“Houston We Have a Podcast” is the official podcast of the NASA Johnson Space Center, the home of human spaceflight, stationed in Houston, Texas. We bring space right to you! On this podcast, you’ll learn from some of the brightest minds of America’s space agency as they discuss topics in engineering, science, technology and more. You’ll hear firsthand from astronauts what it’s like to launch atop a rocket, live in space and re-enter the Earth’s atmosphere. And you’ll listen in to the more human side of space as our guests tell stories of behind-the-scenes moments never heard before.
Episode 26 features Bill Foster, Ground Controller in Mission Control Houston, talks about how space communication networks work and what they will look like for missions into deep space. This episode was recorded on April 13, 2017.
Transcript
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Gary Jordan (Host): Houston, We Have a Podcast. Welcome to the official podcast of the NASA Johnson Space Center, Episode 26, Can You Hear Me Now? I’m Gary Jordan and I’ll be your host for the very first episode in 2018! Happy New Year! So on this podcast, this is where we bring in the experts, NASA scientists, engineers, astronauts, flight controllers, all the coolest people! We bring them right here on the show to tell you all the coolest stuff about what you want to know, about what’s going on here at NASA. So, today, we’re talking about space communications and communication networks with Bill Foster. He’s a ground controller in mission control Houston, and we had a great discussion about how space communication works, what it’ll look like in the future, and why it’s so important to make missions successful. So with no further delay, let’s go lightspeed and jump right ahead to our talk with Mr. Bill Foster. Enjoy!
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[ Music & Radio Transmissions ]
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Bill Foster: Touch on this later if you want to, but one thing that I always wondered about, you know, the Apollo 13, the movie, you see them entering the blackout, and then there’s this big tension because they’re not talking after they’re supposed to be out of the blackout.
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Host: This is after reentry, right?
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Bill Foster: Yep. Reentry, and everybody’s worried and a minute goes back and, you know, the blackout is pretty predictable. You know when you’re going to lose contact, you know when you should get it, so, there’s no contact. Two minutes later or so, they make contact.
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Host: Yeah. But that’s a tense two minutes!
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Bill Foster: So I went over — I was at the space center Houston the other night when they premiered the mission control film.
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Host: That’s right!
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Bill Foster: Which included that aspect of it, and afterwards, Krafton and Kranz and Lonny [phonetic] were all in front taking questions. Somebody asked them, why was the blackout longer than expected? And Kranz’s answer was, we were so happy to hear them, we didn’t really care. [Laughing] Then somebody finally answered the question.
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Host: Yeah.
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Bill Foster: For reentry over water, there was no ground station nearby, and they used what’s called an ARIA, a-r-i-a aircraft.
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Host: Okay.
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Bill Foster: And what they said was, probably the, you know, the areas were always somewhat unreliable in a quarrying contact. They just may have been pointing — looking the wrong way or they may have had an equipment issue onboard, but, you know, they came out of the blackout right when they should have, but it just took a couple of minutes for the aircraft to lock up on them.
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Host: Oh, wow!
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Bill Foster: So that was interesting.
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Host: Yeah! Well, how about that? Did — are we recording? Yeah! [Laughter] We got it! Awesome! Well, that’s great! Okay, so for those, yeah, we are — I have Bill Foster here with me. He is a ground controller in mission control, and he did — he’s ground control — at the ground control console in the mission control center in Houston for the International Space Station. I got to ask him, to start off, how’s Major Tom?
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Bill Foster: We’re still looking for him.
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Host: Oh, okay.
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Bill Foster: And we had a big setback early last year, we think we may have lost all hope of finding him when David Bowie passed away.
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Host: [Laughing] Yeah. Oh, that’s an oldie, but I had — I mean, how often can you do that, right?
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Bill Foster: I bring that up frequently when I’m talking to people, and that’s one of the first things, we’re still looking for Major Tom. It’s not quite as good as it used to be.
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Host: [Laughing] I don’t know, I think it’s pretty good. I was dying to say that for — for this podcast. But, so today we’re going to be talking about space communication, how that works. You know, when you think about mission control Houston, you know, the center of talking with people in space and other centers, really, how does that work? You know, that’s — that’s really the main question, and the thing I really want to answer. So, first of all, if you had to describe a ground controller in one or two sentences, what does a ground controller do?
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Bill Foster: TDRS to toilets. [Laughter] Three simple words.
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Host: Yeah! TDRS to toilets, okay.
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Bill Foster: Ground control is responsible for making sure our communications with the space station and any other human spacecraft is maintained, and that’s the [inaudible] part of it, tracking and data relay satellite. That’s the geosynchronous communication satellites we use to — to talk to spacecraft today. And the toilet reference is just we also are responsible for anything to do with the mission control center facility itself.
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Host: Oh, I see.
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Bill Foster: I have grabbed a mop and headed into the ladies room one time many years ago.
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Host: Really?
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Bill Foster: Yeah, so.
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Host: Wow, okay, so that’s — I like that! So your control of the satellites, the TDRS satellites, and we’ll talk about those later, but those — those are the satellites that are way out in space, right? 23-ish…
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Bill Foster: 22,300 miles up.
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Host: That’s it. Yeah, okay, all the way out there, down to the toilets that are right next to you in mission control? Wow.
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Bill Foster: We had a, coincidentally, had a power hit that affected pretty much all of JSC today.
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Host: Yeah, we just had it here too!
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Bill Foster: Yeah, so that was a big thing in the control center this morning, you know? Fortunately, our — our backup battery systems and our diesel generators out back all kicked in and there was virtually no disruption to operations in the control center. So the ISS mission, they lost air conditioning in their room for about half an hour, you know, that wasn’t enough time for it to heat up appreciably, but, beyond that, there were no notable impact. Some of the simulations, like the one that I was on, and the ISS simulation, they were affected, because the simulator building does not have the backup power. So, yeah, that took about an hour, hour and a half hit to the simulations, but the MCC stayed up.
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Host: Alright, all part of your day-to-day jobs, right? Is maintaining the power. So you do the — are you in charge of the backup power too?
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Bill Foster: We — we have to be aware of it. The Center of Operations Director here at JSC provides that power to us. They — they maintain and — and operate all of the systems, the diesel generators, the — the large banks of batteries that are always online, but if we have a power issue, like we did today, then the GC is the first person that the flight director goes to to find out what’s happening, and we’d have to make sure that our backroom support personnel are working with the center ops personnel to understand what happened, and to take whatever steps are necessary to ensure it’s no impact, or minimal impact, operations.
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Host: Nice. Okay, well, okay, so, another, you know, a big thing that we really want to talk about today is — is your responsibility, as ground controller, is the communication networks that gets us, you know, you in mission control, and — and everyone there, especially CAPCOM oht, talking with the folks in space. That’s really the thing. So, how is that set up? How do you go from the headset down in mission control to, you know, whatever the, I forget what the device is called, but where the astronauts talk into?
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Bill Foster: Well, it’s — it’s a complicated system, but, as you said…
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Host: It’s a loaded question, I guess.
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Bill Foster: Everyone in the control center has a headset all, you know, our biggest tool is communications, whether it’s looking at data coming down to us, being able to send commands up, talking to the crew, or talking to each other. So we have our voice system that we call, DVICE, Digital Voice Interface Communications Equipment, say that a bunch of times.
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Host: Oh, yeah. Yeah, is it — you pronounce it device or is it d-vice? You just do device?
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Bill Foster: I do device, but some people say, d-vice.
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Host: Okay.
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Bill Foster: But it’s just, d-v-i-c-e.
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Host: Oh, okay, so, I boxed out the E, there it is.
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Bill Foster: Sort of stutter into it. So DVICE is a digital voice communication system. So when you put on your headset and you plug it into the console, the jacket that connects it to DVICE, and then you log into your DVICE, that’s establishing a connection into a computer in another part of the building, and once you pull up a given voice conference, or we call them loops to talk on, when you talk, the DVICE system turns that into — to bits, 1’s and 0’s, sends it over a fiber optic cable down to the computer system in the bottom. Sends it back out to anybody else that’s listening on that loop, turns it back into audio. When CAPCOM talks on it, on the — the space-to-ground loops, it goes down to DVICE, gets turned into audio, gets sent over to what we call air-to-ground voice equipment, or AGVE, that equipment takes it and modulates it, adds it to the command link that we have going up to the space station.
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So it produces a combined 32 kilobit link that goes up to the station that has two voice channels, and, I’m sorry, 72 kilobit link, has two 32 kilobit voice channels and a 6 kilobit command channel in it. And onboard the station, the voice is pulled out, turned back into audio that the crew can hear, when they respond, the reverse process happens. It gets digitized, sent down on the link, sent over to AGVE, turned back into a voice signal, goes into DVICE where it’s digitized again. Goes out on the fiber optic cables back up to the CAPCOM or anybody else that’s listening to the space-to-ground and turned back into audible voice that you can hear.
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Host: Oh, wow.
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Bill Foster: So whether you’re talking to the crew or I’m talking to someone at White Sands, New Mexico, that’s the ground station for our TDRS satellites, or anywhere else in the country, or talking to our counterparts in Japan or Germany, our — our Marshall Space Flight Center, that same process is happening, converting it into digital signals, sending it through land-based communications lines to other control centers where their voice system converts it back into something that’s audible for the controllers on that end of the loop.
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Host: Wow! Okay, so, I’m imagining when it gets through the fiber optic cable to the part where it actually sends it to space, right, so you get — you get to that, is that — is that a dish? I’m imagining a dish.
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Bill Foster: At a certain point, it goes through a couple of dishes.
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Host: Oh, okay.
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Bill Foster: So — so from the MCC, it goes out on just commercial T1 lines, basically, just communication lines. It goes to White Sands, New Mexico, it goes through a lot of processing equipment there, and then it goes into this large dish that’s communicating with the TDRS satellite. So there — there’s a composite K-band signal, and K-band is a fairly large bandwidth signal that we send up to the — the satellite. Now the TDRS uplink to the TDRS satellite is much larger because it combines not just ISS for mission control, but potentially other spacecraft users.
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Host: Hmm, so you share that — those satellites?
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Bill Foster: Yeah, so that one dish going up to the satellite is going to a TDRS satellite that has two single access dishes, and each of those dishes can be pointing at a different spacecraft. It also has an array of what they call multiaccess dishes that could be going to up to six other additional satellites. So that uplink from the ground could be supporting up to 6 or 7, maybe even 8 different spacecraft.
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Host: Wow.
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Bill Foster: From the TDRS spacecraft, we always use, for — for ISS or any human spacecraft, we use a single access dish. So we’re the only customer on that particular dish on the TDRS satellite that’s pointing at our spacecraft, ISS this case, and it’s sending — it takes that big KU output going up to it, and breaks out just mission control’s communications, which contains the command and voice and video signals, because we’re going to also send video or other information up to the space station. And sends it out on either S band or K band links to the spacecraft.
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Host: Wow.
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Bill Foster: So the S band link has just the commands and voice part of it. The K band link has two voice channels, typically does not have command data, although it could under certain circumstances, but it also has file uplinks, video uplinks, we can send video programming up to the crew. Now, the crew was there for six months at a time.
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Host: Right.
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Bill Foster: They get off work at the end of the day, they can’t close the door, go get in their car and drive home.
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Host: Right.
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Bill Foster: But just like anybody else, it’s nice to relax after work. So we have the ability to send up sports programming, news programming, depending on the crew, some of them just want to see video coming up from the control center, see the people that are supporting them.
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Host: Oh, cool!
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Bill Foster: So we had the ability to send programming up to them. They also had a lot of pre-recorded material onboard, DVDs, Blu-Rays, whatever, they can pick a lot of what they want ahead of time, to take up with them.
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Host: Very cool! So how — I’m guessing this whole thing, right, of sending information on the S bands and K bands, all the way to the…is that instantaneous? All of that happening, like, as fast as I can snap my finger, or is it happening [inaudible]?
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Bill Foster: It’s happening at the speed of light.
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Host: Oh, okay.
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Bill Foster: But consider light travels 186,000 miles per second, when you’re going from here to White Sands, that’s not that far compared to the speed of light, but now you go from White Sands 22,300 miles up into space, now you’re getting a little bit of distance there. And then 22,300 miles, maybe 100 miles, back down to the orbiting spacecraft, but, of course, they’re not necessarily directly under TDRS, so, you know, it could be a lot further than that.
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Host: Right.
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Bill Foster: So — so just consider, it’s about a 45,000 mile round trip to get there. Well, now you’re talking about a significant fraction of the speed of light, up to a fourth, maybe even a little bit more than a fourth of that, so you are starting to talk about [pause] in the quarter to half a second delay, particularly if it’s — it’s roundtrip, we talk to them, and they respond. Well, now you’re going 90,000 miles roundtrip, plus the time it takes for the crew to hear what you’re saying and respond to it. So, if you’re talking to the crew from the ground, I’ve only done this once, and I’ve seen other people that don’t do it often do the same thing, you talk. They don’t respond in what your mind assumes as a normal response time. So you think they didn’t hear you, and you start talking again, and about that time, their response is coming in. So it’s — it’s real easy to talk over each other. So the — the experience, CAPCOM, knows, say what you’re going to say, wait, the response will be coming, and…
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Host: Oh, wow.
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Bill Foster:…continue that way.
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Host: That’s awesome! I didn’t know. I mean, that — I would have — I would have thought it was instantaneous, but when you talk about, you know, the space station is 250 miles above the earth, that’s not that far compared to 23-ish,000 miles for the — for the satellites to go up and down. So, some recent news, is very soon, I forget how many days, well, at least by the time this comes out, it probably will have already happened, but at the time of this recording, April 13th, it hasn’t happened yet, an ultra-high definition video…
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Bill Foster: April 26th, I think.
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Host: April 26th, yeah.
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Bill Foster: We saw some words on that today, coming up, making sure our ground controllers that will be on console are ready to support that, to go ahead.
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Host: Yeah, so does that — does that use the same network?
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Bill Foster: Yes.
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Host: Oh, and it can support ultra-high definition?
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Bill Foster: Yeah, right — right now, the — the Space Station can support up to a 25-megabit uplink to the station using K band. So that’s a pretty big pipe. But it can support up to 300 megabits downlink.
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Host: Oh!
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Bill Foster: You know, so that 4K ultra video, high-definition video, is going to come through that 300 megabit link down, that same link also supports 6 standard definition video channels down, to normal high-definition channels down, plus a lot of telemetry data, all the voice that comes down, so it — you know, we’re still not using all of it.
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Host: Yeah, wow!
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Bill Foster: However, the purpose of the Space Station is science, and science, sending a lot of the science data down does take a lot of bandwidth, and there are plans in work that are going to upgrade that downlink to a 600 megabit capability.
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Host: Oh, very cool.
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Bill Foster: Yeah, so.
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Host: Are you talking about videos for science too? Or — or mainly, I guess everything, right?
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Bill Foster: Everything.
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Host: Yeah, like all data and video and audio, everything, so.
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Bill Foster: Everything in that — that big pipe coming down.
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Host: That’s — it’s got to be a big pipe to support all that stuff.
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Bill Foster: Yes, sir.
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Host: So let’s go — let’s go back 23,000-ish miles above the earth to the TDRS satellites. So, you know, we keep — we keep saying, TDRS , TDRS , TDRS , but, you know, what is that? What is that network?
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Bill Foster: Yeah, the TDRS network was established back in the early part of the shuttle program. You know, prior to that, and I guess you can take a step back to fully understand it, you know, look back at where we were with Mercury. When the Mercury program came, there was a need to get data from a spacecraft and to communicate to the spacecraft, but nothing existed. And NASA established a manned spaceflight network putting ground stations around the world, they looked at the — the orbital track that a spacecraft was going to go on its first few orbits, launching due east from Kennedy Space Center, or, at that time, Cape Canaveral. And they placed ground stations to cover a lot of that area, in Africa and Australia, Bermuda, across the United States. So you had ground stations in Corpus Christi, for instance, in California, so when you launched, the spacecraft would go over those ground stations, and — and if it was a straight overhead pass, it could last as long as eight minutes.
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And during that time, you could communicate with it, but for Mercury, they really didn’t have a good way to get the data back to the control center at Cape Canaveral. So they…
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Host: Oh, so this is going to the ground stations, right, not to the…?
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Bill Foster: Right, so they sent people out there and they had teletype communications between the ground stations and the mercury control center, where information could be passed back and forth to the people on the ground or the people back there. Well, they knew, as we were moving into Gemini and beyond, that that wasn’t going to work.
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Host: Right.
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Bill Foster: Mission control in Houston was designed to have an integrated communications network, which was — became known as the NASA communications network, or NASSCOM, that would connect all of this together, but you still had the limit that the spacecraft had to be over a ground station. And because of the way they were placed, for 2 or 3 orbits, you could have maybe not quite half of the orbit covered by ground stations, maybe less, but you’d have a lot of that where you can communicate with it. And that’s how we did Apollo. Now for Apollo, they also used several tracking ships and aircraft to cover areas where there were no ground stations, but they knew there was going to be critical events happening. And those were all tied together, and all the data did go back to mission control in Houston. So we didn’t have to send personnel out to the ground stations for Gemini, Apollo, or beyond, all of that came into the control center.
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Host: So there were no satellites established at this point, right? All — all the information from the moon was going to all these different points on the earth?
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Bill Foster: That’s correct. When we landed on the moon, when the first steps on the moon, I believe that was coming to us through Australia, through the Canberra, or — oh, which station? It wasn’t Canberra, but one of the stations in Australia.
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Host: Wow!
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Bill Foster: And all being relayed back to us. So, in fact, there was a — a big controversy, not sure it’s ever been completely settled about what Neil Armstrong actually said when he landed — when he took his first step on the moon, was that, one small step for man or one small step for a man. And he claims he said a man, but you don’t hear it, there’s a lot of effort, including someone that had tapes from the Australian ground station in his attic [laughing], which probably about 10, 15 years ago were — were discovered and sent back and I don’t think that’s still solved the mystery. The assumption was that it — it came down clearly to Australia, but it was distorted in the transmission back to the control center. And I don’t think we’ve ever really resolved that. So, officially, it’s one small step for man.
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Host: Right. Oh, wow! How about that? Just a little bit of a — little bit of a gap there. I remember seeing that, just because I was trying to come up with a name for this podcast, and I was like — I was looking through like historical quotes and stuff, and I was like, I wonder if I can take like a, you know, one small step for man, or something like that? And I found, like, a little parentheses over a, because I guess there was this controversy around it.
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Bill Foster: And, again, I don’t know that it was ever resolved.
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Host: Wow!
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Bill Foster: But we still, again, we still had these gaps in between ground stations that was a concern. And — and moving into shuttle, which was going to be a — a — it never panned out to be what it was going to be, but a — a reusable spacecraft that could be launched many times in the same year, you know, 30, 40, 50 flights a year, for the same orbiter. That would have been nice [laughter]. But communications was going to be even more important and — and that’s where they working to the — the space network, the — the — all the ground stations were part of the ground network. There’s also a deep space network, and when we went to the moon, we used the deep space network that was — it’s based out of the jet propulsion laboratory.
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Host: Okay, in California?
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Bill Foster: Right. So when you go above — too far above low-earth orbit, then ground stations, normal ground stations, and their intent is no longer suffice, and you need the — the very large ground stations, antennas that the deep space network provides, and instead of an antenna so much tracking a spacecraft, it goes across the horizon, the earth is tracking the spacecraft as it rotates around the world, when it gets far enough out.
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Host: Yeah.
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Bill Foster: But the antenna is still moving a little bit, but a lot slower for than something in low-earth orbit.
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Host: Were there — were there large gaps then? If — if there were all these [inaudible]?
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Bill Foster: For when you get far enough away, and the moon’s far enough away, there are no gaps. You handover between Canberra, Australia to Goldstone to Madrid, and those are the three major, the main ground stations in the deep space network, and we will be using that again when we start flying the Orion missions.
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Host: Alright!
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Bill Foster: So, yeah, it would have been — I went out to JPL back in October, as a familiarization visit, to — to look at the Goldstone location, to look at their operations at JPL and to start learning how the ground controllers here at Houston are going to be scheduling those assets in a similar way that we schedule the space network assets.
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Host: Oh, so the deep space network, you gotta — you gotta share too, right?
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Bill Foster: Yeah. And the difference there, when we — when we schedule a space network assets, which are used by a lot o of other users in low-earth orbit, we have to forecast roughly 17 days ahead of time to — to schedule what we think we’re going to need for a week’s worth of — of passes, so, tomorrow we’ll be sending in a schedule request for a week that begins two weeks from Monday.
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Host: Oh, wow.
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Bill Foster: For the JPL, for the deep space network, you put those types of forecast requests in months in advance.
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Host: Oh.
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Bill Foster: And, you know, one of the things we look at, well, you know, for Orion missions, you almost certainly going to have a launch slip. So months in advance, we say, we’re launching this day, we need this support based on our trajectory here, here, and here, and all of a sudden, we slip a day, and all of that’s out the window.
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Host: So during an Orion mission then, so, I guess, you know, you’ll be communicating with Orion, but then there’s going to be periods during that mission, whatever — whatever it may be, where you’re going to have to trade off and maybe someone else is going to have to take priority for a little bit?
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Bill Foster: It’s very possible.
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Host: Okay.
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Bill Foster: You know, for any mission, you’ve got periods that are higher priority than other periods. So you don’t have to maintain constant communications with the spacecraft, and we don’t with ISS. You know, we frequently have 20, 30 minute gaps, unless we need to have continuous comm. Same thing with — with Orion. You know, when you’re getting ready for a maneuver or an orbital burn or an inner-planetary burn, then you want to have communications, you want to be able to talk to the crew, you want to be able to look at the data coming from the spacecraft, particularly after the burn to make sure that it actually did what you expected it to do. So, during those periods, we will — we will have solid communications for as long a period as we need to. But during quiescent periods, it’s not as important, you know, you don’t have to stay in touch the whole time, and other users, you know, are out there that, you know, you got to program Pluto, well, they want communications too.
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Host: Yeah! Yeah! Well, yeah, it makes a lot of sense. So I’m thinking, I mean, right now, I was just reading about Cassini. Cassini’s going to start making passes on the inner rings and then, you know, make a controlled entry into Saturn to…
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Bill Foster: Suicide.
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Host: Yeah, suicide dive, kind of, so, you know, it doesn’t affect [inaudible] or tighten or anything like that, and can cause contamination, so, you know, not to be — not to be mean, but that’s one less spacecraft we have to worry about on the deep space network [laughing].
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Bill Foster: Well, and you’re right. You know, it’s really not a huge issue sharing times, again, for — for most of the planetary spacecraft that are out there, it’s not that difficult for them to plan months ahead of time. You know, they know when we’re going to do this burn in a year and a half. You know, so they can plan when they need that communication.
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Host: Yeah. You guys must be really good at scheduling, if you’re planning that far in advance.
[00:26:51]
Bill Foster: Well, I got to — got to admit, I admire the people at JPL, because the detail they go to, particularly if they’re doing a — a course correction, you know, want to sling around a planet and get a gravity assess to go somewhere else, you know, just the planning for when to make that happen is incredible, but then you also want to have that communications to verify that it’s doing what you’re doing. And, of course, when they do that, you know, when we’re talking to the space station, we talked about the delay, it’s — it’s near instantaneous, within a — a quarter to half a second roundtrip. When you’re talking something out of Pluto, it’s hours.
[00:27:33]
Host: Right.
[00:27:33]
Bill Foster: You know, it’s literally hours. It — it was sort of funny watching some of the Mars landings, and you would see the people at JPL and their control center, and they would get data back that, you know, reentry has started, and they’re up jumping and cheering, you know, and I’m thinking, we don’t do that! Sit down! Behave yourselves! [Laughter] But, be it, there’s nothing they can do at that point. That reentry started 20, 30 minutes ago.
[00:28:01]
Host: Right! At that point, it’s like — it’s like a replay.
[00:28:04]
Bill Foster: Chutes are out! Yeah! Jump and down! You know, it’s — come on, you know, but, you know, for us, when the shuttle landed, chutes were out, you know, we still had work to do, and this was virtually real-time, so it’s — you know, you couldn’t jump up and down and shout and whatever, but for JPL, yeah, that’s okay. They’re watching events that happened. You know, it may have already crashed and burned by that time, but they don’t know it yet.
[00:28:30]
Host: Yeah.
[00:28:31]
Bill Foster: And, fortunately, in most cases, it didn’t, and it lands very nicely and the rovers are wandering Mars, doing great things, years beyond what they were planned to do! So we got to admire those people out there.
[00:28:42]
Host: Oh, yeah! Curiosity…
[00:28:43]
Bill Foster: However, if you go to their control center, right in the center of it, they got this little glass, plexiglass plate with an emblem down there that declares they are the center of the universe. I don’t know about that [laughter].
[00:28:58]
Host: A little egotistical, but okay.
[00:29:00]
Bill Foster: It’s a great place.
[00:29:02]
Host: Oh, yeah. So they were using the deep space network then to watch…
[00:29:04]
Bill Foster: Yeah, so they almost exclusively used the deep space network.
[00:29:08]
Host: Okay, but I would say we use for the International Space Station the TDRS satellite.
[00:29:13]
Bill Foster: Right, the space network. We — we use the G and the ground network for space station, very rarely we use Wallops and White Sands and Armstrong, they’re VHF radio capability as an emergency voice capability for the space station. We don’t — I don’t think we’ve ever had to actually use it in an emergency situation, but we schedule passes several times a year to provide proficiency training for the ground stations, and also for the crew and operating the radios to talk to us. So, you know, we do that, but that’s the only time we actually use ground station. For normal communications, it’s all space network, TDRS.
[00:29:58]
Host: So, the TDRS satellites, you said, you know, some of them are pointing towards the spacecraft and some of them are pointings out towards other things, and this is — and this is a communication network that you have to share. But, you know, that — that’s 23,000 miles up, there’s — there’s several satellites around the earth, right?
[00:30:16]
Bill Foster: Yes. there are.
[00:30:17]
Host: So how many are there, and how do they talk to each other?
[00:30:21]
Bill Foster: We’re [inaudible], I say our, the space network, I believe, on their 12th satellite on orbit. The first one was launched on STS6, back in the 1983 timeframe, I believe. It had problems getting up there. The — the booster that was supposed to take into geosynchronous orbit malfunctioned.
[00:30:46]
Host: On the satellite? Or on the…?
[00:30:49]
Bill Foster: Yeah, for the TDRS satellite, it had an inertial upper stage booster…
[00:30:54]
Host: Oh, okay.
[00:30:54]
Bill Foster: That was attached to it that was going to burn, take into geosynch, then the booster would drop off.
[00:30:59]
Host: Okay.
[00:31:00]
Bill Foster: And the burn didn’t happen correctly. It ended up in a very elliptical orbit, thousands of miles below where it should have been.
[00:31:09]
Host: Oh, so I guess it’s unreliable at that point, right?
[00:31:12]
Bill Foster: What they had to do on that one, because each satellite has a certain amount of fuel onboard, propellant to basically keep it in its orbitor, to make slight adjustments if they need to drift it to a different part of the earth. They had to use a fair amount of that propellant to gently boost it up into the right orbit. So that — that reduced its overall lifetime, it’s no longer operational, but it did provide great support for many years. So that first one covered the Atlantic Ocean region.
[00:31:46]
Host: Oh, okay. So, 23,000 miles up, that’s — you get that sliver, and I guess, you know, they used all the propellant to…
[00:31:53]
Bill Foster: To get it up there, so you get almost a third of the earth.
[00:31:55]
Host: A third of the earth, okay! That’s decent.
[00:31:58]
Bill Foster: So, and we use that beginning with STS-8, and — which, before that point, the shuttles were using ground station just like everything else before it, every other spacecraft before that. So, you know, we had the limitations. You first orbit, you had a good amount of communications, first three orbits, and then you drifted off range of most of the ground stations. You might end up with an 8 minute pass every orbit or every 90 minutes.
[00:32:25]
Host: Wow!
[00:32:26]
Bill Foster: So, you know, from a control center standpoint, you know, that gives you a chance for a bit of a break, but we don’t want that long of a break. We want to stay in touch with them.
[00:32:35]
Host: That’s right. 8 minutes is a long break, but, you know…
[00:32:37]
Bill Foster: So when the first TDRS got up, we didn’t cover a fair part of the orbit — of half of the earth. Yeah, so starting somewhere with the Pacific to right before the Indian Ocean, you could cover communications. Then we later put up the next TDRS, and, unfortunately, it was destroyed in the Challenger accident. So the second TDRS never made it into space. STS-26, the return to flight, put up for the third TDRS, which became the second operational one, and that closed most of the orbit. You had a — a — sort of a banana-shaped sliver over the Indian Ocean that became known as the zone of exclusion.
[00:33:22]
Host: Oh.
[00:33:22]
Bill Foster: Where you didn’t have communications. And the biggest problem there is, you’ve got to, you know, picture the TDRS satellites, they have to communicate through a ground station, and that ground station is in White Sands, New Mexico. So they have to be able to see White Sands. So you — you put one satellite as far east of White Sands as you can, but still maintain good connection with the ground. You put the other one as far west as you can covering the Pacific Ocean region, but still being able to see the ground.
[00:33:55]
Host: And then the other one on the other side?
[00:33:57]
Bill Foster: Well, at — at that point, that’s all we had.
[00:34:01]
Host: Oh!
[00:34:01]
Bill Foster: But we did — I think there was 7 TDRS that went up on shuttles before they started going through the expendables to put them up.
[00:34:10]
Host: Oh, okay.
[00:34:11]
Bill Foster: But, you know, we eventually got enough to have spares on orbit and solidly cover the east and west side. In the late 90’s, there was a scientific satellite, it may have been TRN, but I forget specifically, they had a spacecraft emergency. And as part of the recovery of that, they really needed to have continuous coverage around the earth. So that zone of exclusion was a big hindrance to them. And they took one of the spare satellites, drifted it over the Indian Ocean, they brought up a ground station in the Canberra, Australia, one of the old deep space network stations, I think we still use it for deep space, but they put a capability there to talk to TDRS. And then sent back that — sent that back to White Sand, so we — we were able to close the ZOE.
[00:35:03]
Host: Nice. That happened when?
[00:35:07]
Bill Foster: I want to say ’99, but it was the late — it may have been, maybe it was the early 90’s. Somewhere in the 1990’s. So when I started as a GC, it was already there, and that was ’97, so it was before ’97.
[00:35:22]
Host: Okay.
[00:35:24]
Bill Foster: They — yeah, we need this, and so they built a permanent ground station on Guam, which is known as the Guam Remote Ground Terminal, GRGT, and so we have that today, there’s, you know, and so we have that today, you know, for space station, we have a satellite we call 275, it’s — which is the longitude that it’s at. And we use it to cover the gap. For a long time, there were limitations to that, for instance, the ground link between Guam and White Sands didn’t have enough bandwidth to cover video. So if we were only 275 satellite, we could cover the — the telemetry and command and voice gap, but you couldn’t get video up or down through that. Last year, I believe it was — they upgraded the link between there and now we can have full video service, full bandwidth, so regardless of where we are in the world, we can have a full communications with the International Space Station.
[00:36:28]
Host: Nice!
[00:36:29]
Bill Foster: There’s five satellites that we — that the ISS uses. There’s two over the eastern region, what we call TDRS East and TDRS Spare. There’s two over the western region, TDRS West and a TDRS that we just refer to it by longitude, 171.
[00:36:47]
Host: Okay.
[00:36:47]
Bill Foster: And then we have 275 over the Indian Ocean. So we’ll use three of them, you know, one east, one west, and one in the Indian Ocean to cover the entire orbit, if we need to, for — for EVAs and spacewalks, for robotics operations where we need to have a good link to the ground. We’ll declare a TDRS critical period, and for a period of several hours to maybe a day or more, we will schedule constantly during that period. If we don’t have critical activities going on, then we’ll schedule around important events. If there’s a private conference with the crew, we want to make sure that we have good S band coverage, preferably good K band coverage if it’s a private family conference where we’re setting up a video teleconference capability, then we want to have that K band covered. So, the — the ops plan control — controllers in there that look at what’s being planned, one of their backrooms generates the TDRS coverage request that says these are the times we really need to have that coverage, which is given to another position called pointing, which then uses tools that they have that — that takes in the altitude timeline of the space station.
[00:38:10]
Which is important, because you need to know how the station is pointing it in a particular side to know whether it has a good — a good view of a TDRS satellite or whether there’s blockage to some of its antennas. And then they design which satellites were used at any given time, and that all goes into a forecast request that’s provided to my position, the ground controllers, and then we work with the people out of White Sands to physically schedule those satellites for the time required.
[00:38:40]
Host: I see. And so the ops planner, that’s — that’s another flight controller position, right? Your ground control, ops planner, they’re the ones planning out and they — they determine those times and they send the information to you.
[00:38:50]
Bill Foster: They take inputs from the increment lead team that says this is what the crew needs to do at any given time, and they pull all the science inputs and the crew inputs and everything into one, big package and have to come up with a plan of what coverage is needed to support that. And then it goes, like I said, to pointing, who determines what works and what doesn’t work. You know, we have to be in view of the satellite, but we also have to have good antenna coverage for S band, S band is a lower data rate, and its — doesn’t require as precise pointing.
[00:39:29]
Host: Okay.
[00:39:29]
Bill Foster: So, the coverage for S band is a lot better, generally. K band is a very much higher rate signal that has a dish antenna on the space station that has to be precisely pointed at the dish antenna of the TDRS. And depending on the attitude of the space station, there’s plenty of times where solar rays, trusses, or other structure of the space station block that.
[00:39:54]
Host: And those are predictable, right? So even though you schedule, you prioritize the schedule for, say, a spacewalk, and you prioritize the schedule, you’re still going to have little periods of — of interruptions, and it’s because of that?
[00:40:06]
Bill Foster: Exactly. And — and because of that, you know, you have two satellites over the east, two over the west. Sometimes you’ve got bad KU coverage over one of those satellites, but just because of a slight difference, maybe 3 to 4 degrees difference on orbit, but that’s at 23,000 miles up, so that’s quite an angular distance. You may have better coverage over the other — from the other satellites. So pointing, they’ll look at their tools and they’ll say, well, normally, we would use TDRS East to cover this part of the world, but for this particular request, or requirement, TDRS Spare is going to provide better coverage. :45 Or normally we would take TDRS East until we run out of view of it, and then if we needed 275, hand up to it, or maybe that last portion of the pass is bad coverage, but 275 is good, and since we can do video through that now, then we can move on. They’ll say, let’s schedule this for that period of time.
[00:41:05]
Host: Right. So there’s a lot — there’s a lot going on behind the scenes that creates that clean coverage that we’re just not aware of. There’s handovers and all kinds…
[00:41:13]
Bill Foster: That’s all the forecast period. That’s saying nothing ever changes, but it does change frequently. So in the real time period, you know, we — once the forecast is scheduled and set, you enter the real time period about a week before you actually start using that. Which means pointing outcomes and says, well, the trajectory has changed a little bit since we generated that forecast request. Or this spacewalk has been added here, or something else, due to some reason that wasn’t predicted ahead of time, and now we need different coverage. So that then comes into a — a system where they generate a — what we call a flight note that says, change up our coverage based on this, and the flight director will have to approve that, and then the GC, my position, will go work with White Sands and say, we — we need to give up this time, but get this time, and White Sands may say, well, another user has that time, so what’s the priority?
[00:42:16]
You know, can we bump the other user or, you know, is it a TDRS critical period that’s driving that? In which case, we probably can bump the other use, because human spaceflight has higher priority, in general, than scientific spacecraft.
[00:42:31]
Host: I see.
[00:42:32]
Bill Foster: But not always. It — there’s lots…
[00:42:35]
Host: But in — in times of like a spacewalk or something, then I guess it would take — it would kind of trump it?
[00:42:40]
Bill Foster: Yes. It would — it would trump it. Sometimes we have to get the management at Goddard involved to go arbitrate or — or, you know, help us with our request.
[00:42:51]
Host: Oh, you guys got to fight over the…?
[00:42:52]
Bill Foster: There are times we do. And we — we can never know who the other users are. You know, that’s — that’s their business, not our business, they don’t know who we are when we’re asking for their time. So the terminology is a higher priority user needs this.
[00:43:08]
Host: In general, who are some of the other folks that use the TDRS satellites?
[00:43:11]
Bill Foster: Most of them are like Hubble space — space telescope, TRM was a good example, different satellites doing earth sciences. But Department of Defense also uses them.
[00:43:23]
Host: Oh!
[00:43:24]
Bill Foster: And sometimes when you get a higher priority user, they really are a higher priority user, and we — we can tell from the way things are being told to us that we don’t need to go fight this battle, we’re not going to win [laughter]. But if we have a spacecraft emergency, that bumps us up to the highest priority user.
[00:43:43]
Host: Totally makes sense. So, we’re running out of time just a little bit, but I do want to talk about one more thing before I let you go, and that’s, I know, you know, we’re talking about how the International Space Station has near instantaneous, you’re saying quarter of a second-ish, roundtrip communication. I know if we go to Mars, when we go to Mars, that’s going to take a long time. We’re talking about way longer than just a fraction of a second. Are we — are we training for what that’s going to look like?
[00:44:13]
Bill Foster: Yes, we are! That certainly is a consideration, we actually began several years ago with an experiment. I think it’s been a while since we’ve done it, but we’ve put delay equipment into one of our space-to-ground channels up to the crew. We — only one of them though. And it was a planned experiment with the crew where we would talk from the ground, and it would sit on the ground for 10 minutes before being sent up.
[00:44:42]
Host: Yeah, right.
[00:44:42]
Bill Foster: And the crew would respond, and it would sit on the ground for 10 minutes before being put into our voice system. So you’d have a 20-minute round-time delay. And — and they would practice with simple tasks. You know, and that’s depending on circumstances. You know, a 10 minute or longer one-way trip time is very possible as you head toward Mars.
[00:45:04]
Host: Right.
[00:45:05]
Bill Foster: The other day, when I was at that mission control film, Dr. Kraft was asked, you know, what the next step for NASA should be? And he says, I don’t know why we’re going to Mars?
[00:45:16]
Host: Oh.
[00:45:16]
Bill Foster: He said, you go to the moon and explore its resources, you’re a 3 second voice time away. If you go to Mars, you’re 40 minutes away.
[00:45:25]
Host: Yeah.
[00:45:25]
Bill Foster: And, you know, and there’s a lot of other reasons on that, but — but that’s a good example. So — so we’re thinking along the lines of, well, right now, we talk to the crew, and we say, they’re having a problem, and someone on the ground, well, this procedure says they should go do this, so we tell them that. Then they go do that, and then it doesn’t work, and they say, well, that didn’t work, what should I do next? And, well, go try this. Well, you can’t do that real time when you’re a 20 or 40 minute round trip voice path away.
[00:45:57]
Host: Yeah, you have a problem, you’re not getting an answer for 40 minutes.
[00:46:00]
Bill Foster: So you’ve got to frame your questions and your directions a lot differently. You know, we — we want you to try this step, if that doesn’t work, go to this part of the procedure, if that doesn’t work, go to that part of the procedure. You’ve got to understand and think of what the problems could be ahead of time, and you want to package that conversation one way to include as much information and as much alternate things that they can do as possible, and they get that and they try it, and they’ll have to package their response back in a similar way that says we did this and we did that and we did this, and maybe this worked, or maybe we got this indication, not that indication, you know, and so instead of a quick, 2 second voice uplink, you may have a 2 or 3 minute voice uplink to them, to give them a lot of options, they can go work, and then respond back.
[00:46:58]
So those types of things are part of the planning process, and — and how do we handle this obstacle? We can’t beat physics. So, how do we work with it to the best of our advantage?
[00:47:10]
Host: Right. So the main thing really you discovered is that talking on Mars is going to be really, really annoying, so.
[00:47:16]
Bill Foster: It will be.
[00:47:17]
Host: [Laughing] But you’re coming up with all the right techniques to make sure it’s…
[00:47:20]
Bill Foster: But we go back to the JPL session, you know, when they — because they send back something say it worked, you can jump up and down and cheer, because, you know, you’re not affecting anything real time.
[00:47:31]
Host: Yeah. Very cool! Okay, well, I think that’s — that’s about all the time we have. Bill, thank you so much for coming…
[00:47:37]
Bill Foster: It’s my pleasure.
[00:47:38]
Host:…and talking about space communication. Learned a lot, I’m sure there’s much more to this topic. If there’s anything we missed, stay tuned to after the outro music here, and we’ll tell you about how to talk to us to see if there’s — if you have any suggestions for questions or topics that we can answer. So, Bill, thanks again for coming on the show, and hopefully we’ll see you next time!
[00:47:58]
Bill Foster: You bet! Y’all have a great day!
[00:47:59]
Host: Thanks!
[00:48:00]
[ Music & Radio Transmissions ]
Host: Hey, thanks for sticking around! So, today we talked space communication with Bill Foster, and you can learn way more about it if you go on the internet! A great place to go for more information for pretty much everything, including learning about space communication. So I have a website here called, deepspace.jpl.nasa.gov, or you can just go and search for DSNow, that’s deep space network now. It’s a really cool website where, if you go, you can actually see which satellites are being used for which things in the deep space network. That was one of the main things that Bill and I talked about today. If you want to know more about the International Space Station, where we are sending a lot of our space communication now on a day-to-day basis, you can go to nasa.gov/iss, and learn everything about all the latest updates about the International Space Station.
[00:49:13]
We have blogs and articles and scientific updates on a day-to-day basis, so make sure you go there. We’re also very active on social media for the International Space Station, on Facebook, it’s — the title of the page itself is called, The International Space Station, on Twitter, it’s @space_station, and on Instagram, it’s @ISS. If you go to any one of those, you can find some great information, but you can also use the hashtag, @asknasa, on any one of those platforms, and we’ll take a look and you can submit an idea for a podcast topic or maybe you just have a question, and we’ll try to address it later on a podcast, just make sure to mention, Houston, We Have a Podcast, in that hashtag. This podcast was recorded on April 13th, 2017. Thanks to John Stoll, Alex Perryman, and Matt McKenzie for helping with the script, and thanks again for Bill Foster for coming on the show. We’ll see you next time!