Jane Kaczmarek wasn’t born until more than a decade after Voyager 2 was launched; as a kid, she remembers “staring in amazement” as the spacecraft’s blue and white images of Neptune splashed across her TV screen, in the summer of 1989.
Now, almost 30 years later, Kaczmarek is a staff astronomer at the Parkes Observatory in New South Wales, Australia – and part of a small team of scientists who make sure that when the venerable spacecraft has something to say, our ears are pricked up to hear it.
So when Voyager 2 phoned home on November 5 to say that it is venturing out of our backyard and into the interstellar space, it was Kaczmarek and her colleagues who were the first ones to receive it. The news was made public on December 12.
Launched in 1977 – the year of Star Wars and Annie Hall – Voyager 2 is currently coasting along at about 17 kilometres per second, some 18 billion km from Earth. The craft was launched together with its twin probe Voyager 1 that made it into interstellar space on August 25, 2012. Originally, the probes were designed to study the gas giants in our Solar System, Jupiter and Saturn, and last for five years. But the spacecraft were working so well, the Voyager 2 mission was extended to include flybys of Uranus and Neptune, and both craft were tasked with studying the solar wind (a stream of charged particles emanating from the sun that creates a kind of bubble around our solar system, known as the heliosphere), along with the interstellar medium. This mission extension was dubbed the Voyager Interstellar Mission. The twin spacecraft have now been out there for 41 years, Nasa's longest-running missions.
Both spacecraft have been sending back data on the speed and density of the solar wind, but one such instrument on Voyager 1 failed back in 1980, while those on Voyager 2 are still going strong. And the hardy spacecraft is still sending data back to Earth.
More accurately, Australia. Nasa tracks all of its spacecraft through its Deep Space Network, comprising a trio of radio telescope facilities in southern California, central Spain, and southeastern Australia. The largest of the Australian antennas is the giant 70 metre dish at the Canberra Deep Space Communications Complex, outside Canberra; the massive white dish is the largest radio telescope in the southern hemisphere.
But when things get busy at the CDSCC – as was the case last month, when they were tracking 43 missions simultaneously – they call on the Parkes Observatory, 250km up the road, for help. With a diameter of 64 metres, the Parkes dish is a tad smaller than Canberra’s, but is perhaps better known; it dates from 1961 and played a vital role in receiving the TV transmissions from Apollo 11 in 1969 (as dramatised in the 2000 movie The Dish).
On a recent visit, I happened to be at Parkes during a midday shift change. An astronomer who had been using the telescope remotely to study fast radio bursts – weird and as yet unexplained bursts of energy from deep space – had wrapped up his observing run, and handed control of the telescope back to Kaczmarek. Often, she uses the telescope for her own research; but when Nasa needs a helping hand, that takes priority.
In the Parkes control room, Kaczmarek types in a series of commands on a computer, and moments later metal grinds against metal as the telescope’s enormous dish, weighing more than two 747 jumbo jets, slews toward the spot on the horizon where Voyager 2 is just rising. (It may seem odd to speak of a spacecraft “rising,” but Voyager is so far away that it behaves pretty much like a star; as our planet rotates, Voyager rises and sets.) And if you’re wondering what constellation the spacecraft is in, the answer is Telescopium (“the Telescope”).
Telescopium is a southern constellation, and since the spring of 2012, Voyager has been so far south in the sky that the telescopes in California and Spain can’t see it at all. Without the dishes at Canberra and Parkes, Voyager 2’s calls would go unanswered.
Later, Kaczmarek and her colleague John Sarkissian peer at a computer monitor where the incoming radio waves are converted to a visual readout. A three-pronged spike stands out against the background noise. “You are literally looking at Voyager talking to you right now,” Kaczmarek says, adding that it’s talking “very, very quietly.” The transmitter on board Voyager puts out a mere 23 watts – about the same as the light bulb in your refrigerator. By the time that signal reaches Earth, it carries about one twenty-billionth of the energy you’d need to run a digital watch.
Meanwhile, researchers on Voyager’s scientific team, back at the Jet Propulsion Laboratory in Pasadena, California, have been busy analysing the data encoded in those ultra-weak radio signals. At the time of my Australia visit, in November, all eyes were on the data from the spacecraft’s Plasma Science Experiment, which has been measuring the intensity of the solar wind.
Scientists had already noticed a downturn in the intensity of the solar wind, suggesting that Voyager 2 was on the verge of exiting the heliosphere. Recently they concluded that on November 5 the spacecraft had indeed entered interstellar space.
Over at the Canberra facility, spokesperson Glen Nagle thinks of Voyager 2, along with its twin, Voyager 1, as part of the family. “The Voyagers have been our bread and butter for over 41 years,” he says. “You get a sense of shared pride in their accomplishments.”
In the facility’s control room, TV monitors show the status of multiple missions – every spacecraft that the giant 70 metre dish, along with the site’s seven smaller dishes, are currently tracking. That list includes three different craft on (or orbiting) Mars, our most-visited planet. Travelling at the speed of light, signals from the Red Planet take about 15 minutes to reach us; from Voyager 2 they take 16.5 hours.
That distance, and the weakness of the signals received, means communicating with the Voyager craft requires a great deal of patience. “It’s a long and slow conversation,” Nagle says. “But it’s still a great conversation, even after 41 years.”
This article was originally published by WIRED UK
