It’s always sad to say goodbye, but when we send our robotic emissaries out into the cosmos, it’s just a matter of time before they shut down. Today we’re going to say goodbye to a few missions which have reached the end of their lives. But they were very good robots.
SOFIA Science Center (USRA)
SOFIA flying observatory takes final flight (Astronomy Magazine)
What is a Lagrange Point? (NASA)
Space Launch System (NASA)
Scientific Balloons (NASA)
Airborne Astronomy Ambassadors Program (SETI Institute)
Voyager – Mission Overview (NASA)
Star Trek I: The Motion Picture (Star Trek)
In Depth | Oort Cloud (NASA)
Record-Breaking Voyager Spacecraft Begin to Power Down (Scientific American)
How Do Gravitational Slingshots Work? (Universe Today)
Voyager – Operations Plan to the End Mission (NASA JPL)
Transcriptions provided by GMR Transcription Services
Fraser: Astronomy Cast, episode 661. Saying goodbye to missions that ended. Welcome to Astronomy Cast for weekly facts-based journey through the cosmos. We help you understand not only what we know, but how we know what we know. I’m Fraser Cain. I’m the publisher of Universe Today. I’ve been a space and astronomy journalist for over 20 years. With me is Dr. Pamela Gay, a scientist from the Planetary Science Institute, and the director of CosmoQuest. Hey, Pamela. How’re you doing?
Pamela: I am doing well. It is solidly winter here, which means we have gone through the part of the year where I have to turn off the air conditioning to record, to the part of the year where I have to turn off the head to record. And, what I’ve realized is there’s a lot of thermodynamic suffering that takes place for this podcast.
Fraser: Yeah. We’re at the end of a really nice stretch of weather, and it’s about to get cold and snowy. And, I am nervous because the only person who handles snow plowing on our mountain hill has decided he doesn’t wanna do it anymore. So, I’m not really sure how we’ll escape our house. Anyway, let’s get on with the show. It’s always sad to say goodbye, but when we send our robot emissaries out into the cosmos, it’s just a matter of time before they shut down. Today, we’re gonna say goodbye to a few missions which have reached the end of their lives, but they were very good robots. All right. Let’s talk about some robots that are about to just turn into chunks of metal.
Pamela: Well, they were always just chunks of metal. They were just slightly more animated chunks of metal in the past.
Fraser: Smarter metal.
Pamela: Smarter metal. Yes.
Fraser: Yeah. More mobile metal. Yeah.
Pamela: So, my favorite Mars mission – And, I never thought I would have a favorite Mars mission. My favorite Mars mission InSight is estimated to cease to function in a meaningful way sometime this month as dust builds up on its solar panels and they’re trying to measure every last possible earthquake they can. But, its time is coming, and it’s a good time to look back on what has become one of the most creatively engineered mid-stream along the way mission that we have so far sent to Mars.
Fraser: So now, Mars InSight is solar powered.
Fraser: So, why is it coming to an end? The sun’s still there.
Pamela: The sun is still there. The problem is that dust has a habit of building up between the solar panel and the sun, and limiting just how much sunlight is able to get to those photovoltaic cells and power the systems including the heaters that are needed to keep it going over time.
Fraser: But, wait. NASA is aware of dust. Why didn’t they think of a way to remove the dust from the spacecraft?
Pamela: I know this is the constant question.
Fraser: It’s like half the comments that I get on my videos.
Pamela: I know. And, what I love is this is the first mission that has gone out of its way to try and remove dust from its own solar panels. They scooped up a scoopful of sand and used it to essentially remove the dust from the solar panels. But, they don’t have a lot of electricity.
Fraser: Yeah. That method, though. I just wanna talk about that method. So, what they figured out, normally, the rovers have their solar panels dusted off by dust tunnels. But, for some weird freak of Martian weather, the place where InSight went hasn’t been getting visited by dust tunnels. And so, they figured out this really clever way where they scoop regolith with the little shovel, they dump it on the solar panels, and the dirt collects up this electrostatically charged dust and drags a bunch of it off. And, they dramatically extended the light of the rover using this technique that nobody knew it was even possible, which is wonderful.
Pamela: Yes. And, this is one of those things where they weren’t able to keep going with all the instrumentation. But, the thermal sensor they had decided long ago that it was not going to be cooperative anyways. And so, as they prolonged the mission, they simply say, “We’re gonna let that one go.” So, to go back to the beginning, this little spacecraft landed back in 2018. It had two primary instrumentations. It had the seismograph and it had the mole.
And, the mole’s goal was to drive itself down through the dirt on the surface, embed itself a couple of meters under the ground along the way, measure the thermal properties, and allow us to finally know if all of our models for how the temperature varies as a function of depth on Mars are accurate or not. And, what we learned was the dirt on Mars is more clay-like than we had anticipated. And, the mole did not dig. It –
Fraser: Bounced. Yeah.
Pamela: They tried everything.
Fraser: Yeah. I have very clay soil where I am, and when it dries out, it is concrete. And obviously, regolith on Mars has dried out.
Pamela: And, the way the mole was supposed to work is it was a long cylinder that had essentially a thumper just like out of the movie Dune. It embedded inside and it would slowly rise up and then smash down. And, the smash down was supposed to drive the entire thing downward through the soil. And, it just kinda stayed in place. They tried pushing it down with that wonderful arm. It just refused to go. So, we didn’t learn anything about the thermal profile. But, the creative solutions, they just kept trying until senior review said, “Stop. Just stop.” Were truly delightful.
The other instrument was a seismograph that was designed to measure marsquakes, and they weren’t sure what they would detect when they built this instrument. They figured if nothing else, they would catch the waves of space rocks, asteroids hitting the surface of Mars and sending shockwaves reverberating through the planet. And, what they found instead was Mars is continuing to have quakes. It has a over 1,000 kilometer across molten core that is a lower density than had previously been estimated, and that lower density is responsible for completely different thermodynamics than what had been predicted, allowing it to continue to have this molten core far longer than we had thought possible.
Its surface crust is thinner than we thought. And, we learned all of this because the planet periodically just has marsquakes, and we’ve been measuring them, and a bunch of them are located within the same geographic region. And so, this world is a whole lot more interesting that we had thought, and we now need more seismographs, please.
Fraser: Right. Yeah. Everywhere. Seismographs everywhere. Yeah. And, I facetiously ask the question about the Mars dust, but the answer is fairly simple. The spacecraft was designed for one year. So, they gave it this solar power capacity for one year, and it ended up lasting four years. Way beyond what it was expected to. And, could there be a system, some kind of mechanism that dusts, or blows, or wipes, or cleans, or electrostatically charges or scrapes dust off? Maybe. But, each one of these devices adds to the weight. Adds to the budget. And, they were given a set budget to work with and they designed all of their science goals within that set budget, and they launched their mission.
But, on that note, actually NASA is developing a really interesting sort of coating that they can put on everything. That is clear. That is electrostatically charged so that you can – Or, can be electrostatically charged so that you can actually run a current through it and repel things like the dust because the stuff on Mars, imagine when you open up a package and you get the little Styrofoam.
Pamela: Yes. Yeah. The little white beads.
Fraser: Yeah. The little Styrofoam beads that just cling to everything. You try to wipe them off, and now they’re all on your hands. And, you wipe them again on something else. Now, they’re all over that. It’s the electricity that’s holding them. Anyway, so they’ve developed this new coating and they’re actually testing it on the International Space Station right now. It’s actually on the exterior. They have a bunch of experiments on the exterior of the station. And, if it works, then they can apply it to solar panels, to camera systems, to science instruments, to anything.
So, just by default, any new rover will be equipped with this coating, and then all of these surfaces, they can run through charge through them whenever they want to, to try and repel the stuff. So, my point is, is NASA’s aware that there’s dust, and they’ve thought of ideas, and they’ve had to reject all of them. And, if you were in their meetings, you would have, too. All right. We’re gonna talk about another mission that we’re gonna say goodbye to in a second. But, it’s time for another break.
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Fraser: And, we’re back. All right. What mission do you wanna say goodbye to next?
Pamela: So, the SOFIA Airborne Observatory I think is one that will eventually deserve its entire own show, but they only did its last flight in September. September of this year, 2022. And, we’re still waiting for all of its latest round of data to get its first round of processing. So, that highlights episode will have to come in the future. But, for now, we have to say goodbye.
Fraser: So, what was SOFIA?
Pamela: So, SOFIA is the Stratospheric Observatory for Infrared Astronomy. It’s a modified 747 that has a over two meter telescope just kind of hanging out in the back with a door that they can open and point the telescope out. Allowing them to, as they fly through up to 10 hours’ worth of night will allow them to observe the infrared sky in colors that we can’t see, even from our highest mountains because they’re able, with the aircraft, to get up above the worst of the water.
SOFIA flies up at 41,000 feet. So, this is higher than your standard 747 on a consumer flight. And, this specially designed observatory, it had vibration compensators. It had some of the coolest technology. Literally, because it’s infrared you have to have cool technology.
Fraser: Pun intended.
Pamela: Of our time. Allowing it to do everything from – I think one of the most surprising, and we covered this earlier, discoveries was they directly measured water in the regolith. Being able to see that it was in places that it hadn’t been anticipated previously. They were able to see helium hydride, which was a molecule that it was expected that it existed in the early universe, but we hadn’t seen it prior to SOFIA spotting it in a planetary nebula. This is one of the few molecules that helium is willing to be a part of where, basically, a proton and a rogue hydrogen core is able to share an electron with a helium atom.
Over and over, this telescope allowed us to see wavelengths that otherwise required a spacecraft, but using instrumentation that got to be brought home at the end of the flight, and modified, and improved, and constantly changed as our technology changed. And, it was this fabulous hybrid between a ground based facility with all of its atmospheric limitations and a space based observatory with all of its lack of modification limitations.
Fraser: So, why are they shutting this down? It’s not like its solar panels are getting covered with dust.
Pamela: Yeah. This is the great question. It basically comes down to NASA only has so much money to run all of the observatories at any given moment. And, JWST is the great sink of infrared funding right now. So, with JWST fully functional, the argument was made that we don’t need a two and a half meter telescope pointing out the side of an aircraft when we have this significantly larger telescope sitting out at L2. And –
Fraser: And, James Webb completely overlaps the capability of SOFIA except that SOFIA can look at the moon. JWST can’t look at the moon. And, JWST could make the observations that SOFIA might make in one flight, it could probably make that in a fraction of the time. It’s more powerful. It’s out in space.
Pamela: Yes. But, SOFIA lets you continue to innovate and test new technologies.
Fraser: Right. And, that is huge.
Pamela: Yeah. We need to be able to experiment. And, I’ve brought this up before. I am very much a fan of design and test, design and test, and just keep moving with incremental design. JWST, SLS, these are all it works or it doesn’t. Kind of all or nothing. And, no. I don’t like that.
Fraser: Yeah. But, that’s the programmer in you, though, right? That process of iterative development and design is baked right into creating something new. It is complicated. And, I 100 percent agree with you. There is another track where this stuff gets built, and designed, and tested, and that’s balloons. So, NASA still has a very vibrant balloon astronomy pathway. We actually just did an article on Universe Today about all of the cool balloon missions coming up in the next 10 years.
They’re putting a lot of investment into developing new instruments, putting them on balloons, flying them at high attitude, and they can go way higher than SOFIA can. Testing out to see whether they work, iterate, iterate, and then these things start to show up on spacecraft down the road. So, I do think that there is another pathway. And so, I guess that’s probably it is that in terms of pure productivity, SOFIA just doesn’t hold a candle to JWST. You are burning jet fuel. You are contributing to climate emissions.
There are downsides of running a 747 for 15 hours. And then, all the other ongoing expenses. So, it just sounds like somebody just said, “Well, I think it’s time to shut this thing down.” And, it is unfortunate because it’s a wonderful glorious instrument. It’s such a great idea and has produced so many wonderful findings. And yet, it’s just like the landscape has changed.
Pamela: Yes. I do wish that they allowed it to stay commissioned kind of like Old Ironsides in Boston. One of the old tall ships stayed commissioned where no one expects Old Ironsides to sail out into battle anymore. But, to have it continue doing its teacher programs, and to still be there if it’s ever needed to fly once again.
Fraser: If there’s an asteroid passing in between the Earth and the moon, and JWST just can’t watch it. Then, you can get Bruce Willis to fly SOFIA. Yeah. All right. What else would you like to say goodbye to?
Pamela: Yes. So, Voyager is shutting down.
Fraser: No. La, la, la. Don’t say it. Voyager’s fine. It’ll live forever.
Pamela: Voyager will live forever.
Fraser: There you go.
Pamela: This is entirely, entirely true.
Fraser: In that the physical atoms will exist in some kind of coherent form for a few billion years. Sure.
Pamela: And, come back. I’m trying to figure out how to make a good pun.
Fraser: Are you trying to make a Star Trek reference?
Pamela: I was trying to make a Star Trek reference. I failed.
Fraser: It’ll find an alien intelligence, merge consciousness, return to Earth, and search for whales? No, wait. Now, I’m starting to blend my sci-fi references. All right. But, tell us. What is the state of the Voyagers? ‘Cause I feel like I’ve been bracing for impact for the loss of the Voyagers for about a decade now.
Pamela: So, Voyager 1 and Voyager 2 are thought to have finally, actually, this time, for real have left our solar system’s sun interacting environment and are on their way beyond it. Now, they’re still within the confines of the Oort cloud. Our solar system really feels like it goes on forever. But, they have exited the area that is defined by the sun’s influence, and they are now able to experience the cosmic rays at the higher level to experience the interstellar conditions better. And, they were sending data back, and they continue to try to send data back.
But, it reached the point where they did have to turn off more instruments. And, I think what was more of a it’s time to start to say goodbye than just shutting down more instruments. They’ve been doing that on a regular basis pretty much as long as we’ve been alive. The real thing was Edward Stone, the project scientist, retired after 50 years. And, right now, what we’re seeing isn’t so much in planetary science, the retirement of the Apollo era folks ‘cause that’s rocketry.
Yes, we have a few of them. Harrison Schmitt still attends meetings. There’s no greater way to confuse the speaker than to start your question with, “Harrison Schmitt, Apollo program.” That is what causes speakers to tremble.
Fraser: For real, for real. Yes. 50 years. Yeah. Yep. Buzz Aldrin, Apollo.
Pamela: Yeah. Well, he doesn’t attend conferences and ask early career researchers questions the same way.
Fraser: Right, right. Yeah. In the way that Dr. Harrison Schmitt does. Yeah.
Pamela: But, Edward Stone, he was part of this young group of researchers that didn’t all even have advanced degrees as they were planning out exploration of our solar system. A lot of these people, they were basically making up what mission planning looked like as they went because this was the first massive solar system exploration program we had had, and it was put together on basically lack of computers to plan out the orbits.
Fraser: Yeah. Think about the gravitational slingshot maneuvers they had to do to go past four planets.
Pamela: By hand.
Fraser: By hand. Yeah.
Pamela: Slide rule.
Fraser: Yeah. They must’ve used computers to some extent. But still, it was an astonishing piece of work to do that.
Pamela: And so, now we’re starting to lose that first generation of real planetary scientists who planned out these missions and were there from day zero to see the exploration of the outer solar system to – Well, they missed Pluto the first round. But hey, that’s what got us New Horizons. But, the understanding that we got of Uranus and Neptune, Saturn and Jupiter. Seeing Io’s vulcanism. The icy cracks of Europa for the first time. Titan’s haze layers. We didn’t understand, prior to Voyager, that all these moons of other worlds were worlds in their own right.
And today, we continue to see. I don’t think kids are upset about Pluto and the definition of planet any longer, but planetary scientists really, really are. And, the number of people that want to classify all the major satellites as planets in their own right is not trivial. And, that fight was basically started by the Voyager missions, and I don’t know what will end the fights. But –
Fraser: Right. Yeah. But, it is different. When you think about the Voyagers, they’ve been shutting those instruments down one by one. And, I think it’s like when you care for somebody in your family, someone who is getting older, and you’re sort of seeing this constant decline and it’s happening in real time for you. As opposed to an accidental loss. The feelings of grief are different. And, it definitely feels very similar to me.
Obviously, it’s just a robot. But, you feel. You’re like oh. Now, it only has this many watts? Oh. It doesn’t have the power to run that anymore? And, the last thing that we’ll hear, the last transmission to be shut down, will be its ability to transmit home.
Pamela: Yeah. Communicate.
Fraser: Yeah. And, it’ll all just be from declining power. If you could replace its nuclear battery, it would be back up and operational. Probably. Who knows how much damage is happening. But, you could then send it to another planet and have it observe some more. But obviously, there’s no more other places for it to see. There are no interesting places for it to pass in the future. It’s just going to run out of power, and go silent, and then drift in the Milky Way for another few billion years until cosmic radiation and space dust grind it away to nothing.
Pamela: And, it’s estimated they will live to the 2030’s and beyond that. They just won’t have the power to go on.
Fraser: Yeah. We’re within a decade of saying goodbye to them. All right. Well, we’ve reached the end of our show. Thank you, Pamela.
Pamela: Thank you, Fraser. And, thank you to all of you out there who make this show possible through our patronage at Patreon.com/astronomycast. And, we are starting with this episode to put out a ad free version just for our Patreon community. So, go check that out. Join us.
And, this week, I would like to thank, in particular, Cemanski, Camy Raissian, Sean Martz, the mysterious Mark, Glenn McDavid, Dwight Illk, James Rodger, Gabriel Gauffin, Paul L. Hayden, Karthik Venkatraman, Gfour184, Benjamin Davies, Planetar, Steven Coffey, the lonely sand person, Andrew Stephenson, Brian Kilby, Naila, arctic fox, Bart Flaherty, the air major, Sam Brooks and his mom, John Öiseth, Dean, Nathe Detwiler, John Drake, Corinne Dmitruk, Lew Zealand, Jordan Turner, Leigh Harbourne, Jason Kardokus, Ron Thorrsen, Paul Esposito, Arthur Latz-Hall, Frank Stuart, Ganesh Swaminathan?
Bob Zatzke, Tim Gerrish, Ruben McCarthy, Robert Hundl, Kim Barron, timelord Iroh, Daniel Donaldson, Ian Abdilla, and Georff MacDonald. And, if you want me to pronounce your name closer to true, please include a pronunciation guide. Otherwise, I’m just gonna make it up.
Fraser: All right. Thanks, everyone. And, we’ll see you next week.
Pamela: Thank you all so much.
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