When rocket rose into the sky north of Los Angeles in dazzling evening launch 10 years ago this week, the satellite it carried was destined to usher in new era of space research focusing on unsolved questions of the world's oceans and weather.
The satellite, Seasat, tested payload of advanced sensing instruments. During its 3-1/2-month mission, Seasat collected what scientists have called an explosion of oceanographic information -- comparable to century's worth of observations from fleet of ships.
Because of the way it showed how space sensors could be used in oceanography, Seasat also became parent to new generation of missions planned by handful of countries.
Those missions could provide answers to some of the world's most baffling -- and threatening -- weather phenomena.
Seasat's influence has reached beyond oceanography to affect other research work at JPL. Instruments derived from the 10-year-old mission are due to fly to Venus and Mars on interplanetary probes in next year's Magellan mission and 1992's Mars Observer.
An international symposium celebrating Seasat's launch anniversary will be hosted in London next Tuesday through Thursday (June 28-30) by the British National Space Centre. Gene Giberson, JPL's project manager for Seasat, and Peter Woiceshyn, JPL scientist who has worked on Seasat continuously since its inception, will be featured speakers.
"The impacts Seasat has had on both Earth science studies and even deep-space research at JPL have been remarkable," said Giberson. "This single mission has produced offspring that have shaped the future direction of many of our programs."
Launched on June 26, 1978, on an Atlas-Agena rocket from Vandenberg Air Force Base, Calif., Seasat carried payload of five scientific instruments unlike any package on any previous remote-sensing satellite.
Previous Earth remote-sensing satellites were generally equipped with camera and perhaps one or two other passive instruments.
Seasat, on the other hand, carried complex array of active sensing devices, such as radars and other microwave instruments, to monitor broad range of oceanographic phenomena.
(Passive sensors simply collect natural energy such as sunlight reflected by the Earth -- similar to camera taking pictures in available light. Active sensors such as radars emit energy of their own to collect data -- somewhat like camera equipped with its own flash attachment.)
Among the experimental instruments Seasat pioneered were synthetic aperture radar, which provided highly detailed images of ocean and land surfaces; radar scatterometer, to measure near-surface wind speed and direction; radar altimeter, to measure the height of the ocean surface and waves; and scanning multichannel microwave radiometer, to measure surface temperature, wind speeds and sea ice cover. The satellite also carried passive visual and infrared radiometer to provide supporting data for the other four experiments.
With Seasat's proof that the instruments would work as intended, other projects at JPL and at space centers around the world have borrowed from the mission's concepts.
Key among them is host of international projects scheduled over the next decade to probe the world's oceans and weather in unprecedented detail. Scientists say those missions can help solve currently baffling questions that would provide variety of benefits with possibly enormous cost savings -- and could avert potential disasters.
El Nino, an unusual water warming in the eastern Pacific Ocean in 1982 and 1983, for example, caused billions of dollars in damage and considerable loss of life. Scientists have also been puzzled by an increase of carbon dioxide in the atmosphere, which could have severe consequences on plants and animal life. Missions derived from Seasat are expected to help scientists understand both phenomena.
In addition, the new generation of oceanographic missions is expected to provide important, cost-saving aids for such industries as fishing, shipping and offshore oil production, and for agencies such as the National Oceanic and Atmospheric Administration (NOAA) and the U.S. Navy.
Among the new projects are two NASA efforts managed by JPL -- TOPEX/Poseidon and the NASA Scatterometer (NSCAT).
TOPEX/Poseidon, joint satellite mission with the French space agency, is scheduled for late 1991 launch on an Ariane rocket. It will map the circulation of the world's oceans using radar altimeter.
NSCAT is second-generation instrument being developed to measure wind speed and direction over the oceans' surfaces. proposal to fly NSCAT as part of the payload on Japan's planned Advanced Earth Observation Satellite (ADEOS) is currently under review.
Both TOPEX/Poseidon and NSCAT are intended to support oceanographic studies during the 1990s under the World Ocean Circulation Experiment (WOCE) and the Tropical Oceans Global Atmospheres Experiment (TOGA). These decade- long programs, sponsored by the World Climate Research Program, involve studies at and below the ocean surface in all parts of the world's seas.
Still another U.S. mission whose heritage can be traced to Seasat is Geosat, U.S. Navy satellite launched in 1985 with an altimeter similar to Seasat's.
International projects scheduled for the near future include the European Space Agency's first remote- sensing satellite, Earth Resources Satellite 1 (E-ERS-1), due for launch in 1990; Japan's Earth Resources Satellite 1 (J-ERS-1), scheduled for 1992 launch; Japan's ADEOS, proposed for launch in 1993; and the international Radarsat, a proposed 1994 mission that would be cooperative venture between Canada and the United States.
Seasat's impacts, however, have not been limited to satellite oceanography. Instruments that are direct descendants of those in Seasat's payload have found their way into variety of other NASA missions at JPL.
One of the most prominent is JPL's Shuttle Imaging Radar (SIR), series of synthetic aperture radar experiments flown on NASA's Space Shuttle. They are direct follow-ons of Seasat's synthetic aperture radar, which marked the first time NASA had flown that advanced radar instrument in space.
The first and second experiments in the series -- SIR-A, which flew on shuttle mission in 1981, and SIR-B, shuttle payload in 1984 -- offered scientists several unexpected discoveries. During airborne tests, for example, SIR-A pierced cloud-covered rain forests of Guatemala to reveal previously unknown agricultural canals dug by the ancient Maya. SIR-B "saw" through the sands of Egypt to produce picture of riverbed buried for many centuries.
JPL is currently working on SIR-C, the third SIR experiment, slated for 1991 shuttle mission. Also planned is an advanced radar system that will be flown on an Earth Observing System (Eos) platform as part of NASA's Space Station program in the late 1990s.
A radar like the one first flown on Seasat is also set to go into deeper space on the NASA/JPL Magellan mission to Venus in April 1989. Magellan will use synthetic aperture radar to pierce Venus' dense cloud cover to provide the most complete, highest-resolution images of the planet's surface ever made.
Another planetary mission benefiting from Seasat is Mars Observer, scheduled for launch in 1992. That spacecraft will orbit the red planet to conduct extensive studies of the Martian surface with instruments including an altimeter derived from the Seasat payload.
At JPL, Giberson was Seasat project manager; Dr. James A. Dunne was project scientist. S. W. McCandless Jr. was Seasat program manager at NASA Headquarters in Washington, D.C.
Seasat was funded by NASA's Office of Space Science and Applications.
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