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As we’ve mentioned before, the Sun is a terrifying ball of plasma. It’s a good thing we’re keeping an eye on it. And that eye is the Solar and Heliospheric Observatory, or SOHO. Operating for more than 18 years now, SOHO has been making detailed observations of the Sun’s activity though an almost entire solar cycle. With so many years of operation, SOHO has some amazing stories to tell?
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This episode is sponsored by: Swinburne Astronomy Online, 8th Light
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Voice Over: This episode of Astronomy Cast is brought to you by Swinburne Astronomy Online – the world’s longest running online astronomy degree program. Visit astronomy.swin.edu.au for more information.
Fraser Cain: Astronomy Cast episode 322: SOHO. Welcome to Astronomy Cast, our weekly facts-based journey through the cosmos where we help you understand not only what we know, but how we know what we know. My name is Fraser Cain. I’m the publisher of Universe Today, and with me today is Dr. Pamela Gay, a professor at Southern Illinois University Edwardsville, and the director of CosmoQuest. Hi, Pamela. How are you doing?
Dr. Pamela Gay: I’m doing well. How are you doing today, Fraser?
Fraser Cain: Good, although it’s early in the morning for me on the West Coast.
Dr. Pamela Gay: Yeah, sorry. Thank you. For those who don’t know, I’m about to abandon the United States yet again, and fly off to Indonesia via all airports in between here and there, and give a talk at the Southeast Asian Young Astronomer’s Conference.
Fraser Cain: How long is the trip going to take you?
Dr. Pamela Gay: Yeah, it hurts. It’s four hours from here to L.A., then, it’s 16 hours to Hong Kong, and then it’s six hours to Jakarta, and then it’s a six hour bus ride to Bandung.
Fraser Cain: Wow! But, you’re going to be streaming this live. Although, I guess when people hear this, it will have already happened. But, anyway –
Dr. Pamela Gay: Ah, they’ll watch the YouTube channel.
Fraser Cain: Yeah, you can watch the YouTube channel. You can see what happened, and you’re going to be – what’s the purpose of the conference?
Dr. Pamela Gay: It’s to basically bring together the youngest, brightest astronomers from all throughout Southeast Asia and help give them a leg up on how to be successful in their careers as they bring astronomy to these developing nations – and very developed in some cases.
Fraser Cain: Right. But, I mean, the great thing is you can see what we’re doing. We use all these free tools to reach wide audiences around the world. I live in Canada; you live in the States. The people on our teams are all around the world, and it doesn’t matter.
Dr. Pamela Gay: Right. And what’s going to be kind of awesome about this is I get to walk in and give the message, “It no longer matters where you are.” There are things like money that are useful at really big universities, but there’s so much you can do for free right now, and this is something that we have to figure out every day at Southern University Illinois Edwardsville because we just don’t have the resources. And as I said in the pre-op for this show, all I want for Christmas is donations to CosmoQuest.
Fraser Cain: All right. Well, donations to CosmoQuest. Go to CosmoQuest or –
Dr. Pamela Gay: .org. CosmicQuest.org/donate.
Fraser Cain: There you go. And donate.
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Fraser Cain: So, as we’ve mentioned before, the sun is a terrifying ball of plasma. It’s a good thing we’re keeping an eye on it, and that eye is the Solar and Heliospheric Observatory, or SOHO. Operating for more than 18 years now, SOHO has been making detailed observations of the sun’s activity through an almost entire solar cycle. In so many years of operation, SOHO has some amazing stories to tell. So, this is one of my favorite missions, I’ve got to admit. Because it gave us a view of the sun that I’d never seen before, the pictures coming out of SOHO were just transformational. So, let’s talk about the mission. So, where did SOHO come from?
Dr. Pamela Gay: It started out of a European mission that had been conceived – a small mission, initially that was planned to just look at the sun constantly. Some astronomers who had gone down to Antarctica in the late ‘70s and done 24-hour observations during the summer months down there realized how much more there is to learn through constant observation of the sun. And so, planning began for a mission that they hoped would launch in the early ‘80s that would simply sit out in the L1 Lagrange point between the earth and the sun – that gravitational balancing point that allows you to orbit the sun at the same point that the earth is orbiting, and just send back image, after image, after image allowing us to understand all the different activities that our sun is capable of, and also provide an early warning system for some of the nastier things it’s capable of.
Fraser Cain: And I think we’re so used to it now. I mean, we have SOHO, we have SDO, we have [inaudible] [00:05:21]. There’s all of these spacecraft –
Dr. Pamela Gay: Stereo-A and –B.
Fraser Cain: Stereo-A and –B. So, we have all these spacecraft now watching the sun because this is important. But, this was the first really permanent eye in space watching the sun, right?
Dr. Pamela Gay: And what’s kind of neat is even though it was developed to be a little tiny European mission initially and ended up not being funded and instead they went after an infrared mission, the idea was considered so important that rather than scrapping it or waiting for funding for another tiny mission, they partnered with NASA and ended up creating a much larger spacecraft capable of doing a lot more science. And so, when this mission finally launched in 1995, it had nearly a dozen instruments capable of everything from measuring the solar wind, to looking at the surface of the sun, to blocking out the sun and measuring the solar corona, and unexpectedly discovering comet, after comet, after comet, after comet.
Fraser Cain: Right. So, what were the main objectives, then, of the spacecraft? What was it’s real mission?
Dr. Pamela Gay: Well, it’s fundamental mission was to provide 24-monitoring day, after day, after day of the solar surface and the surrounding corona, to watch for solar flares, to watch for coronal mass ejections and start to piece together what are the details of the solar cycle. How is it that our sun changes over the course of those 11 years as it goes from minimum to maximum and then reverses its path? It’s done that like a champ and we’ve realized that the sun was so interesting that coming up after this was the Solar Dynamic Orbiter that took what SOHO started and increased resolution by a bazillion, it feels like – increase the cadence of how quickly the images are taken. And this was that first low-res camera compared to SDO that let us in on how it is that solar flares develop, let us in on how it is that coronal mass ejections break and release energy into the corona and upper levels of the sun.
Fraser Cain: Some of the instruments, if you go to the SOHO website, you can actually see the views of the sun that are in sometimes almost real-time images, and it’s based on the instruments. So, you’ll see the LASCO image, right? They’ll load outer corona, and then that’s one –
Dr. Pamela Gay: That’s the one that’s used for comets.
Fraser Cain: Yeah! And so, it’s interesting how I’ve become quite familiar with the instruments because that’s how they describe the images that you’re seeing, like, “Oh, this is a LASCO image. This is a –” I think they’ve done a really good job of sort of helping us understand what instruments are on board. But what are some of the instruments on board the spacecraft?
Dr. Pamela Gay: So, you have the Coronal Diagnostic Spectrograph, which is out there trying to get at what are the different spectral lines that we can see in those outer parts of the sun. What basically is that hot gas? And with spectrograph, you can start to understand the temperatures – the fluctuations in temperature. There’s CELIAS, which is the Charge Element and Isotope Analysis System. And that first instrument, it came from Rutherford Appleton in the UK. This next one came from the University of Bern in Switzerland. This is an amazingly multinational spacecraft. There’s COSTEP, which is the Comprehensive Suprathermal – I love that word – and Energetic Particle Analyzer. It’s from the University of Kiel, which is also in Germany. You have the Extreme Ultraviolet Imaging Telescope, which is one of the ones that make those amazing all-disc images that we all love to just eat up. It’s from the Institut d’Astrophysique Spatiale in France. There’s the Energetic and Relativistic Nuclei and Electron Experiment. So, here, we’re looking at what’s the lag between the visible images that we see, the flares we see, the coronal mass ejections and when the high-energy particles actually start to get to L1. That one comes from the University of Turku, which is in Finland.
There’s the Global Oscillations at Low Frequencies instrument, which is also coming from France. And there, we’re starting to look at, well, our sun is actually a variable star, but the surface is essentially jiggling like Jell-O in a very mathematically precise kind of way. There’s LASCO, the Large Angle and Spectrometric Coronagraph, which is where we’re finding comets. That one’s actually a United States instrument coming from the Naval Research Lab. There’s the Michelson Doppler Imager from Stanford. This is where we’re starting to get at the speed of how things are moving on the surface. There’s the Solar Ultraviolet Measurements of Emitted Radiation – the SUMER instrument, which is from Max-Planck. SWAN – the Solar Wind Anisotropies from France. Ultraviolet Coronagraph Spectrometer from Harvard. The Variability of Solar Irradiance and Gravity Isolations – VIRGO – which is from Switzerland. It just goes on and on.
This is a mission where basically every heliophysicist in the world goes, “Oh, my God. If only we could.” And they built the instruments that, for their time, were basically the best you could get for observing how the sun’s surface fluctuates, how the corona heats up, cools off, changes what things look like. Invisible, ultraviolet, just all those imaging high energy colors, and then starting to get a sense of what are the particles coming at us.
Fraser Cain: And I know the mission was only supposed to last for two years, but as I mentioned, we’re closing in on 18 years now.
Dr. Pamela Gay: Right. So, this was a mission that when they launched it, the goal was keep costs down. It got bigger when they added NASA and ESA, but it was kind of an experiment. How will this work? They developed all these new technologies and it’s producing such great data that the just keep expanding it out, expanding it out, expanding it out. It’s currently funded to go through 2014 unless something really bad happens in both the European and US economies.
Fraser Cain: Right. I mean, I know that there’s some funding issues for a lot of the missions right now. I mean, I’ve heard that some missions may get defunded and have to get shut down.
Dr. Pamela Gay: Yeah.
Fraser Cain: Yeah. And so, I keep offering. I speak for all of Canada that if any of this gets shut down, we’ll pick up the tab and keep these missions going. I promise.
Dr. Pamela Gay: If only it were that easy. Sadly, it is –
Fraser Cain: The prices are very low. The amount to keep Cassini and stuff going, very inexpensive. We could totally afford it. So, 18 years of operation, what’s great is that’s almost a full solar cycle.
Dr. Pamela Gay: Right. And as we head towards 2014, we’re going to get to see another turning point for maximum towards minimum and start to see how does the sun look as it changes from one phase in its cycle to the next. And this is a mission that really, by putting everything live in almost real-time, it’s constantly being listened to. There are hundreds of kilobytes per second coming back from the spacecraft, which when my internet runs that slow, I get annoyed. But when it’s a spacecraft, that’s kind of awesome. And the mission’s been consistently putting all of its data online as quickly as it can, and this has allowed everyday people to participate in the science the mission’s capable of, and showcase what can be done in real-time by NASA and people working together.
Fraser Cain: Yeah. And, I mean there’s been tons of discoveries, and of course the one that you’ve mentioned a couple of times is this discover of comets.
Dr. Pamela Gay: Right. So, we always knew that there was a class of comets that basically, they’re the suicide comets – the sungrazers. And they’re on extremely elliptical orbits where they pass sometimes so close to the sun that it’s not passing past the sun, but rather diving straight in. And, we knew they existed, but we didn’t know how many of them existed. A lot of these things, they’re so small, we just don’t notice them. They’re on orbits that cause us to never really get to see them because they’re constantly in daylight – a whole myriad of different reasons. But, with this particular instrument, they have a chronograph – a disc that blocks out the main part of the sun and allows us to see the beautiful gas of the upper levels of the sun’s atmosphere. And it also captures all of these comets. In fact, people discover comets at a rate of one or two every three days, and that’s kind of amazing when you think about it. Since it launched, they’ve discovered over 2,400 different comets. One particular individual is responsible for over 100 of these discoveries, and that’s Mike Oakes. And they actually named an asteroid – which I find amazing. They named an asteroid after this comet discoverer and there’s actually a really good TED talk by Erin McKean where all of these amazing discoveries and how if you give people access to data, they’ll do science. All of this is highlighted in her TED talk.
Fraser Cain: Yeah. I mean, it’s just like, where else can you do this? You can look through this data from the spacecraft, and be the first person to spot comets crashing in to the sun, and help contribute to our understanding of this phenomenon. It’s awesome! Now, SOHO’s been going for 18 years, but it hasn’t been without its problems.
Dr. Pamela Gay: No.
Fraser Cain: Now, what kind of problem did it suffer?
Dr. Pamela Gay: Well, I think the most traumatic and one of those mistakes that leads me to believe I’m not allowed to touch the software for a spacecraft because I am not that careful, it actually was sent some bad commands. And this sent it into a fascinating shutdown mode where we thought we might have lost it forever. Couldn’t contact it, couldn’t contact it, couldn’t contact it, ended up using powerful radar to confirm it was still where we thought it should be; but it essentially lost its ability to be pointed at the sun for a little while. And it entered a very slow tumble, and they were able to realize, “Okay. It’s about to realign itself with the sun. Let’s try again to get contact with it,” and they were able to reestablish communications, fix the software and get it going again. And that’s one of those really amazing rescues that can happen. And, it’s kind of frustrating to think that it happened due to bad software, but then it got fixed.
Fraser Cain: That is terrifying, because to a software developer – we’re both software developers and how many times have you pushed a new update of your code, and everything breaks, and you have to go and physically get access to the machine and fix it. But, with spacecraft, you can’t physically go there and access them. So, every time you push an update, there is a chance that you have bricked your spacecraft.
Dr. Pamela Gay: I never thought of it that way, but you’re totally right! It’s bricking it. Yeah!
Fraser Cain: You are bricking it, and there’s no way. You can’t get in there and swap out the hard drive or reinstall the operating system. It’s done. It’s gone.
Dr. Pamela Gay: Yeah. There’s no shutting off your instance and returning to the prior image of it. Yeah.
Fraser Cain: But, you know what? That is not the problems that I was – I mean, I knew about that one, but –
Dr. Pamela Gay: Oh, you were thinking of the gyroscopes.
Fraser Cain: The gyroscopes! I’m going to call this the Fraser Initiative – Cain Initiative, which is to always send more gyroscopes. “So, what did it do? Ran out of gyroscopes.”
Dr. Pamela Gay: Yeah. It’s the standard problem is over time, the gyroscopes essentially wear out and stop doing their job balancing the spacecraft. But, this is a spin-stabilized spacecraft and they were able to figure out how to use its wheels to keep it going, essentially turning reaction wheels into gyroscopes in a certain way.
Fraser Cain: Yeah. Well, I know initially, the relied on the thrusters and realized that that was going to run them out of fuel really quickly, and then they came up with a method of using their reaction wheels, and problem solved.
Dr. Pamela Gay: And what’s kind of neat is this method, figuring this out allowed them to keep FUSE, which is a different spacecraft I think that we’ve talked about. They managed to keep it going longer. Over time, we are finding ways to escape the great gyroscope debacle that so many spacecraft happen to deal with. It wasn’t useful for Kepler, which is still kind of limping out of commission, but with this spacecraft, they brought it back.
Fraser Cain: So, what does the future hold, then for SOHO? Where do we stand now and what’s coming up?
Dr. Pamela Gay: Well, it’s going until at least 2014. I think many of us are eagerly waiting to see what happens as Comet ISON passes around the sun and we’re able to observe that in SOHO. I apparently like to abuse solar missions for comets. Then of course, as we exit this solar cycle, it’s suite of instruments plays a role along with SDO and all of the others in trying to put together the detailed picture of how do we predict when coronal mass ejections are going to happen? How do we predict when sunspots are going to form? How do we predict when they’re going to lead to solar flares? And we’re working to build a model for understanding the sun’s weather, hopefully better than we understand our own weather here in the middle of the United States. Weather prediction, no matter what they system is, is extremely complicated, but with the sun, the better we get, the safer our astronauts, the safer our spacecraft, and the safer our power grid.
Fraser Cain: Yeah, I mean. That cycle, we mentioned it’s a 22-year cycle – 11 years to go from minimum to maximum, then 11 years to go from maximum back to minimum. And so, we’ve gone from minimum all the way to maximum or some combination of this.
Dr. Pamela Gay: Right.
Fraser Cain: Right. But, we haven’t seen sort of the full cycle to get right back to the starting point from when SOHO made its observations. And then, even better, more amazing would be to come back around and see the cycle a second time with the same instruments, and then you could really put together all of that data.
Dr. Pamela Gay: And that’s where funding starts to become such an issue. It’s only alive until 2014, and that doesn’t get us 22 years. We’re going to need another four or five years of funding depending on whether or not the sun recovers on time; the sun doesn’t hold strictly to 11 years from cycle to cycle. And so, we’re now in the “are we going to be allowed to have Stereo, and SDO and SOHO all being funded” in this age where we’ve brought on ALMA and we’re building the Large Synoptic Survey Telescope. And we have James Webb, and we still need to fund human beings. It’s a scary time and we’re going to have to start turning things off, and choices are going to have to be made. So, I don’t know if we’ll get to those 22 years. I’m hoping to see it through 2014 because I know people that work on the mission. It’s kind of ugly out there.
Fraser Cain: Well, there’s not a lot in the L1 point. So, is that a stable spot? Will it stay there forever?
Dr. Pamela Gay: So, to be clear, it’s not precisely in the L1 position, because if it was, we’d have difficulties with radio communications with it. It’s actually orbiting in a plane perpendicular to the orbit of the earth around the sun, going around and around that L1 point in this elliptical orbit around a geometric place in the solar system. It’s a pseudo-stable position. Corrections do have to get made. So, it will stay there a while, but they do need to have fuel to keep it in a healthy orbit.
Fraser Cain: I see. I see. So, it’s sort of like it’s orbiting around this point so that we can still communicate with it, and it can still watch the sun.
Dr. Pamela Gay: Yeah.
Fraser Cain: That’s really cool.
Dr. Pamela Gay: So, we’re able to be in constant communications with it, and it still needs to use its thrusters to maintain its stability.
Fraser Cain: I’m going to see if I can try to get a spacecraft into that orbit in Kerbal Space Program.
Dr. Pamela Gay: That would be awesome.
Fraser Cain: Yeah. They’ve updated it – the game. So now, they’ve got a campaign mode now, so if you have it already, Kerbal Space Program, definitely check it out. Cool! I have one last question for you, Pamela.
Dr. Pamela Gay: Okay.
Fraser Cain: Do you know where your passport is?
Dr. Pamela Gay: Yes! I know where my passport is. It’s my airplane pillow that I have no clue where it is. So –
Fraser Cain: Well, you’re going to need it.
Dr. Pamela Gay: Yeah. I’m about to shred my house very, very quickly.
Fraser Cain: All right. Well, have a safe trip and I’m sure I’ll be watching what you do while you’re in Indonesia, and we’ll see you when you get back.
Dr. Pamela Gay: And all of our videos – the video of this live recording and all the videos from what we’re doing at the Southeast Asian Young Astronomer’s Conference, they’re all going to land on Astrospherevids thanks to Richard Drum who’s really helping us out.
Fraser Cain: Thanks, Richard. All right. Well, we’ll see you whenever I see you next.
Dr. Pamela Gay: Okay. Sounds good, Fraser.
Fraser Cain: All right. Have a good trip.
Dr. Pamela Gay: Bye-bye.
Fraser Cain: Thanks for listening to Astronomy Cast – a non-profit resource provided by Astrosphere, New Media Association, Fraser Cain and Dr. Pamela Gay. You can find show notes and transcripts for every episode at Astronomycast.com. You can email us at info@astronomycast.com, tweet us at AstronomyCast, like us on Facebook, or circle us on Google Plus. We record our show live on Google Plus every Monday at 12 pm Pacific, 3 pm Eastern, or 2000 Greenwich Mean Time. If you missed the live event, you can always catch up over at CosmoQuest.org. If you enjoy Astronomy Cast, why not give us a donation? It helps us pay for bandwidth, transcripts, and show notes. Just click the “Donate” link on the website. All donations are tax deductible for US residents. You can support the show for free, too. Write a review, or recommend us to your friends. Every little bit helps. Click “Support the Show” on our website to see some suggestions. To subscribe to this show, point your podcatching software to Astronomycast.com/podcast.xml, or subscribe directly from iTunes. Our music is provided by Travis Earl, and the show is edited by Preston Gibson.
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Duration: 27 minutes
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