Exploring the Oceans    Remote Sensing

The Water PlanetOceans in MotionLife in the SeaScientist at SeaResources


Satellite Images

This image represents a 3-dimensional view of ocean surface topography taken by the TOPEX/Poseidon satellite. Fluctuations in sea surface height result from changes in ocean circulation. The total relief of ocean topography is about 2 meters. The mission of this project is to better understand global ocean circulation and its tie to Earth's climate.

Using instruments that are more sensitive than the human eye, satellites measure the fantastic array of colors in the ocean. Different colors may reveal the presence and concentration of phytoplankton, sediments and dissolved organic chemicals which in turn tells us about the health and chemistry of the ocean. Mapping ocean color reveals productive areas, areas where phytoplankton and marine animals are found.

Satellites can measure ocean surface temperatures shown in computer-generated colors. Blue and green represent colder water while red and yellow represent warm water. This image shows the Gulf Stream, a warm ocean current that moves north along the coast of Florida, turning eastward off North Carolina and flowing to the northeast across the Atlantic. It is one of the strongest currents in the ocean.

Because the great area of the world's oceans makes it impossible to equip enough research vessels to study more than a small area of one ocean at one time, and because what happens in any one area of an ocean is dependent on processes at at work in other parts of the world's oceans, oceanographers need the ability to study the oceans as a total system. Oceanographers are using remote sensing via satellites with specialized sensors and measuring devices to provide total ocean surveillance and data on a global scale.

Remote sensing data are usually displayed as images created by a computer. Each data point gathered by a remote sensor represents an individual unit or parcel of Earth's atmosphere or surface. These data points are translated to the grid system of a computer monitor. Thus, remotely sensed images are more like maps than like photographs. In fact, they often contain far more information than maps.

The great advantage of remotely sensed images is that they show considerable environmental detail while also providing the widest possible context. The detail and beauty they reveal have changed our knowledge and our view of the planet. This will continue as the satellites and programs of the Earth Observing System are put into place. The monitoring of global change as part of NASA's Earth Science Enterprise will be of major scientific importance in the next several decades. New satellites and new programs mean vast amounts of new data being collected. These data and their interpretation will help us to find important pieces of the puzzle that oceanographers and other Earth scientists face as they work to develop a better understanding of the linkages between the ocean and other Earth systems.

TOPEX/Poseidon is a partnership between the U.S. and France to monitor global ocean circulation, discover the tie between the oceans and atmosphere, and improve global climate predictions. Every 10 days, the TOPEX/Poseidon satellite measures global sea level with unparalleled accuracy.

The Sea-viewing Wide Field-of-view Sensor (
SeaWiFS) provides quantitative data on global ocean bio-optical properties.


Satellites are useful in tracking sea surface temperatures and currents, but they cannot penetrate below the ocean's surface. New technologies now allow satellites to infer the depth of the ocean. Sonar uses sound waves reflecting back from objects to track schools of fish, locate submerged submarines and map the ocean floor. Try taking ocean soundings yourself!

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