)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: We built a device for translating a GPS antenna on a positioning table to simulate the ground motions caused by an earthquake. The earthquake simulator is accurate to better than 0.1 mm in position, and provides the "ground truth" displacements for assessing the technique of high-rate GPS. We found that the root-mean-square error of the 1-Hz GPS position estimates over the 15-min duration of the simulated seismic event was 2.5 mm, with approximately 96% of the observations in error by less than 5 mm, and is independent of GPS antenna motion. The error spectrum of the GPS estimates is approximately flicker noise, with a 50% decorrelation time for the position error of approx.1.6 s. We that, for the particular event simulated, the spectrum of dependent error in the GPS measurements. surface deformations exceeds the GPS error spectrum within a finite band. More studies are required to determine whether a generally optimal bandwidth exists for a target group of seismic events.
    Keywords: Geophysics
    Type: Geophysical Research Letters (ISSN 0094-8276); 33
    Format: text
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  • 6
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    Global Distortion of GPS Networks Associated with Satellite Antenna Model Errors (2007)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Recent studies of the GPS satellite phase center offsets (PCOs) suggest that these have been in error by approx.1 m. Previous studies had shown that PCO errors are absorbed mainly by parameters representing satellite clock and the radial components of site position. On the basis of the assumption that the radial errors are equal, PCO errors will therefore introduce an error in network scale. However, PCO errors also introduce distortions, or apparent deformations, within the network, primarily in the radial (vertical) component of site position that cannot be corrected via a Helmert transformation. Using numerical simulations to quantify the effects of PC0 errors, we found that these PCO errors lead to a vertical network distortion of 6-12 mm per meter of PCO error. The network distortion depends on the minimum elevation angle used in the analysis of the GPS phase observables, becoming larger as the minimum elevation angle increases. The steady evolution of the GPS constellation as new satellites are launched, age, and are decommissioned, leads to the effects of PCO errors varying with time that introduce an apparent global-scale rate change. We demonstrate here that current estimates for PCO errors result in a geographically variable error in the vertical rate at the 1-2 mm/yr level, which will impact high-precision crustal deformation studies.
    Keywords: Geophysics
    Type: (ISSN 0148-0227)
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  • 7
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    Can Spatially Unresolved 3D Mixtures of Clouds & Aerosols Be Disentangled Using Multi-angle Polarized Radiance Observations? (2012)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Geophysics
    Type: International Radiation Symposium; Aug 06, 2012 - Aug 10, 2012; Dahlem Cube, Berlin; Germany
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  • 8
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    Four Interstellar Dust Candidates from the Stardust Interstellar Dust Collector (2011)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: In January 2006, the Stardust sample return capsule returned to Earth bearing the first solid samples from a primitive solar system body, Comet 81P/Wild2, and a collector dedicated to the capture and return of contemporary interstellar dust. Both collectors were approx. 0.1 sq m in area and were composed of aerogel tiles (85% of the collecting area) and aluminum foils. The Stardust Interstellar Dust Collector (SIDC) was exposed to the interstellar dust stream for a total exposure factor of 20 sq m/day. The Stardust Interstellar Preliminary Examination (ISPE) is a consortium-based project to characterize the collection using nondestructive techniques. The goals and restrictions of the ISPE are described . A summary of analytical techniques is described.
    Keywords: Geophysics
    Type: JSC-CN-22742 , 42nd Lunar and Planetary Science Conference; Mar 07, 2011 - Mar 11, 2011; The Woodlands, TX; United States
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