Engineering topics

Menard, Yves

Publications and source records attributed to Menard, Yves.

6 records

NASA NTRS2005

Seasat--A 25-Year Legacy of Success

Thousands of scientific publications and dozens of textbooks include data from instruments derived from NASA's Seasat. The Seasat mission was launched on June 26, 1978, on an Atlas-Agena rocket from Vandenberg Air Force Base. It was the first Earth-orbiting satellite to carry four complementary microwave experiments--the Radar Altimeter (ALT) to measure ocean surface topography by measuring spacecraft altitude above the ocean surface; the Seasat-A Satellite Scatterometer (SASS), to measure wind speed and direction over the ocean; the Scanning Multichannel Microwave Radiometer (SMMR) to measure surface wind speed, ocean surface temperature, atmospheric water vapor content, rain rate, and ice coverage; and the Synthetic Aperture Radar (SAR), to image the ocean surface, polar ice caps, and coastal regions. While originally designed for remote sensing of the Earth's oceans, the legacy of Seasat has had a profound impact in many other areas including solid earth science, hydrology, ecology and planetary science.

Scanning Multichannel Microwave Radiometer↗

NASA NTRS1994

TOPEX/POSEIDON mission overview

TOPEX/POSEIDON is the first space mission specifically designed and conducted for studying the circulation of the world's oceans. A state-of-the-art radar altimetry system is used to measure the precise height of sea level, from which information on the ocean circulation is obtained. The satellite, launched on August 10, 1992, has been making observations of the global oceans with unprecedented accuracy since late September 1992. To meet the stringent measurement accuracy required for ocean circulation studies, a number of innovative improvements have been made to the mission design, including the first dual-frequency space-borne radar altimeter capable of retrieving the ionospheric delay of the radar signal, a three-frequency microwave radiometer for retrieving the signal delay caused by the water vapor in the troposphere, an optimal model of the Earth's gravity field and multiple satellite tracking systems for precision orbit determination. Additionally, the satellite also carries two experimental instruments to demonstrate new technologies: a single-frequency solid-state altimeter for the technology of low-power, low-weight altimeter and a Global Positioning System receiver for continuous,precise satellite tracking. The performance of the mission's measurement system has been tested by numerous verification studies. The results indicate that the root-sum-square accuracy of a single-pass sea level measurement is 4.7 cm for the TOPEX system and 5.1 cm for the POSEIDON system; both are more than a factor of 2 better than the requirement of 13.7 cm. This global data set is being analyzed to improve understanding of the global ocean circulation as well as the ocean tides, geodesy, and geodynamics, and ocean wind and waves. The mission is designed to last for at least 3 years with a possible extension to 6 years. The multiyear global data set will go a long way toward understanding the ocean circulation and its variability in relation to climate change. A summary of the mission's systems and their performance as well as the mission's science team is presented.

Fu, Lee-Lueng↗

NASA NTRS1991

The western Mediterranean Sea: An area for a regional validation for TOPEX/Poseidon and a field for geophysical and oceanographic studies

The research project has two kinds of objectives. The first is focused on the regional validation of the altimeter, orbit, and mean sea surface; it will be performed in close cooperation with the local validation performed at Lampedusa/Lampione (Italy). The second deals with the geophysical and oceanographic research of interest in this area.

Barlier, Francois↗

NASA NTRS1991

Assimilation of altimeter topography into oceanic models

The primary goals of the authors are to build an intuition for assimilation techniques and to investigate the impact of variable altimeter topography on simple or complex oceanic models. In particular, applying various techniques and sensitivity studies to model and data constraints plays a key role. We are starting to use quasi-geostrophic, semigeostrophic, and primitive-equation (PE) models and to test the schemes in regions of interest to the World Ocean Circulation Experiment (WOCE), as well as in the northeast Atlantic and the Mediterranean. The impact of scatterometer wind forcing on the results is also investigated. The use of Geosat, European Remote Sensing satellite (ERS-1), and TOPEX/POSEIDON altimetry data is crucial in fine tuning the models and schemes to the selected areas of interest.

Demey, Pierre↗

NASA NTRS1991

Geophysical validation of TOPEX/Poseidon altimetry products

The objectives of this study are the following: (1) to assess the quality of the sea level observed by altimetry on a global scale, especially in tropical regions where the atmospheric effects are the most critical, and to prepare the altimeter data for their assimilation into tropical Oceanic General Circulation Models; and (2) to validate and calibrate the altimeter-derived sea state parameters, to assimilate these parameters into numerical models, and to estimate the altimeter's sea state and electromagnetic biases.

Menard, Yves↗

NASA NTRS1991

Study of mass and heat transport of the tropical Atlantic Ocean using models and altimeter data

The specific objectives of this proposal are: (1) to assess the quality of the TOPEX/POSEIDON surface altimeter data in regard to its use for a large, low-frequency monitoring of the surface topography of the tropical Atlantic Ocean; (2) to develop a method, on a demonstration basis, to derive from the tropical Atlantic the depth of the thermocline and the heat content changes from the surface altimeter data field; (3) to develop a method of assimilation of altimeter data into Oceanic General Circulation Models (OGCM's) for the purpose of preparing an operational, permanent, three-dimensional now casting of the tropical Atlantic Ocean (a TOGA objective); and (4) to derive from these models global circulation fields and a time series of mass and meridional heat transports across the tropical Atlantic region (a WOCE objective).

Merle, Jacques↗