Comparing the historic event to Neil Armstrong first setting foot on the moon, Voyager project scientist Ed Stone, based at the California Institute of Technology, described it as "a new era of exploration," during a press conference on Thursday. "What does it mean to reach interstellar space? It's what we had hoped for 40 years ago. This journey is a tribute to individuals responsible for the Voyager mission," Stone said.
For about a year, Voyager 1 has been traveling through plasma, or ionized gas that's present in the space between stars. The spacecraft is in a transitional region outside the solar bubble, experiencing some effects from the Earth's sun. Scientists were able to interpret the Voyager's location by running simulations on supercomputers, which showed plasma jumping from the solar side to the interstellar side during a massive burst of solar wind and magnetic fields in March 2012. Voyager 1 doesn't have a working plasma sensor, but its plasma wave instrument detected the movement 13 months later in April 2013.
Voyager 1's instruments transmit data to Earth typically at 160 bits per second. The data is then captured by NASA Deep Space Network stations and transmitted to NASA Jet Propulsion Laboratory, which built and operates the twin Voyager spacecraft. A signal from Voyager 1, traveling at the speed of light, takes about 17 hours to reach Earth. The spacecraft travels approximately 1 million miles per day.
"The team's hard work to build durable spacecraft and carefully manage the Voyager spacecraft's limited resources paid off in another first for NASA and humanity," Jet Propulsion Laboratory's Voyager project manager Suzanne Dodd, said in a statement. "We expect the fields and particles science instruments on Voyager will continue to send back data through at least 2020. We can't wait to see what the Voyager instruments show us next about deep space."
Voyager 1 and its twin spacecraft, Voyager 2, embarked on their missions in 1977. Both spacecraft flew by Jupiter and Saturn, while Voyager 2 also passed by Uranus and Neptune. Voyager 2 is the longest continuously operated spacecraft, according to NASA. It launched before Voyager 1 and is about 9.5 billion miles away from the sun. Voyager 1 is about 12 billion miles from the sun. The cost of both missions is approximately $988 million through September.
Scientists have yet to see when Voyager 1 will reach the undisturbed part of interstellar space, where there is no influence from the sun. They believe Voyager 2 is not far behind Voyager 1 in crossing into interstellar space.