NEWPORT, RI Any serious sailor can tell you that the key to winning a boat race is keeping up with the three Ws: winds, weather and water conditions.

So when the worlds top yachters gathered last Friday to participate in this years 635-mile (1,022-kilometer) Newport-to-Bermuda race, it was clear that most had done their homework. But it was also obvious that sailors today are relying not so much on pure skill to chart their courses through treacherous sea waters, but on a relatively new tool: the orbiting satellites.

One of the best "tutors" in the field of ocean satellite imagery is Jenifer Clark, a seasoned oceanographer and one of the first people to ever create maps of the Atlantic out of satellite images. Known to most sailors in the racing world as the "Gulf Stream lady," Clark has made a booming business out of selling satellite measurements of Gulf Stream temperatures, currents and sea-surface heights to sailors prior to important races.

"Im the only person in the world who does this, so my work has been really important to these races," said Clark of her five-year-old business -- Jenifer Clarks Gulfstream. This year, a record 115 boats 60 percent of this years entire Newport-to-Bermuda sailing fleet opted to use her services. At $20 a chart, sailors often spend up to $700 for information prior to any one race. Why are sailors willing to shell out so much for Clarks help? Simply put, she reads the sea like a book.

Clark takes raw data from several Earth-orbiting satellites NASAs TOPEX/Poseidon satellite and the two National Oceanic and Atmospheric Administration (NOAA) polar orbiting satellites and translates them into coded charts of ocean temperatures and heights, which sailors can easily read and use on race day. Months, days and hours before the race, sailors keep close track of Clarks charts, which give them an excellent idea of how the often tempestuous Gulf Stream area will be acting up when they get there.

A typical color-enhanced chart of the Gulf Stream, as presented by Jenifer Clarks Gulfstream

Tracking and navigating around whirling eddies near the Gulf Stream can be the most important part of a sailors preparation because these features are ever changing and crucial to the outcome of the race. Since current speeds within and around warm and cold eddies can be much faster than the speeds of surrounding waters, it often pays for a sailor to position himself way to the side of an eddy in order to take advantage of its favorable currents. But only if a sailor knows precisely where this eddy lies will he be able to take advantage of its flow. This is where Clarks charts can be of tremendous help.

The main satellites being used by Clark are NOAAs polar-orbiting satellites, which circle Earth between only 200 and 300 miles (320 and 480 kilometers) above the surface. Their low altitude allows them to make very detailed measurements of ocean surface temperatures.

"We have two operational satellites, and theyre in a sun-synchronous orbit," said Clarks husband and business partner Dane, who is also Data Services Manager for NOAAs polar orbiters. "These satellites pull energy from the Earth as the radiation is being re-emitted back to space. So what were measuring is actually radiation, but what you calculate is temperature. Then through analysis, youre able to come up with a pattern of where the Gulf Stream is, and where the cold and warm eddies are."

Sailors on this years Newport Bermuda yacht race

The other satellite system Clark uses is the TOPEX/Poseidon satellite, which orbits Earth at about 830 miles (1,340 kilometers). This satellite carries a radar altimeter, which can measure the height of the sea to an accuracy of nearly 2 inches (5 centimeters). It works by transmitting pulses of energy down to the sea and measuring the time it takes for the pulse to bounce back to the satellite.

Unfortunately, because the TOPEX/Poseidon data is presented as a composite of 17 days worth of data, its more useful for researchers like Clark than for sailors themselves. "If you want to get down and dirty with the race course and want to know exactly whats going on, its tough to read a lot is missed in 17 days," said Michael Crowley, director of the Marine Remote Sensing Lab at Rutgers Universitys Institute of Marine and Coastal Sciences.

But the TOPEX/Poseidon data can do one important thing that the NOAA satellites cant: it can "see" through clouds and that means nothing but good news for sailors of this years race and beyond. "Now that I have the altimetry data, I can tell where these features are, whether theres a cloud cover or not," said Clark. "Thats been tremendously helpfulI dont know what Id do without it."