September 5, 2012
Voyager 1 Celebrates 35th Anniversary, About To Cross Threshold Into Interstellar Space
Lawrence LeBlond for redOrbit.com - Your Universe Online
Celebrating its 35th anniversary in space today, NASA´s Voyager 1 spacecraft is about to cross the threshold of our solar system, to boldly go where no man, nor machine, has ever gone before. While it is difficult to pinpoint the exact moment when the American space company´s premier long distance journeyer will cross the boundary of the heliosphere, expert measurements have indicated that it is very close.
Complete with the most sophisticated equipment the 1970s had to offer, including computers with 8,000-word memory databanks and eight-track tape recorders, Voyager 1, along with its sister ship Voyager 2, which celebrated its 35th anniversary just a few short weeks ago, is making history.
These spacecraft “were the first fully automated spacecraft that could fly themselves,” Ed Stone, chief Voyager project scientist, said in an interview with the Los Angeles Times on Tuesday. “They were the peak of technology.”
Now, after being commissioned to explore the planets of Jupiter and Saturn, these stellar stalwarts are on a collision course with the unknown. Voyager 1 is now more than 11 billion miles from the Sun. And its sister Voyager 2, is not far behind at 9 billion miles.
The dynamic duo have spent the last five years exploring the outer layers of the heliosphere, according to NASA. What is perhaps most remarkable, is that these twin crafts had far surpassed NASA expectations.
Suzanne Dodd, Voyager project manager at NASA's Jet Propulsion Laboratory in La Canada Flintridge, California, said the crafts were still in great shape. They had survived the “dangerous radiation environment” of Jupiter and had endured the frigidness of space for decades.
“When Voyager was launched, the space agency itself was only 20 years old,” noted Stone. “We always hoped we would reach interstellar space.”
But ℠hoped´ is not a word that most NASA scientists use. This mission is something they said they had planned for. Voyager´s CRS--Cosmic Ray Subsystem--was intended specifically for use in interstellar space, Stone noted.
While the mission was for Voyager to measure many things, its main “purpose was determining the interstellar spectrum of cosmic rays,” he told LA Times´ Amy Hubbard. “This is a major milestone“¦This will be the first spacecraft to enter interstellar space. We'll know exactly how big this bubble is.”
The size of the bubble (heliosphere), a hot and turbulent area created by a stream of charged particles from the Sun, as described by an earlier Associated Press report, has been estimated to reach out from the star somewhere between 11 billion and 14 billion miles. And since Voyager is only traveling at a million miles per day, it could still be another decade before it crosses the threshold if the heliosphere does extend out to 14 billion miles.
So the best guess right now is that Voyager 1 could be crossing over into interstellar space any day, any week, any month, or even any year, now.
But scientists have been receiving strong indications that Voyager 1 will make that leap into the unknown sooner rather than later, after an incidence beginning in May that showed an increase in cosmic rays battering the spacecraft. But still, those measurements have fluctuated up and down, indicating that, while the spacecraft is near the threshold, it may still be some time before it crosses over.
“The question is, how much further is it to the heliopause?” Stone asked during a lecture at the (JPL) headquarters in Pasadena, California. “We don't know whether we're dancing along the edge of a new region which is connected to the outside," or if we are still billions of miles away.
Before the surge in cosmic rays hitting Voyager in May, researchers said they expected the spacecraft to pass over the heliopause sometime between the end of the Sun's influence and the next star system--within two years.
Once Voyager does cross over, Stone said it will measure the strength and direction of the magnetic field that´s pressing against the outside of the heliosphere. And will also be able to take “quality measurements” of the cosmic rays, including the ionized rays that are unable to penetrate into our solar system.
The equipment onboard Voyager, prehistoric by technology standards, includes a computer with less than 100,000th the amount of memory of an 8 gb iPod Nano. Scientists, attempting to preserve power, shut off Voyager 1´s camera after it passed Neptune in 1989. The spacecraft, if it continues to function normally, will start shutting down other onboard instruments after 2020 to further preserve power. If all goes as planned, Voyagers 1 and 2 should continue to race through the cosmos for another 13 years before exhausting their power supply.
After that, these intrepid adventurers will “orbit the center of our galaxy essentially forever,” said Stone.
Voyager 1, although launched after its companion, Voyager 2, was the first to reach Jupiter and Saturn, observing the volcanoes of Jupiter´s moon Io and the twisted nature of Saturn´s outermost main ring, and the deep, hazy atmosphere of it´s moon Titan, wrote TG Daily´s Emma Woollacott.
Voyager 1 also took the mission´s last image: the famous solar system family portrait showing Earth as a pale blue dot.
Dodd said the mission scientists “continue to listen to Voyager 1 and 2 every day.”