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  • Space Communications, Spacecraft Communications, Command and Tracking  (7)
  • 2000-2004  (7)
  • 1970-1974
  • 1
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    Optimizing Satellite Communications With Adaptive and Phased Array Antennas (2004)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A new adaptive antenna array architecture for low-earth-orbiting satellite ground stations is being investigated. These ground stations are intended to have no moving parts and could potentially be operated in populated areas, where terrestrial interference is likely. The architecture includes multiple, moderately directive phased arrays. The phased arrays, each steered in the approximate direction of the satellite, are adaptively combined to enhance the Signal-to-Noise and Interference-Ratio (SNIR) of the desired satellite. The size of each phased array is to be traded-off with the number of phased arrays, to optimize cost, while meeting a bit-error-rate threshold. Also, two phased array architectures are being prototyped: a spacefed lens array and a reflect-array. If two co-channel satellites are in the field of view of the phased arrays, then multi-user detection techniques may enable simultaneous demodulation of the satellite signals, also known as Space Division Multiple Access (SDMA). We report on Phase I of the project, in which fixed directional elements are adaptively combined in a prototype to demodulate the S-band downlink of the EO-1 satellite, which is part of the New Millennium Program at NASA.
    Keywords: Space Communications, Spacecraft Communications, Command and Tracking
    Type: ESTC 2004; Jun 21, 2004 - Jun 23, 2004; Palo Alto, CA; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Analysis and Optimization of Thin Film Ferroelectric Phase Shifters (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Microwave phase shifters have been fabricated from (YBa2Cu3O(7-delta) or Au)/SrTiO3 and Au/Ba(x)Sr(1-x)TiO3 films on LaAlO3 and MgO substrates. These coupled microstrip devices rival the performance of their semiconductor counter-parts parts at Ku- and K-band frequencies. Typical insertion loss for room temperature ferroelectric phase shifters at K-band is approximately equal 5 dB. An experimental and theoretical investigation of these novel devices explains the role of the ferroelectric film in overall device performance. A roadmap to the development of a 3 dB insertion loss phase shifter that would enable a new type of phased array antenna is discussed.
    Keywords: Space Communications, Spacecraft Communications, Command and Tracking
    Type: Materials Issues in Tunable RF and Microwave Devices; Nov 29, 1999 - Dec 03, 1999; Boston, MA; United States
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    NASA TECHNICAL REPORTS
  • 3
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    The Case for Deep Space Telecommunications Relay Stations (2004)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: Each future mission to Jupiter and beyond must carry the traditional suite of telecommunications systems for command and control and for mission data transmission to earth. The telecommunications hardware includes the large antenna and the high-power transmitters that enable the communications link. Yet future spacecraft will be scaled down from the hallmark missions of Galileo and Cassini to Jupiter and Saturn, respectively. This implies that a higher percentage of the spacecraft weight and power must be dedicated to telecommunications system. The following analysis quantifies this impact to future missions and then explores the merits of an alternative approach using deep space relay stations for the link back to earth. It will be demonstrated that a telecommunications relay satellite would reduce S/C telecommunications weight and power sufficiently to add one to two more instruments.
    Keywords: Space Communications, Spacecraft Communications, Command and Tracking
    Type: NASA/CR-2004-213053 , E-14489
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  • 4
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    Electrical Characterization of Polyaniline/polyethylene Oxide Nanofibers for Field Effect Transistors (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Nanofibers comprised of polyaniline/polyethylene oxide (PANI/PEO) are being developed for novel logic devices. We report the electrical conductivity of PANI/PEO nanofibers with diameters in the 100 to 200 nm range. We measured conductivity values of approx. 0.3 to 1.0 S/cm, which is higher than the values reported for thicker nanofibers, but less than the bulk value of PANI. The electrical measurements were performed by depositing the fibers on pre-electroded, oxidized silicon (Si) substrates. The excellent adherence of the nanofibers to the SiO2 as well as the gold (Au) electrodes may be useful in the design of future devices.
    Keywords: Space Communications, Spacecraft Communications, Command and Tracking
    Type: NASA/TM-2002-212016 , E-13707 , NAS 1.15:212016 , 2003 Nanotechnology Conference and Trade Show; Feb 23, 2003 - Feb 27, 2003; San Francisco, CA; United States
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  • 5
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    Interplay Between Thin Film Ferroelectric Composition, Microstructure and Microwave Phase Shifter Performance (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: One of the keys to successfully incorporating ferroelectric films into Ku-band (12 to 18 GHz) phase shifters is to establish the composition, microstructure, and thickness required to meet the tuning needs, and tailor the film properties to meet these needs. Optimal performance is obtained when the film composition and device design are such that the device performance is limited by odd mode dielectric losses, and these losses are minimized as much as possible while still maintaining adequate tunability. The parameters required to maintain device performance will vary slightly depending on composition, but we can conclude that the best tuning-to-loss figures of merit (K-factor) are obtained when there is minimal variation between the in-plane and out-of-plane lattice parameters, and the full-width half maximum values of the BSTO (002) peaks are less than approximately 0.04 deg. We have observed that for phase shifters in which the ferroelectric crystalline quality and thickness are almost identical, higher losses are observed in films with higher BaISr ratios. The best performance was observed in phase shifters with Ba:Sr = 30:70. The superiority of this composition was attributed to several interacting factors: the B a: Sr ratio was such that the Curie temperature (180 K) was far removed from room temperature, the crystalline quality of the film was excellent, and there was virtually no difference between the inplane and out-of-plane lattice parameters of the film.
    Keywords: Space Communications, Spacecraft Communications, Command and Tracking
    Type: NASA/TM-2003-211987 , E-13426 , NAS 1.15:211987 , 13th International Symposium on Integrated Ferroelectrics; May 28, 2002 - Jun 01, 2002; Nara; Japan
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  • 6
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    Linking Satellites Via Earth "Hot Spots" and the Internet to Form Ad Hoc Constellations (2004)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: As more assets are placed in orbit, opportunities emerge to combine various sets of satellites in temporary constellations to perform collaborative image collections. Often, new operations concepts for a satellite or set of satellites emerge after launch. To the degree with which new space assets can be inexpensively and rapidly integrated into temporary or "ad hoc" constellations, will determine whether these new ideas will be implemented or not. On the Earth Observing 1 (EO-1) satellite, a New Millennium Program mission, a number of experiments were conducted and are being conducted to demonstrate various aspects of an architecture that, when taken as a whole, will enable progressive mission autonomy. In particular, the target architecture will use adaptive ground antenna arrays to form, as close as possible, the equivalent of wireless access points for low earth orbiting satellites. Coupled with various ground and flight software and the Internet. the architecture enables progressive mission autonomy. Thus, new collaborative sensing techniques can be implemented post-launch. This paper will outline the overall operations concept and highlight details of both the research effort being conducted in 〈he area of adaptive antenna arrays and some of the related successful autonomy software that has been implemented using EO-1 and other operational satellites. Keywords: collaborative remote sensing smart antennas, adaptive antenna arrays, sensor webs. ad hoc constellations, mission autonomy and
    Keywords: Space Communications, Spacecraft Communications, Command and Tracking
    Type: SPIE 2004; Nov 08, 2004 - Nov 12, 2004; Honolulu, HI; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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    Liquid Crystal-Based Beam Steering Device Development for NASA Applications (2004)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The NASA Computing, Information and Communications Technology (CICT) Program is supporting the development of liquid crystal-based beam steering devices. The device would use inexpensive, light-weight, optical components, and it would have the following capabilities: electronic beam scanning to angles above 1 milliradian, and submicroradian beam pointing accuracy. In order to correct for the imperfections resulting from the space-deployable optics, the technique of wave-front correction would be implemented. Hence, the output beam quality would be maintained. The potential applications could include satellite tracking, near-Earth inter-satellite communications, deep-space communications, and optical phased array systems. The status of the beam steering device development based on the liquid crystal technology and its relationship to prospective NASA mission scenarios will be described.
    Keywords: Space Communications, Spacecraft Communications, Command and Tracking
    Type: Great Lakes Photonics Symposium; Jun 07, 2004 - Jun 11, 2004; Cleveland, OH; United States
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