WEBVTT 00:06.050 --> 00:08.910 Hello, welcome to Satellite Orbits 101. 00:09.350 --> 00:16.170 I'm Matthew Murray, your presenter, and today I'll be walking you through some of the fundamental terminology surrounding satellite orbits. 00:20.610 --> 00:25.950 Now, as the title implies, this presentation isn't intended to turn you into a rocket scientist. 00:26.230 --> 00:35.690 It's meant to peel away some of the mysticism surrounding the terms involved in the journey of satellites or space vehicles and give a better understanding of the meaning behind them. 00:35.690 --> 00:44.210 To that end, I've intentionally stayed away from any intense math or physics and just focused on scratching at the upper layer of this topic. 00:50.510 --> 00:59.090 Before we jump into what the word orbit really involves, it's worth mentioning a few things and covering a few terms to help inform you and calibrate your understanding. 00:59.470 --> 01:02.270 The first matter worth discussing is launch locations. 01:02.370 --> 01:03.630 They aren't random. 01:04.430 --> 01:06.110 Ever notice how the ones in the U.S. 01:06.110 --> 01:08.070 always seem to happen in Florida? 01:08.390 --> 01:10.890 Clear sunny days really do matter. 01:11.290 --> 01:24.990 A strong enough wind can adversely affect the trajectory of a launched craft, and lightning doesn't happen just down here on Earth, it happens in the sky too, and a lightning strike as a craft moves through the atmosphere could cause huge problems. 01:25.490 --> 01:28.130 Launch locations aren't just about weather either. 01:28.310 --> 01:42.030 Depending on where you intend to place a satellite in terms of orbital distance and location, oftentimes the rotation of the Earth, which is fast as at the equator, is used to give a vehicle an extra push in launch. 01:50.530 --> 01:52.970 Once you achieve orbit, you have to keep it. 01:53.230 --> 01:57.730 Fuel on board the vehicle is used periodically to maintain or augment the orbit. 01:57.830 --> 02:07.450 The surface of the Earth isn't flat and smooth, so the changes in the surface or the topology of the Earth, all those mountains and valleys, can affect how the Earth pulls on the satellite over time. 02:08.190 --> 02:13.010 The other bodies in our solar system, like the Sun and the Moon, can also have a gravitational effect. 02:13.610 --> 02:24.050 Depending on where the vehicle is in relation to the atmosphere, even a very thin layer of air and particles up there can produce enough drag and resistance to affect an orbit. 02:24.730 --> 02:27.870 This can even increase when the Sun comes around. 02:27.910 --> 02:35.150 Just like heat makes air expand down here, the warming of the atmosphere can make drag even worse up there. 02:35.550 --> 02:43.070 And let's not forget all the junk that satellites and the people who fly those satellites have to dodge in order to make a journey around the Earth. 02:43.070 --> 02:49.770 There's more than 128 million separate pieces, parts, and objects roaming around our planet right now. 02:53.960 --> 02:56.840 All right, so let's start to dig a little bit deeper. 02:57.200 --> 03:02.560 All orbit means, in its most generic terms, is one body or object moving around another. 03:02.960 --> 03:08.840 So when that body, the object is moving around, is the Earth, the orbit is called geocentric. 03:08.840 --> 03:15.620 There are several types of geocentric orbits, and each of those types plays a part in what the satellite is up there to do. 03:16.240 --> 03:23.960 The shape of the orbits can come in different eccentricities, and all that refers to is the type of curve the orbit has. 03:23.980 --> 03:27.460 Is it circular, or is it more of an oval or an ellipse? 03:31.310 --> 03:37.010 Once we begin to consider the type of curve an orbit might have, then we can begin to lump them into categories. 03:37.370 --> 03:42.970 Periodic orbits repeat in some consistent fashion, and they're either elliptical or circular in nature. 03:43.330 --> 03:47.650 Because there's not a break in the pattern, these are sometimes referred to as closed orbits. 03:47.970 --> 03:54.410 There is another class of orbit under the topic of eccentricity that's not meant to stay in a repeating pattern around the Earth. 03:54.870 --> 04:00.610 These are called escape or open orbits, and they're used to move vehicles away from the Earth in particular ways. 04:01.190 --> 04:09.370 Parabolic orbits are used to complete minimum energy escapes if they're moving away from the Earth, and captures if they're moving towards a planet. 04:10.030 --> 04:13.430 Hyperbolic orbits can send a vehicle off at a much higher speed. 04:13.550 --> 04:21.310 These orbits are factors in gravitational slingshots, where a vehicle flies by a planet and uses its gravitational pull to pick up speed. 04:26.180 --> 04:30.180 There are also terms for the direction a satellite is moving in around the Earth. 04:30.640 --> 04:40.340 Prograde orbits move in the same direction as the Earth's rotation, and to us here below, if we were to see a satellite in prograde, it would appear to us as if the satellite was moving to the east. 04:41.320 --> 04:43.020 Retrograde means the opposite. 04:43.580 --> 04:52.500 A satellite in this type of orbit is moving against the rotation of the Earth, and if we were to see a satellite in retrograde, it would appear to us to be moving to the west. 04:53.100 --> 04:56.100 This type of orbit is rare, and it's because of the cost. 04:56.620 --> 05:01.600 Remember what we talked about earlier, about using the planet's rotation to help in launches? 05:02.000 --> 05:05.660 Well, that doesn't really work very well when you're trying to achieve retrograde. 05:09.810 --> 05:15.590 Inclinations describe the position of a satellite in relation to the equator of the Earth, as though it were an angle. 05:15.710 --> 05:27.330 So a satellite with an inclination of zero would be right above the equator, and one with an inclination of 90 or negative 90 is over the north or south pole, respectively. 05:31.450 --> 05:36.250 All right, so there's four types of orbits to talk about with all this in mind. 05:36.250 --> 05:43.490 LEO, or Low Earth Orbit, is an orbit that happens at 1,240 miles or less above the Earth's surface. 05:43.530 --> 05:53.910 It can be circular or elliptical, as can all the other types, and a vehicle at this type of orbit would take 128 minutes or less to make a trip around the Earth. 05:54.270 --> 06:00.790 There's a lot of stuff in LEO orbit right now around the Earth, including the International Space Station. 06:06.170 --> 06:11.830 Let's take a look at what a LEO orbit would look like using some SDK software visualizations. 06:12.010 --> 06:15.850 Notice how close those satellites and orbital paths are to the Earth. 06:33.810 --> 06:44.210 MEO, or Medium Earth Orbits, happen above that 1,240 mile LEO threshold, but below 22,236 miles. 06:44.450 --> 06:48.290 These orbits can take between 2 and 24 hours to get around the Earth. 06:48.330 --> 06:56.770 The coverage, or amount of surface, the satellite can see at this distance gives us things like GPS and other navigation satellite constellations. 06:56.990 --> 07:01.330 Constellations just means there's way more than one satellite doing that job. 07:06.400 --> 07:10.760 Now let's take a look at what a MEO orbit looks like in comparison to LEO. 07:26.060 --> 07:33.940 Geosynchronous orbits happen at that upper MEO threshold and match the planet's rotation in a journey around the Earth at about 24 hours. 07:34.520 --> 07:43.280 Geostationary orbits are a kind of geosynchronous orbit where it would look to us from below as if the satellite's not moving and that it's fixed in one place. 07:43.280 --> 07:47.860 This is useful in communications between Earth antenna and satellites. 07:48.080 --> 07:50.540 It's how you get satellite TV and radio. 07:54.340 --> 07:58.140 So what's a geosynchronous orbit look like in comparison to the others? 08:27.530 --> 08:30.530 Lastly, there's HEO, or High Earth Orbit. 08:30.570 --> 08:34.370 This is anything beyond the geosynchronous MEO threshold. 08:34.750 --> 08:41.690 Naturally, these orbits take longer than 24 hours, and a vehicle in one of these is actually moving slower than the Earth's rotation. 08:41.910 --> 08:49.250 This is another situation where it would look to us, because it's moving slower than the Earth's rotation, as though the satellite were moving to the west. 08:49.250 --> 08:50.950 But it's not retrograde. 08:51.590 --> 08:56.830 This type of orbit is where we park space telescopes and long-range monitoring satellites. 09:02.580 --> 09:04.540 Now let's put it all together. 09:28.470 --> 09:34.350 Here's another interesting view where you can see both circular and elliptical orbits at varying distances. 10:05.540 --> 10:08.200 Sadly, all satellites don't go to heaven. 10:08.920 --> 10:18.820 In the end, when a satellite has come to the end of its usefulness, the satellites in lower orbits that we've discussed will be put into a controlled fuel burn and put on a course to burn up in the atmosphere. 10:19.220 --> 10:24.620 The ones in orbits further out will be guided away from Earth into the expanse. 10:25.260 --> 10:26.700 And that's it. 10:27.060 --> 10:34.520 Hopefully this discussion has scratched the surface of orbital terminology for you, and you've learned a couple of new things. 10:34.900 --> 10:37.760 Thanks for your time, and enjoy the rest of the conference.