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Tech Life

Celebrating NASA’s Voyager Probes — And The Team That’s Still Supporting Them

Aug 13th, 2017 3:00am by
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In the summer of 1977 NASA launched two identical space probes — two weeks apart — hoping they’d survive their four-year journey so they could send back photographs from Jupiter and Saturn.

But they didn’t stop exploring after the moons of Jupiter — the unexpected volcanos on Io, the eerie ice shell of Europa — or the braided rings of Saturn. And now those same plucky probes are celebrating their 40th anniversary in space — still beaming back more data than humanity can handle, offering an inspiring story about what can be accomplished with good technology and a dedicated team.

And it’s especially inspiring for anyone who’s ever had to maintain a legacy system.

To celebrate the longevity of this particular data-generating system, NASA is now asking humanity to come up with a short, uplifting message that Voyager will beam into the vast reaches of the interstellar space beyond our solar system on September 5th. Messages can be submitted anytime before midnight (PDT) on August 15th, by using the #MessageToVoyager hashtag on Twitter, Instagram, Facebook, Google+ or Tumblr. The winner will be decided by a public vote.

And the anniversary is also being marked with a new PBS documentary premiering August 23, “The Farthest: Voyager in Space”:

The documentary’s producer remembers that when the probes were first launched, “They didn’t think it would last 40 years.” Spacecraft at that time weren’t designed for long-term missions. “That’s one of the reasons they made two of them! You could lose one at launch,” he said.

Each probe weighs 1,704 pounds — of which 231 pounds is scientific instruments — and over the decades their instruments have measured everything from the mass of moons and the temperatures of atmospheres to gravity, radiation and magnetic fields. The mission was cleverly timed to exploit a rare planetary alignment that happens once every 176 years, remembered Science News, so the gravity from Jupiter and Saturn could help hurl the probes on their way, sending Voyager 2 off towards Uranus and Neptune.

One story has president Nixon telling a NASA administrator, “The last time the planets were lined up like that, President Jefferson was sitting at your desk. And he blew it.”

The path of the Voyager probes

This time turned out to be a scientific bonanza. “At the time, every picture was the best planetary picture ever taken. Much of what is known about the outer solar system now — Jupiter’s moon Io has volcanoes, Europa has an ocean, Neptune has a great churning hurricane that never stops — was glimpsed for the first time with Voyager,” Science News reported.

The probes kept chugging along, and in 2004, Voyager neared the edge of the solar system, where the solar winds meet interstellar space. Ions slowed, magnetic fields surged, and on August 25, 2012, the New York Times reported, Voyager suddenly swam into a new sea of space particles. “It had crossed the threshold of interstellar space.”

Voyager’s onboard computers have 235,000 times less memory and 175,000 times less speed than a 16GB smartphone.

Wikipedia notes that no human object has ever travelled as far.

But the Voyager probes are now nearing the end of their ongoing conversation with its handlers back on earth. The power supplies on both probes are expected to run down by 2030, and now the flight team faces some tough decisions, according to the New York Times. “To conserve power on the spacecraft, the engineers must decide what to turn off when, and for how long.” But the Times also couldn’t help seeing a poignant human counterpoint.

“As the Voyager mission is winding down, so, too, are the careers of the aging explorers who expanded our sense of home in the galaxy.”

Ending a 53-Year Mission

In a fascinating profile for the Times, reporter Kim Tingley noted that the project initially took 1,500 engineers, five years, and $200 million. But that was 40 years ago. This week Tingley visited the team’s nine aging flight-team engineers — most of them who’ve been there since the 1980s. Only one of the them is under the age of 50 — and only one has a replacement already standing by. In 2016 the project’s most experienced programmer gave six-months notice, and used the time to train his successor.

Ed Stone, the 81-year-old science-team leader, acknowledges “I certainly had no idea that it would last as long as it has.”

The team is full of quiet examples of loyalty. Two years ago 65-year-old engineer Enrique Medina — who’d been onboard since 1986 — told the reporter “I will not leave Voyager until it ceases to exist. Or until I cease to exist.” Since they can’t focus on other missions, Tingley writes that their work has come with a sacrifice. “Over decades, the crew members who have remained have forgone promotions, the lure of nearby Silicon Valley and, more recently, retirement, to stay with the spacecraft.”

And of course, it’s much more than that.

“The mission quite possibly represents the end of an era of space exploration in which the main goal is observation rather than commercialization. … NASA funding, which peaked during the Apollo program in the 1960s, has dwindled, making it next to impossible to recruit young computer-science majors away from the likes of Google and Facebook.”

Over the mission’s lifetime, the team has seen many milestones. They witnessed the “debuts” of Uranus in 1986 and Neptune in 1989. Then they laid off 150 engineers, and moved into smaller quarters — the former offices of a mainframe-computer company in Sierra Madre, California. Thirteen years later there were more staff cuts, another move to Altadena, California, and a NASA review to see if the program should be canceled altogether.

But Tingley’s article suggests the nine remaining flight engineers represent a dream team that’s simply irreplaceable. “Their fluency in archaic programming languages will become only more crucial as the years go on. … They also may be the last people left on the planet who can operate the spacecraft’s onboard computers, which have 235,000 times less memory and 175,000 times less speed than a 16-gigabyte smartphone.”

Science News described the probes as having “as much computing power as a modern car key fob.”

But what’s even more impressive is they’re doing their historic work under conditions that are unmistakably humble. Tingley visits “a squat concrete building beside Scott-Fox Puppy Preschool” outside Los Angeles, where project manager Suzanne Dodd “pointed out a used microfiche reader that Tom Weeks, a hardware engineer and the self-described mission librarian, purchased on eBay to read old diagnostics reports.”

Their lack of equipment definitely affects the amount of data they receive from the Voyager probes’ radio signals. “The three antenna dishes big enough to register them are shared, so Voyager gets only four to six hours of reception time per spacecraft per day; outside these often odd windows, their data dissipate into the ether.” The probes have to transmit around the clock — since Voyager’s computer memory has only 4kB of storage — with radio signals taking up to 19 hours to reach earth.

 Voyager spacecraft structure

Through the decades, the team has faced an ongoing parade of unique challenges to maintain their forever-remote system from 1977. “Bits have been known to ‘flip’ to the opposite value,” the Times notes. Once in 1998, Voyager 2 mis-read a command and turned off the exciter which generated its own radio signal. Amazingly, the team was able to guess exactly how the command had been garbled — and restored communications.

And there have been other close calls. When the first Voyager probe was launched from Cape Canaveral, all the shaking inadvertently sent its onboard computer into “safe mode,” reports Science News. And a gas leak on the second Voyager probe meant it came within 3.5 seconds of running out of gas before reaching Jupiter’s orbit.

The New York Times also remembers how the platform with the cameras got stuck just seven months into the mission. “As the engineers scrambled to figure out what they could do from more than 100 million miles away, someone forgot to send a weekly command to reset a timer on the other spacecraft. When it ran down without hearing from Earth, it triggered so-called fault-protection software, 600 lines of code that respond to malfunctions automatically.” Voyager switched over to a back-up receiver, though eventually — on its own, and after an agonizing wait — Voyager reactivated its original receiver.

Which then shorted out.

The Earth Says Hello

This mission has also made possible something truly awe-inspiring. Famous cosmologist Carl Sagan curated the creation of special gold-plated records that are attached to the probes — each containing a collection of earth sounds. There’s several pieces of music — everything from Beethoven and Bach to Chuck Berry’s “Johnny B. Goode” and, appropriately for the vast reaches of space, the blues song “Dark Was The Night” by Blind Willie Johnson:

You can find the whole Gold Record as a YouTube playlist, and a Kickstarter campaign to release the sounds on vinyl raised $1,363,037 from 10,768 backers. A “second edition” of that record is now being pressed, as well as a two-CD set.

And it also includes the sound of Carl Sagan’s son saying, “Hello from the children of planet Earth.”


Images courtesy of NASA.

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