It is 8 a.m. at NASA's sprawling Jet Propulsion Laboratory in Pasadena, Calif. Five scientists, one of them Carl Sagan, are huddled over a TV monitor in a stuffy cubicle. As blurry images of the moons of Saturn appear, the air crackles with scientific exchange.

"There's your first violet. I'll do a P-stretch."

"Here's your friend methane!"

"You still have the same hot corner."

"The particle flux may be more important than the UV because the UV absorption of methane down at 1,200 angstroms isn't going to be all that great."

"Oh, wow! Holy smoke!"

An hour passes in animated discussion of such arcana as "ring occupation," "neutral hydrogen" and "large-particle bombardment." Then someone says, "Okay, Carl, it's the end of the pack; we're going back to raw." The screen dissolves into emptiness. "Wait!" Sagan jokes, pointing at the blank monitor. "Let's linger on that one awhile!"

It's 3:39 the next morning. A red-eyed Sagan is propped in a chair waiting to be cued for a live interview with David Hartman in New York on Good Morning America. Just before air time Sagan waves distractedly at the TV monitor and notices with fascination that there is a 1¼-second delay before his image waves back. Sagan promptly calculates the distance in space of the satellite transmitting his image to New York and back. "It's almost the exact time delay as that of an astronaut on the moon sending a message down to earth," he informs the camera crew. Then producer Howie Masters announces, "Okay, Carl, put on your happy face." Suddenly Sagan is transformed. He is wide-awake, enthusiastic, both ingratiating and formidably articulate as he briefs Hartman and a sleepy nation on the results of Voyager I's trip to Saturn.

Carl Sagan has never won a Nobel Prize and probably never will. Even his admirers concede that his best scientific work is solid but not distinguished. Yet, at 46, Sagan is beyond a doubt the most famous scientist in the world. More important, he is a teacher equally at home working with colleagues on the "imaging" team analyzing photos transmitted from Voyager I or lecturing a national television audience. Three of his books on science became best-sellers and one (The Dragons of Eden) was awarded the Pulitzer Prize. His $10.5 million series Cosmos is drawing the largest audience of any program in public television history. Last month his spinoff book from the series entered the New York Times best-seller list at No. 1, an astonishing feat for a relatively demanding volume priced at $19.95.

In Pasadena, Sagan was less a scientific celebrity than a working scientist. He has participated in NASA's unmanned space flights since they began in 1960. Early on, he contributed fundamental studies that explained the nature of Mars' dusty surface and the hot, gaseous atmosphere of Venus. "Carl has a tremendous advantage," says Ed Danielson, his colleague on the Saturn photo team, "because he straddles three areas of study: Saturn's rings, atmosphere and satellites. Our disadvantage is that we only get a small percentage of his time." Indeed, during the week-long Voyager flyby Sagan had to juggle his time in the imaging lab with media commitments. He starred in an hour-long live telecast to Japan, sat for interviews on ABC's Nightline, headlined a cable-TV seminar with Ray Bradbury, hosted a dinner for the Planetary Society and shot a recruiting film for Cornell, where he teaches.

As a paladin of the planets, Sagan has so won over amateur astronomers like Johnny Carson that he is the Tonight show's intellectual in residence (and was recently the butt of a friendly Carson spoof). Exposure like that has assured Sagan celebrity status. So has his lifestyle. He is a vigorous, boyishly handsome man who has been through two marriages and spent much of the past three years in airplane seats (first-class, by the window, no smoking) while on leave from Cornell. The license plate on his orange Porsche bears the name of his favorite Martian moon, PHOBOS. He is shadowed everywhere by a full-time secretary, 52-year-old Shirley Arden, who maternally guards his schedule and supplies him with such amenities as fluffy towels, baby shampoo and chocolate bars (Sagan is an unregenerate chocaholic).

Inevitably, Sagan's public success has drawn crossfire. "His talent for popularization is quite unusual in science," observes JPL director Bruce Murray, "so it carries some bitter fruit among elitists." Noting Sagan's sanctimonious manner and rhapsodic delivery on Cosmos, some critics longed for the more detached urbanity of an Alistair Cooke. One friend jokingly called the show "Carl Cosmos' Sagan." In some scientific circles he is suspected of being more interested in Sagan than science. "He can be arrogant and a pain in the ass," says one former colleague, who takes refuge in anonymity. The more common view is that Sagan's critics are simply jealous. "Many scientists are envious of Carl," says planetary geologist Larry Soderblom. "Most of them come across in the media like a pot of old dishwater. Quite honestly, I think his time is better spent popularizing, because he's so skilled and we need it."

Sagan tries valiantly to bridge the two worlds—with immense drive, among other things. During the Saturn project, he stayed at JPL 60 hours at a stretch, catnapping on sofas. In his crusade to bring science to the public he is nothing short of messianic. "The primary objective of Cosmos was to show that science is a delight and to end people's artificial alienation from it," Sagan explains. "We cut people off from themselves if we teach them that science is something they can't understand. While Cosmos is filled with facts, it is about attitude. The world can be understood by everyone, not just by funny people in white lab coats."

Sagan's efforts are now aimed at sustaining public support for unmanned exploration of the solar system, scheduled to end after Voyager II reaches Uranus in 1986. "This is the first moment in the 4½-billion-year history of the earth that things are leaving it and exploring our surroundings," says Sagan. "One thousand years from now missions like this will be recalled in the same way that Vasco da Gama and Christopher Columbus are remembered today. The costs are extremely small compared to other things we spend money on. The entire planetary program probably costs less than the bubblegum budget of the U.S. But if we scientists don't explain what we're doing with public funds, why should we expect to continue to get them?"

Sagan's closest confidante is Ann Druyan, a 31-year-old novelist he met six years ago at a dinner party given by writer Nora Ephron. "We were friends and collaborators for several years," says Druyan, "and suddenly we fell in love. At first we didn't allow ourselves to think about it. Once it was out, we moved heaven and earth to be together." "Until I met Annie I thought love was a hype to sell movie magazines to teenage girls," Sagan admits. "The idea that it really could be the kind of feeling that popular songs claim was a revelation."

The two of them are inseparable, working together on Cosmos (she wrote several of the shows) and on a two-hour copper record that was placed on Voyager I and II to carry messages from earth to extraterrestial beings, if they exist. At Druyan's suggestion, the sounds of human brain waves were included on the disc. Sagan picked Ann as the subject to be recorded. "I was so moved thinking I would be the only spokesperson for the species," she remembers. They are now finishing a film treatment about contact with extraterrestrial intelligence. "Carl is insistent that the science be exactly right," she says.

Sagan dates his curiosity about the stars to his boyhood in Brooklyn, where he grew up the son of an American mother and a Russian immigrant garment cutter. (His father died of cancer during the filming of Cosmos.) "My parents always encouraged me to read," he remembers. "Every now and then I would think, gee, wouldn't it be terrific if I had a friend to talk to about the stars, but there wasn't one."

At 16, he graduated from high school and enrolled at the University of Chicago. On a typical date during his postgraduate work there, Sagan says, "A girlfriend would invite me home for dinner, and her father would ask what I was interested in. I'd say, naively, oh, going to the planets, and suddenly realize that they were looking not only at me but at her in a very strange way."

With a combination of degrees in physics, astrophysics and astronomy, Sagan held research and teaching positions at Berkeley, Stanford and Harvard before moving to Ithaca, N.Y. as director of Cornell's Laboratory for Planetary Studies.

Sagan's first marriage ended in divorce in 1963 after seven years. His ex-wife, Lynn Margulis, is now remarried and teaching biology at Boston University, where she has custody of their two sons, Dorion, 21, and Jeremy, 20. Carl is currently embroiled in an acrimonious divorce suit with his second wife, Linda Salzman Sagan, an artist. She is the mother of his 10-year-old son Nicholas, whom friends describe as "a miniature Carl" and who lives in Ithaca with his mother.

Sagan remains ambivalent about fame. For one thing, it has meant a flood of angry letters, largely from astrology buffs ("They're just plain wrong," he snorts) and creationists who say they count him in their prayers, which Sagan says "I consider a generous offer from their point of view." He adds, "I don't see how any scientist could not be spiritual. If you penetrate even a little deeply into nature, you find an elegance which is stunning."

Unimpressed by the lack of evidence so far, Sagan continues to believe in the probability of other intelligent life in the universe. "I've tended to go to fairly large questions, like the early history of the planets, the origins of life, the possibility of life elsewhere. Some of these may be too difficult to be resolved in this particular century," he acknowledges. "I suppose there are other, safer questions I could have gone after. But these interested me, so why not?"

In January Sagan looks forward to resettling in rustic Ithaca, where he will advise graduate students, teach a course on planetary physics and concentrate on a handful of experiments with colleagues. An ongoing project is an attempt to duplicate in a sealed chamber the chemical reactions that led to the first life on earth. "When Carl's away from science," Annie says, "his energies begin to flag." His fantasy, Sagan says, is to hole up with piles of photographs of the Saturn system. "I have this image of long winter nights with the snow falling outside and there I am lost in the haze layer of Titan." Titan is Saturn's largest moon.

Sagan is fond of telling the story of the 17th-century astronomer Christian Huygens, who commented on Galileo's discovery of Jupiter's four largest moons. "He wrote, it must have been with no small rapture that Galileo first saw those moons," Sagan marvels. "And that's how I feel—no small rapture when I am looking at another world for the first time in human history."