Engineering topics
Christensen, E.
Publications and source records attributed to Christensen, E..
An Overview of the TOPEX/Poseidon Outreach Program
The TOPEX/Poseidon program will observe ocean circulation for 3 to 5 years and monitor the effects of currents on global climate change. To communicate the results of this study to the public, this project will use printed materials, CD-ROM tutorials, a computer network, and lecturers.
Observations of TOPEX/Poseidon Orbit Errors Due to Gravitational and Tidal Modeling Errors Using the Global Positioning System
Satellite altimetry must measure variations in ocean topography with cm-level accuracy. The TOPEX/Poseidon mission is designed to do this by measuring the radial component of the orbit with an accuracy of 13 cm or better RMS. Recent advances, however, have improved this accuracy by about an order of magnitude.
TOPEX/POSEIDON Mission Global Measurements of Sea Level at Unprecendented Accuracy
This paper describes the TOPEX/POSEIDON mission, ...with particular emphasis on measurement capabilities and performance.
TOPEX/POSEIDON Mission - Global Measurements of Sea Level at Unprecedented Accuracy
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TOPEX/POSEIDON Mission Overview
TOPEX/POSEIDON, a space mission jointly conducted by the United States and France, is the first space mission specifically designed and conducted for the study of the circulation of the world oceans.
Observing Geographically Correlated Errors in the Orbit of TOPEX/Poseidon Using GPS
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First Assessment of GPS-Based Reduced Dynamic Orbit Determination of TOPEX/Poseidon
The reduced dynamic tracking technique has been applied for the first time as part of the GPS experiment on TOPEX/Poseidon.
Flat-plate solar array project. Volume 4: High-efficiency solar cells
The High Efficiency Solar Cell Task was assigned the objective of understanding and developing high efficiency solar cell devices that would meet the cost and performance goals of the Flat Plate Solar Array (FSA) Project. The need for research dealing with high efficiency devices was considered important because of the role efficiency plays in reducing price per watt of generated energy. The R&D efforts conducted during the 1982 to 1986 period are summarized to provide understanding and control of energy conversion losses associated with crystalline silicon solar cells. New levels of conversion efficiency were demonstrated. Major contributions were made both to the understanding and reduction of bulk and surface losses in solar cells. For example, oxides, nitrides, and polysilicon were all shown to be potentially useful surface passivants. Improvements in measurement techniques were made and Auger coefficients and spectral absorption data were obtained for unique types of silicon sheets. New modelling software was developed including a program to optimize a device design based on input characteristics of a cell.
Viking Radio Occultation Measurements of the Martian Atmosphere and Topography: Primary Mission Coverage
Radio occultation measurements were made at approximately 50 locations on Mars with the Viking Orbiter 1 S (2.3 GHz) and X (8.4 GHz) band tracking links during October 1976. The measurements have been used to study the topography and atmosphere of Mars at latitudes ranging from about 75 deg S to 70 deg N. By using the ingress and egress times obtained from the observed limb diffraction effects together with the best ephemerides available for the orbiter and the planet we have determined the surface elevations at the occultation points relative to the reference areoid. The observations agree with Mariner 9 and radar data to within 2 km. The mean atmospheric pressure at the areoid level was found to be 5.9 mbar during the northern midsummer season, a value which agrees quite well with data obtained at the landing sites. By comparing the new electron density measurements with earlier Mariner data we have determined that the temperature and the plasma scale height of the upper atmosphere appear to be functions of solar activity.