NASA\u2019s Voyager 1 and Voyager 2 spacecraft are still going strong after nearly 37 years in space.<\/p>\n
\u201cBoth spacecraft are still operating, still very healthy. I guess as healthy as we are at the table right now,\u201d Suzanne Dodd, the Voyager project manager at NASA\u2019s Jet Propulsion Laboratory (JPL) said, drawing a big laugh from the audience at the SpaceFest VI conference in Pasadena, California, on May 11.<\/p>\n
Dodd was fresh out of college in 1985 when JPL recruited her as it geared up for Voyager 2\u2019s upcoming encounter with Uranus. Nearly 30 years later, she is project manager of the Voyager Interstellar Mission under which the two spacecraft continue to explore the vast expanse of space beyond the planets.<\/p>\n
Dodd was actually the youngster on the Voyager reunion panel. She was joined by Voyager Project Scientist Ed Stone and retired Voyager Mission Design Manager Charley Kohlhase, who were both on the project when it was in the planning stages in the early 1970s.<\/p>\n
When the Voyagers were launched in 1977, NASA expected them to last four or five years, long enough to get them through close encounters with Jupiter and Saturn. But, they just kept going and going.<\/p>\n
Voyager 2 went on to flybys of Uranus in 1986 and Neptune in 1989. It is now about 105 astronomical units from Earth. (One AU is the average distance between the Earth and sun, about 92 million miles.) Voyager 1, which flew out of the plane of the solar system after its 1980 flyby of Saturn, is in interstellar space at 127 AUs.<\/p>\n
Stone and Kohlhase recalled their astonishment when an image showing two exploding volcanoes on Jupiter\u2019s moon Io came into JPL late on a Friday afternoon in March 1979. The plumes went hundreds of miles above the surface, and the fallout covered an area the size of France.<\/p>\n
\u201cWe had what I call a terracentric view, which was based on understanding Earth,\u201d Stone said. \u201cBefore Voyager, the only known active volcanoes in the solar system were on Earth. Then we flew by Io, a little moon about the size of our moon, with 10 times the volcanic activity of Earth. And suddenly our terracentric extrapolation just was falling way short, and that was happening time after time after time.<\/p>\n
\u2026<\/p>\n
\u201cThe key thing about Voyager that was a revolution was it was a totally computer-controlled spacecraft that flies itself and has fault protection on board so that if something goes wrong, it takes action,\u201d he said. \u201cBecause now it takes us 17 and a half hours to get a command up there, and it\u2019s 17 and a half hours before we know if anything has happened.\u201d<\/p>\n
\u2026<\/p>\n
Dodd says the Voyager mission continues to throw up challenges today. The spacecraft have 20-watt transmitters \u2013 the equivalent of a refrigerator light bulb \u2013 and signals are only 1 billionth of a billionth of a watt in strength by the time they reach Earth. JPL uses the powerful antennas of the Deep Space Network to communicate with the distant spacecraft.<\/p>\n
\u201cThe engineering challenges are extremely unique to Voyager,\u201d Dodd said. \u201cYou\u2019re operating instruments below temperatures that we can\u2019t even measure. Challenges of finding out if we turn on a component that\u2019s next to a hydrazine line, would that hydrazine line freeze or not. We don\u2019t know.<\/p>\n
\u2026<\/p>\n
\u201cLooking forward, we expect to get 10 more years of scientific data out of the Voyager spacecraft,\u201d Dodd said. \u201cWe basically turned off everything we can turn off to save power. Backup heaters are off, backup systems are off. We\u2019re having some serious discussions about how to move forward, because we\u2019re almost down to the scientific instruments now.\u201d<\/p>\n
After that, the spacecraft could continue on for another five to seven years sending engineering signals to Earth. Engineers are already in discussions with the Deep Space Network about what experiments could be conducted with those signals before the spacecraft fall silent.<\/p>\n