Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Satellite”

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.

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

At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

A 15.3 GHz satellite-to-ground diversity experiment utilizing the ATS-5 satellite

During 1970 and 1971 the characteristics of a diversity satellite-to-ground communication link were measured using the ATS-5 15.3 GHz downlink. These data were gathered at two ground receiving terminals spaced 4 km apart during 1970 and 8 km apart during 1971 in the vicinity of Columbus, Ohio. These data have been subsequently analyzed to determine the improvement in link performance resulting from the use of space diversity. The results of this analysis have shown that substantial improvements in link performance may be gained through the use of space diversity on satellite-to-ground paths. For example, the durations of fades having depths exceeding 10 dB were reduced by more than two orders of magnitude for both the 4 and 8 km site separation distances.

Hodge, D. B.↗
NASA NTRS1974

Doppler factors in satellite-to-satellite tracking

The Doppler factors occurring in range rate satellite-to-satellite tracking measurements are derived with special relativistic effects included. The error resulting from the use of simplified expressions for these factors is discussed.

Marini, J. W.↗
NASA NTRS1974

GEOS-C orbit determination with satellite to satellite tracking

The feasibility of employing satellite to satellite tracking in lieu of ground based tracking to satisfy the orbit determination requirements of the GEOS-C mission was studied. It is shown that with proper estimation procedures it is possible to obtain from S.S.T. data a GEOS-C orbit whose altitude error averages about 1 meter. The usefulness of this type for geopotential recovery is also indicated.

Argentiero, P.↗
NASA NTRS1974

A 15.3 GHz satellite-to-ground path-diversity experiment utilizing the ATS-5 satellite

During several months in 1970 and 1971, the characteristics of a diversity satellite-to-ground communication link were measured using the ATS-5 15.3 GHz downlink. These data were gathered at two ground receiving terminals spaced 4 km apart during 1970 and 8 km apart during 1971 in the vicinity of Columbus, Ohio. These data have subsequently been analyzed to determine the improvement in link performance resulting from the use of space diversity. The results of this analysis have shown that substantial improvements in link performance may be gained through the use of space diversity on satellite-to-ground paths. For example, the durations of fades having depths exceeding 10 dB were reduced by more than two order of magnitude for both the 4 and 8 km site separation distances.

Hodge, D. B.↗
NASA NTRS1970

Multipath study for a low altitude satellite utilizing a data relay satellite system

Technical considerations associated with a low altitude satellite operating in conjuction with a data relay satellite system are reported. Emphasis was placed on the quantitative characterization of multipath phenomenon and determination of power received via both the direct and earth reflection paths. Attempts were made to develop a means for estimating the magnitude and nature of the reflected power.

Eggert, D.↗
NASA NTRS1974

Orbit-spectrum sharing between the fixed-satellite and broadcasting-satellite services at 12 GHz

This paper identifies and evaluates strategies for sharing the geostationary orbit in the band 11.7 to 12.2 GHz between domestic systems in the fixed-satellite and broadcasting-satellite services. The effectiveness of two distinct types of sharing strategies, referred to as spectrum division and orbit division, is determined for various deployments of selected baseline systems representing the two services and for various combinations of sharing tactics such as frequency interleaving, crossed-polarization operation, and crossed-beam operation. Effectiveness is measured by the 'utilization factor', defined as the number of channels provided by the baseline systems when using an assigned share of the orbit-spectrum resource, relative to what they could provide if given the entire resource. Computer simulation is used to verify the intra- and interservice interference compatibility of the assumed deployments. It is concluded that total utilization factors close to 100 percent can be achieved with both spectrum-division and properly-chosen orbit-division strategies.

Reinhart, E. E.↗
NASA NTRS1975

Recovery of atmospheric refractivity profiles from simulated satellite-to-satellite tracking data

Techniques for recovering atmospheric refractivity profiles from simulated satellite-to-satellite tracking data are documented. Examples are given using the geometric configuration of the ATS-6/NIMBUS-6 Tracking Experiment. The underlying refractivity model for the lower atmosphere has the spherically symmetric form N = exp P(s) where P(s) is a polynomial in the normalized height s. For the simulation used, the Herglotz-Wiechert technique recovered values which were 0.4% and 40% different from the input values at the surface and at a height of 33 kilometers, respectively. Using the same input data, the model fitting technique recovered refractivity values 0.05% and 1% different from the input values at the surface and at a height of 50 kilometers, respectively. It is also shown that if ionospheric and water vapor effects can be properly modelled or effectively removed from the data, pressure and temperature distributions can be obtained.

Murray, C. W., Jr.↗
NASA NTRS1976

Interactions of satellite-speed helium atoms with satellite surfaces. 2: Energy distributions of reflected helium atoms

Energy transfer in collisions of satellite-speed (7,000 m/sec) helium atoms with a cleaned 6061-T6 satellite-type aluminum surface was investigated using the molecular-beam technique. The amount of energy transferred was determined from the measured energy of the molecular-beam and the measured spatial and energy distributions of the reflected atoms. Spatial distributions of helium atoms scattered from a 6061-T6 aluminum surface were measured. The scattering pattern exhibits a prominent backscattering, probably due to the gross surface roughness and/or the relative lattice softness of the aluminum surface. Energy distributions of reflected helium atoms from the same surface were measured for six different incidence angles. For each incidence angle, distributions were measured at approximately sixty scattering positions. At a given scattering position, the energy spectra of the reflected helium atoms and the background gas were obtained using the retarding-field energy analyzer.

Liu, S. M.↗
NASA NTRS1976

Probing the earth's gravity field using Satellite-to-Satellite Tracking (SST)

Satellite-to-Satellite (SST) tests, namely: (a) the ATS-6/GEOS-3 and (b) the ATS-6/Apollo-Soyuz experiment and some of the results obtained are described. The main purpose of these two experiments was first to track via ATS-6 the GEOS-3 as well as the Apollo-Soyuz and to use these tracking data to determine (a) both orbits, that is, ATS-6, GEOS-3 and/or the Apollo-Soyuz orbits at the same time; (b) each of these orbits alone; and (c) test the ATS-6/GEOS-3 and/or Apollo-Soyuz SST link to study local gravity anomalies; and, second, to test communications, command, and data transmission from the ground via ATS-6 to these spacecraft and back again to the ground. The Apollo-Soyuz Geodynamics Experiment is discussed in some detail.

Vonbun, F. O.↗
NASA NTRS1975

GEOS-C orbit determination with satellite to satellite tracking

This report studies the feasibility of employing satellite to satellite tracking in lieu of ground based tracking to satisfy the orbit determination requirements of the GEOS-C mission. It is shown that with proper estimation procedures it is possible to obtain from S.S.T. data a GEOS-C orbit whose altitude error averages about 1 meter. The usefulness of this data type for geopotential recovery is also indicated.

Argentiero, P.↗
NASA NTRS1975

ATS-6 - Satellite-to-satellite tracking and data relay experiments

The paper describes the utilization of ATS-6 to relay tracking and telemetry data from Geos-5 and then from Nimbus-6. The experiment configuration consists of a ground station which receives data from ATS-6 through C-band links; ATS-6, in turn, transmits command data and receives telemetry data from the low-orbit satellites through S-band links. The ground and satellite equipment are described along with results of ground tests.

Schmid, P. E.↗
NASA NTRS1977

Probing the earth's gravity field by means of satellite-to-satellite tracking

Two satellite-to-satellite tracking (sst) tests are described in detail: (1) the ATS-6/Geos-3 and (2) the ATS-6/Apollo-Soyuz experiment. The main purpose of these two experiments was to track via ATS-6 the Geos-3, as well as the Apollo-Soyuz and to use these tracking data to determine both of the orbits at the same time, each of the orbits alone, and to test the two sst links to study local gravity anomalies. A second purpose was to test communications, command and data transmission from the ground via ATS-6 to these spacecraft and back again to the ground.

Vonbun, F. O.↗
NASA NTRS1977

Coordinated rocket and satellite measurements of an auroral event. I - Satellite observations and analysis

Results of a coordinated auroral experiment involving the Atmosphere Explorer C satellite and a sounding rocket are reported. Auroral primary electron fluxes and neutral gas densities measured by instruments on the satellite are used in a model calculation of the thermospheric manifestation of the aurora. There is encouraging agreement between the calculated and measured electron density, electron temperature, secondary electron flux, and O I emissions at 5577 and 6300 A. A discrepancy between the calculated and the rocket-measured 3914-A emission profile is discussed in terms of experiment geometry and auroral physics. The coordinated measurements are used to infer vertical fluxes of ionization and of electron thermal energy at high altitudes

Rees, M. H.↗