Down to Earth : JPL Radar Project on Shuttle Sets Its Sights Homeward


Outer space is the Jet Propulsion Laboratory’s usual playground, where its planetary probes rendezvous with asteroids, piggyback on the solar wind and zip to the fringes of the solar system. But these days, the NASA agency’s high-tech wizardry is rediscovering an old world--planet Earth.

In an unlikely twist for a space agency, JPL’s new Spaceborne Imaging Radar, or SIR-C, is turning its focus homeward as part of NASA’s Mission to Planet Earth, a $1-billion project created to study the global environment on what scientists say is an unprecedented scale. Starting today, the $360-million radar system embarks aboard the space shuttle Endeavour on the second of three trips to send back striking images from our own back yard: a tropical rain forest in Mexico, volcanoes in the western Galapagos Islands, and the habitat of endangered mountain gorillas in war-torn Rwanda.

“We just cannot wait until most of the tropical forests are gone before we do something about it,” said Charles Elachi, assistant lab director of JPL in Pasadena. “We cannot wait until the ozone layer is mostly destroyed before we do something about it. . . . If we are to be a good custodian of our planet for the next generation, or the generation after that, we must really understand what we’re doing to our planet.”



SIR-C is unique in its ability to work on three frequencies, allowing scientists to probe an area with three different looks at the same image. SIR-C is the world’s most advanced civilian radar, capable of penetrating clouds, vegetation, ice, dry sand, soil and darkness.

By comparison, other radars work only on a single frequency. The difference, experts say, is like looking at an X-ray instead of a photograph.

And for the first time, SIR-C will produce high-resolution images of the world as a single ecosystem, showing how land, water, carbon and heat interact.

SIR-C’s projects include a look at the Sierra Nevada snowpacks to determine how much water is inside. Eventually, researchers hope to be able to tell how much runoff water is available, how fast the snow melts and how quickly the soil absorbs the water. With that information, farmers could decide which crops are best to plant and when.

In another case, scientists play Indiana Jones, aiming the radar at the once-lost Arabian city of Ubar, probing under the shifting desert sands for clues on what life was like nearly 5,000 years ago.

The fortress city, celebrated in the Koran and “A Thousand and One Arabian Nights” as a shipping center for frankincense, was discovered in December, 1991. A Los Angeles-based team of amateur and professional archeologists made the find with the help of another JPL radar system--a precursor to the one flying on Endeavour.

And from Rwanda, the radar will produce images of the endangered mountain gorilla’s mist-shrouded forest, where the shy animals rummage for berries, wild celery and stinging thistles. Until now, researchers in the remote region have been armed only with outdated maps from the 1950s and handwritten notes from naturalist Dian Fossey, whose story was told in the movie “Gorillas in the Mist.” Fossey, who was murdered in 1985, used enlarged copies of crude forest maps--ones that lacked contours--and marked the gorilla’s movements with a pen. For the first time, the radar images, along with satellite data, will help researchers make a comprehensive analysis of the gorillas’ movements and habits.

“It’s an incredible difference in terms of the kinds of research questions that can be asked. . . (instead of) an individual researcher sitting in the bamboo forest with a Xerox map and a felt-tip pen,” said Scott Madry, a Rutgers University researcher who works with the executive director of the Dian Fossey Gorilla Fund.


In such cases, the radar casts JPL in an unexpected role as global eco-warrior--a shift that some say is overdue.

“For many of us, even those of us who have a great interest in space, we’ve been regularly astounded on the amount of time (is spent) looking beyond our own planet for planetary exploration when there’s still a lot to learn about our own planet,” said Cynthia Rust, a spokeswoman for Greenpeace in San Francisco.

Other projects have focused only on parts of the ecosystem. In 1993, NASA’s Nimbus-7 satellite found that global ozone levels were 2% to 3% lower than any previous year. In another NASA project, satellite observations confirmed last year that Mt. Pinatubo’s eruption in June, 1991, resulted in a temporary cooling of the Earth by about 1 degree.

JPL worked on the radar project with the German and Italian space agencies, which together put up half the cost; NASA funded the other half, or $180 million. SIR-C’s 23,100-pound antenna is the biggest piece of flight hardware ever built at JPL.



In most cases, SIR-C can peer deep into the Earth--beneath thick vegetation canopies, through cloud cover, under desert floors--and reveal previously inaccessible regions.

A 52-member international science team is still studying data from April’s mission, which probed 5% of the world’s land surface, said JPL scientist Diane Evans, the U.S. project leader.

In April, the radar flew aboard Endeavour (results have not yet been released) and was scheduled to fly again in August over most of the same 400 sites to measure seasonal differences. But a last-minute glitch forced NASA to abort the flight from Cape Canaveral, Fla., and reschedule the 10-day mission. A third flight is proposed for January, 1996.


The radar’s targets include last fall’s Los Angeles burn areas, for a global study on how fires affect vegetation, and the Missouri River flood areas from 1993, for research on how the environment recovers from floods. Among the 19 “super sites,” or high-priority targets during the 10-day mission, are four U.S. locations, including Death Valley’s Andes Mountains for a study on climate changes.

Space exploration is still a NASA priority, but at the same time, NASA Administrator Daniel S. Goldin has named Mission to Planet Earth as one of the agency’s top five projects. In fact, since the agency began work on the project in 1991, 25% of JPL’s work has been devoted to it.

Besides the radar project, Mission to Planet Earth includes 27 projects through 2000. Other projects include the use of shuttle-based lasers to study the atmosphere and a radar satellite that will study icebergs and oceanography in the Arctic Ocean.

Earth science is the fastest growing part of NASA, said Charles Kennel, associate administrator for Mission to Planet Earth, on leave as a UCLA physics professor. The mission started with a $668-million budget; its 1995 budget is expected to be $1.2 billion.


NASA is getting more involved in Earth projects as the planet’s problems worsen, Kennel said.

Still, Greenpeace’s Rust said, NASA is only taking a first step.

“Perhaps,” she said, “the money might be better spent on cleaning up some of the messes and developing some of the ecological alternatives to maintaining the ecosystem rather than documenting its decline.”