Artificial satellites are objects put into orbit around the Earth and other cellestial bodies. For our purposes, an orbit is a trajectory that is periodic in nature, and does not consider the special case of objects leaving the realm of the body they orbit into interplanetary space. *
Hey, who's there. Oh, it's you again. Have you been surfing our site? Well you should CHECK OUT the other pages, but since you're here come on in. It's a bit "spacey" on this page.. It's all about satellites and oceans. You know what a satellite is, of course....Hm-m-m, You're not sure? Well you're on a satellite right now. Yeah, for real! A satellite is an orbiter--something that travels around another object. Planet Earth is a satellite of--you guessed it--the sun. The gravity of the sun holds us in orbit. Without the gravitaional pull of the sun, we would go zooming out in to space--never-never land. The moon is a satellite of Earth.What do you suppose holds the moon in orbit around Earth? Right! Gravity! Earth and Moon are natural satellites. Humans have learned how to create artificial satellites. Don't let that word "artificial" throw you. The satellites are real. Artificial simply means "not natural" because they are made by humans.
Humans have been putting satellites into orbit for quite some time now. You're probably asking about now--WHY? Satellites are used to help us learn more about something such as the weather, oceans, conditions in outer space, and to spy on other countries. Oops, forget that last one. I will deny having ever said it. You didn't hear it from me. Well, back to satellites...
Before satellites were used to study the ocean, we had to rely on information collected by ships, buoys, tide gauges, and such. This is all covered about two web pages over, so I won't go into details here. So what's the problem you ask? Why did we need to bother with satellites? Well, just think about it! How big is the ocean? The oceans cover about 71% of Earth's surface. For example, if you cut a candy bar into four equal pieces and you took three of the peices and gave your baby brother one of the pieces, you would have the "ocean share" of the candy bar and your baby brother would have the continental (land) share of the candy bar. The surface area (here we go with those math terms) of all the oceans and seas is about 361,254,000 kilometers squared. That's BIG!
THE GYRE
Picture a ship that's not even one kilometer long trying to study all of the ocean. It would take forever to cover that much territory. You would have to do repairs on the ship from time to time, refuel (that's expensive), hire a crew and feed the crew, survive storms at sea, navigate tricky currents and on and on. Satellites on the other hand use solar energy once they are launched into orbit. Old Man Sun hasn't figured out a way to charge us yet for using his "free" solar energy. Satellites are unmanned (no crew to feed or pay--that is if you don't count the ground crew that controls the satellite from the Mission Control Office). From a satellite, the entire surface of the world's oceans can be seen and surveyed (covered) in just a few days. Satellites can sometimes be damaged by particles from the sun, so there are hazards. Both satellites and ships are expensive to build, but once the satellite is employed--we gain a lot of information in a short time at a lot less cost. We still need data collected from ships, buoys, and gauges so we can compare them to the satellite data for accuracy. There are still some things about the ocean that a satellite can't tell us. Perhaps, you will be the scientist of the future who develops an instrument for satellites that will tell us all we want to know. Any way you look at it, Satellite observations have truly revolutionized (changed in a big way) ocean sciences.
(Photo courtesy of CNES-website http://www-aviso.cnes.fr)
Instruments on satellites measure wind, waves, temperature of the sea surface, ocean color, ocean surface currents, and tides. All of these measurements are used to get a clear picture of what is happening in the ocean. Many times oceanographers put the measurements from the satellite into special computer programs called "numerical models." The models calculate (here we go with math again) what is happening deeper inside the ocean. The models also use measurements made from ships and drifting buoys. One such satellite is TOPEX/Poseidon.This "little guy" has mapped the ocean's surface (topography) since August of 1992. T/P (as we affectionately call him) has far exceeded our expectations. He is like the "Ever Ready Rabbit--he just keeps going and going and going. Radar altimeters on TOPEX/Poseidon (T/P) accurately measure the satellite's distance from the ocean's surface and tell us about the ocean's surface currents, winds, and wave-heights.
TOPEX/Poseidon data are used to predict the position of swift currents that appear to be connected with eddies. Eddies are spinning water currents--like a giant whirlpoo the size of West Virginia. Eddies are considered to be the "weather of the oceans." TOPEX/Poseidon revealed multiple eddies both north and south of the Gulf Stream, a major "river" of water coursing through the Atlantic toward Europe. Knowing the locations of eddies can increase the safety of wokers on oil production platforms (rigs) at sea. So you see, T/P may help to save lives by providing this information.
The TOPEX/Poseidon satellite really made headlines during the 1997-98 El Nino. Scientists were able to track this El Nino in a way never before possible--thanks to T/P. Since scientists can't stop El Nino, you may wonder why knowing all this is important. Being able to predict the occurance of El Ninos might lessen their impact. TOPEX/Poseidon covers the entire planet every 10 days--an impossibility for a ship. Although TOPEX/Poseidon has done an outstanding job, it's time to retire him and let his big brother Jason-1 take over. Named for the mythological hero, Jason-1 will help us to understand longer-term changes in our oceans and improve the computer models used to predict climate change. To find out more details about TOPEX/Poseidon and Jason-1, visit them on their own web pages here at Ocean World.
