Most days, University of Idaho professor of engineering Dave Atkinson (’80 B.S., ’89 Ph.D. Elec. Engr.) sits quietly in front of a computer screen. The astrophysics expert, who as a kid loved learning about outer space, is thoughtful and soft spoken. Looking in his nondescript office stacked with science papers and textbooks, you wouldn’t think that for a few hours last winter, he was at the center of an interplanetary drama.
For 18 years, Atkinson has been quietly concocting an experiment to measure the winds on Titan, one of Saturn’s moons. And last winter he had a once-in-a-lifetime shot at putting his painstakingly crafted project to use.
To those who may wonder why one might want to measure the weather on Titan when we can’t even get it right here on earth, Atkinson says, “Exactly!” Studying Titan is like getting to know one of earth’s long-lost siblings, says Atkinson. Nearby planets and moons are valuable laboratories for learning about our own planet, because they make it possible to compare experimental conditions-spinning slowly versus spinning faster, ocean on the surface versus no ocean. Like Earth, Titan’s atmosphere is made up mostly of nitrogen. And like Earth, Titan spins on its axis. We may be able to learn more about our own planet’s weather by looking at this moon.
In 1987, Atkinson devised a simple experiment to measure wind speed and direction on Titan. The Huygens probe was to be parachuted through Titan’s atmosphere, emitting radio signals as it fell. Using methods similar to the way in which one determines wind direction by observing the movement of an overhead kite, Atkinson and his colleagues planned to use the Doppler shift of the radio signal to mark the probe’s path and assess wind speed and direction. The probe was aboard the Cassini spacecraft when it was launched in 1997, heading for Saturn and Titan. In late December 2004-after a seven-year journey-Cassini released the probe. On January 14, Huygens entered Titan’s atmosphere and began its two-hour descent to the surface. Cassini was set to receive data from the probe for two and a half hours, the to relay the data to Earth.
At the European Space Agency’s Mission Control Center in Germany, Atkinson and his colleagues waited eagerly for the data to arrive. After 18 years of work, they were finally about to get some answers. They had only to wait out the several hours it would take for Cassini to process the data and transmit it across the immense distance from Titan to Earth. At long last, on the morning of the 14th, the first signals arrived. The probe was alive!
“We were all very excited,” says Atkinson.
But as the data started coming in late that afternoon, Atkinson noticed a red message on his computer screen, indicating that while the receiver on Cassini was turned on, Atkinson’s instrument on the orbiter remained off. He and his team waited for it to switch on, growing increasingly nervous as the minutes wore on. All the other experiments on the probe were running. But somehow, no one had given the simple command to turn on Atkinson’s experiment. And because the events they were witnessing had occurred six hours before, they could only wait helplessly for the red message to go away, watching as the probe made its way to the surface. Here was a thoroughly dedicated and conscientious group that had worked for years to make the mission a success. And now, it seemed, that work was being undone, simply because the telecommand to turn on the experiment had been forgotten.
How do you describe the feeling of watching 18 years worth of work come to nothing? Shock. Numbness. A sinking in the stomach. Atkinson wanted to cry, to punch something. His colleagues on the experiment left to get a beer. In that moment of failure, these scientists realized that for all their sophisticated instrumentation and high-tech gear, they remained, after all, fallible human beings.
“These missions are incredibly hard,” Atkinson says. “These are very dedicated people, but they are real people, and they sometimes mess up. You have to be ready for the fact that sometimes it doesn’t work.”
But on that January day, the Cassini team wasn’t quite ready to concede failure. An hour after dispersing in despair, they came together again, this time with a glimmer of hope. Hadn’t the telescopes on Earth picked up radio signals? Atkinson had had the same thought.
“We’ve still got data.” These have to be the happiest words a scientist exploring distant planets can hear.
Over the next 10 days, the researchers studied the signals that had come in. They rewrote software. At first, they couldn’t read the data. What they ended up with is a “sparse” data set, but a data set nonetheless. Instead of the eight measurements per second they had planned for, they got one measurement every 10 or 20 seconds with one gap of 1,500 seconds. Still, it was enough to make rough measurements. The researchers found that the winds on Titan blow in the direction the planet spins, from west to east. In the upper reaches of the atmosphere, wind speeds are about 200 to 250 miles per hour. In a zone about 70 kilometers above the surface, the winds decrease inexplicably. Closer to the surface, wind speed drops to almost nothing.
“Things worked out as well as possible,” says Atkinson. “This was an unbelievably successful mission. All of a sudden, we were really able to salvage something worthwhile.”