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  • 1
    Publication Date: 2018-12-01
    Description: Attendant upon the use of synthetic aperture radar (SAR) in upcoming planetary missions, is the need to assess errors in the pointing angles of the instrument boresight due to spacecraft ephemeris errors. Developed herein are the constrained analytic partials of these boresight angles not only with respect to a motion-related, cartesian frame but also with respect to classical orbital elements. While both systems have great utility for spacecraft based instruments, the former system should prove useful for SAR instruments on aircraft.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Type: AIAA PAPER 86-2012
    Format: text
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  • 2
    Publication Date: 2018-11-30
    Type: paper
    Format: application/pdf
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  • 3
    Publication Date: 2011-08-24
    Description: For most imaging sensors, a constant (dc) pointing error is unimportant (unless large), but time-dependent (ac) errors degrade performance by either distorting or smearing the image. When properly quantified, the separation of the root-mean-square effects of random line-of-sight motions into dc and ac components can be used to obtain the minimum necessary line-of-sight stability specifications. The relation between stability requirements and sensor resolution is discussed, with a view to improving communication between the data analyst and the control systems engineer.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Journal of the Astronautical Sciences (ISSN 0021-9142); 40; 4; p. 557-576.
    Format: text
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  • 4
    Publication Date: 2011-08-19
    Description: An essential aspect of the design of control systems for large, flexible spacecraft is fault tolerance. Because it is anticipated that a large number of sensors and actuators will be required to realize good control over these assemblies, the detection and isolation of component failures cannot be based on direct comparisons among replicated components. Instead, the notion of 'analytic redundancy' must be employed for the FDI function. Unfortunately this makes the FDI function sensitive to modeling errors which are certain to exist in the large space structure problem due to model truncation and parameter uncertainty. This paper addresses the robustness to model error of one method of FDI residual generation - the failure detection filter. Initial designs were found to be extremely sensitive to modeling error. The sources of this sensitivity are analyzed and modifications to the design are suggested. The improved filter is shown to have much better visibility of the failure signatures relative to the background due to modeling error.
    Keywords: CYBERNETICS
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  • 5
    Publication Date: 2019-07-13
    Description: Mars Science Laboratory (MSL) will use the Skycrane architecture to execute final descent and landing maneuvers. The Skycrane phase uses closed-loop feedback control throughout the entire phase, starting with rover separation, through mobility deploy, and through touchdown, ending only when the bridles have completely slacked. The integrated ADAMS simulation described in this paper couples complex dynamical models created by the mechanical subsystem with actual GNC flight software algorithms that have been compiled and linked into ADAMS. These integrated simulations provide the project with the best means to verify key Skycrane requirements which have a tightly coupled GNC-Mechanical aspect to them. It also provides the best opportunity to validate the design of the algorithm that determines when to cut the bridles. The results of the simulations show the excellent performance of the Skycrane system.
    Keywords: Mechanical Engineering
    Type: IEEE Aerospace Conference; 3-10 Mar. 2012; Big Sky, MT; United States
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  • 6
    Publication Date: 2019-07-13
    Description: On August 5, 2012, the Mars Science Laboratory (MSL) mission successfully delivered the Curiosity rover to its intended target. It was the most complex and ambitious landing in the history of the red planet. A key component of the landing system, the requirements for which were driven by the mission ambitious science goals, was the Guidance, Navigation, and Control (GN&C) system. This paper will describe the technical challenges of the MSL GN&C system, the resulting architecture and design needed to meet those challenges, and the development process used for its implementation and testing.
    Keywords: Lunar and Planetary Science and Exploration; Spacecraft Instrumentation and Astrionics
    Type: AAS/AIAA Spaceflight Mechanics Meeting; 10-14 Feb. 2013; Kauai, HI; United States
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  • 7
    Publication Date: 2019-07-13
    Description: The Mars Science Laboratory project recently places the Curiosity rove on the surface of Mars. With the success of the landing system, the performance envelope of entry, descent and landing capabilities has been extended over the previous state of the art. This paper will present an overview to the MSL entry, descent and landing system design and preliminary flight performance results.
    Keywords: Lunar and Planetary Science and Exploration; Space Transportation and Safety
    Type: AAS 13-236 , Space Flight Mechanics Meeting; 10-14 Feb. 2013; Kauai, HI; United States
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  • 8
    Publication Date: 2019-07-13
    Description: Mixing function vs time relationship for liquid propellant explosion hazards prediction, noting thermocouple grid for maximum information
    Keywords: PROPELLANTS
    Type: ; ADEMIE DES SCIENCES|NEW YORK ACADEMY OF SCIENCES, CONFERENCE ON PREVENTION OF AND PROTECTION AGAINST ACCIDENTAL EXPLOSION OF MUNITIONS, FUELS AND OTHER HAZARDOUS MIXTURES; OCT. 10-13, 1966; NEW YORK, NY
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  • 9
    Publication Date: 2019-07-12
    Description: A proposed instrument would project a narrow laser beam that would be frequency-modulated with a pseudorandom noise (PN) code for simultaneous measurement of range and velocity along the beam. The instrument performs these functions in a low mass, power, and volume package using a novel combination of established techniques. Originally intended as a low resource- footprint guidance sensor for descent and landing of small spacecraft onto Mars or small bodies (e.g., asteroids), the basic instrument concept also lends itself well to a similar application guiding aircraft (especially, small unmanned aircraft), and to such other applications as ranging of topographical features and measuring velocities of airborne light-scattering particles as wind indicators. Several key features of the instrument s design contribute to its favorable performance and resource-consumption characteristics. A laser beam is intrinsically much narrower (for the same exit aperture telescope or antenna) than a radar beam, eliminating the need to correct for the effect of sloping terrain over the beam width, as is the case with radar. Furthermore, the use of continuous-wave (CW), erbium-doped fiber lasers with excellent spectral purity (narrow line width) permits greater velocity resolution, while reducing the laser s power requirement compared to a more typical pulsed solid-state laser. The use of CW also takes proper advantage of the increased sensitivity of coherent detection, necessary in the first place for direct measurement of velocity using the Doppler effect. However, measuring range with a CW beam requires modulation to "tag" portions of it for time-of-flight determination; typically, the modulation consists of a PN code. A novel element of the instrument s design is the use of frequency modulation (FM) to accomplish both the PN-modulation and the Doppler-bias frequency shift necessary for signed velocity measurements. This permits the use of a single low-power waveguide electrooptic phase modulator, while simultaneously mitigating the effects of speckle as a noise source in the coherent detection.
    Keywords: Man/System Technology and Life Support
    Type: NPO-40403 , NASA Tech Briefs, February 2005; 9-10
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  • 10
    Publication Date: 2019-07-12
    Description: A report describes the Laser Mapper (LAMP) -- a lightweight, compact, low-power lidar system under development for guidance of a spacecraft or exploratory robotic vehicle (rover) at Mars or another planet. The LAMP is intended especially for use during rendezvous of two spacecraft in orbit, for mapping terrain during descent and landing of a spacecraft, for capturing a sample that has been launched into orbit, or navigation and avoidance of obstacles by a rover traversing terrain. The LAMP includes a laser that emits high-power, short light pulses. The laser beam is aimed in azimuth and elevation by use of a mirror on a two-axis gimbal, which scans the beam across a field of regard. Light reflected by a target is collected by a telescope, and the distance to the target is determined by measuring the round-trip travel time for reflected light pulses. The distance information is combined with directional information to construct a three-dimensional map of targets in the field of regard.
    Keywords: Communications and Radar
    Type: NPO-30887 , NASA Tech Briefs, February 2004; 33
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