sands of dollars in prize money are at 

 stake in super-competitive billfish 

 tournaments. Even the commercial 

 fishermen who train their gear on 

 king mackerel use the satellite- 

 generated charts. 



The measurements from space 

 are astonishingly accurate — within 

 1/4 of a degree Fahrenheit — 



ENVIRONMENTAL SCIENCE - 

 MEASURING THE PLANET'S VITAL 

 SIGNS - IS A FAST-EMERGING FIELD 

 FOR SATELLITE TECHNOLOGY. 



ARE 



considering the altitude and speed 

 that the satellites travel. In 14 north- 

 south orbits around the Earth, each of 

 the two satellites scours the entire 

 globe in a day. 



Radiometers on board measure 

 the ocean's emissions of thermal 

 infrared radiation, which is a needle- 

 fine gauge of water temperature, says 

 Emanuele Bohm, a graduate research 

 assistant in the MEAS department 



sea-surface temperatores 

 gathered dy satellite 

 osed to track episodes 

 of red tide that pollote shellfish. 



help predict flooding 

 in the Pamlico and 

 albemarle sounds and 

 monitor the movement of water 

 laden with fish and shrimp larvae. 



and a doctoral candidate in physical 

 oceanography. 



With east-west sweeps that frisk 

 a 1 ,550-mile stretch in one-sixth of a 

 second, the satellites scan the earth in 

 pixels — areas nearly 1 square mile. 

 In the span of 24 hours, each satellite 

 has recorded 1 billion pixels of sea- 



surface, land and cloud-top tempera- 

 tures. 



The final product is not a 

 photograph, but a profile of elec- 

 tronic data that can be charted onto 

 maps showing water masses of 

 different temperatures snaking 

 through the world's oceans. 



Off the North Carolina coast, the 

 single most striking feature of these 

 images — and the most significant 

 to fishermen — is the Gulf Stream, a 

 salty, 80-degree current shown in 

 deep red, jetting north-northeast 

 from Florida. The charts also show 

 gradients of cooler water that ease 

 shoreward from red to yellow to 

 green to the cooler blue waters of the 

 Labrador current dipping south past 

 Virginia. 



These images are critical because 

 fish tend to congregate in nutrient- 

 rich frontal zones where ocean 

 waters of different temperatures and 

 salinities meet but don't mix. 



Also, the prizeworthy billfish 

 follow the Gulf Stream, which has 

 an inherent ability to meander. 

 Warm fingers of the current twist 

 away from its fringes to create prime 

 fishing spots for marlin, wahoo, 

 dolphin fish and king mackerel. And 

 these areas shift with the Gulf 

 Stream as it responds to winds, 

 currents and storm patterns. 



The satellite charts can help 

 fishermen home in on these fishing 

 grounds with an overlay of coordi- 

 nates. 



"A fisherman has a great advan- 

 tage if he doesn't have to go running 

 around the ocean with his hook out," 

 Pietrafesa says. "If he can run 

 around the ocean within an area (1 

 mile square), and he knows that 

 those fish are going to be somewhere 

 between, he has a big advantage. 

 That's a great savings in fuel and 

 time. And if you're a commercial 

 fisherman, that's a real advantage." 



The ability to sample sea-surface 

 temperatures from space has existed 



4 NOVEMBER/DECEMBER 1992 



