Speaker 1: Welcome to Text Stuff, a production from my Heart Radio.
Speaker 1: Hey there, and welcome to tech Stuff. I'm your host,
Speaker 1: Jonathan Strickland. I'm an executive producer with I Heart Radio
Speaker 1: and I love all things tech and today's episode is
Speaker 1: in response to a request Carlos wrote to me and
Speaker 1: asked me this. He said, Hey, Jonathan, great work on
Speaker 1: your podcast. I am looking at satellite communications and I
Speaker 1: find it hard to understand how are they used for
Speaker 1: Internet access, why they use mega hurts instead of megabits
Speaker 1: per second, and in general, how they communicate to Earth
Speaker 1: perhaps a continuation episode. Well that's a great topic, and
Speaker 1: I get how it can be confusing when a technology
Speaker 1: uses different but similar sounding terms. So today we're going
Speaker 1: to break down satellite communications and how they work. Now,
Speaker 1: the simple and there to the question is that satellites
Speaker 1: communicate using radio waves, and in fact that's where the
Speaker 1: mega hurts stuff comes in. But that doesn't really create
Speaker 1: an understanding of what's going on. To do that, we
Speaker 1: need to jump into some history. And you might think
Speaker 1: I would start with nineteen fifty seven with the first
Speaker 1: satellite to achieve orbit, but you're wrong. We're going back
Speaker 1: a bit further I'm going to start all the way
Speaker 1: back in nineteen o three, which sounds crazy, right, but
Speaker 1: that's when a Russian scientist named Konstantine Selkovsky worked out
Speaker 1: the mass that suggested that, yeah, it would be possible
Speaker 1: to build a rocket that we could launch from Earth
Speaker 1: and lift a payload into space, so that that payload,
Speaker 1: that object would be in an orbit around Earth. Now,
Speaker 1: see gravity pulls downward, or if you prefer it, pulls
Speaker 1: towards a center of mass, because you know, once we
Speaker 1: get out into space, concepts like up and down don't
Speaker 1: have so much meaning. Inertia of a moving body tends
Speaker 1: to make it move in a in a straight line.
Speaker 1: So think of it as we have a perfectly leveled table.
Speaker 1: Now we've got a ball on the table, and you
Speaker 1: give a push on the ball, it will tend to
Speaker 1: travel in a straight line in the same direction as
Speaker 1: your push. So if there is a balance between gravity
Speaker 1: and inertia, an object will continue in a straight line
Speaker 1: while being pulled toward a center of mass. So, if
Speaker 1: the object is moving fast enough, the ground of the
Speaker 1: Earth will curve away from its path as it falls
Speaker 1: towards the Earth. So it's kind of in a constant
Speaker 1: state of falling. This, by the way, is one of
Speaker 1: many proofs that the Earth is round, because if it weren't,
Speaker 1: orbits would not work. But we know they work because
Speaker 1: we built stuff, we put it in orbit, We depend
Speaker 1: on that stuff on a day to day basis, So
Speaker 1: that alone is proof that the Earth is round. Now,
Speaker 1: Silkovski proved that an orbiting satellite was possible from a
Speaker 1: mathematical point of view, but there was no real, you know,
Speaker 1: rush to prove him right. For one thing, what the
Speaker 1: heck would the ding dang durn thing do once it
Speaker 1: was up there? I mean, would we just be throwing
Speaker 1: resources at something just to say we did it? I mean,
Speaker 1: this would be the equivalent of answering the question why
Speaker 1: do you want to climb Mount Everest with because it's there?
Speaker 1: That might not be the best answer for all situations. Besides,
Speaker 1: Silkowsky's work wasn't widely known for many years. In fact,
Speaker 1: two decades later, a Romanian scientist named herman O Birth
Speaker 1: essentially worked out the same stuff completely independently of Solkovsky's work.
Speaker 1: He wasn't aware of Silkovsky. But again, even ober It's
Speaker 1: work was confined to a relatively small circle of physicists,
Speaker 1: or as the British would say, Boffin's he. Even well
Speaker 1: read physicists in the United States had never heard of
Speaker 1: either of these two people, and while they were all
Speaker 1: thinking about space, none of them had actually proposed an
Speaker 1: artificial satellite as of yet. Robert Goddard, an American, made
Speaker 1: another important contribution to our space efforts. While pursuing post
Speaker 1: graduate studies at Princeton University. He demonstrated that rocket propulsion
Speaker 1: would work even in the airless environment of space, and
Speaker 1: this was around nineteen sixteen or so, and he built
Speaker 1: a solid fuel rocket in nineteen eighteen. But his funding
Speaker 1: dried up around the time that World War One ended,
Speaker 1: and this is going to be an ongoing theme in
Speaker 1: the space industry. Scientists seem to get way more funds
Speaker 1: when there are possible military applications to the technology they're developing,
Speaker 1: you know, beyond just putting stuff up into space. Goddard
Speaker 1: would continue his work through various colleges up until World
Speaker 1: War Two, when a again he would receive funding to
Speaker 1: work on rocketry with applications for the military, in this
Speaker 1: case largely in the world of jet assisted takeoff or
Speaker 1: j to j A. T O. Germany also famously pursued
Speaker 1: rocketry in World War Two, using it to great effect
Speaker 1: with devastating weapons like the V two rocket. One of
Speaker 1: the scientists chiefly responsible for that V two rocket was
Speaker 1: Werner von Braun, sort of Germany's equivalent of Goddard. Von
Speaker 1: Braun was interested in spaceflight, but like Goddard, he put
Speaker 1: his mind to work for a military in an effort
Speaker 1: to fund his research. Germany used von Braun's rockets to
Speaker 1: fire upon cities like London, killing thousands and devastating entire
Speaker 1: sections of the city. Von Braun wasn't necessarily the most
Speaker 1: ardent supporter of the Nazi regime during World War Two,
Speaker 1: but he joined the Nazi Party and became a member
Speaker 1: of the s S and while he didn't seem to
Speaker 1: share any real political views with the Nazis, he did
Speaker 1: see the allegiance to the party as a necessity for
Speaker 1: him to get the resources he wanted to pursue the
Speaker 1: goal of space flight, so to him, the ends justified
Speaker 1: the means. In nineteen forty three, scientists working for the U. S.
Speaker 1: Navy began to look into the possibility that the Nazis
Speaker 1: were developing rockets capable of putting an artificial satellite into orbit.
Speaker 1: Their worry was that a device like that might be
Speaker 1: used for reconnaissance or spy technology, or maybe even as
Speaker 1: a weapon, whether a weapon capable of actually creating physical
Speaker 1: destruction or a more psychological weapon to terrorize people into
Speaker 1: thinking they'd be subjected to death rays or something. The
Speaker 1: scientists concluded that it could be possible to launch a
Speaker 1: satellite into orbit. Essentially, they were retreading the ground that
Speaker 1: Siolkovsky and o Berth had already walked, and there was
Speaker 1: some early interest in exploring that as an actual option.
Speaker 1: In nineteen four be four, while at a party, Von
Speaker 1: Brown got inebriated and he let it slip that he
Speaker 1: thought the war wouldn't end well for Germany, which was
Speaker 1: pretty much a foregone conclusion, but it was essentially a
Speaker 1: treasonous act. To actually suggest that Germany would lose the
Speaker 1: war was an act of treason. So he was arrested. However,
Speaker 1: he was never incarcerated. It did send a message to him,
Speaker 1: you know, Von Brown said, Wow, my place here is
Speaker 1: not as secure as I would like it to be.
Speaker 1: So he and several other rockets scientists went into hiding.
Speaker 1: Upon hearing that Hitler had committed suicide, these scientists surrendered
Speaker 1: to American soldiers and they were part of a negotiation
Speaker 1: to come to America and essentially pursue the same sort
Speaker 1: of work they had been doing for Germany, but in
Speaker 1: the United States. Now. This was known in classified circles
Speaker 1: as Operation paper Clip, and it involved bringing more than
Speaker 1: fifteen hundred scientists from Germany to the United States. Von
Speaker 1: Braun would continue developing rockets in the US under various
Speaker 1: military projects and research facilities, still with the dream of
Speaker 1: achieving space flight. Now to say that he's a controversial
Speaker 1: historical figure is really putting it mildly, but he's definitely
Speaker 1: an inspiration for science fiction authors who like to create
Speaker 1: sort of those amoral scientists who pursue their obsession with
Speaker 1: no regard for the consequences, you know, following in that
Speaker 1: old Jurassic Park line of you spent so much time
Speaker 1: thinking if you could, you never thought if you should.
Speaker 1: That kind of thing. Anyway, German and American scientists would
Speaker 1: work together in numerous laboratories run by several universities as
Speaker 1: well as the military branches, and they created rockets that
Speaker 1: carried payloads holding scientific equipment designed to measure phenomena in
Speaker 1: the upper atmosphere. So these were rockets that wouldn't escape
Speaker 1: into orbit, but they would go very, very very high up.
Speaker 1: As early as nineteen forty six, these different facilities were
Speaker 1: looking at the possibility of launching a satellite into orbit,
Speaker 1: but they largely concluded that these technologies weren't sophisticated enough
Speaker 1: to make that a reality just yet. It was, however,
Speaker 1: a long term goal. Now this brings us up to
Speaker 1: the nineteen fifties. That's when the United States and the
Speaker 1: then Soviet Union were deep in the Cold War. The
Speaker 1: two nations had become more antagonistic to one another since
Speaker 1: the end of World War Two, and each nation was
Speaker 1: attempting to keep the other in check while expanding its
Speaker 1: own power. They were also both racing to develop technologies
Speaker 1: that can demonstrate superiority over the other. This is part
Speaker 1: of what fueled the space race. Now, I don't want
Speaker 1: to take anything away from the thousands of scientists, engineers, pilots,
Speaker 1: and everyone else who worked on those early days in
Speaker 1: the space industry. Though at this point it wasn't yet
Speaker 1: an industry, there were lots of people who genuinely wanted
Speaker 1: to use technology to explore beyond what humans had previously
Speaker 1: been capable of and to push back our boundaries of ignorance.
Speaker 1: There were a lot of brilliant people who worked on
Speaker 1: projects with the motivation to further our scientific knowledge. But
Speaker 1: the reason they really got the chance to do this
Speaker 1: was because governments were willing to pour a lot of
Speaker 1: resources into the endeavor in an effort to try and
Speaker 1: get ahead of the opposition. So that's the backdrop, but
Speaker 1: let's get to some details. In nineteen fifty two, the
Speaker 1: International Council of Scientific Unions established that the period of
Speaker 1: July one, nineteen fifty seven to December thirty one, nineteen
Speaker 1: fifty eight, would be the international geophysical year to coincide
Speaker 1: with a cycle of increased solar activity. And in case
Speaker 1: you didn't know, the Sun goes through these cycles in
Speaker 1: which there's more solar events like solar flares that happen
Speaker 1: in that cycle. Then that's followed by a period of
Speaker 1: decreased solar act ativity, not no solar activity, but less
Speaker 1: of it. And these are regular and predictable, though the
Speaker 1: individual activities the individual flares are not as predictable. Then
Speaker 1: in nineteen fifty four, this same council said, Hey, you
Speaker 1: know what would be really needo if we figured out
Speaker 1: how to launch a scientific device up so that could
Speaker 1: enter Earth's orbit. Such a thing had never been done before,
Speaker 1: and the proposed goal was a device that would be
Speaker 1: capable of mapping the surface of the Earth, giving us
Speaker 1: the most accurate vision of the Earth's surface to date.
Speaker 1: Several organizations had been looking at the logistics of getting
Speaker 1: a payload up into orbit, though not necessarily as part
Speaker 1: of the Council's proposal. The dream back in nineteen six
Speaker 1: had never really gone away. It just was on the
Speaker 1: back burner because it wasn't really possible. And then something
Speaker 1: happened to spur the American government to put more support
Speaker 1: behind this endeavor. A nineteen fifty four broadcast on Moscow
Speaker 1: our radio revealed that the Soviets were seriously gearing up
Speaker 1: to push for space flight. Now, that bit of information
Speaker 1: didn't reach the general American public, but you can bet
Speaker 1: that the federal government was very much aware of it.
Speaker 1: A year later, in nineteen fifty the US government announced
Speaker 1: a plan to launch a satellite, and that timing is
Speaker 1: definitely not a coincidence. The government began to request proposals
Speaker 1: from various laboratories to assist in getting this done, essentially saying,
Speaker 1: give us your plan so we can figure out where
Speaker 1: we're going to put our money. The Naval Research Laboratory
Speaker 1: responded to this request for proposals with a project called Vanguard,
Speaker 1: while other groups had alternative proposals and lacking a real
Speaker 1: sense of urgency, the White House kind of waffled on this.
Speaker 1: They delayed on selecting an option. They were kind of
Speaker 1: weighing all of the choices, and this was somewhat understandable
Speaker 1: as any path was going to require millions of taxpayer dollars,
Speaker 1: so if the project was a success, it would be
Speaker 1: a high point in science history. But if it failed,
Speaker 1: taxpayers would get mighty miffed at what had been seen
Speaker 1: as a huge waste of money, Like you took millions
Speaker 1: of our dollars and you put it towards something that
Speaker 1: didn't even work. That would be disastrous. Ultimately, the White
Speaker 1: House chose Project Vanguard, and the hope was to be
Speaker 1: the first nation to launch a man made satellite into orbit.
Speaker 1: But that's not how things turned out. While Project Vanguard
Speaker 1: was underway, the Soviets had been busy, and on October fourth,
Speaker 1: nineteen fifty seven, the USSR shocked the world by launching
Speaker 1: a nearly four pound or eighty three point six kilogram
Speaker 1: satellite into orbit. That satellite's name was Sputnik. It was
Speaker 1: about the size of a beach ball, and it would
Speaker 1: orbit the Earth every hour and a half or so,
Speaker 1: and it also essentially went beep. It sent out a
Speaker 1: radio ping signal that could be picked up by radio
Speaker 1: stations as the satellite passed overhead. That included radio sets
Speaker 1: that were operated by amateurs, so ham radio operators could
Speaker 1: hear as the satellite passed over and this launch shocked
Speaker 1: the American public. Americans were under the belief that the
Speaker 1: Soviet Union was far behind the United States from a
Speaker 1: scientific and technological standpoint. Spot Nik flew in the face
Speaker 1: of that, and it also raised a terrifying possibility. If
Speaker 1: the USSR could launch a payload into space, could it
Speaker 1: also create a weapon that could be fired from across
Speaker 1: the world and still hit the United States. Spot Nik
Speaker 1: launch spurred the U s Government into emergency mode. Vanguard
Speaker 1: was still on the books, but the White House would
Speaker 1: turn to the Army Redstone Arsenal Team led by one
Speaker 1: Werner von Braun for an alternative, and it would be
Speaker 1: called the Explorer one, and it would become the first
Speaker 1: satellite launched by the United Dates. We have a bit
Speaker 1: more history to go through when we come back, but
Speaker 1: after that we'll go into how we get these satellites
Speaker 1: into orbit, and then how they communicate with each other
Speaker 1: and with stations here on Earth. But first let's take
Speaker 1: a quick break. The first Spotnik satellite orbited the Earth
Speaker 1: in October nineteen fifty seven, and it was never intended
Speaker 1: to be a permanent fixture. It's orbit gradually decayed until
Speaker 1: in January nineteen fifty eight, it burned up while re
Speaker 1: entering the Earth's atmosphere. The Soviets launched spot Nick two
Speaker 1: in November of nineteen fifty seven, and that's all I'm
Speaker 1: going to say about that story. I've covered it before,
Speaker 1: and that story makes me super sad and I hate
Speaker 1: to talk about it. So the United States would launch
Speaker 1: Explorer one on January thirty one, nineteen fifty eight, So
Speaker 1: several months after both spot Nik and spot Nick two,
Speaker 1: it did more than beep. Explore one did not just beep.
Speaker 1: It also didn't kill a dog, So that's two things
Speaker 1: that made it more advanced than either of the Sputnik satellites.
Speaker 1: It carried scientific equipment designed to detect cosmic rays, and
Speaker 1: the fact that it sent data with lower cosmic raid
Speaker 1: counts than was anticipated. Let a scientist named James Van
Speaker 1: Allen to hypothesize about the existence of a belt of
Speaker 1: charged particles that were trapped by Earth's magnetic field. A
Speaker 1: second satellite confirmed this hypothesis a couple of months later,
Speaker 1: and the scientific community would name the charged particles the
Speaker 1: Van Allen Belts. It took Explore one just under one
Speaker 1: fifteen minutes to complete an orbit around the Earth, so
Speaker 1: it would go around the planet about twelve and a
Speaker 1: half times per day. It stayed in orbit a little
Speaker 1: longer than Sputnik did. While the Soviet satellite burned up
Speaker 1: on reentry just a few months after being launched, the
Speaker 1: Explorer one remained in orbit from ninety eight until eighteen seventy.
Speaker 1: It completed fifty eight thousand trips around Earth. The era
Speaker 1: of the satellite was just beginning. While a lot of
Speaker 1: media attention would shift towards space flights with humans and spacecraft,
Speaker 1: the scientific community around the world continued to develop new
Speaker 1: satellites for all sorts of purposes, from scientific research to
Speaker 1: military reconnaissance to eventually global communications. One other thing I
Speaker 1: want to mention before getting into the communications tech is
Speaker 1: how a science fiction author proposed a type of satellite
Speaker 1: that would be capable of communicating with a ground station
Speaker 1: every hour of the day. See, if you have a
Speaker 1: satellite in orbit like Explorer one, there's going to be
Speaker 1: times when that satellite cannot send communications back to a
Speaker 1: specific ground station because it's going to be out of sight.
Speaker 1: Once the satellite passes a certain point overhead, communications will
Speaker 1: start to drop. Placing ground stations around the world can
Speaker 1: saw of that problem, but that gets into the issue
Speaker 1: of establishing listening stations in places that you know aren't yours,
Speaker 1: and that gets tricky from a political and real estate standpoint.
Speaker 1: But obviously, if a satellite is on the opposite side
Speaker 1: of the Earth from a listening station, the radio signals
Speaker 1: can't get to the listening station, so you really only
Speaker 1: have a window where you can have useful communications with
Speaker 1: that particular type of satellite. For an effective communication satellite,
Speaker 1: you need something in orbit that will remain over the
Speaker 1: same fixed point here on Earth or in a pattern
Speaker 1: that keeps it over the same general area of the Earth.
Speaker 1: The satellite would need to travel around an orbital path
Speaker 1: that keeps pace with the rotation of the Earth itself,
Speaker 1: and this is called a geosynchronous orbit. The satellite will
Speaker 1: travel over the same general region of the Earth because
Speaker 1: it will orbit at the rate of once per day,
Speaker 1: the same as the Earth's rotation. Now, science fiction author
Speaker 1: Arthur See Clark, known for writing stuff like two thousand
Speaker 1: one a Space Odyssey, made a sort of observation and
Speaker 1: prediction back in nine It was published in a magazine
Speaker 1: called Wireless World, and it proposed the idea of a
Speaker 1: geo stationary satellite. Clark stated that a satellite at sufficient altitude,
Speaker 1: and he was talking about a an altitude of forty
Speaker 1: two thousand, one sixty four kilometers or around thirty five thousand,
Speaker 1: seven eighty seven miles above the Earth's surface and placed
Speaker 1: over the equator would have an orbital period equal to
Speaker 1: the Earth's rotation, and so would remain above the same
Speaker 1: fixed point on the equator. Now, forty two thousand, sixty
Speaker 1: four kilometers altitude is obviously a lot, but without any context,
Speaker 1: it's hard to say that's not so bad or wow,
Speaker 1: that's way the heck out there. So just for comparison's sake,
Speaker 1: it's good to remember that the International Space Station, which
Speaker 1: isn't in geo sin grannous orbit, is a mirror four
Speaker 1: hundred kilometers in altitude typically four hundred versus forty two thousand,
Speaker 1: one d sixty four. Wow. Still as far out as
Speaker 1: geosynchronous orbital areas are. That's not even halfway to the Moon.
Speaker 1: The Moon is three four thousand, four hundred kilometers from Earth,
Speaker 1: So a geostationary orbit is a specific subset of orbits
Speaker 1: that fall into the geosynchronous orbit category. A satellite in
Speaker 1: geosynchronous orbit will remain over a general region of Earth,
Speaker 1: but if the satellite isn't directly above the equator, that
Speaker 1: region varies a bit due to the Earth's tilt. In fact,
Speaker 1: from the Earth's standpoint, it looks like the satellite is
Speaker 1: moving in a figure eight pattern across the Earth's surface.
Speaker 1: That's because the path of the satellite crosses above and
Speaker 1: below the equator during the orbit and the Earth's rotation
Speaker 1: throughout the day. A geo stationary orbit has to be
Speaker 1: above the equator, and a satellite along that orbital path
Speaker 1: will remain over its fixed point on Earth. Uh with
Speaker 1: some caveats that I'll get to. Such a satellite could
Speaker 1: remain in constant contact with the exact same ground stations,
Speaker 1: and those ground stations would never need to move their
Speaker 1: antenna to maintain contact, right they would just point their
Speaker 1: antenna where the satellite is, and that's where the satellite
Speaker 1: is going to stay. So it really makes it simplified
Speaker 1: to communicate with that particular satellite. A network of those
Speaker 1: types of satellites could communicate with one another as well
Speaker 1: as their respective ground stations, and boom, you've got your
Speaker 1: framework for a global communications infrastructure using radio signals beamed
Speaker 1: out into space and then beamed back down to the Earth. Now,
Speaker 1: Clark's idea was sound, but there wasn't really any practical
Speaker 1: way to achieve it. Back in it would take twenty
Speaker 1: years before the world would see the first commercial geo
Speaker 1: stationary communications satellite, and that was called the Intel SAT one.
Speaker 1: I think it would be handy for us to look
Speaker 1: at what makes putting satellites into geo stationary orbits so tricky,
Speaker 1: because it gives us an appreciation for the amount of
Speaker 1: science and technology required to make stuff like communication networks
Speaker 1: actually work. So let's start with just putting something into orbit. First,
Speaker 1: you gotta put your satellite on a launch vehicle. Now,
Speaker 1: essentially what we're talking about is a rocket. Now, back
Speaker 1: in the old days, it was the Space Shuttle. We
Speaker 1: often use the Space Shuttle to put satellites up into orbit,
Speaker 1: and the Space Shuttle had rocket boosters attached to it
Speaker 1: as well as its own rocket engine. But these days
Speaker 1: we don't have a space Shuttle. We're talking about a
Speaker 1: rocket here. Usually from our perspective, we launch those rockets
Speaker 1: straight up from the Earth's surface. And there's a good
Speaker 1: reason for this when you think about it. If you're
Speaker 1: looking anywhere from above the horizon in one direction across
Speaker 1: the entire arc of the sky to the horizon, and
Speaker 1: the other direction. So let's say you're doing it from
Speaker 1: east to west. Well, the whole time you do that,
Speaker 1: you're technically looking out towards space. So why would you
Speaker 1: launch straight up if every direction in that arc is
Speaker 1: out towards space. What's because the shortest distance between two
Speaker 1: points is a straight line, and launching straight up means
Speaker 1: you're taking the shortest path to push through the thickest
Speaker 1: part of the atmosphere. You're doing it in the most
Speaker 1: efficient way, and that's really important because that means you're
Speaker 1: consuming less fuel. Since fuel is one of the expensive
Speaker 1: factors in space launches, and since adding more fuel adds
Speaker 1: more weight to your launch vehicle, which means you then
Speaker 1: have to factor that weight into your calculations, being frugal
Speaker 1: with stuff is generally a really good idea. Once the
Speaker 1: rocket reaches a certain altitude, the flight plan will call
Speaker 1: for the rocket to adjust its direction so that the
Speaker 1: payload our satellite in other words, gets to where it's
Speaker 1: supposed to be, and a system called the inertial guidance
Speaker 1: system will calculate the specific adjustments needed to put the
Speaker 1: rocket on the correct path. That system uses accelerometers to
Speaker 1: measure the various stresses it's experiencing in order to interpret
Speaker 1: that as how the rocket is oriented with respect to
Speaker 1: the Earth and what altitude it's at. Those accelerometers are
Speaker 1: in gimbals so that they remain in the same orientation
Speaker 1: with respect to the Earth. Typically, the rocket will head
Speaker 1: toward the east once it reaches that altitude. So why
Speaker 1: does it go toward the east was because the Earth
Speaker 1: rotates to the east, and by going in that direction,
Speaker 1: the rocket gets a bit of a boost, and you'd
Speaker 1: get the best boost in speed if you happen to
Speaker 1: be traveling along the path of the equator and going east.
Speaker 1: The circumference of the Earth is approximately forty thousand kilometers,
Speaker 1: and we know the Earth rotates once every twenty four hours,
Speaker 1: not exactly twenty four hours, but close enough, so that
Speaker 1: means a point on the equator must travel at a
Speaker 1: speed of one thousand, six hundred sixty nine kilometers per hour.
Speaker 1: If you are further north or south of the equator
Speaker 1: and you are traveling east, you don't get quite that
Speaker 1: same speed boost. For example, at Cape Canaveral, which is
Speaker 1: in Florida in the United States, you start off at
Speaker 1: a latitude that is twenty eight degrees thirty six minutes
Speaker 1: twenty nine point seven seconds north of the equator, and
Speaker 1: at this latitude the rotational speed of the Earth is
Speaker 1: one thousand, four hundred forty kilometers per hour, so a
Speaker 1: little bit less than the equatorial speed of one thousand,
Speaker 1: six hundred sixty nine kilometers per hour. It might not
Speaker 1: seem like a huge difference, but again that speed boost
Speaker 1: means that you consume less fuel, So a flight path
Speaker 1: that moves closer to the equator also means you need
Speaker 1: less juice to get to your final orbit, as long
Speaker 1: as that orbit is also near the equator. To escape
Speaker 1: Earth's gravity, a rocket would have to accelerate to at
Speaker 1: least forty thousand, three hundred twenty kilometers per hour. That
Speaker 1: is Earth's escape velocity. If you move slower than that,
Speaker 1: gravity claims the rocket, it will go into an orbit,
Speaker 1: it won't escape Earth's gravitational pull, and eventually it'll fall
Speaker 1: back to Earth if it's uh. If it's inertia, isn't
Speaker 1: enough to keep it in space. But to put a
Speaker 1: satellite into orbit, you don't need escape velocity, right, You're
Speaker 1: not trying to escape Earth's gravity because an orbit is
Speaker 1: a kind of controlled fall. It depends upon a gravitational pull.
Speaker 1: So instead you have to reach orbital velocity. That's that
Speaker 1: balance between a satellite's inertia and moving in a generally
Speaker 1: straight line and the force of gravity that's pulling it downward.
Speaker 1: That speed is dependent upon altitude. The closer the satellite
Speaker 1: is to Earth, the greater the orbital velocity is required
Speaker 1: in order to balance out the force of gravity. If
Speaker 1: the satellite we're at two kilometers over the Earth, it
Speaker 1: would have to travel at twenty seven thousand, four hundred
Speaker 1: kilometers per hour to maintain orbit and not come falling
Speaker 1: back down. But in a geo stationary orbit much much
Speaker 1: much further out from Earth, it can travel at a
Speaker 1: comparatively sluggish eleven thousand, three hundred kilometers per hour to
Speaker 1: keep pace. Now remember that's to stay in a fixed
Speaker 1: position above a point on the Earth that's traveling at
Speaker 1: one thousand, six hundred sixty nine kilometers per hour. So
Speaker 1: the satellite has to cover more distance because it's further
Speaker 1: out in the same amount of time as the fixed
Speaker 1: point on Earth, which is why it has to travel
Speaker 1: faster than that relative position. And this is also why
Speaker 1: we need to remember that those satellites that are closer
Speaker 1: to us, they're actually going around the Earth more than
Speaker 1: once per day. They might not be a whole lot
Speaker 1: more than once per day, depending on how far out
Speaker 1: it is, but they are not maintaining a fixed position
Speaker 1: above a point on the Earth, so they actually do
Speaker 1: have to travel faster. Not around in altitude, the rocket
Speaker 1: will fire smaller thrusters to change that rocket's altitude and orientation,
Speaker 1: so it enters into a more horizontal position relative to
Speaker 1: the Earth, and at that orientation, the rocket releases its payload.
Speaker 1: The satellite will part ways with the rocket and the
Speaker 1: rocket will then fire some other thrusters that will help
Speaker 1: create separation between the rocket and the satellite. Okay, so
Speaker 1: we've boosted a satellite with a rocket so that it
Speaker 1: can move into its orbital path. Upon separation, the satellite
Speaker 1: is at the parage. Now, this is the lowest point
Speaker 1: of its orbit, the closest it will be to the Earth. Now,
Speaker 1: the satellite may cross the equator a couple of times
Speaker 1: and it will reach its apogee, or its highest point
Speaker 1: at at this section. And you can think of this
Speaker 1: orbit is looking like it's spiraling out from the Earth,
Speaker 1: like it starts off close and then as the satellite
Speaker 1: goes around the planet, it starts to get further away
Speaker 1: before it starts to come back in. So when we
Speaker 1: talk about lowest and highest points, there's really quite a range.
Speaker 1: So for example, the g Sat fourteen communications satellite, which
Speaker 1: had a geostationary orbit, had a parody of KOs that's
Speaker 1: where it's separated from its launch vehicle and its APOGE
Speaker 1: was thirty six thousand kilometers now an appo G. The
Speaker 1: satellite will conduct a series of controlled burns with onboard
Speaker 1: thrusters on the satellite itself. This helps reshape the orbit
Speaker 1: from being an elliptical path where it's further out from
Speaker 1: the Earth on one side and closer to the Earth
Speaker 1: on the other side, into a more circular path where
Speaker 1: the Earth is at the center. This typically takes a
Speaker 1: few different controlled burns. You could technically do it in one,
Speaker 1: but it would probably require a lot more fuel, so
Speaker 1: it's more frequently done in short bursts to gently reshape
Speaker 1: that orbit. Ultimately re each in orbit where the satellite
Speaker 1: remains in a fixed position above a specific point somewhere
Speaker 1: along the equator. However, the satellite won't stay there forever
Speaker 1: if you just leave things the way they are, because
Speaker 1: stuff like the Moon and even the Earth itself will
Speaker 1: affect the satellite's path through gravitational pull. Earth's gravitational field
Speaker 1: is not uniform and these forces will slowly but surely
Speaker 1: pull the satellite out of position, so once in a
Speaker 1: while the satellite has to use those thrusters to correct
Speaker 1: for that. It's another reason why it's really important to
Speaker 1: conserve fuel. It conserves the lifespan of that satellite. The
Speaker 1: more fuel you use, the less time that satellite is
Speaker 1: going to be able to maintain that position, and it
Speaker 1: will ultimately have an orbital decay and eventually it will
Speaker 1: fall back to the Earth and break apart upon re entry. Now,
Speaker 1: when we come back, we'll talk about how these satellites
Speaker 1: actually communicate. But first let's take another quick break. Okay,
Speaker 1: we've covered the early history of satellites and the challenges
Speaker 1: of getting one into geo stationary orbit. Let's tackle how
Speaker 1: they communicate. Now. I mentioned that a geostationary satellite is
Speaker 1: ideal for communications because it will always maintain its relative
Speaker 1: position above the Earth. So once you know where the
Speaker 1: satellite is, you point your antenna in that direction and
Speaker 1: you can pick up signals from that satellite. So let's
Speaker 1: say you are a satellite TV subscriber and the company
Speaker 1: providing your signal beams information up to a communication satellite
Speaker 1: that's up in orbit, which then can broadcast that same
Speaker 1: signal back down toward a region on Earth. If your
Speaker 1: satellite dish is pointed toward that satellite, you should be
Speaker 1: able to pick up on that signal. But what do
Speaker 1: I mean when I say signals. So we're talking about
Speaker 1: the electro magnetic spectrum, and specifically we're talking about radio waves.
Speaker 1: So remember that the electro magnetic spectrum is huge. On
Speaker 1: one end, you have the long are electromagnetic waves that
Speaker 1: carry less energy. We have radio waves in that section.
Speaker 1: On the opposite side, you have very short waves that
Speaker 1: carry more energy. Gamma rays are on that side. So
Speaker 1: within this spectrum, if we go longest to shortest in
Speaker 1: wavelength of the types of electromagnetic radiation we have discovered,
Speaker 1: keeping in mind, there can be others out there on
Speaker 1: either end of the spectrum, we just have no way
Speaker 1: of really detecting them. We have radio waves on alongside,
Speaker 1: than microwaves, then infrared radiation, than visible light, than ultra
Speaker 1: violet radiation, then X rays, and finally gamma raise. All
Speaker 1: of these forms of energy travel at the speed of light,
Speaker 1: which makes sense right. I mean, light is one of
Speaker 1: the forms of electromagnetic energy. But they all have different
Speaker 1: frequencies and that can get a little confusing. And this
Speaker 1: is where an audio podcast really hits the challenge. So
Speaker 1: let's imagine first second, that you've got a sheet of
Speaker 1: graph paper in front of you, and you draw a
Speaker 1: center line in the middle of that sheet, so there's
Speaker 1: a solid center line, and you start on the left
Speaker 1: side of the sheet at that center line, and you
Speaker 1: start drawing a curve that moves upward from the center
Speaker 1: line and has a peak that's at five squares above
Speaker 1: the center line. Then you curve it back down so
Speaker 1: it crosses that center line. You keep going past it,
Speaker 1: and you draw essentially the mirror image of that curve,
Speaker 1: but you're going down now to you hit five squares
Speaker 1: below center. Then you slowly go back up to the
Speaker 1: center again. That's sort of a representation of a sign wave.
Speaker 1: You've drawn one full wavelength. So electromagnetic energy travels in
Speaker 1: waves like this, but radio waves have much longer wavelengths
Speaker 1: than gamma waves. That's, by the way, a heck of
Speaker 1: an understatement. Radio waves carry less energy than gamma rays
Speaker 1: as well, But there are a couple of reasons that
Speaker 1: we you radio waves for communication. One is that they
Speaker 1: require way less energy to generate than stuff like light.
Speaker 1: But another very practical reason is that light waves and
Speaker 1: shorter wavelengths of electromagnetic radiation get absorbed and scattered by
Speaker 1: the Earth's atmosphere. In fact, gamma rays can even penetrate
Speaker 1: the air, which is really good news for us, because
Speaker 1: otherwise life as we know it would not have formed
Speaker 1: on this planet. Gamma radiation would have wiped out anything
Speaker 1: remotely resembling life as we know it. Radio waves, though
Speaker 1: lower energy, can pass through the atmosphere without distortion, so
Speaker 1: they are ideal for communication. And because the radio waves
Speaker 1: are longer, fewer full wave lengths will pass a given
Speaker 1: fixed point within a second than with gamma waves. Now,
Speaker 1: I always use the analogy of a road to understand
Speaker 1: this concept. So let's say you're standing by a road
Speaker 1: and there's going to be a line of smart cars
Speaker 1: that are travel bumper to bumper, and they're all going
Speaker 1: to pass by you. The cars are all going fifty
Speaker 1: kilometers per hour, and your job is to count the
Speaker 1: number of smart cars that go past you in thirty seconds.
Speaker 1: Then you've got to do the exact same thing, except
Speaker 1: this time, instead of using smart cars, we're using double
Speaker 1: length buses. Those double length busses are also going by
Speaker 1: bumper to bumper. They're also traveling at fifty kilometers per hour. Now,
Speaker 1: the smart cars and the buses are all traveling at
Speaker 1: the same speed. Right, they're all traveling at fifty kilometers
Speaker 1: per hour, but you're going to count way more smart
Speaker 1: cars in those thirty seconds because they're shorter, more can
Speaker 1: fit in that space within that time. Well, the same
Speaker 1: thing is true with electromagnetic radiation. The speed limit is
Speaker 1: set right the speed of light. It's the length of
Speaker 1: the vehicles that changes. Now we measure of frequencies in
Speaker 1: hurts h E R t Z. This refers to the
Speaker 1: number of cycles or wavelengths that pass a fixed point
Speaker 1: within a second. So one hurts would mean one wavelength
Speaker 1: would pass in one second. The U. S. Navy initiated
Speaker 1: a project that would transmit radio signals at frequencies as
Speaker 1: low as thirty hurts, so that's thirty wavelengths in a second. Now,
Speaker 1: keep in mind this is energy that's traveling at the
Speaker 1: speed of light. The speed of light is two hundred thousand,
Speaker 1: seven kilometers per second, so if we divide that number
Speaker 1: by thirty cycles per second, we would see that the
Speaker 1: wave length for thirty hurts is somewhere around nine thousand,
Speaker 1: nine hundred nine three kilometers per cycle. So that means
Speaker 1: a thirty hurts radio signal has a wavelength that is
Speaker 1: nearly ten thousand kilometers long. Using that to communicate is
Speaker 1: tricky because typically we need antenna to be some regular
Speaker 1: fraction of the length of the wavelength that we're transmitting
Speaker 1: and receiving, and a very common one is to have
Speaker 1: an antenna that is one half or one quarter the
Speaker 1: length of the wavelength of radio wave. But at ten
Speaker 1: thousand kilometers, even half or one quarter is still way
Speaker 1: too long, right, So practically we use much shorter wavelength
Speaker 1: radio communications. Uh, it just doesn't make sense to build
Speaker 1: antenna for the longer ones, and different countries chop up
Speaker 1: the radio spectrum and designate bands of frequencies for specific uses.
Speaker 1: For example, in the United States, AM radio uses a
Speaker 1: frequency range between five dred twenty five killer hurts that
Speaker 1: means five twenty five thousand cycles per second, so five
Speaker 1: five thousand wavelengths will pass a fixed point in a
Speaker 1: second at that frequency all the way up to one thousand,
Speaker 1: seven hundred five killer hurts, which would be one million,
Speaker 1: seven hundred five thousand cycles per second or one point
Speaker 1: seven oh five mega hurts if you want to think
Speaker 1: of it that way. And here we get too part
Speaker 1: of that original question. The hurts here refers to the
Speaker 1: radio frequency we're using as a carrier signal. It's all
Speaker 1: about the frequency used to transmit and to receive information.
Speaker 1: It has nothing to do with the amount of information
Speaker 1: in that signal. It's specifically the frequency we're using to
Speaker 1: transmit that signal. It's not directly related to the amount
Speaker 1: of information being sent or processed. This is the medium
Speaker 1: through which we're sending data. So you can think of
Speaker 1: it as serving the exact same purpose as a physical
Speaker 1: wire or cable, except instead of sending a signal down
Speaker 1: a physical piece of hardware, we're sending it through the
Speaker 1: air and through space as radio waves. Now, you could
Speaker 1: try and communicate with a basic unaltered radio wave, but
Speaker 1: you would really be limited by just doing pulses. Right,
Speaker 1: the wave is either on or it's off, and this
Speaker 1: would be kind of like sending Morse code. And maybe
Speaker 1: do you leave it on for a short amount, like
Speaker 1: a very short pulse as a dot, and maybe you
Speaker 1: leave it on a little bit longer as a dash.
Speaker 1: And when you don't have it on, there's a gap, right,
Speaker 1: You know that that's a gap between individual pulses, But
Speaker 1: that's not terribly useful. It's also really easy to have
Speaker 1: errors introduced in that kind of signal, so we don't
Speaker 1: typically use it that way. Instead, radio communications take a
Speaker 1: basic frequency as a carrier signal, like I mentioned a
Speaker 1: minute ago, and this is sort of the baseline. You've
Speaker 1: got a basic signal at a specific frequency. By altering
Speaker 1: that signal or modulating it, we can encode information with it,
Speaker 1: and the deviations from the carrier signal all have meaning.
Speaker 1: As long as we define what those deviations from the
Speaker 1: carrier signal represent, we can encode and decode information sent
Speaker 1: along that carrier wave. I mentioned a M radio a
Speaker 1: couple of moments ago, and that stands for amplitude modulation.
Speaker 1: Amplitude describes the measure of change in a single period
Speaker 1: or cycle. But what does that actually mean in practical terms. Well,
Speaker 1: in our drawing of a sign wave, when we drew
Speaker 1: that that curve that went up and down, that amplitude
Speaker 1: would describe how tall the peak and how deep the
Speaker 1: trough is. And in our example we said it was
Speaker 1: five squares, So that would be the amplitude of that
Speaker 1: sign wave. If we were describing amplitude in terms of
Speaker 1: squares with sound waves, amplitude corresponds with volume. The greater
Speaker 1: the amplitude of a sound wave, the louder it is.
Speaker 1: This does not affect the frequency, which with sound waves
Speaker 1: we would experience as pitch. Right, a higher frequency would
Speaker 1: be a higher pitch sound, So amplitude and pitch are
Speaker 1: not connected. There are two different things. By making precise
Speaker 1: changes in the amplitude of a radio wave as a
Speaker 1: carrier wave, you can encode information on that radio wave.
Speaker 1: A receiver tuned to the proper frequency will pick up
Speaker 1: this incoming signal. It will detect those changes in amplitude
Speaker 1: and it will decode that into useful information. So all
Speaker 1: you really need to do to make this work is
Speaker 1: to come up with a set of rules that corresponds
Speaker 1: to the changes you're going to make in that signal.
Speaker 1: If you say, if I change the amplitude in this way,
Speaker 1: it means X, and if I change it in that way,
Speaker 1: it means why. And then you have a decoder that
Speaker 1: follows those same rules, but just reverses the process. You
Speaker 1: can encode and decode information. It's a really elegant way
Speaker 1: of being able to send data. But what about FM
Speaker 1: radio Then, well, that that still involves modulation. But now
Speaker 1: we're talking about frequency modulation. So you take that carrier
Speaker 1: signal of a very specific radio frequency, and then you
Speaker 1: make small changes to that frequency, not not big ones,
Speaker 1: just small one. You're actually changing the wavelength of the
Speaker 1: wave that you're sending out, making it slightly shorter or
Speaker 1: slightly longer, and you can encode information onto the carrier
Speaker 1: signal in a way similar to you could with amplitude modulation.
Speaker 1: Now you can't change the wavelength too much or else
Speaker 1: you'll push the signal outside of the effectiveness of your
Speaker 1: transmitting and receiving antenna. But you actually have a good
Speaker 1: deal of leeway there. With communication satellites, the modulation is
Speaker 1: a little more complicated than changing amplitude or frequency. Satellites
Speaker 1: use what is called phase modulation. So for this, let's
Speaker 1: imagine you've got two radio waves, and let's say that
Speaker 1: they are absolutely identical radio waves. They both have the
Speaker 1: same frequency, and they have it where the crest of
Speaker 1: one wave is lined up with the crest of another wave.
Speaker 1: So wave one's crest and wave two's crest are perfectly
Speaker 1: in alignment, and because they're the same frequency, they match
Speaker 1: up all the way down the line. So they're in
Speaker 1: box step with each other, or they're in phase with
Speaker 1: one another. However, if you offset those two waves even
Speaker 1: just a little bit, they are out of phase with
Speaker 1: each other, and we can measure that bit by degrees,
Speaker 1: if it's a lot or a little. If you have
Speaker 1: two waves that are one degrees out of phase with
Speaker 1: each other, it would mean that the crest of wave
Speaker 1: one would match up with the lowest point of the
Speaker 1: trough of wave two. They would be as out of
Speaker 1: phase as they possibly could be. So phase modulation first
Speaker 1: establishes a baseline wavelength of the signal. Then you begin
Speaker 1: to alter the phase of that signal by moving that
Speaker 1: wave out of phase in predetermined ways to represent a
Speaker 1: zero or a one communicating in binary data. And you
Speaker 1: can do this at incredibly fast speeds. And this is
Speaker 1: where we get to data throughput, which we measure in
Speaker 1: bits per second. Remember a bit is a basic unit
Speaker 1: of digital information. It's a zero or a one. A
Speaker 1: high throughput satellite can communicate at really high data throughput rates.
Speaker 1: We're talking about on the order of a hundred gigabits
Speaker 1: per second or more, and a gigabit is one billion bits,
Speaker 1: so one billion basic units of digital information every second.
Speaker 1: One billion bits per second. That's a lot of information.
Speaker 1: So now we see what the mega hurts versus megabits
Speaker 1: thing really comes down to. Mega hurts refers to the
Speaker 1: frequency of the radio wave signal that we're using as
Speaker 1: a medium. It's really just telling us the type of
Speaker 1: connection being used, the signal that's being sent out by
Speaker 1: a transmitter and the signal that's being picked up by
Speaker 1: a receiver. The receiver is ignoring all other signals except
Speaker 1: for the one that it's tuned into. Otherwise you would
Speaker 1: just be getting tons of noise and you wouldn't be
Speaker 1: able to tell what was the signal you were looking
Speaker 1: for versus everything else. There are a few other factors
Speaker 1: that allow a receiver to lock into a specific transmission,
Speaker 1: but that gets a lot more technical and uh, mega
Speaker 1: hurts does not directly correlate to data throughput. Uh. The
Speaker 1: frequency does have an effect, but I'll have to go
Speaker 1: into more detail in the future episode because it requires
Speaker 1: a more involved discussion about the nature of frequencies versus
Speaker 1: data throughput. Megabits or gigabits or kill a bits or
Speaker 1: whatever just tells us how much information can be transmitted
Speaker 1: per unit of time per second, for example. Now, I
Speaker 1: hope all of this gives you, guys a deeper understanding
Speaker 1: of what's going on with satellites, including how amazing it
Speaker 1: is the humans figured out how to get stuff out
Speaker 1: into space in the first place, let alone use it
Speaker 1: to communicate information back to Earth. It's a phenomenal achievement
Speaker 1: and really a remarkable display of how a deep understanding
Speaker 1: of science leads to us being able to leverage that
Speaker 1: understanding through technology. It's also why I argue that exploratory
Speaker 1: science is a great thing in gen a role where
Speaker 1: you set out to understand more about the universe, not
Speaker 1: for a specific application, but more just to get that understanding,
Speaker 1: because you never know what kind of applications could come
Speaker 1: from that as we learn more about how the universe works.
Speaker 1: That's why I think funding for sciences is so important.
Speaker 1: You never know what we'll learn and then how we'll
Speaker 1: put that learning to use to benefit people in the future.
Speaker 1: So um fund science, I guess, is what I'm saying.
Speaker 1: All right, guys, that wraps up this discussion about communications satellites,
Speaker 1: very very high overview pun intended of communication satellites. We
Speaker 1: can get into a lot more detail if you guys
Speaker 1: want to um, but it does get pretty tricky. Also,
Speaker 1: it gets tricky for me because I have to get
Speaker 1: a deeper understanding myself in order to be able to
Speaker 1: communicate it properly. And also just figuring out how to
Speaker 1: explain stuff without visual aids is always a challenge. If
Speaker 1: you have any other suggestions, maybe there's some other topic
Speaker 1: totally unrelated to satellite communications that you would like me
Speaker 1: to talk about. Reach out to me on Twitter. The
Speaker 1: handle is text stuff h s W and I'll talk
Speaker 1: to you again really soon y. Text Stuff is an
Speaker 1: I Heart Radio production. For more podcasts from my Heart Radio,
Speaker 1: visit the i Heart Radio app, Apple Podcasts, or wherever
Speaker 1: you listen to your favorite shows.