美国国家公共电台 NPR--25 years later, looking back on the accomplishments of the Mars Pathfinder

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25 years later, looking back on the accomplishments² of the Mars Pathfinder

Transcript³

More than two decades ago a small probe carrying an even smaller rover landed on Mars. Pathfinder and the Sojourner⁴ rover paved the way for sophisticated robotic explorers that have landed since 1997.

RACHEL MARTIN, HOST:

It was a long shot that proved successful in the end. Twenty-five years ago today, a mission on Mars ended.

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UNIDENTIFIED PERSON: Scientists at NASA's Jet Propulsion Laboratory in Pasadena, Calif., have lost contact with the Pathfinder lander on Mars and are afraid the mission may be over.

MARTIN: Pathfinder's mission was only supposed to last one month. In fact, it lasted almost three. It was remarkable⁵ in many respects from the way it landed on Mars to the people who chose to work on the project. Science correspondent Joe Palca covered the Pathfinder mission for NPR. He visited the Jet Propulsion Lab recently and has this look back at the historic accomplishment¹.

JOE PALCA, BYLINE⁶: Before Pathfinder, the only other time NASA successfully landed on Mars was in 1976, when the two Viking missions touched down. The Vikings were flagship missions supported by lots of engineers and technicians and buckets of money. By comparison, Pathfinder was built on a shoestring⁷, part of NASA's faster, better, cheaper mantra at the time. It had a small team of engineers and scientists, and it used technologies that had never been tried. Many old hands at JPL shied away from the project, thinking it would never succeed. Even some of the people who did work on it were skeptical⁸.

JENNIFER HARRIS TROSPER: We weren't sure it was going to work. I really, truly was in the camp of this may or may not work.

PALCA: Jennifer Harris Trosper was one of the young engineers on the project. Only 29 at the time, she was a flight director on landing day. She says a small team working against the odds⁹ gave the project some advantages. Everybody had a get-it-done attitude.

HARRIS TROSPER: That's just how it was. You just - you found whatever the problem was, and you got the right people, and you solved it, you know, as good as you could in the time that you had.

PALCA: She nearly didn't work on Pathfinder at all. She came to JPL straight out of college, but then decided¹⁰ to take a leave from the lab.

HARRIS TROSPER: I went over to the former Soviet¹¹ Union - now Sevastopol, Ukraine, in the Crimea - and I taught English.

PALCA: After a while, though, she had second thoughts about leaving JPL.

HARRIS TROSPER: There was one point in time when I was, like, eating a cold chicken leg at an outdoor cafe, drinking beer at 9 a.m. in the morning. And I thought, what have I - am I ever going to get back to America? What have I done with my life?

PALCA: So she let some people at JPL know she was interested in coming back.

HARRIS TROSPER: My phone rang one day, and it was Joe Savino. He's like, hey, Jennifer, you want to do this new job? Nobody wants to take it. It's on this new mission. I can't get anybody to take it. You want to take it? I'm like, sure. I need a job.

PALCA: Another young engineer who joined the project was Rob Manning. Like Trosper, Manning's background didn't necessarily prepare him for Pathfinder. He knew a lot about electronics and software.

ROB MANNING: But I really didn't know anything about parachutes. I didn't know about heat shields. I really didn't know much about, you know, the mechanics of flying through space.

PALCA: Pathfinder was going to use a simple but untried landing system. As it plunged¹² into the Martian atmosphere on landing day, the probe would still rely on a heat shield and parachutes and small rockets to do most of the slowing, but then it was going to smack¹³ into the Martian surface, protected only by airbags, and bounce like a giant beach ball until it finally came to rest. Manning was in charge of the landing sequence. When we spoke¹⁴ earlier this month, we were in the Space Flight Operations building. I asked if this was where he was on landing day.

MANNING: Yes, I was upstairs, right above us in our little control room, surrounded by glass - a small group of us, maybe 10 of us in the room.

PALCA: NASA brass¹⁵ stood outside. Network television cameras peered through the glass. The tension was off the charts. Nobody knew if the airbag scheme was going to work. Manning says there was only one way to know for sure whether Pathfinder touched down safely.

MANNING: I could hear on my audio set voices from Spain.

PALCA: Outside of Madrid, there's a giant radio telescope. JPL had sent Sami Asmar to Spain so he could use that antenna¹⁶ to listen for a signal from Pathfinder. The control room at JPL could hear Asmar, and he could hear the control room.

SAMI ASMAR: I could sense that they were very nervous. The time has come for the spacecraft to kind of announce itself, and there was a slight delay.

MANNING: No signal. And then...

ASMAR: I think I see a weak signal, and it's coming in and out. And that's when I heard an explosion of cheers and cries.

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PALCA: Success.

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PALCA: Yes, there was joy. But Manning says for an engineer responsible for designing the mission and building the spacecraft, there was something else, too.

MANNING: The real reason we're cheering is that we're relieved because up until that moment, we're constantly thinking about what was it we forgot to do? What didn't we check? What didn't we see? How - where did we go wrong?

HARRIS TROSPER: Yeah, it was certainly relief, but for me it was elation¹⁷, and I swear I feel that way every single time we land something successfully on Mars. But then the other piece of it that I experienced with Pathfinder that was unique and the first-time experience for me was this idea that we were the first ones there in this other place in our solar system exploring.

PALCA: Both Trosper and Manning stayed on at JPL and worked on other successful Mars missions. Manning is now chief engineer at JPL, and Trosper is his deputy. He says there's been a shift in the way missions are developed and tested.

MANNING: In the past, we worried about - that the thing breaks.

PALCA: Now the hardware is reliable, but controlling that hardware, writing the code to make it work has become more and more complex. And it's tricky¹⁸ to even know when you've made an error. And in the days of Pathfinder, at least some on the team knew how each system on the spacecraft worked - maybe not in intimate detail, but in general how they worked individually and together. That's gone.

MANNING: And today, we can't hold our systems in our heads anymore. It's - they're far bigger than any human being can comprehend. It's just too many things inside, and our brains aren't big enough to hold it.

PALCA: Since we're not likely to grow bigger brains, it's going to take some new strategies to manage these complex missions. And in a way, each time a mission succeeds, the pressure mounts. Success is no longer an ambitious dream. It's an expectation. But then, despite the pressure and the complexity¹⁹, both Trosper and Manning seem to think the reward is worth it.

Joe Palca, NPR News.

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