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  • 1
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    Mass properties measurement for drag-free test masses (2009)
    Institute of Physics
    Details
    Publication Date: 2009-03-01
    Print ISSN: 1742-6588
    Electronic ISSN: 1742-6596
    Topics: Physics
    Published by Institute of Physics
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    PAPER CURRENT
  • 2
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    Modular gravitational reference sensor development (2009)
    Institute of Physics
    Details
    Publication Date: 2009-03-01
    Print ISSN: 1742-6588
    Electronic ISSN: 1742-6596
    Topics: Physics
    Published by Institute of Physics
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    PAPER CURRENT
  • 3
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    Gravitational mass attraction: properties of a right-angled parallelepiped for the LISA drag-free system (2006)
    Institute of Physics
    Details
    Publication Date: 2006-04-25
    Print ISSN: 0264-9381
    Electronic ISSN: 1361-6382
    Topics: Physics
    Published by Institute of Physics
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  • 4
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    Star Tracker Performance Estimate with IMU (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A software tool for estimating cross-boresight error of a star tracker combined with an inertial measurement unit (IMU) was developed to support trade studies for the Integrated Radio and Optical Communication project (iROC) at the National Aeronautics and Space Administration Glenn Research Center. Typical laser communication systems, such as the Lunar Laser Communication Demonstration (LLCD) and the Laser Communication Relay Demonstration (LCRD), use a beacon to locate ground stations. iROC is investigating the use of beaconless precision laser pointing to enable laser communication at Mars orbits and beyond. Precision attitude knowledge is essential to the iROC mission to enable high-speed steering of the optical link. The preliminary concept to achieve this precision attitude knowledge is to use star trackers combined with an IMU. The Star Tracker Accuracy (STAcc) software was developed to rapidly assess the capabilities of star tracker and IMU configurations. STAcc determines the overall cross-boresight error of a star tracker with an IMU given the characteristic parameters: quantum efficiency, aperture, apparent star magnitude, exposure time, field of view, photon spread, detector pixels, spacecraft slew rate, maximum stars used for quaternion estimation, and IMU angular random walk. This paper discusses the supporting theory used to construct STAcc, verification of the program and sample results.
    Keywords: Space Communications, Spacecraft Communications, Command and Tracking
    Type: GRC-E-DAA-TN19688 , AIAA SciTech Conference; Jan 05, 2015 - Jan 09, 2015; Kissimmee, FL; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Precision Mass Property Measurements Using a Five-Wire Torsion Pendulum (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A method for measuring the moment of inertia of an object using a five-wire torsion pendulum design is described here. Typical moment of inertia measurement devices are capable of 1 part in 10(exp 3) accuracy and current state of the art techniques have capabilities of about one part in 10(exp 4). The five-wire apparatus design shows the prospect of improving on current state of the art. Current measurements using a laboratory prototype indicate a moment of inertia measurement precision better than a part in 10(exp 4). In addition, the apparatus is shown to be capable of measuring the mass center offset from the geometric center. Typical mass center measurement devices exhibit a measurement precision up to approximately 1 micrometer. Although the five-wire pendulum was not originally designed for mass center measurements, preliminary results indicate an apparatus with a similar design may have the potential of achieving state of the art precision.
    Keywords: Engineering (General)
    Type: DFRC-E-DAA-TN5544 , 27th Annual Meeting of the American Society for Precision Engineering; Oct 21, 2012 - Oct 26, 2012; San Diego, CA; United States
    Format: application/pdf
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  • 6
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    The Influence of Dihedral Angle Error Stability on Beam Deviation for Hollow Retro-Reflectors (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: Retro-reflectors consist of three reflective optical surfaces, which are oriented to reflect the input beam by 180 . For retro-reflector components, it is common to specify an angular beam deviation tolerance, or rather the deviation from the exact 180 def return direction. Precision-aligned retro-reflectors provide 180 deg beam deviation with tolerances on the order of an arcsecond. It is well known that the performance of the retro-reflector depends on the ability to precisely orient the reflective surfaces at mutually perpendicular angles. Precision assembly is therefore critical to ensure highly accurate beam deviation. The dihedral angle errors, and hence the reflected beam deviation, can be measured for the retro-reflector after fabrication, typically by using interferometric techniques. Yet, what is not commonly reported for a fabricated retro-reflector is the stability of the angular beam deviation. For instance, thermo-mechanical effects of the components will contribute to variations in the return beam direction. While the actual stability is design-specific one can develop a mathematical representation for the expected change in the reflected beam direction as a function of the variation in the dihedral angle errors. Presented here is a mathematical formulation for a hollow retro-reflector's beam deviation as a function of the dihedral angle error stability.
    Keywords: Optics
    Type: NASA/TM-2018-219946 , E-19557 , GRC-E-DAA-TN58909
    Format: application/pdf
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  • 7
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    Data Analysis Techniques for a Lunar Surface Navigation System Testbed (2011)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: NASA is interested in finding new methods of surface navigation to allow astronauts to navigate on the lunar surface. In support of the Vision for Space Exploration, the NASA Glenn Research Center developed the Lunar Extra-Vehicular Activity Crewmember Location Determination System and performed testing at the Desert Research and Technology Studies event in 2009. A significant amount of sensor data was recorded during nine tests performed with six test subjects. This paper provides the procedure, formulas, and techniques for data analysis, as well as commentary on applications.
    Keywords: Communications and Radar
    Type: NASA/TM-2011-217113 , E-17789
    Format: application/pdf
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  • 8
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    Localization Using Visual Odometry and a Single Downward-Pointing Camera (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: Stereo imaging is a technique commonly employed for vision-based navigation. For such applications, two images are acquired from different vantage points and then compared using transformations to extract depth information. The technique is commonly used in robotics for obstacle avoidance or for Simultaneous Localization And Mapping, (SLAM). Yet, the process requires a number of image processing steps and therefore tends to be CPU-intensive, which limits the real-time data rate and use in power-limited applications. Evaluated here is a technique where a monocular camera is used for vision-based odometry. In this work, an optical flow technique with feature recognition is performed to generate odometry measurements. The visual odometry sensor measurements are intended to be used as control inputs or measurements in a sensor fusion algorithm using low-cost MEMS based inertial sensors to provide improved localization information. Presented here are visual odometry results which demonstrate the challenges associated with using ground-pointing cameras for visual odometry. The focus is for rover-based robotic applications for localization within GPS-denied environments.
    Keywords: Instrumentation and Photography
    Type: NASA/TM-2012-216043 , E-18443 , GRC-E-DAATN5688
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  • 9
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    EVA Radio DRATS 2011 Report (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: In the Fall of 2011, National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) participated in the Desert Research and Technology Studies (DRATS) field experiments held near Flagstaff, Arizona. The objective of the DRATS outing is to provide analog mission testing of candidate technologies for space exploration, especially those technologies applicable to human exploration of extra- terrestrial rocky bodies. These activities are performed at locations with similarities to extra-terrestrial conditions. This report describes the Extravehicular Activity (EVA) Dual-Band Radio Communication System which was demonstrated during the 2011 outing. The EVA radio system is designed to transport both voice and telemetry data through a mobile ad hoc wireless network and employs a dual-band radio configuration. Some key characteristics of this system include: 1. Dual-band radio configuration. 2. Intelligent switching between two different capability wireless networks. 3. Self-healing network. 4. Simultaneous data and voice communication.
    Keywords: Communications and Radar
    Type: NASA/TM-2012-217635 , E-18280
    Format: application/pdf
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  • 10
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    Air Mobility Data & Reasoning Fabric (2019)
    In:  CASI
    Details
    Publication Date: 2019-11-28
    Description: Throughout the world, especially in dense urban environments, the quality of life is being negatively impacted by ever growing commute time. Travel, beyond commuting, is increasingly driven by door-to-door challenges ? not just gate-to-gate considerations. Air Mobility may be an approach to address these challenges, as it can effectively convert our 2D mobility system to a 3D mobility system, vastly increasing mobility options.
    Keywords: Aeronautics (General)
    Type: ARC-E-DAA-TN75871 , Air Mobility presentation to AirXOS; Nov 25, 2019; Moffett Field, CA; United States
    Format: application/pdf
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