Ep. 521: The Deep Space Network

We always focus on the missions, but there’s an important glue that holds the whole system together. The Deep Space Network. Today we’re going to talk about how this system works and how it communicates with all the spacecraft out there in the Solar System.

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Show Notes

Deep Space Network – 3 facilities
Goldstone Deep Space Communications Complex
(Official site for Goldstone)
Madrid Deep Space Communications Complex
(Official Site for Madrid DSC)
Canberra Deep Space Communication Complex (CDSCC)
(Official site for CDSCC)

Operations Control Center at JPL

NASA Eyes website – see DSN’s current communication targets live


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Fraser: Astronomy Cast, Episode 521: The Deep Space Network. Welcome to Astronomy Cast, a weekly facts-based journey though the cosmos where we help you understand not only what we know, but how we know what we know. I’m Fraser Cain, publisher of Universe Today. With me, as always, is Dr. Pamela Gay, a senior scientist for the Planetary Science Institute and the director of CosmoQuest. Hey, Pamela, how you doing?

Pamela: I’m doing well. How are you doing, Fraser?

Fraser: Great. Sorry, everyone. We are recording this episode live at a different time, and that’s because I wasn’t here on Friday, and that’s because I was in Costa Rica with my good friend Dr. Paul Sutter on our next Astro Tour. I’m not even gonna remember which number this is now. I think it’s No. 4, but this was amazing. We were in Costa Rica, we got a chance to see the Arenal Volcano, got to do river cruises, lake cruises – well, one of each so not “s”. We saw many different kinds of monkeys.

Probably my highlight was the hummingbird forest or hummingbird preserve where they set up, I don’t know, 40 hummingbird feeders, and there was probably 100 hummingbirds, like 10 different kinds of hummingbirds up in the cloud forest. It was absolutely amazing. We had a great time. Thanks everyone who joined us.

And we recorded an episode all about dust, which I think is a topic we haven’t covered too much. So, dust and how that led to the BICEP2 results being overturned, so it’s sort of a fascinating story. And Paul was on the Planck team that helped overturn the results, so he had an inside scoop on the whole story. So, we’re gonna put this in as a bonus episode at some point this week or early next week. All right, Pamela, I don’t know if you had anything to say? Should we just go right into the show?

Pamela: Well, I mean, if you wanna join us on future Astro Tours, check out astrotours.co, and you can join me in the future. I’m gonna be going along with Fraser, and we are going to be doing in June a Joshua Tree National Park trip. This is the All-Stars trip with us, Paul Matt Sutter, John Godier, Skylias. It’s kinda gonna be amazing. So, if you looked before at the price and went, “Oh, no, can’t,” well, look again because the prices went down, and we’re really hoping that you can join us out under the dark skies.

Fraser: So, the price has been reduced, so go back to astrotours.co, and then just go to the All-Stars Party, and you can see the new price. The reservation date has been pushed back a couple of weeks. You’ve still got a couple more weeks to make a decision on that, so definitely go and check that out. All right, let’s get into the show. So, we always focus on the missions, but there is an important glue that holds the whole system together, the deep space network. Today, we’re gonna talk about how the system works and how it communicates with all the spacecraft out there in the solar system.

All right, Pamela, it is a big oversight. I know some people will spend some time talking about the Deep Space Network, but I don’t think people really think about how we are getting all of this data from all of these missions back on earth at different distances, some of them are in different locations. What is the mechanism? And that’s the Deep Space Network. So, what is it?

Pamela: It is three different sites on the planet Earth that are distributed from east to west here in the United States: out in Goldstone in California, or near Goldstone – Goldstone is actually a ghost town that now I really wanna go to after prepping for this show – outside Canberra in Australia, and outside of Madrid in Spain.

These three different locations, the way they’re spread out from east to west mean that once you’re located high enough above the planet Earth, you are always within sight of one of these three facilities, each of which is built kind of within a natural bowl in a valley between various mountains. This protects the telescopes from all the radio noise that you can get here on the surface of the planet, allowing them to focus on everything out there somewhere.

Fraser: All right, so you’ve got three facilities at essentially three different portions on the globe so that at least two or one is always being able to see the entire sky so that all spacecraft can always be communicated with. What are the actual facilities like? What are they?

Pamela: Well, they are each a set of different telescopes. This is one of the things that I think gets missed in the story a lot. It’s not like there is the Goldstone telescope. Well, there is the Goldstone, but Deep Space Network at Goldstone is actually a suite of a bunch of different telescopes. Madrid is a suite of a bunch of different telescopes. And each of these different facilities has one 34-meter telescope, has two or more – let me start that over. Each of these facilities has one 34-meter high-efficiency antenna, so this is the “hey, I got you, we’re listening close right now”. There’s also two or more 34-meter beam waveguide antennas, there’s some 26-meter dishes, and one 70-meter antenna per facility.

And it’s these 70-meters that we’re used to seeing in the pictures. They’re big, they’re dramatic. Goldstone, in addition to being used to receive sound, is also used to – well, it’s also a radar dish, and so there is the occasional death to things like bees when they’re igniting the radar on it to not just catch the radar signals but measure precisely where all of this stuff is in space.

Fraser: So, at each facility, there is the collection of telescopes, and the big one is the 70-meter telescope, and then there are these other ones as well. And people always make this joke to me when we talk about how we’re able to still communicate with the Voyagers and New Horizons, and they’re so far away. “Oh, we can communicate with a satellite that’s billions of kilometers away, but I can’t receive a cell phone signal.” If you were willing to care a 70-meter telescope in your pocket, you would always be able to get a cell phone signal. That would be no problem.

Pamela: Unless you were, of course, one of these 70-meter telescopes because they’re in radio quiet zones. So, there’s a certain irony. They way they’re set up, they are good for everything that is 30,000 kilometers and higher above the surface of the earth, but you start getting lower down, and the shape of the planet, the mountains that surround them, all of these different things serve to isolate them from signals. So, this is where the deep space and the Deep Space Network comes from is, well, you have to be high enough above the surface of the planet to make sure you’re always within sight of one of these different dishes.

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Fraser: All right, and so then how does operationally, how does this actually work?

Pamela: It’s all controlled out of the Jet Propulsion Lab out in Pasadena, California. This is a NASA facility that is owned and operated by Caltech. It actually had its roots as an Air Force facility back before 1958, got transferred over to NASA with the beginning of, well, Mercury and all of those humans going into space, and it was set up as a way to get signals back from the Mariner missions to get signals back from all of these early missions in the 1950s. Now, with Explorer, it wasn’t all that formalized.

It was more a matter of we’re gonna send these facilities out, we’re gonna have mobile radio receivers out in places like middle-of-nowhere Nigeria. Nigeria isn’t in the middle of nowhere, but where they went sure was. And this combination of distributing human beings around the world with radio dishes meant that we could distribute spacecraft around the solar system and get the signals back to Earth. Unfortunately, planetary rotation does mean you have to distribute things around, and as we launched more and more facilities, it became clear that we needed to have a permanent facility here on the planet Earth dedicated to listening to what was going on out there.

Now, in the 1960s when this was really starting to pick up steam, we had the 1966 version of this which included Goldstone, which has always been included in the network. Then we also had Woomera, Australia, Canberra, Australia where we still have locations. At that point, we included Johannesburg, South Africa as well as Madrid, Spain, and then of course we had launch support out of Cape Canaveral and the Ascension Islands.

Over the years, the facilities have become fewer in number but more and more important in what they’re able to do, and they’ve added more and more dishes that increase their capacity. And at this point, we are in the numbers in the 60s where they have numbered each successive dish as they have continued to upgrade the systems at the various locations. And so, out in Goldstone, we have Nos. 11-14 in ‘74, but today, if you go to Deep Space Network now, you’re gonna find, well, those numbers aren’t entirely the same as dishes have been replaced and upgraded.

Fraser: If you actually go – I mean, this is one of the best things that you can do – go to…it’s eyes.nasa.gov/dsn, and then go to the Deep Space Network Now. And so, just as an example, at the time that we’re recording right now, out at Madrid, the big dish is talking to the Mars Reconnaissance Orbiter, and the next dish is also talking to MRO, and then one is talking to ACE – I’m not sure which that is – the Advanced Composition Explorer, and then the other one is talking to OSIRIS-Rex. Our of Goldstone, one is talking to STEREO A, another is talking to the Geotail, one is talking to Juno, and one is talking to Hayabusa-2.

In Canberra, the big telescope is offline right now, but one of them is talking to Voyager 2, one is talking to Juno, and the other is talking to Voyager 2. So, you can just see. Go to Deep Space Network Now, and you can see exactly which dishes are talking to which spacecraft, how long it takes for the information to get, and this is what I love. For example, Voyager 2, it takes 1.39 days for the light to get to and from Voyager 2 because of its distance into the solar system. Just an amazing technical accomplishment. And you can see why the amount of data it can get is so low because they’re so far.

Pamela: And as we’re starting to get more and more of these small space probes out at great and greater distances, some of which count as no longer in our solar system, we’re also having to expand how the network works. And one of the things that they’re working on doing now is increasing the way the dishes work so that they can array them together and get multiple individual dishes working as an array to all listen in on the same signal. And this ability to combine dishes has been used before. There were issues with the Galileo probe when it was out at Jupiter where it just didn’t have a high-gain antenna that worked the way it was supposed to.

And so, they had to use, well, more resources than were originally planned to get what data they could back down to earth. And at various points throughout history, when there have been issues with spacecraft, they have combined multiple telescopes, they’ve brought in additional telescopes, sometimes using the Parkes telescope in Australia, so that they can catch these weaker signals to rescue spacecraft that just might need an extra hand up.

Fraser: Now, I mean, radio waves are one of those few wavelengths where you can actually quite easily in real-time or even after the fact combine the data signals together, so are they using interferometry –

Pamela: They are.

Fraser: – to combine the signals? And then I’m sure many of these dishes were brought in for the Event Horizon Telescope where they turn the entire planet into one big telescope to be able to observe the supermassive black hole at the heart of the Milky Way. So, I didn’t know that they used that method to be able to get some of those weaker signals as necessary. That’s really interesting.

Pamela: And what’s interesting is there are a lot of assumptions that get made about how these different telescopes get used and where they do and don’t get used. I’ve heard quite often, and I suspect we’ve even screwed up and said it before here on this show that Arecibo gets used as part of the Deep Space Network, and it does not. The Deep Space Network is specifically these Goldstone, Madrid, and Canberra facilities, and where the confusion comes in is Goldstone has other dishes that are used for other things. It uses its large dish also for radar work, and Goldstone and Arecibo work together as radar facilities to help us measure asteroids and other objects as needed.

And there’s a few other radar dishes out there: Haystack Observatory in Massachusetts, there’s facilities out in the U.K., so we have other radar dishes around the world. But it’s this combination of Arecibo and Goldstone are two of our main radar dishes, and Goldstone is also part of the Deep Space Network that leads to some of these confusions. In general, this is a facility that is quite happy to sit there going, “We shall listen to spacecraft and leave science to all those other dishes out there.”

Fraser: And so, I can sort of imagine that in some cases, all the spacecraft are out there, and they’re gathering up all of their science, and then they’re waiting for their turn to transmit the signals home. And so, we would probably get more science from these spacecraft if we had more facilities. Is it like the more mission you have, the more capacity you need in the network? Are one of these behind one of the other?

Pamela: With the Space Flight Operations Facility that they’ve built out at JPL, they do a lot of cue systems where they’re like, “Okay, so this spacecraft is here in this orbit. It will be visible to the earth at this point, so we schedule it now.” And so, there’s a lot of careful choreography that goes into getting signals back to Earth. We also are starting to find that radio systems are cheap enough to build and are efficient enough to build that some places like the advanced physics laboratory out on the East Coast at Johns Hopkins University, they’re in some cases building their own receivers.

We also see that some of the European Space Agency facilities have their own radio receivers. And with the ability of smaller institutions to get all of their data down for themselves, it’s this balancing of, yes, the Deep Space Network does need to build more telescopes that it can use to receive the signals from these distant space probes, but at the same time, some of these space probes can also just send their messages straight back to their principle investigator’s institution.

And the Deep Space Network isn’t for all the lower Earth orbit stuff. It’s only for the more distant objects, and that frees up the network as well when it doesn’t have to listen to things like Discover as it – well, Discovers are on planet Earth.

Fraser: So, I mean, do you think that we’re at a point where bigger telescopes are gonna be necessary? More telescopes? Or do you feel like we’re at a point where – I mean, it’s interesting to see how the Europeans have their own version of this. I’m sure the Russians have their ability to communicate with all of their spacecraft, and yet when needed, I know you get these – sometimes you’ll see this in press releases where some really interesting thing is happening at a time when, say, the European network isn’t gonna be able to see it, and so NASA will pitch in.

As I mentioned, right now, the Deep Space Network is observing the Hayabusa mission, so you can see that they’re getting involved. So, I mean, do we see this collaboration between the different nations coming together to be able to help each other out as scientists?

Pamela: There is definitely a great deal of collaboration that goes on. This is part of the treaties in many cases between the different nations where there are trades for getting instruments to fly in spacecrafts, getting time on the Deep Space Network, getting data. All of these different things can be traded with no-cost agreements where the U.S. will provide something that they pay for on their side and get something that isn’t money in exchange that has real value for us. So, when we look to missions like Hayabusa, yes, they totally use the Deep Space Network. SpaceIL is going to be using the Deep Space Network with their little Beresheet lander when it gets to the moon.

And all of these different agreements work together to get more science done. Now, one of the interesting things to me in terms of how do we choose to expand the Deep Space Network to meet the coming needs of the future. We have two things happening simultaneously. One is the miniaturization of the transmitters that are going on spacecraft where we’re capable to more effectively send back signals than we could in the past, and we can send back tighter signals than we could in the earliest spacecraft. And on the earth, that same miniaturization is making our systems more and more sensitive.

So, as we’re able to essentially shout into the void more effectively with all of our spacecraft, we are also able to more effectively listen in from the surface of the planet. As this trade-off continues, yes, we’re going to continue to need these large dishes, but how do we choose to expand? And it looks like the answer is going to be building arrays of dishes instead of building the large single dishes that we built in the past.

Fraser: And that was sort of my next question was do we need a bigger dish? But it sounds like that’s not the plan. The plan is more but smaller.

Pamela: And the other thing that we haven’t figured out that’s definitely going to affect long-term planning is what is the role of CubeSats going to be because a CubeSat by its nature is not going to be able to have a massive power source and a massive high-gain antenna to send data back to the earth. And if we move to building more and more CubeSats like the ones that we sent to Mars alongside the InSight lander, that may necessitate changing how we think about the Deep Space Network.

Fraser: It’s interesting as well, I mean, even just the name, right? Deep Space Network, you imagine that it is this network out in the solar system of all of these spacecraft that are sending all these communications back and forth, but it’s all just here on Earth. The point is that it’s communicating with space, with stuff that’s out deep in space, and as you mentioned, not orbiting close to the earth, but out, the missions that are out exploring the solar system. But if we did wanna take it to that next level and actually expand the infrastructure off Earth, what would you wanna do?

Pamela: So, the irony of expanding the Deep Space Network off Earth –

Fraser: Into space.

Pamela: – is then you have to have all of the receivers on Earth to receive the signal from the Deep Space Network that you’ve now put into space. So, there’s a certain level of irony involved in that, which tells me, “Let’s not do that.” I think what we need in order to expand the capacity of the Deep Space Network is I’d like to see more redundancy in sites, more redundancy in the receivers that we’re using.

One of the issues that we have today is if you need to do maintenance on one of the receivers, if you wanna upgrade one of your receivers, you have to take it offline, which means that there can be gaps in coverage for some of those space probes that are out there that require specific of the receivers here on Earth. So, greater redundancy and greater coverage. You never know when the weather is going to strike, the world is going to rumble, something’s going to happen that knocks one of these facilities offline. So, for me, it’s all about the redundancy and keeping it on Earth to in this one case reduce the irony.

Fraser: Now, we talked briefly about some of the science that gets done using these facilities, but I wanted to sort of talk a bit about what kinds of projects can you use this, when you’re not just communicating to spacecraft and you’re actually using these dishes for astronomical science. What are some projects that they’ve gotten involved in?

Pamela: Well, as I mentioned, the Goldstone also has the capacity to be a radar. This means that when asteroids get close enough to the planet Earth, we are capable of using radar to determine their shapes. Essentially, you blast them with light, and where there’s a hollow on the asteroid, it takes longer for that light to bounce back to earth. Where there’s a hill, it gets back a little bit faster. And this is one of the cooler uses.

Now, in addition to this, they can also of course be used to listen to the radio waves that are coming from objects near and far, whether it be listening to Jupiter and the interactions of its magnetic field, and the lightening, and all the fabulous other things that generate radio signals from Jupiter. That’s one possibility. You can also listen to active galactic nuclei in many cases. These accretion discs around supermassive black holes are giving off radio light. Their jets are giving off radio light. Young stars, T Tauri stars, have radio emissions.

All of these different sources that give off light in these longer wavelengths that are identical to the ones that your radio picks up, and much longer – much, much longer – as well, all of these longer wavelengths are things that these facilities have the capacity to study. And of course, there’s always that capacity that we don’t use all that often to go searching for extraterrestrial intelligence.

Fraser: Was that you setting up for us to search for extraterrestrial intelligence?

Pamela: No, that’s just me setting up to prevent all of the emails of “but you didn’t say…”

Fraser: They would be wonderful tools for searching for extraterrestrial intelligence, but they’re busy, and very rarely are they ever called on to do that, and that’s why you’ve got the private antenna like the Allen Array and things like that and the SETI Institute. People don’t, I think, realize. I mean, using these big radio telescopes for searching for aliens is a no-no. The SETI Institute uses private funding and their own private radio telescope network –

Pamela: The Allen Telescope Array.

Fraser: – the Allen Telescope Array to be able to do their own searches. And I think occasionally, like a couple of times, they’ve transmitted signals out into space to let the aliens know that we’re here.

Pamela: And that’s the Deep Space Communications Network, just to be confusing when you google. So, Deep Space Network, DSN, is how we listen to spacecraft and sometimes radar image asteroids. The Deep Space Communications Network is completely separate, and that is how we send signals potentially to other life in the solar system and beyond.

Fraser: And we won’t get into the argument on whether that’s a good idea or not.

Pamela: It’s true.

Fraser: Cool. Well, that’s awesome. I’m excited. I’m really glad we covered this topic because it is literally like if this system wasn’t functioning, none of the other science would be getting back to Earth. It is the bedrock that all of the stuff requires.

And you just watch the Deep Space Network Now and just watch who’s communicating, and your brain starts to understand a little bit more about just where the spacecraft are in the solar – this orientation, which I think we lose sight of that the earth is spinning, and the spacecraft are out there in the solar system, and they’re moving around, and there are times when you can communicate with things and times when you can’t, and I love to be able to do that. So, thanks for going into this topic.

Pamela: Well, and thank you for being here and thank you, audience, for being here. And before we end, I just wanna take a brief –

Fraser: You remembered.

Pamela: I did remember.

Fraser: That’s awesome.

Pamela: I just wanna take a moment to thank some of our Patreons. We thank patrons right here on air, and if you want to hear your name read out and know how grateful I am for everything that you do that lets me pay Susie –

Fraser: Before you read the names, can I just give one quick explanation why this is important?

Pamela: Yeah.

Fraser: When you look at what’s happening on the internet today, various people are trying to figure out business models to be able to operate what they do. You’re seeing either really awful advertising or people gathering up your information on your cellular phone and then selling it, selling your personal privacy information. You’re seeing paywalls going up which are block people’s access to be able to get information. And so, what are the options for us as content creators? We want our information to be an educational resource that can get out there and be available to as many people as humanly possible.

We don’t wanna block the information, but at the same time, as you mentioned, Pamela, we wanna be able to pay Susie, our editor, we wanna be able to cover our hosting cost, we wanna be able to pay for service. Still, to this day, I think you and I are still doing this on a volunteer basis, and that is because we’ve chosen getting the content out there over us being able to put it behind some kind of paywall and do it. So, Patreon is the solution that allows a small group of people to be able to fund what gets done so that the largest possible group of people can receive the podcast without having to put it behind a paywall and without having to put a mountain of advertising on it over top of it.

And as we can move towards it being more of a Patreon-covered model, then you move into, I think, this beautiful future world where a small group of fans help allow a piece of content to exist, to be available to a larger group of fans, and it is a beautiful system, and we’re in this uncomfortable in-between times where we have to have advertising or people have to start putting things behind paywalls. So, I think it’s just important. Even not just in generally specifically for this podcast but for any content that you enjoy where you’ve got a much smaller, more intimate relationship with the creators who make this kind of thing.

You can support their work directly, and it doesn’t take a lot of people to be able to make the content that you love available forever across all of the platforms and not have to put it behind paywalls and stuff. So, again, just wherever you are, if there’s things that you enjoy, consider supporting them directly, and, of course, consider supporting what I do on Universe Today, and what we do here with Astronomy Cast, and what Pamela does as well. So, that done, thanks to…

Pamela: Thanks to John Jorst, Jordan Young, Burry Gowen, Ramji Anatmatu, Andrew Polestra, David Trogue, Brian Kegel, The Giant Nothing, Laura Kettleson, Robert Polazma, and Emily Patterson. And there will be more names next week. Thank you all so much for being here.

Fraser: All right. And thanks, Pamela, for bringing the brain. We’ll see you next week.

Pamela: Bye-bye, everyone.

Announcer: Thank you for listening to Astronomy Cast, a nonprofit resource provided by the Planetary Science Institute, Fraser Cain, and Dr. Pamela Gay. You can find show notes and transcripts for every episode at Astronomy Cast. You can email us at info@astronomycast.com, tweet us @AstronomyCast, like us on Facebook, and watch us on YouTube. We record our show live on YouTube every Friday at 3:00 p.m. Eastern, 12:00 p.m. Pacific, or 19:00 UTC. Our intro music was provided by David Joseph Wesley, the outro music is by Travis Searle, and the show was edited by Susie Murph.

[End of Audio]

Duration: 34 minutes

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