“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,” said Suzanne Dodd, Voyager project manager, based at NASA’s Jet Propulsion Laboratory (JPL), Pasadena, Calif. “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.” Indeed. Thank you and congratulations, NASA!Although scientists estimated Voyager had reached the outer limits of the heliosphere – the 10,000 km thick magnetic sheet that extends over 8 billion miles from the sun – they needed data for evidence. The data they needed unexpectedly materialized beginning in April 2013.
Thirteen months after a March 2012 solar event, when the sun ejected a giant coronal mass – a burst of solar wind and magnetic fields – the radiation reached the Voyager. On April 9, Voyager’s plasma wave instrument detected the movement. The pitch or frequency of the oscillations helped determine the density of the plasma. These particular oscillations meant the spacecraft was bathed in plasma more than 40 times denser than what they had encountered in the outer layer of the heliosphere. That level of density is that which is expected in interstellar space. The new data was compared with earlier solar event data from October and November 2012 when Voyager was known to be reaching the edge of but still inside our sun’s heliosphere. From the 2012 data, in which the plasma-generated oscillations were less, the team of scientists extrapolated between data sets to determine that Voyager 1 first entered interstellar space in August 2012.
Voyager 2 is expected to cross into interstellar space soon. Voyager 1 and its twin, Voyager 2, were launched 16 days apart on September 5, 1977 and August 20, 1977 respectively. Both spacecraft flew by Jupiter and Saturn. Voyager 2 also flew by Uranus and Neptune. Both successful missions have provided a wealth of images and data to advance astronomy. Voyager 2 is about 9.5 billion miles (15 billion kilometers) away from our sun. Voyager 2 is the longest continuously operated spacecraft.
Voyager mission controllers still communicate with or receive data from the two Voyagers daily. The emitted signals are currently very dim, at about 23 watts — the power of a refrigerator light bulb. By the time the signals get to Earth, they are a fraction of a billion-billionth of a watt. Data from Voyager 1’s instruments are transmitted to Earth typically at 160 bits per second, and captured by 34- and 70-meter NASA Deep Space Network stations. Traveling at the speed of light, a signal from Voyager 1 takes about 17 hours to travel to Earth. After data is processed by JPL science teams, Voyager data are made publicly available.
Voyager’s crossover into interstellar space is a first for mankind. Count ourselves blessed to be a part of the society that achieved this. As we scientifically measure and vicariously observe its sentimental journey, the Voyager carries forth our messages of “peace” to intelligent life on its Golden Record. If only today we would listen and practice at home. We leave Voyager this Irish blessing:
A sunbeam to warm you,
A moonbeam to charm you,
A sheltering angel, so nothing can harm you.