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At least 73 records · Page 4

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NASA NTRS1976

TDRSS operations control analysis study

The use of an operational Tracking and Data Relay Satellite System (TDRSS) and the remaining ground stations for the STDN (GSTDN) was investigated. The operational aspects of TDRSS concepts, GSTDN as a 14-site network, and GSTDN as a 7 site-network were compared and operations control concepts for the configurations developed. Man/machine interface, scheduling system, and hardware/software tradeoff analyses were among the factors considered in the analysis.

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NASA NTRS1976

TDRSS telecommunications system, PN code analysis

The pseudo noise (PN) codes required to support the TDRSS telecommunications services are analyzed and the impact of alternate coding techniques on the user transponder equipment, the TDRSS equipment, and all factors that contribute to the acquisition and performance of these telecommunication services is assessed. Possible alternatives to the currently proposed hybrid FH/direct sequence acquisition procedures are considered and compared relative to acquisition time, implementation complexity, operational reliability, and cost. The hybrid FH/direct sequence technique is analyzed and rejected in favor of a recommended approach which minimizes acquisition time and user transponder complexity while maximizing probability of acquisition and overall link reliability.

Dixon, R.↗

NASA NTRS1977

Navigation for IUS deployment. TDRSS navigation accuracy in support of IUS deployment, phase 1

The navigation accuracy for tracking the orbiter prior to interim upper stage (IUS) deployment using the tracking data relay satellite system (TDRSS) was studied. The orbiter navigation accuracy for both one and two TDRSS satellites, for short and long data arcs, and for Doppler-only and Doppler-plus range solutions was examined. All test cases were run with the orbiter in a 150-n. mi. circular orbit, 28.5 degree inclination, at the time interval from the completion of the orbital maneuvering system (OMS)-2 maneuver to OMS-2 plus 2 hours (approximate time for IUS deployment). The data used were simulated by the simulation navigation (SIMNAV) program. The software tool used to process the TDRS data was the Shuttle Navigation Analysis Program (SNAP), a Kalman filter tool used to solve for the orbiter position and velocity. Results summarize the expected navigation accuracy using the TDRS system. It was concluded that: (1) data from both TDRS satellites were essential for accurate navigation results: (2) range data were essential for the short arc test case but were not needed for the long arc test case; and (3) with Doppler and range data from both TDRS satellites, the results converged to a reasonable solution after 5 to 10 minutes of data.

Wylie, A. D.↗

NASA NTRS1978

TDRSS system configuration study for space shuttle program

This study was set up to assure that operation of the shuttle orbiter communications systems met the program requirements when subjected to electrical conditions similar to those which will be encountered during the operational mission. The test program intended to implement an integrated test bed, consisting of applicable orbiter, EVA, payload simulator, STDN, and AF/SCF, as well as the TDRSS equipment. The stated intention of Task 501 Program was to configure the test bed with prototype hardware for a system development test and production hardware for a system verification test. In case of TDRSS when the hardware was not available, simulators whose functional performance was certified to meet appropriate end item specification were used.

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NASA NTRS1977

Space Shuttle utilization of TDRSS services

This paper provides a general description of how the tracking and data relay satellite system (TDRSS) will be utilized by the Space Shuttle. The design approaches which were necessitated for both the Shuttle S-band and Ku-band subsystems are functionally described, and current performance estimates are summarized for each communications link. The operational advantages and disadvantages of TDRSS to Shuttle are briefly considered, and both the technical and operational problem areas which have been identified to date are described.

Batson, B. H.↗

NASA NTRS1978

STDN in the TDRSS and Shuttle Era

NASA presently maintains a worldwide system of ground tracking stations to provide communication support (tracking, telemetry and command) to all authorized user spacecraft missions. The set of ground stations supporting earth orbiting missions, and their supporting communication links (called NASCOM) to various NASA centers, is designated as the Spaceflight Tracking and Data Network (STDN). Major users of the STDN in the 1980's include LANDSAT-D, SEASAT-B and the Shuttle, all of which are capable of generating data at rates that cannot be handled by the present STDN ground stations. The expanded capabilities of the STDN in the 1980's to provide support to these missions and other users is addressed. The newest asset of the STDN, the Tracking and Data Relay Satellite System (TDRSS) is described, as are the remaining STDN ground stations (called the GSTDN). The Shuttle communications support is not only for the Shuttle itself, but also for the Spacelab, attached payloads (within the Shuttle bay), and detached payloads being either deployed or retrieved by Shuttle. The specific communications support being provided by STDN (both by TDRSS and by the GSTDN) to the Shuttle is also described.

Schwartz, J. J.↗

NASA NTRS1980

Differential correction capability of the GTDS using TDRSS data

A differential correction (DC) capability was implemented in the Goddard Trajectory Determination System (GTDS) to process satellite tracking data acquired via the Tracking and Data Relay Satellite System (TRDRSS). Configuration of the TDRSS is reviewed, observation modeling is presented, and major features of the capability are discussed. The following types of TDRSS data can be processed by GTDS: two way relay range and Doppler measurements, hybrid relay range and Doppler measurements, one way relay Doppler measurements, and differenced one way relay Doppler measurements. These data may be combined with conventional ground based direct tracking data. By using Bayesian weighted least squares techniques, the software allows the simultaneous determination of the trajectories of up to four different satellites - one user satellite and three relay satellites. In addition to satellite trajectories, the following parameters can be optionally solved: for drag coefficient, reflectivity of a satellite for solar radiation pressure, transponder delay, station position, and biases.

Liu, S. Y.↗

NASA NTRS1979

Satellite time transfer via TDRSS and applications

The satellite time transfer terminal design concept for the Tracking and Data Relay Satellite System (TDRSS) and the application of the time signal in autonomously operated spacecraft clock are presented. Some pertinent TDRSS parameters and corrections for the propagation delay measurement as well as the time code used to transfer the time signal are given.

Chi, A. R.↗

NASA NTRS1980

Analysis of estimation algorithms for autonomous navigation with TDRSS data

Estimation techniques for onboard orbit determination using Tracking and Data Relay Satellite System (TDRSS) data are investigated. The two user satellite orbits studied are similar to Landsat-D (near-circular, 700 kilometers altitude, near-polar inclination). The following estimation algorithms are identified as candidates for use in autonomous navigation: (1) the extended Kalman filter with process noise, (2) the EKF with consider parameters, (3) the sequential Kalman filter with consider parameters, and (4) the batch least-squares differential correction technique. The candidate estimators are evaluated with respect to their performance with both baseline and worst TDRSS measurement errors and tracking configurations.

Dunham, J.↗

NASA NTRS1980

Role of TDRSS in tracking and data acquisition

The integration and operation of the Tracking Data Relay Satellite System (TDRSS) into the NASA Communications Network (NASCOM) equipment and services is described. The system concept employs spacecraft in geosynchronous orbit, operating as communications front-ends, and a single ground terminal, which provides primary tracking and data acquisition services for earth-orbiting user satellites and for the Space Shuttle. The TDRSS system is further characterized by real-time throughput of user data and a high degree of automation.

Spearing, R. E.↗

NASA NTRS1984

Lessons learned during the first year of the TDRSS

The Tracking and Data Relay Satellite System (TDRSS) is the National Aeronautics and Space Administration's (NASA) newest capability for tracking and communicating with NASA's low-earth orbiting scientific and operational satellites. This support will eventually be provided through three identical satellites in geosynchronous orbit. They will relay data through a single ground station located in New Mexico. This paper discusses both the overall TDRSS concept and NASA's experience to date with the first of the three relay satellites on station.

Aller, R. O.↗

NASA NTRS1985

JPL emergency support of TDRSS and compatible satellites

The Tracking and Data Relay Satellite System (TDRSS) will consist of three identical satellites in geosynchronous orbits and a dedicated ground receiving station. The first two satellites (TDRS East and TDRS West) will form the operational TDRS service network providing near-global real-time user satellite coverage. The third TDRS satellite will act as an in-orbit spare. Since the TDRSS satellite are supported by a single ground station, a method of providing emergency support for TDRS and user satellites is needed. The support to be provided by JPL's Deep Space Network is described.

Fanelli, N. A.↗

NASA NTRS1990

One-way return-link Doppler navigation with the Tracking and Data Satellite System (TDRSS) - The ultrastable oscillator (USO) experiment on the Cosmic Background Explorer (COBE)

The principal objectives of the USO experiment on the COBE spacecraft are defined, and results of space qualification studies for the COBE USO experiment are summarized. The principal objectives of the experiment are: (1) to determine flight performance of the USO coupled to the second-generation TDRSS transponder; (2) space qualify TDRSS noncoherent one-way return-link Doppler tracking; and (3) analyze algorithms for one-way navigation with real data. The three objectives of the experiment have been met in the first stage of the experiment analysis.

Dunham, J. B.↗

NASA NTRS1991

TDRSS momentum unload planning

A knowledge-based system is described which monitors TDRSS telemetry for problems in the momentum unload procedure. The system displays TDRSS telemetry and commands in real time via X-windows. The system constructs a momentum unload plan which agrees with the preferences of the attitude control specialists and the momentum growth characteristics of the individual spacecraft. During the execution of the plan, the system monitors the progress of the procedure and watches for unexpected problems.

Cross, George R.↗

NASA NTRS1990

Sensitivity of high-accuracy Tracking and Data Relay Satellite System (TDRSS) user spacecraft orbit determination to tracking schedules

The results of a study to analyze the dependence of TDRSS user spacecraft orbit determination consistencies on varying tracking schedules are presented. In this study, the TDRS-East orbit determination results obtained utilizing Bilateration Ranging Transponder System data were evaluated. Six state parameters, three position and three velocity components and the solar radiation pressure coefficient, are estimated for TDRS-East. It is concluded that, in order to achieve high-precision orbit determination, the tracking coverage should not fall below 10 minutes every two orbits as decreasing it to every four orbits will significantly degrade the accuracy; present state-of-the-art consistency in orbit determination using TDRSS tracking is approximately 15 to 20 meters.

Doll, C. E.↗

NASA NTRS1990

Success of the Tracking and Data Relay Satellite System (TDRSS)

The paper provides historical data and presents two parameters for evaluating the success of the Tracking and Data Relay Satellite System (TDRSS). The TDRSS provides high rate data from missions such as the Shuttle and Landsats, and lower rate data from missions such as the Solar Mesosphere Explorer and the Earth Radiation Budget Satellite. Two parameters have been established as measurements of the ability of the system to transmit user commands and telemetry data, i.e., availability and proficiency. Availability is the system's readiness to support any and all user requirements 24 hours per day, 7 days per week. Proficiency is the ratio of actual support provided to scheduled support.

Harris, David W.↗

NASA NTRS1991

Cosmic background explorer (COBE) navigation with TDRSS one-way return-link Doppler in the post-helium-venting phase

A navigation experiment was performed which establishes Ultra-Stable Oscillator (USO) frequency stabilized one way return link Doppler TDRSS tracking data as a feasible option for mission orbit determination support at the Goddard Space Center Flight Dynamics Facility. The study was conducted using both one way and two way Tracking and Data Relay Satellite System (TDRSS) tracking measurements for the Cosmic Background Explorer (COBE) spacecraft. Tracking data for a 4 week period immediately follow the depletion of the helium supply was used. The study showed that, for both definitive orbit solution and short term orbit prediction (up to 4 weeks), orbit determination results based on one way return link Doppler tracking measurements are comparable to orbit determination results based on two way range and two way Doppler tracking measurements.

Nemesure, M.↗

NASA NTRS1991

Ionospheric refraction effects on TOPEX orbit determination accuracy using the Tracking and Data Relay Satellite System (TDRSS)

This investigation concerns the effects on Ocean Topography Experiment (TOPEX) spacecraft operational orbit determination of ionospheric refraction error affecting tracking measurements from the Tracking and Data Relay Satellite System (TDRSS). Although tracking error from this source is mitigated by the high frequencies (K-band) used for the space-to-ground links and by the high altitudes for the space-to-space links, these effects are of concern for the relatively high-altitude (1334 kilometers) TOPEX mission. This concern is due to the accuracy required for operational orbit-determination by the Goddard Space Flight Center (GSFC) and to the expectation that solar activity will still be relatively high at TOPEX launch in mid-1992. The ionospheric refraction error on S-band space-to-space links was calculated by a prototype observation-correction algorithm using the Bent model of ionosphere electron densities implemented in the context of the Goddard Trajectory Determination System (GTDS). Orbit determination error was evaluated by comparing parallel TOPEX orbit solutions, applying and omitting the correction, using the same simulated TDRSS tracking observations. The tracking scenarios simulated those planned for the observation phase of the TOPEX mission, with a preponderance of one-way return-link Doppler measurements. The results of the analysis showed most TOPEX operational accuracy requirements to be little affected by space-to-space ionospheric error. The determination of along-track velocity changes after ground-track adjustment maneuvers, however, is significantly affected when compared with the stringent 0.1-millimeter-per-second accuracy requirements, assuming uncoupled premaneuver and postmaneuver orbit determination. Space-to-space ionospheric refraction on the 24-hour postmaneuver arc alone causes 0.2 millimeter-per-second errors in along-track delta-v determination using uncoupled solutions. Coupling the premaneuver and postmaneuver solutions, however, appears likely to reduce this figure substantially. Plans and recommendations for response to these findings are presented.

Radomski, M. S.↗