Voyager reaches interstellar space
After decades of exploration, Voyager 1 is officially the first human-made object to venture into interstellar space. Courtesy NASA.PT2M8S http://www.canberratimes.com.au/action/externalEmbeddedPlayer?id=d-2to6n 620 349 September 13, 2013
Pasadena, California: The spacecraft's technology was laughable by today's standards: it carried an eight-track tape recorder and computers with 240,000 times less memory than a low-end iPhone. When it left Earth 36 years ago, it was designed as a four-year mission to Saturn, and everything after that was gravy.
But Voyager I has become - unexpectedly - the Little Spacecraft That Could. On Thursday, scientists declared that it had become the first man-made object to exit the solar system, a breathtaking achievement that NASA could only fantasise about back when it was launched in 1977, the same year that Star Wars was released.
Voyager 1 is expected to keep sending back data - with a 23-watt transmitter, about the equivalent of a refrigerator light bulb - until roughly 2025.
"I don't know if it's in the same league as landing on the moon, but it's right up there - Star Trek stuff, for sure," said Donald Gurnett, a professor of physics at the University of Iowa and the co-author of a paper published Thursday in the journal Science about Voyager's feat. "I mean, consider the distance. It's hard even for scientists to comprehend."
Scientists at NASA have declared Voyager 1 to become the first human-made object to leave the solar system and enter interstellar space. Photo: NASA
Even among planetary scientists, who tend to dream large, the idea that something they built could travel so far for so long and pierce the sun's reach is an impressive one. Plenty of telescopes gaze at the far parts of the Milky Way, but Voyager 1 can now touch and feel this unexplored region and send back detailed dispatches. Given the distance, it takes about 17 hours for Voyager's signals to reach NASA's Jet Propulsion Laboratory here.
"This is historic stuff, a bit like the first exploration of Earth, and we had to look at the data very, very carefully," said Edward Stone, 77, NASA's top Voyager expert, who has been working on the project since 1972.
Ever the stoic scientist, he does get excited about what comes next.
On the edge ...an artist's concept released by NASA/JPL-Caltech in 2012 shows Voyager 1 and Voyager 2 at the edge of the solar system. Never before has a human-built spacecraft traveled so far. NASA's Voyager 1 probe has officially left the solar system and is now wandering the galaxy." Photo: AFP/NASA/JPL-Caltech
"It's now the start of a whole new mission," he said.
The lonely probe, which is 18.8 billion kms from Earth and hurtling away at 38,000 mph, has long been on the verge of bursting through the heliosphere, a vast, bullet-shaped bubble of particles blown out by the sun. Scientists have spent this year debating whether it had done so, interpreting the data Voyager sent back in different ways.
But now it is official that Voyager 1 passed into the cold, dark and unknown vastness of interstellar space, a place full of dust, plasma and other matter from exploded stars. The article in Science pinpointed a date: August 25, 2012.
"This is the moment we've all been waiting for," Jia-Rui Cook, the media liaison at NASA's Jet Propulsion Laboratory, said. "I can't even sleep it's so exciting!"
Coincidentally, the same month that Voyager 1 left the solar system, Curiosity, NASA's state-of-the-art rover, landed on Mars and started sending home gorgeous snapshots. Soon afterward, Curiosity's exploration team, some 400 strong, dazzled the world by driving the US$2.5 billion ($2.68 billion) robot across a patch of Martian terrain, a feat that turned the engineers and scientists of Building 264 of the Jet Propulsion Laboratory campus into rock stars. A spoof video, "We're NASA and We Know It," recorded to the beat of the song "Sexy And I Know It," generated 2.8 million views on YouTube.
Voyager, meanwhile, stopped sending home pictures in 1990, to conserve energy. In its heyday, it pumped out never-before-seen images of Jupiter and Saturn, but lately there has not been much to see.
As the mission lost its sizzle, its 12-person staff was booted from the laboratory's campus and sent to cramped quarters down the street next to a McDonald's. Suzanne Dodd, the Voyager project manager, said that when she has attended meetings in Building 264, she has kept a low profile in deference to the Mars team.
"I try to stay out of the elevator and take the stairs," Dodd said. "They're doing important work there, and I'll only slow them down."
Now she and her team seem poised to be back in the spotlight, perhaps for years to come. Stone, vice provost for special projects at the California Institute of Technology and former director of the Jet Propulsion Laboratory, expects Voyager 1 to keep sending back data - with a 23-watt transmitter, about the equivalent of a refrigerator light bulb - until roughly 2025.
Not that the aging spacecraft has made things easy. An instrument that measures the energy of particles in plasma stopped working in 1980. But scientists still have access to a related sensor, a spindly antenna that records electron oscillations in plasma. The catch is that these oscillations don't occur all the time; they typically happen when stirred up by a solar eruption.
Voyager 1's plasma wave antenna picked up audible vibrations in April and May that allowed Gurnett and his colleagues to calculate the density of the plasma around the spacecraft, which would help them determine whether the craft was still in the solar system.
"It was exactly what we expected for interstellar plasma," Gurnett said.
Moreover, by combing through older oscillation data collected by Voyager 1, the team discovered that the edge of the solar system - the threshold that was crossed in August 2012 - was roughly where Gurnett predicted it would be back in 1993 by using different solar storm calculations.
"Am I bragging here? No," he said. "All right. I admit it. It's bragging a little."
As the solar system's edge grew tantalisingly close, NASA asked Dodd and her team to increase the amount of data collection. The problem: 8-track recorders from 1977 are not exactly bursting with extra space. Could she even find anyone who specialised in that piece of recording technology?
"These younger engineers can write a lot of sloppy code, and it doesn't matter, but here, with very limited capacity," said Dodd, "you have to be extremely precise and have a real strategy."
At 52, Dodd is a relative newcomer to Voyager, first working on the mission in 1984, when Voyager 2 - a companion spacecraft also launched in 1977 and still inside the solar system - was headed toward Uranus. But she was able to find her man: Lawrence Zottarelli, 77, a retired NASA engineer. He came up with a solution. But would it work?
Zottarelli waited at Voyager mission control one afternoon last month to find out. The first of the newly programmed data dumps was set to come down. Dodd, Stone and Zottarelli watched two old Sun Microsystems computers like children watching for a chick to peck through an egg.
"Nine, eight, seven," Stone counted down.
"Everything's fine," said Zottarelli, flashing a thumbs up and hiking up his trousers. "You're on your own now."
The relief was written all over Dodd's face, too. "It's not easy flying an old spacecraft," she said.
Her eyes moved to Stone, who was peering at a computer through his trifocals.
"There are lots of old missions," he responded, a sly smile taking over his face. "But not many are doing exciting new things."
New York Times