Pertaining to the use of semiconductors rather than electromechanical relays and electron tubes.
The Deep Space Network (DSN) is a NASA’s primary tracking and communications system which is under the system management and technical direction of the Jet Propulsion Laboratory (JPL) in Pasadena, California. The DSN is formed by a group of worldwide ground stations and designed for two-way communications with unmanned spacecraft traveling approximately 16,000 km (10,000 miles) from Earth to or beyond the outermost planets through 26 m antennas. There are three primary DSN stations in the world. They are located in Goldstone California, Madrid Spain and Canberra (Tidbinbilla) Australia, one of which is always in view of an orbiting spacecraft for the continuous tracking. č go to DSN Home Page (http://deepspace1.jpl.nasa.gov/dsn/)
NASA Communications (NASCOM) Network is a global telecommunication system operated by NASA Communications Division, which provides support for all NASA projects. The primary switching and control center is located at the NASA Goddard Space Flight Center (GSFC) in Greenbelt, Maryland and it manages all its communications links along with secondary switching and control centers, which are located in Madrid Spain, Canberra Australia, Jet Propulsion Laboratory (JPL) California, Kennedy Space Center (KSC) Florida.
When the orbit of a spacecraft is synchronized to the rotation of the Earth, the spacecraft seems to be "fixed" in space over the same spot on the surface of the Earth. The spacecraft is in what known as a geosynchronous Earth orbit (GEO). Especially when the orbit is equatorial, the spacecraft seems to be "fixed" over one spot on the equator. The spacecraft in what known as a geostationary orbit. Thus, a geostationary orbit is a special case of a geosynchronous orbit.
The inclination "i" is the angle between the K -axis and the angular momentum vector H, that is, the angle of the orbital plane with respect to the equatorial plane. The inclination angle is measured counterclockwise and it ranges from 0 to +180 degree. When i = 0 or +180 degree, the orbit is an equatorial orbit. When 0 < i < 90 degree, the spacecraft orbits eastward and its orbit is called a direct (or prograde) orbit . When i = 90 degree, the orbit is a polar orbit. When 90< i < 180 degree, the spacecraft orbits westward and its orbit is called a retrograde orbit.
The semi-major axis is a constant that defines the size of the conic orbit. In the case of TOPEX /Poseidon, it is approximately equal to the radius of its orbit, which is 7714 km (4793 miles) [radius of the Earth plus altitude] because it is almost circular.
The Geophysical Data Records (GDR) is the science data that contains sea surface height, sensor corrections, and geophysical information.
Ocean (or sea surface) topography is the shape of a ocean surface that shows "hills and valleys" of the ocean that come with the currents, more technically, the height difference between the mean sea level and the geoid.
The (ocean) geoid is the equipotential surface that corresponds to the mean sea level. Roughly speaking, it is the average sea level of an ocean at rest which is influenced by the gravitational potentials of the Earth and the Moon.
The periodic rise and fall of sea level resulting from gravitational interactions between the Sun, Moon, and Earth.
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This page is created by Masaharu Suzuki The University of Texas at Austin