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  • Electronics and Electrical Engineering  (8)
  • Space Communications, Spacecraft Communications, Command and Tracking  (8)
  • 2010-2014  (16)
  • 2000-2004
  • 1935-1939
  • 11
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    A Study of an Optical Lunar Surface Communications Network with High Bandwidth Direct to Earth Link (2011)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A lunar surface systems study explores the application of optical communications to support a high bandwidth data link from a lunar relay satellite and from fixed lunar assets. The results show that existing 1-m ground stations could provide more than 99% coverage of the lunar terminal at 100Mb/s data rates from a lunar relay satellite and in excess of 200Mb/s from a fixed terminal on the lunar surface. We have looked at the effects of the lunar regolith and its removal on optical samples. Our results indicate that under repeated dust removal episodes sapphire rather than fused silica would be a more durable material for optical surfaces. Disruption tolerant network protocols can minimize the data loss due to link dropouts. We report on the preliminary results of the DTN protocol implemented over the optical carrier.
    Keywords: Space Communications, Spacecraft Communications, Command and Tracking
    Type: 2011 IEEE International Conference on Space Optical Systems and Applications (ICSOS); May 11, 2011 - May 13, 2011; Santa Monica, CA; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 12
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    Optical PAyload for Lasercom Science: OPALS (2013)
    In:  Other Sources
    Details
    Publication Date: 2019-08-13
    Description: No abstract available
    Keywords: Space Communications, Spacecraft Communications, Command and Tracking
    Type: Joint CSA/ESA/JAXA/NASA Increment 37 and 38 Science Symposium; May 28, 2013 - May 29, 2013; Webinar; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 13
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    Accelerated Aging in Electrolytic Capacitors for Prognostics (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The focus of this work is the analysis of different degradation phenomena based on thermal overstress and electrical overstress accelerated aging systems and the use of accelerated aging techniques for prognostics algorithm development. Results on thermal overstress and electrical overstress experiments are presented. In addition, preliminary results toward the development of physics-based degradation models are presented focusing on the electrolyte evaporation failure mechanism. An empirical degradation model based on percentage capacitance loss under electrical overstress is presented and used in: (i) a Bayesian-based implementation of model-based prognostics using a discrete Kalman filter for health state estimation, and (ii) a dynamic system representation of the degradation model for forecasting and remaining useful life (RUL) estimation. A leave-one-out validation methodology is used to assess the validity of the methodology under the small sample size constrain. The results observed on the RUL estimation are consistent through the validation tests comparing relative accuracy and prediction error. It has been observed that the inaccuracy of the model to represent the change in degradation behavior observed at the end of the test data is consistent throughout the validation tests, indicating the need of a more detailed degradation model or the use of an algorithm that could estimate model parameters on-line. Based on the observed degradation process under different stress intensity with rest periods, the need for more sophisticated degradation models is further supported. The current degradation model does not represent the capacitance recovery over rest periods following an accelerated aging stress period.
    Keywords: Electronics and Electrical Engineering
    Type: ARC-E-DAA-TN4396 , Annual Reliability and Maintainability Symposium; Jan 23, 2012; Reno, NV; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 14
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    Towards Prognostics of Electrolytic Capacitors (2011)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A remaining useful life prediction algorithm and degradation model for electrolytic capacitors is presented. Electrolytic capacitors are used in several applications ranging from power supplies on critical avionics equipment to power drivers for electro-mechanical actuators. These devices are known for their low reliability and given their criticality in electronics subsystems they are a good candidate for component level prognostics and health management research. Prognostics provides a way to assess remaining useful life of a capacitor based on its current state of health and its anticipated future usage and operational conditions. In particular, experimental results of an accelerated aging test under electrical stresses are presented. The capacitors used in this test form the basis for a remaining life prediction algorithm where a model of the degradation process is suggested. This preliminary remaining life prediction algorithm serves as a demonstration of how prognostics methodologies could be used for electrolytic capacitors.
    Keywords: Electronics and Electrical Engineering
    Type: ARC-E-DAA-TN3303 , Infotech at Aerospace 2011; Mar 29, 2011 - Mar 31, 2011; St. Louis, MO
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 15
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    A Study of an Optical Lunar Surface Communications Network with High Bandwidth Direct to Earth Link (2011)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Analyzed optical DTE (direct to earth) and lunar relay satellite link analyses, greater than 200 Mbps downlink to 1m Earth receiver and greater than 1 Mbps uplink achieved with mobile 5cm lunar transceiver, greater than 1Gbps downlink and greater than 10 Mpbs uplink achieved with 10cm stationary lunar transceiver, MITLL (MIT Lincoln Laboratory) 2013 LLCD (Lunar Laser Communications Demonstration) plans to demonstrate 622 Mbps downlink with 20 Mbps uplink between lunar orbiter and ground station; Identified top five technology challenges to deploying lunar optical network, Performed preliminary experiments on two of challenges: (i) lunar dust removal and (ii)DTN over optical carrier, Exploring opportunities to evaluate DTN (delay-tolerant networking) over optical link in a multinode network e.g. Desert RATS.
    Keywords: Space Communications, Spacecraft Communications, Command and Tracking
    Type: 2011 IEEE International Conference on Space Optical Systems and Applications (ICSOS); May 11, 2011 - May 13, 2011; Santa Monica, CA; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 16
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    Advanced Communications, Navigation and Technology Concepts for a Mars 2018 Orbiter (2013)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Space Communications, Spacecraft Communications, Command and Tracking
    Type: IEEE Aerospace Conference; Mar 02, 2013 - Mar 09, 2013; Big Sky, MT; United States
    Format: text
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    NASA TECHNICAL REPORTS
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