On a chilly March morning, Steve Howard, aged 65, is at work in his office on the northern edge of Pasadena, California. Two computer screens are squeezed on to his corner desk along with family photos, a tissue box and tins of Altoids Curiously Strong Peppermints. The office is in a quiet business park by a workaday main road. Next to it is a McDonald’s, where people linger for hours over a $1 coffee, seemingly to keep warm. Over the road there’s a scruffier burger joint, Jim’s, with an M missing from its sign – and, visible from Howard’s window, a landscaping supplies yard.

If the few people walking by on West Woodbury Road, Altadena, or popping into the landscaping place for some patio paving slabs were to peer into Howard’s office, they might guess, seeing the graph-covered twin screens and a third PC at the other end of the desk, that he was, perhaps, a financial adviser or a day trader. But what Steve Howard is actually doing makes this very ordinary all-American scene quite extraordinary.

Howard is a Nasa mission controller. He is sending instructions to a probe in interstellar space, 12 billion miles from Earth, beyond Pluto and escaping our Solar System at 1 million miles a day. The 815kg craft, Voyager 1, is one of two identical machines that for many years now have been the furthest human-made objects from Earth. Howard’s computer code takes 17 hours at the speed of light to reach Voyager 1, the furthest travelled. Voyager 2, which is leaving the solar system in a different direction, is 3bn miles closer. The responses, from transmitters on the twin probes running 23 watts of power – have the power of a billionth of a billionth of a watt by the time they reach Earth.

“So here, see, I have Voyager 1’s status and information up, at least as it was 17 hours ago,” Howard explains. “Right now I’m connected to our Canberra station, and these are seven commands, set to radiate one every five minutes starting 30 minutes from now. They’re to verify that the spacecraft can receive and reset its timer. Such is the speed of light, I will not get confirmation that all is OK until late tomorrow night, but it will have entailed a 25bn-mile round trip, so that’s not too bad.”

Facebook Twitter Pinterest Gold standard: unveiling the LP which each space probe carries. The record has 115 photos and messages in 55 languages. Photograph: Time Life Pictures/Time & Life Pictures/Getty Image

It is no hyperbole to say, then, that the man tapping away at his keyboard on the office park next to McDonald’s is a key figure in the greatest-ever feat of human exploration. There was nothing like the Voyager 1 and 2 missions to the outer planets before they launched in 1977, and although three outer planet probes launched last decade are still on mission, no new ventures into deep space are planned.

Space exploration tends to be more inward looking today than in the so-called Space Age. The famous Curiosity rover is of course still working wonders on Mars, but almost all the US’s coming spacecraft will be restricted to studying our own planet, with special attention to environmental issues. The Voyagers and the people like Howard who still work on them full-time – having, in many cases, done so their entire adult life – are from a different era, when budgets were unrestrained, audaciousness (and showing off to the Soviets) was in vogue and the environment was a concern only for hippies.

Voyager’s spindly limbed, Transit-van-sized machines have been travelling at around 37,000mph for almost 38 years. When they were launched, wooden-framed Morris 1000 Traveller cars had only recently stopped being produced by British Leyland in Oxford. The Voyagers’ on-board computers are early 1970s models that were advanced then but are puny now – an iPhone’s computer is some 200,000 times faster and has about 250,000 times more memory than Voyager’s hardware.

The Voyager mission’s early 70s-inspired and -equipped trip, originally meant to last four years, took the craft initially to Jupiter, then Saturn, then, as a bonus since everything was working well, to Uranus and finally Neptune, after which they spun off into their journey around the Milky Way. Against all expectations their vintage electronics and thrusters are still, mostly, working in the intense -253C cold of outer space. What’s more, their sensors are sending data all day every day, as some will continue to do until 2036. That said, by 2025 almost all the instruments sending worthwhile scientific information will be turned off as the ships’ tiny plutonium-238 power sources dwindle.

The on-board camera on each Voyager, for instance, was deactivated to save power 25 years ago last Valentine’s Day. This was after Voyager 1 took a now-iconic “family portrait” of the solar system from almost 4bn miles out. It captured Neptune, Uranus, Saturn, Jupiter, Venus, Earth (seen, in the late astrophysicist Carl Sagan’s phrase, as a “pale blue dot”) and the Sun, by then just a tiny point of light. By 2036 the craft will be nearly out of the solar system altogether and will remain dead, although in perfect condition, probably for eternity.

Facebook Twitter Pinterest ‘One of us is always on call’: Steve Howard in his office in Pasadena, California. Messages sent from his computer take 17 hours at the speed of light to reach Voyager 1. Photograph: Jonathan Margolis/Observer

It is the Voyager spacecrafts’ longevity, despite their becoming a bit arthritic in later years, that has led to their Mission Control being moved out to an office park. The problem for Nasa – more correctly for the California Institute of Technology’s Jet Propulsion Laboratory, which runs most robotic missions for Nasa – is that high-profile later expeditions, most notably Curiosity, have used the available space on CalTech’s campus. Proud as JPL is of the amazing Voyager story, the craft are not taking photos or doing a lot of sexy science any more and may not encounter anything of much interest for another 40,000 years, by which time they will be deaf and mute. So, like a great grandfather who stubbornly refuses to do the decent thing, the Earth end of the Voyager programme and the spacecraft’s devoted carers have been put in a somewhat off-piste rest home.

Engineers are not given to emotion, but the romance of this incredible voyage of discovery has, by their own account, kept the ageing mission team together. Even latecomers, who were at school when Voyager was launched, have been working on the same mission for 30 years and more. “I’m in my mid-50s and treat the craft like my ageing parents,” says Suzy Dodd, who was 16 at launch, joined as a graduate student and whose card now proclaims surely one of the cooler job titles in science: Project manager, Voyager Interstellar Mission.

“You treat them with a certain amount of reverence; you know they’re stately spacecraft, venerable senior citizens, and you want to do everything possible for them to have a healthy lifetime,” she says. “You need to help them a bit because things have failed and you want to be careful other things don’t. Most of the engineers here have dedicated their career to this project. They have turned down opportunities for promotions and other things because they like Voyager so much they want to stay with it.”

It is clear talking to Voyager staff that they genuinely love their spacecraft, even though most were too young to see them before they flew, and it is more than possible that the older ones will have died before the Voyagers bleep their last. But as engineers, they have mixed feelings about the most famous aspect of that romance, the “golden record” that each craft carries. This is a gold-covered copper LP, packed with a needle and cartridge (plus instructions), and containing, in groove form, 115 photos from Earth, a selection of natural sounds from surf to whales, music from a variety of cultures and eras (the modern west is represented by Chuck Berry’s “Johnny B Goode”) and spoken greetings in 55 languages, from Akkadian, spoken in Sumer about 6,000 years ago, to Welsh.

Carl Sagan, who had the initial idea for the record, wrote in the 1970s: “The spacecraft will be encountered and the record played only if there are advanced spacefaring civilisations in interstellar space. But the launching of this bottle into the cosmic ocean says something very hopeful about life on this planet.” Sagan’s son Nick, then an infant, now a science-fiction novelist and screenwriter (his credits include Star Trek episodes), recorded the English message: “Hello from the children of planet Earth.” But one sure to make many tear up is the Mandarin: “Hope everyone’s well. We are thinking about you all. Please come here to visit when you have time.” (The messages are on the Voyager website, voyager.jpl.nasa.gov).

Voyager’s mission controllers are less starry-eyed than Sagan about the golden records. You sense some feel that it was too much of a bow to religious sentiment. Steve Howard is one of the more positive on the record question. “Even though Earth may not be here, some intelligent being could pick it up and detect it. I would say that many of the civilisations are much more advanced and would detect something like that and simply go in and decipher it,” he says.

Suzy Dodd’s view is more typical of the team’s. “I think it’s a great idea to get humans and mankind thinking what-ifs. Let’s send a picture of ourselves vintage 1977 and put it on a spacecraft and send it out there forever. I think it’s done to connect us to the spacecraft more than for an alien running into it. I’m of the opinion that space is very empty and the chances of something finding it are remote. But that doesn’t diminish the fact that we’ve got a little time capsule out there travelling through space and now orbiting around in our galaxy. And that’s us.”

For the mission’s much-honoured chief scientist and spokesman since 1972, CalTech professor Ed Stone, aged 79, the romance of Voyager lies more in what it has discovered since he joined the project aged 36. “Yes, the Space Age was a young man’s game back then,” he says, not a little ruefully, sitting on a park bench on the green university campus. “We all knew we were on a mission of discovery. We just had no idea how much discovery there would be. We just kept finding things we didn’t know were there to be found.

Facebook Twitter Pinterest Final frontier: Voyager control centre at the California Institute of Technology (Caltech), Pasadena California, 1980. Photograph: NASA/Getty Images

“For example, before Voyager, the only known volcanoes in the solar system were here on Earth. Then we flew by Jupiter’s moon, Io, which had 10 times the volcanic activity of Earth. Ten times! We detected hot lakes of lava on the surface. That was the first major discovery and it set the tone for the rest of the mission. And there are five instruments still working. But by 2025 the last will go off.”

He doesn’t quite add that by then he will be nearly 90, but does say, smiling: “Thing is, if you want to do space experiments, you have to be optimistic that it’s all going to work and that you’re going to find something worth the work. And you have to be patient, because nothing happens fast in space.”

Stone explains how, although it’s widely considered freakish that the Voyager crafts are still working so well – a TV left permanently on since Jim Callaghan’s day would be hardly working today – it’s less surprising to people like him who built them. To anyone familiar with the inside of a vintage radio or TV, the hand-soldered circuit boards, capacitors, transistors, resistors and so on that run a Voyager would look reassuringly familiar, which isn’t the case with a modern computer or phone, whose microchip-studded innards look more like something out of a UFO.

But the parts in Voyager weren’t as ordinary as they looked. Suzy Dodd, a “newcomer” to the project with just over 30 years’ service, has also been intrigued by the spacecraft’s durability. “The robustness is unique,” she says. “If you talk to the older engineers, they’ll say: ‘Well, we were told to make a four-year mission, but we realised if you just used this higher-rated component, it would last twice as long.’ So they did that. They just didn’t tell anybody. The early engineers were very conscious of trying to make this last as long as possible and, quite frankly, being not as forthcoming with information about the types of parts they were using.”

Even so, Ed Stone says, there have been problems. A ground controller’s error in April 1978 meant that Voyager 2 switched itself irretrievably to its back-up receiver – meaning that the craft has been receiving transmissions from Earth on a dodgy back-up radio for almost the entire mission. One of the original thrusters also failed.

For spacecraft 12bn miles from home and in their dotage, the Voyagers are quite tranquil machines today, but they do need watching. As Steve Howard is in his office inputting code in primordial programming language, on the floor of what passes for the main mission control Enrique Medina, 65, is watching streams of engineering data from the craft. A computer engineer, Medina is another of the eight full- and part-time controllers.

“One of us is always on call,” he says. “We’re all connected all the time by our smartphones. We will hear, that way, which engineering channel is out of tolerance and then we will connect from home with secure IDs and special codes, troubleshoot, determine and sometimes fix it from home. Or in some cases, one of us will drive in. That usually happens four to five times a month.

“Sometimes people are away, but we love Voyager so much that though it’s not part of our employment we’ll come in and do it anyway. Attitude control is my sub-system, but if the propulsion or the power needs attention, we all do multiple jobs,” he adds. “I’ve been working on Voyager since the Uranus encounter in 1986, and I will retire when Voyager retires in 2025. My wife doesn’t like that idea at all, as we already have a retirement place by the beach back in Mexico.”

Medina’s devotion to the Voyager is clear to see. “This has been part of my life for so long, and they pay us to do it, so how can you stop doing something you love? I even talk about the spacecraft like it’s a person, especially if it’s my sub-system.”

Steve Howard feels the same. “I just love to think of everything, all those 65,000 parts on each craft, working up there,” he says. “Oh man, it really is something. Every time we come in here, it’s just a gift. And you know that one day it could stop.”

Do these engineers ever think it might be more fun to be at the controls of Curiosity on the CalTech campus a couple of miles away?

“Yes, maybe,” says Medina, “but after so many years, you’re invested. It’s like being married to someone. It would be interesting to go out with Angelina Jolie, but do I want to give up my wife of 44 years, and my grandkids? I don’t think so. I would not give this up for something more interesting or newer.”

For the most part, Voyager is the reality of space – slow, patient science, humdrum perhaps, but real. It’s only a 20-minute drive from Altadena to Hollywood, where brilliant fake versions of space exploration like Christopher Nolan’s recent Interstellar are confected.

But Voyager, starring real people who keep tissues and tins of Altoids on their desks and real buildings rather than set designers’ glamorous fantasies, just happens to be the only real interstellar mission there will probably be in the lifetime of anyone alive today. It is surely one of the most amazing things in human history.

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