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  • 1
    Publication Date: 2006-01-11
    Description: A historic account of the activities of the Satellite OD Group during the MM'71 mission is given along with an assessment of the accuracy of the determined orbit of the Mariner 9 spacecraft. Preflight study results are reviewed, and the major error sources described. Tracking and data fitting strategy actually used in the real time operations is itemized, and Deep Space Network data available for orbit fitting during the mission and the auxiliary information used by the navigation team are described. A detailed orbit fitting history of the first four revolutions of the satellite orbit of Mariner 9 is presented, with emphasis on the convergence problems and the delivered solution for the first orbit trim maneuver. Also included are a solution accuracy summary, the history of the spacecraft orbit osculating elements, the results of verifying the radio solutions with TV imaging data, and a summary of the normal points generated for the relativity experiment.
    Keywords: SPACE SCIENCES
    Type: Its Mariner 9 Navigation; p 119-192
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  • 2
    Publication Date: 2019-06-28
    Description: The subject of navigation of the Venus Radar Mapper (VRM) spacecraft is presented in the light of challenges to the accomplishment of a high accuracy in spacecraft navigation, within operational constraints, in support of quality science return (sensor performance) for the VRM mission. The paper addresses major navigational challenges arising from inherent mission constraints and describes current navigational plans as well as expected performance. The VRM mission will be the first mission to use radio interferometric data on a daily basis for spacecraft navigation. While the dependency on narrowband Delta-VLBI data for navigation accuracy has been shown in this paper, aspects of scheduling, transmission, correlation, and reliability of VLBI observations for VRM operational use remain complex. Implementation of such a system for successful VRM navigation will constitute a significant advance in application of VLBI technology.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Type: IAF PAPER 85-259
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  • 3
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    Publication Date: 2018-06-08
    Type: Second MIT DSM Workshop; Cambridge, MA; United States
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  • 4
    Publication Date: 2018-06-08
    Description: Projects executed under an international agreement require special arrangements in order to operate within confines of regulations issued by the State Department and the Commerce Department. In order to communicate enterprise-level guidance and procedural information uniformly to projects based on interpretations that carry the weight of institutional authority, a process was developed. This paper provides a script for designing processes in general, using this particular process for context. While the context is incidental, the method described is applicable to any process in general. The paper will expound on novel features utilized for dissemination of the procedural details over the Internet following such process design.
    Type: 2003 IEEE Aerospace Conference; Big Sky, MT; United States|IEEE Transactions - 2003 IEEE Aerospace Conference
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  • 5
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    Publication Date: 2019-06-28
    Description: Attention is drawn to the benefits of simultaneous dual baseline radio interferometric measurements for low altitude planetary orbiter navigation. The radio interferometric data types constitute a valuable addition to conventional tracking data in the establishment of orbit-plane orientation, thanks to their measurement of inertial reference cross-track velocity. The present results show that only a few Delta-VLBI measurements, taken at either end of a conventional tracking arc, suffice for the realization of a positional accuracy of better than 1 km for the case of a Venus Orbiting Imaging Radar-type planetary orbiter. This is comparable to Deep Space Net accuracies, despite the use of a shorter baseline.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Type: Journal of the Astronautical Sciences (ISSN 0021-9142); 31; Jan
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  • 6
    Publication Date: 2019-06-28
    Description: This paper describes the use of stochastic differential correction models in refining the Seasat orbit based on post-flight analysis of tracking data. The objective is to obtain orbital-height precision that is commensurate with the inherent Seasat altimetry data precision level of 10 cms. Local corrections to a mean ballistic arc, perturbed principally by atmospheric drag variations and local gravitational anomalies, are obtained by the introduction of stochastic dynamical models in conjunction with optimal estimation/smoothing techniques. Assessment of the resulting orbit with 'ground truth' provided by Seasat altimetry data shows that the orbital height precision is improved by 32% when compared to a conventional least-squares solution using the same data set. The orbital height precision realized by employing stochastic differential correction models is in the range of 73 cms to 208 cms rms.
    Keywords: ASTRODYNAMICS
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  • 7
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    Publication Date: 2019-06-28
    Description: The Venus Radar Mapper (VRM) mission is sponsored by NASA to put a single spacecraft in orbit around Venus to map the surface of Venus using a synthetic aperture mapping radar. The spacecraft is scheduled to be launched in April 1988 using a Shuttle-Centaur G combination. The spacecraft arrives at Venus in late July 1988 and begins its mapping mission which lasts for one Venus rotation or 243 days. This paper describes the VRM mission at its present state of design. The science objectives and project constraints are described. Key features of the spacecraft system and radar system are discussed. The interplanetary and mapping orbit design are covered. Navigation strategy is explained, including trajectory maneuvers and mapping phase orbit determination. Finally, the mapping sequences to optimize planet coverage are described.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: AIAA PAPER 84-0212
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  • 8
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    Publication Date: 2019-07-13
    Description: Ocean current measurement applications in physical oceanography require knowledge of inertial ship velocity to a precision of 1-2 cm/sec over a typical five minute averaging interval. The navigation accuracy must be commensurate with data precision obtainable from ship borne acoustic profilers used in sensing ocean currents. The Navstar Global Positioning System is viewed as a step in user technological simplification, extension in coverage availability, and enhancement in performance accuracy as well as reliability over the existing systems, namely, Loran-C, Transit, and Omega. Error analyses have shown the possibility of attaining the 1-2 cm/sec accuracy during active GPS coverage at a data rate of four position fixes per minute under varying sea-states. This paper is intended to present results of data validation exercises leading to design of an experiment at sea for deployment of both a GPS y-set and a direct Doppler measurement system as the autonomous navigation system used in conjunction with an acoustic Doppler as the sensor for ocean current measurement.
    Keywords: COMMUNICATIONS AND RADAR
    Type: AIAA PAPER 82-0314 , Aerospace Sciences Meeting; Jan 11, 1982 - Jan 14, 1982; Orlando, FL
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  • 9
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    Publication Date: 2019-07-13
    Description: The navigational accuracy of an oceangoing vessel using conventional GPS p-code data is examined. The GPS signal is transmitted over two carrier frequencies in the L-band at 1575.42 and 1227.6 MHz. Achievable navigational uncertainties of differenced positional estimates are presented as a function of the parameters of the problem, with particular attention given to the effect of sea-state, user equivalent range error, uncompensated antenna motion, varying delay intervals, and reduced data rate examined in the unaided mode. The unmodeled errors resulting from satellite ephemeris uncertainties are shown to be negligible for the GPS-NDS (Navigation Development) satellites. Requirements are met in relatively calm seas, but accuracy degradation by a factor of at least 2 must be anticipated in heavier sea states. The aided mode of operation is examined, and it is shown that requirements can be met by using an inertial measurement unit (IMU) to aid the GPS receiver operation. Since the use of an IMU would mean higher costs, direct Doppler from the GPS satellites is presented as a viable alternative.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Type: AAS PAPER 81-208 , Astrodynamics Specialist Conference; Aug 03, 1981 - Aug 05, 1981; Lake Tahoe, NV; US
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  • 10
    Publication Date: 2019-07-13
    Description: Results of postflight orbit determination for the Mariner 9 trajectory (Mariner-Mars 1971 mission) using Doppler data combined with optical data in the form of TV photographs of the natural satellites and Mars' surface features. It is shown that the combined data yield a solution which is a factor of 3 to 5 better than that obtained from Doppler-only solutions for the node of the orbit relative to the plane perpendicular to the Earth-Mars line. Consequently, these optical data types have a demonstrated potential to significantly improve planetary orbiter navigation accuracies.
    Keywords: NAVIGATION
    Type: AIAA PAPER 74-829 , Mechanics and Control of Flight Conference; Aug 05, 1974 - Aug 09, 1974; Anaheim, CA
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