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  • 1
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    RF coverage analysis and performance for Shuttle communication links (1978)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: This paper describes the current work at NASA/Johnson Space Center in the area of RF coverage analysis and performance-assessment for the Space Shuttle Program communication and tracking radio links. Trajectories, antenna data, ground station and Shuttle hardware performance characteristics and RF link math models were assimilated to generate RF link performance predictions for the three basic mission phases - ascent, on-orbit, and descent. Results identify some earlier deficiencies that required re-configuration of the ground station. Overall performance is currently satisfactory.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Type: IEEE Transactions on Communications; COM-26; Nov. 197
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Shuttle STS-2 mission communication systems RF coverage and performance predictions. Volume 1: Ascent (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The RF communications capabilities and nominally expected performance for the ascent phase of the second orbital flight of the shuttle are provided. Predicted performance is given mainly in the form of plots of signal strength versus elapsed mission time for the STDN (downlink) and shuttle orbiter (uplink) receivers for the S-band PM and FM, and UHF systems. Performance of the NAV and landing RF systems is treated for RTLS abort, since in this case the spacecraft will loop around and return to the launch site. NAV and landing RF systems include TACAN, MSBLS, and C-band altimeter. Signal strength plots were produced by a computer program which combines the spacecraft trajectory, antenna patterns, transmit and receive performance characteristics, and system mathematical models. When available, measured spacecraft parameters were used in the predictions; otherwise, specified values were used. Specified ground station parameter values were also used. Thresholds and other criteria on the graphs are explained.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-84853 , JSC-17625-VOL-1 , NAS 1.15:84853
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Interference effects on Space Station Freedom and Space Shuttle Orbiter Ku-band single access return links (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: In a Ku-band single access return (KSAR) communication link via the tracking and data relay satellite system (TDRSS), the interference between spacecraft can be discriminated by opposite antenna polarizations, pseudo-noise code, and by TDRSS antenna beam pointing. For the Space Station Freedom (SSF) KSAR and the Space Shuttle Orbiter (SSO) KSAR links, the pseudo-noise coding technique is not exploited. In addition, the two KSAR links use the same carrier frequency. Therefore, if the SSF and SSO are in close proximity, it is expected that mutual interference will be significant. Mutual interference effects on the SSO-KSAR I-channel and the SSF-KSAR links are analytically derived and compared to the simulation results. For the analysis, the channel is assumed ideally bandlimited and linear. It is demonstrated that a simplified (linear bandlimited channel) analytical approach yields results of adequate accuracy in an estimation of the signal degradation by interference.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Orbiter Interface Unit and Early Communication System (2004)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: This report describes the Orbiter Interface Unit (OIU) and the Early Communication System (ECOMM), which are systems of electronic hardware and software that serve as the primary communication links for the International Space Station (ISS). When a space shuttle is at or near the ISS during assembly and resupply missions, the OIU sends groundor crew-initiated commands from the space shuttle to the ISS and relays telemetry from the ISS to the space shuttle s payload data systems. The shuttle then forwards the telemetry to the ground. In the absence of a space shuttle, the ECOMM handles communications between the ISS and Johnson Space Center via the Tracking and Data Relay Satellite System (TDRSS). Innovative features described in the report include (1) a "smart data-buffering algorithm that helps to preserve synchronization (and thereby minimize loss) of telemetric data between the OIU and the space-shuttle payload data interleaver; (2) an ECOMM antenna-autotracking algorithm that selects whichever of two phased-array antennas gives the best TDRSS signal and electronically steers that antenna to track the TDRSS source; and (3) an ECOMM radiation-latchup controller, which detects an abrupt increase in current indicative of radiation-induced latchup and temporarily turns off power to clear the latchup, restoring power after the charge dissipates.
    Keywords: Man/System Technology and Life Support
    Type: MSC-23385 , NASA Tech Briefs, June 2004; 31
    Format: application/pdf
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  • 5
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    Space Station GPS Multipath Analysis and Validation (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: To investigate the multipath effects on the International Space Station (ISS) Global Positioning System (GPS) measurement accuracy, experimental and computational investigations were performed to estimate the carrier phase errors due to multipath. A new modeling approach is used to reduce the required computing time by separating the dynamic structure elements from the static structure elements in the multipath computations. This study confirmed that the multipath is a major error source to the ISS GPS performance and can possibly degrade the attitude determination solution. It is demonstrated that the GPS antenna carrier phase errors due to multipath can be analyzed using the electromagnetic modeling technique such as the Uniform Geometrical Theory of Diffraction (UTD).
    Keywords: Aircraft Communications and Navigation
    Type: Vehicular Technology; May 17, 1999 - May 21, 1999; Houston, TX; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Radio frequency interference effect on PN code sequence lock detector (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The authors find the probabilities of detection and false alarm of the pseudonoise (PN) sequence code lock detector when strong radio frequency interference (RFI) hits the communications link. Both a linear model and a soft-limiter nonlinear model for a transponder receiver are considered. In addition, both continuous wave (CW) RFI and pulse RFI are analyzed, and a discussion is included of how strong CW RFI can knock out the PN code lock detector in a linear or a soft-limiter transponder. As an example, the Space Station Freedom forward S-band PN system is evaluated. It is shown that a soft-limiter transponder can protect the PN code lock detector against a typical pulse RFI, but it can degrade the PN code lock detector performance more than a linear transponder if CW RFI hits the link.
    Keywords: COMMUNICATIONS AND RADAR
    Type: MILCOM ''91- IEEE Military Communications Conference; Nov 04, 1991 - Nov 07, 1991; McLean, VA; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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    Optimal Placement Of Multiple Antennas (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Computer program based on pair of algorithms selects approximately optimal locations of antennas and approximately optimal number of elements in each antenna of multiple-antenna communication system. Obscuration in field of view at given antenna location taken into account in choice of number of antenna elements mounted there. Directional coverages of combinations of up to four antenna elements computed in search for combination to cover clear portion of field of view. Developed to aid design of antenna system of conceptual space station. Applied to system aboard ship or aircraft, on building in city, or in any location where transmission and reception blocked in some directions from each potential antenna-mounting point.
    Keywords: ELECTRONIC COMPONENTS AND CIRCUITS
    Type: MSC-21291 , NASA Tech Briefs (ISSN 0145-319X); 13; 1; P. 21
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    NASA TECHNICAL REPORTS
  • 8
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    Ku-band interferences for the Space Station multiple access link (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The multiple access (MA) system, an essential part of the United States Space Station, will be used to provide simultaneous communication services, voice and command, telemetry and video, between the Space Station and all the different coorbiting user vehicles. The system is designed to operate in the Ku-band frequencies between 14 GHz and 14.89 GHz. Within this band, there are other users that could pose serious interference potential. The extent of the interference and its impact on the system operations are analyzed using a Monte Carlo simulation. Worst-case analysis indicated that certain links are very susceptible to interference. Mitigation techniques involving both hardware changes and operation constraints are presented. With the modification of some of the design and implementation of some of the mitigation techniques, the interference levels were found to be only a few percent and to occur in a burst manner.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Type: GLOBECOM ''89 - IEEE Global Telecommunications Conference and Exhibition; Nov 27, 1989 - Nov 30, 1989; Dallas, TX; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 9
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    Orbital Maneuvering Vehicle space station communications design (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The authors present an Orbital Maneuvering Vehicle space station communications systems design approach which is intended to satisfy the stringent link requirements. The operational scenario, system configuration, signal design, antenna system management, and link performance analysis are discussed in detail. It is shown that the return link can transmit up to 21.6 Mb/s and maintain at least a 3-dB link margin through proper power and antenna management control at a maximum distance of 37 km. It is suggested that the proposed system, which is compatible with the space station multiple-access system, can be a model for other space station interoperating elements or users to save the development cost and reduce the technical and schedule risks.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Type: GLOBECOM ''88 - IEEE Global Telecommunications Conference and Exhibition; Nov 28, 1988 - Dec 01, 1988; Hollywood, FL; United States
    Format: text
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    NASA TECHNICAL REPORTS
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