SEARCH · Search NASA

Results for “TOPEX/POSEIDON”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6

All sources NASA NTRS DOE OSTI

NASA NTRS1990

Navigation accuracies for GPS demonstration on Topex/Poseidon

When Topex/Poseidon, is launched in June 1992, the joint United States/French oceanographic satellite mission will carry a developmental Global Positioning System (GPS) receiver on board to support the planned GPS demonstration experiment. The navigation operations aspect of the demonstration will develop software and operational procedures for the GPS Data Processing Facility (GDPF) at NASA's Jet Propulsion Laboratory. This paper presents simulations and covariance analysis of operational scenarios in support of the GDPF. Multi-orbit filter techniques using GPS carrier phase and P-code pseudo-range are studied both to tune the filter parameters and to determine feasible arc lengths for use in operations. In addition, a baseline operational scenario is presented with performance results given in terms of end-to-end processing times and computational loading based on a prototype version of the operational software.

Williams, B. G.↗

NASA NTRS1990

Gravity field improvement using GPS data from Topex/Poseidon - A covariance analysis

A covariance analysis is performed using a realistic scenario for processing 10 days of GPS data, to obtain the expected improvement to the GEM-T2 gravity field. The gravity bin technique has been refined to compute the covariance matrix associated with the spherical harmonic gravity field. It is shown that the GPS data from one ten-day arc of Topex/Poseidon with no a priori can improve medium degree and order (3-26) sigmas for the parameters in the GEM-T2 gravity field by more than an order of magnitude.

Bertiger, Willy I.↗

NASA NTRS1991

Consideration of permanent tidal deformation in the orbit determination and data analysis for the Topex/Poseidon mission

The effects of the permanent tidal effects of the Sun and Moon with specific applications to satellite altimeter data reduction are reviewed in the context of a consistent definition of geoid undulations. Three situations are applicable not only for altimeter reduction and geoid definition, but also for the second degree zonal harmonic of the geopotential and the equatorial radius. A recommendation is made that sea surface heights and geoid undulations placed on the Topex/Poseidon geophysical data record should be referred to the mean Earth case (i.e., with the permanent effects of the Sun and Moon included). Numerical constants for a number of parameters, including a flattening and geoid geopotential, are included.

Rapp, Richard H.↗

NASA NTRS1990

An augmented MMS MACS for the Topex/Poseidon mission and beyond

The augmented Modular Attitude Control Subsystem (MACS) is described, with emphasis on the significant hardware modifications that have been incorporated into the Landsat MMS (Multimission Modular Spacecraft) MACS design to satisfy the Topex/Poseidon mission attitude control and determination requirements. Particular attention is given to a modification consisting in the addition of an earth pointing safe hold mode utilizing yaw coarse sun sensors to provide a yaw-slew capability for maintaining adequate illumination of the solar array. The design utility of this augmented MACS module for future spacecraft applications is pointed out.

Williams, R. J.↗

NASA NTRS1991

Dynamic attitude command and control of the TOPEX/Poseidon spacecraft

The dynamic control laws utilized by the TOPEX/Poseidon (T/P) spacecraft attitude determination and control subsystem to command and maneuver the satellite during normal mission mode (NMM) laws are described. Results show that the vehicle is able to respond to the dynamic attitude commands while at the same time providing ample disturbance rejection capability.

Zimbelman, D. F.↗

NASA NTRS1991

Ocean topography experiment (TOPEX/Poseidon): Emergency support

The DSN (Deep Space Network) mission support requirements for the Ocean Topography Experiment (TOPEX/Poseidon) and the Global Positioning System (GPS) demonstration are summarized. The TOPEX mission consists of a single spacecraft which will be placed in a high earth circular orbit, with an altitude of 1334 km and a 63-deg inclination. The TOPEX mission objectives are outlined and the DSN support requirements are defined through the presentation of tables and narratives describing the spacecraft flight profile; DSN support coverage; frequency assignments; and tracking support responsibility.

Stiver, R. A.↗

NASA NTRS1992

Structural development of Topex/Poseidon satellite

The Topex/Poseidon satellite's structural development approach adhered to more stringent requirements than previous efforts, since this spacecraft must withstand not only launch/flight loads but also those planned for the 'protoflight' vehicle's structural and environmental tests. There requirements encompassed conservatively estimated design loads, high safety factors, and extensive analytical simulations. The structural adequacy of the satellite was verified by means of a ground testing program to comply with both JPL institutional requirements and Arianespace requirements. Modal survey tests of the satellite have been successfully completed.

Lou, Michael C.↗

NASA NTRS1992

TOPEX/Poseidon orbit acquisition maneuver design

The current baseline injection orbit for the jointly sponsored NASA/CNES TOPEX/Poseidon mission is near-circular, approximately 30 km below the desired operational orbit altitude and at the operational orbit inclination. A baseline maneuver sequence to retarget from this injection orbit to the desired operational orbit has been designed based upon the expected worst-case 3-sigma injection and maneuver execution errors. The sequence requires seven maneuvers, including an initial calibration burn, and achieves the operational orbit with the desired ground track pattern in 30 days. A delay sensitivity analysis has been conducted to estimate the allowable operational delay for each maneuver without increasing the total orbit acquisition period. The baseline sequence provides back-ups for a one-revolution delay for each maneuver and one-day delay for most maneuvers. It is also shown that a higher injection orbit allows the maneuver sequence to achieve the operational orbit in 26 days under a worst-case scenario.

Bhat, Ramachandra S.↗

NASA NTRS1991

Electrical design and analysis of the TOPEX/Poseidon solar array

TOPEX/Poseidon, a scientific satellite to be launched into low earth orbit, will map the surface topography of the earth's oceans. The satellite derives its primary electrical power from a deployable, sun tracking, rigid, single wing, rectangular solar array with overall dimensions of approximately 26 by 11 ft. The requirements which affect the electrical performance of the solar array and the method by which each requirement is satisfied are addressed. The worst-case power calculations used to size the solar array and to verify power capability are discussed. Also included is a detailed description of the solar array configuration and a summary of the qualification and acceptance testing.

Roufberg, Lew↗

NASA NTRS1992

Precision orbit determination for the TOPEX/Poseidon mission

Computation of precise orbits for the TOPEX/Poseidon (T/P) spacecraft is analyzed focusing on gravity field modeling, nonconservative force modeling, satellite tracking technologies, and orbit determination software. It was found that the radial orbit error budget for T/P allows 10 cm rms error due to gravity field mismodeling, 3 cm due to solid earth and ocean tides, and 6 cm due to radiative forces, and 3 cm due to atmospheric drag. It is concluded that the current models are capable of achieving the radial orbit error requirements.

Nerem, R. S.↗

NASA NTRS1992

An assessment of gravity model improvements using TOPEX/Poseidon TDRSS observations

The contribution of TOPEX/Poseidon (T/P) TDRSS data to geopotential model recovery is assessed. Simulated TDRSS one-way and Bilateration Ranging Transponder System (BRTS) observations have been generated and orbitally reduced to form normal equations for geopotential parameters. These normals have been combined with those of the latest prelaunch T/P gravity model solution using data from over 30 satellites. A study of the resulting solution error covariance shows that TDRSS can make important contributions to geopotential recovery, especially for improving T/P specific effects like those arising from orbital resonance. It is argued that future effort is desirable both to establish TDRSS orbit determination limits in a reference frame compatible with that used for the precise laser/DORIS orbits, and the reduction of these TDRSS data for geopotential recovery.

Putney, B. H.↗

NASA NTRS1992

Structural verification of the TOPEX/Poseidon satellite

The prototype flight structural design and verification concept developed for TOPEX/Poseidon is presented. The structural configuration, design requirements, verification plan, analysis, and system level testing are described. The principal goal of the mission is to observe and measure ocean currents via radio altimetry, for enhanced knowledge of the interaction between the atmosphere and ocean.

Larkin, Paul A.↗

NASA NTRS1991

TOPEX/POSEIDON Science Investigations Plan

TOPEX/POSEIDON is a satellite mission that will use the technique of radar altimetry to make precise measurement of sea level with a primary goal of studying the global ocean circulation. The mission represents the culmination of the development of satellite altimetry over the past two decades. The major thrust of the mission is a commitment to measuring seal level with an unprecedented accuracy such that the small-amplitude, basinwide sea level changes that bear significant effects on global change can be detected. The mission will be conducted jointly by the United States National Aeronautics and Space Administration and the French space agency, Centre National d'Etudes Spatiales. The 3- to 5-year mission will study the long-term mean and variability of ocean circulation. This document provides brief descriptions of the planned investigations as well as a summary of the major elements of the mission.

Fulton, David↗

NASA NTRS1991

Geophysical investigations with TOPEX/Poseidon altimetry data

In the proposed research, TOPEX/POSEIDON altimeter data will be used with Geosat and European Remote Sensing satellite (ERS-1) data to compute global, region, and local oceanic geoid surfaces. These observations will then be analyzed to conduct geophysical studies relative to the structure of the oceanic lithosphere and mantle.

Cazenave, Anny↗

NASA NTRS1991

South African TOPEX/Poseidon altimeter experiment

The area surrounding the southern tip of Africa contains a juxtaposition of a variety of interesting and climatically relevant features. On the Indian Ocean side, the Agulhas Current with its tributaries form a conduit through which much of the southern Indian Ocean surface flow is focused. South of the continent, this flow is fragmented and partially injected into the Atlantic Ocean and across the Subtropical Convergence into the Southern Ocean. To the west of the subcontinent, the circulation of the South Atlantic subtropical gyre in the Cape Basin interacts with the vigorous Benguela upwelling regime. The creation, transformation, and transport of water masses and the intra-annual and climatic importance of all these processes have been specifically recognized by the World Ocean Circulation Experiment (WOCE). The South African TOPEX/POSEIDON Altimeter Experiment addresses many of these issues through four mutually complementary and interrelated subprojects.

Gruendlingh, Marten L.↗

NASA NTRS1991

Studies of tropical ocean dynamics using the TOPEX/Poseidon altimeter-derived sea surface topography

Our primary objective is to carry out studies of tropical ocean dynamics using the TOPEX/POSEIDON altimeter-derived sea level data set in conjunction with the large in situ sea level data set available at the Tropical Ocean Global Atmosphere (TOGA) Sea Level Center. These studies will be supported by an interaction with numerical model simulations of tropical ocean variability. Five specific objectives can be identified: (1) research products; (2) short-term climate variations; (3) tropical-current variations; (4) synoptic-scale variability; and (5) model simulations.

Lukas, Roger↗

NASA NTRS1991

Global ocean tide mapping using TOPEX/Poseidon altimetry

The investigation's main goals are to produce accurate tidal maps of the main diurnal, semidiurnal, and long-period tidal components in the world's deep oceans. This will be done by the application of statistical estimation techniques to long time series of altimeter data provided by the TOPEX/POSEIDON mission, with additional information provided by satellite tracking data. In the prelaunch phase, we will use in our simulations and preliminary work data supplied by previous oceanographic missions, such as Seasat and Geosat. These results will be of scientific interest in themselves. The investigation will also be concerned with the estimation of new values, and their uncertainties, for tidal currents and for the physical parameters appearing in the Laplace tidal equations, such as bottom friction coefficients and eddy viscosity coefficients. This will be done by incorporating the altimetry-derived charts of vertical tides as boundary conditions in the integration of those equations. The methodology of the tidal representation will include the use of appropriate series expansions such as ocean-basin normal modes and spherical harmonics. The results of the investigation will be space-determined tidal models of coverage and accuracy superior to that of the present numerical models of the ocean tides, with the concomitant benefits to oceanography and associated disciplinary fields.

Sanchez, Braulio V.↗

NASA NTRS1993

GTARG - The TOPEX/Poseidon ground track maintenance maneuver targeting program

GTARG is a computer program used to design orbit maintenance maneuvers for the TOPEX/Poseidon satellite. These maneuvers ensure that the ground track is kept within +/-1 km with of an = 9.9 day exact repeat pattern. Maneuver parameters are determined using either of two targeting strategies: longitude targeting, which maximizes the time between maneuvers, and time targeting, in which maneuvers are targeted to occur at specific intervals. The GTARG algorithm propagates nonsingular mean elements, taking into account anticipated error sigma's in orbit determination, Delta v execution, drag prediction and Delta v quantization. A satellite unique drag model is used which incorporates an approximate mean orbital Jacchia-Roberts atmosphere and a variable mean area model. Maneuver Delta v magnitudes are targeted to precisely maintain either the unbiased ground track itself, or a comfortable (3 sigma) error envelope about the unbiased ground track.

Shapiro, Bruce E.↗