0 00:00:00,000 --> 00:00:30,000 Dear viewer, these subtitles were generated by a machine via the service Trint and therefore are (very) buggy. If you are capable, please help us to create good quality subtitles: https://c3subtitles.de/talk/717 Thanks! 1 00:00:13,980 --> 00:00:16,259 What do you think 2 00:00:16,260 --> 00:00:18,569 when I say 3 00:00:18,570 --> 00:00:20,100 lasers in space, 4 00:00:22,020 --> 00:00:23,250 lightsabers, 5 00:00:25,860 --> 00:00:27,929 what do you think about when 6 00:00:27,930 --> 00:00:30,329 I say space and airborne 7 00:00:30,330 --> 00:00:31,859 laser platforms? 8 00:00:33,360 --> 00:00:35,040 Deathstar, what else? 9 00:00:37,410 --> 00:00:39,479 What do you think about when I 10 00:00:39,480 --> 00:00:41,549 say laser based 11 00:00:41,550 --> 00:00:44,349 propulsion for space travel? 12 00:00:44,350 --> 00:00:46,949 Oh, frickin complicated navigation 13 00:00:46,950 --> 00:00:49,409 math with way too many variables. 14 00:00:50,690 --> 00:00:52,619 OK, no, seriously, 15 00:00:54,390 --> 00:00:56,549 in the next talks, we will learn what's 16 00:00:56,550 --> 00:00:57,930 really behind this terms. 17 00:00:58,950 --> 00:01:01,439 Peter Bush camp would teach us 18 00:01:01,440 --> 00:01:03,689 not only basic physics, 19 00:01:03,690 --> 00:01:05,969 but he will also teach us about 20 00:01:05,970 --> 00:01:08,039 the boundaries of lasers 21 00:01:08,040 --> 00:01:09,040 in space. 22 00:01:10,000 --> 00:01:11,829 And we will learn about space travel with 23 00:01:11,830 --> 00:01:13,839 lasers, which absolutely sounds like 24 00:01:13,840 --> 00:01:15,939 science fiction, but apparently 25 00:01:15,940 --> 00:01:17,169 is already a reality. 26 00:01:18,920 --> 00:01:21,139 Peter Buscombe works for 27 00:01:21,140 --> 00:01:23,239 the infrared group of the Max 28 00:01:23,240 --> 00:01:26,269 Planck Institute for Extraterrestrial 29 00:01:26,270 --> 00:01:28,339 Physics, where 30 00:01:28,340 --> 00:01:30,949 he's building the world's most sensitive 31 00:01:30,950 --> 00:01:34,369 instruments for space observation. 32 00:01:34,370 --> 00:01:36,169 He's also active in the Munich Pyfrom 33 00:01:36,170 --> 00:01:38,959 community where he's building backbones. 34 00:01:38,960 --> 00:01:41,299 And he was the head of the Public 35 00:01:41,300 --> 00:01:43,459 Astronomical Observatory in Bielefeld. 36 00:01:44,660 --> 00:01:46,819 Are you sure about the Bielefeld 37 00:01:46,820 --> 00:01:47,820 part? 38 00:01:48,820 --> 00:01:50,929 Yeah, please give a 39 00:01:50,930 --> 00:01:52,889 warm hand for applause for Roskam. 40 00:02:01,310 --> 00:02:02,310 All right. 41 00:02:03,090 --> 00:02:04,969 Yeah, this is essentially a follow up 42 00:02:04,970 --> 00:02:07,249 talk from 43 00:02:07,250 --> 00:02:08,250 last year. 44 00:02:09,380 --> 00:02:12,169 I don't know who was there last year. 45 00:02:12,170 --> 00:02:14,359 I talked about how to shoot 46 00:02:14,360 --> 00:02:16,579 lasers into the sky and 47 00:02:16,580 --> 00:02:19,119 use them for astronomical purposes, 48 00:02:19,120 --> 00:02:20,959 essentially to correct the atmosphere 49 00:02:20,960 --> 00:02:21,960 above us, to get 50 00:02:23,090 --> 00:02:25,369 clean and undisturbed images 51 00:02:25,370 --> 00:02:28,489 here on the ground and not just 52 00:02:28,490 --> 00:02:29,490 from space 53 00:02:31,040 --> 00:02:32,989 telescopes on satellite platforms. 54 00:02:32,990 --> 00:02:35,169 So this year, it's lasers in the sky. 55 00:02:37,250 --> 00:02:38,250 I'm. 56 00:02:40,040 --> 00:02:41,539 It's only 30 minutes. 57 00:02:41,540 --> 00:02:43,669 Sorry, I 58 00:02:43,670 --> 00:02:46,549 will give a brief overview of 59 00:02:46,550 --> 00:02:49,339 some topics, what is actually 60 00:02:49,340 --> 00:02:52,069 now already flying above our heads, 61 00:02:52,070 --> 00:02:54,259 what is what 62 00:02:54,260 --> 00:02:56,599 some people think should be flying 63 00:02:56,600 --> 00:02:58,969 soon above our heads, and 64 00:02:58,970 --> 00:03:00,979 some others are pure speculation. 65 00:03:02,120 --> 00:03:04,159 So first, want to talk about laser 66 00:03:04,160 --> 00:03:05,579 propulsion? 67 00:03:05,580 --> 00:03:08,179 Actually, this is the second reason 68 00:03:08,180 --> 00:03:10,219 this talk came to be because I was 69 00:03:10,220 --> 00:03:11,899 talking to Liz and she wanted to do 70 00:03:11,900 --> 00:03:13,819 something about interstellar and 71 00:03:13,820 --> 00:03:15,909 interplanetary colonization and said, OK, 72 00:03:15,910 --> 00:03:18,289 cool, maybe we can combine it 73 00:03:18,290 --> 00:03:20,659 and then talk about also about 74 00:03:22,070 --> 00:03:23,929 photonic propulsion and so on. 75 00:03:23,930 --> 00:03:25,399 And then we just skipped it into the next 76 00:03:25,400 --> 00:03:27,529 talk to have more time for other stuff in 77 00:03:27,530 --> 00:03:28,530 the other talk. 78 00:03:29,930 --> 00:03:32,359 After that, we're talking about 79 00:03:32,360 --> 00:03:33,360 laser brooms, 80 00:03:34,670 --> 00:03:36,769 how to clear up the skies 81 00:03:36,770 --> 00:03:38,089 above us with lasers. 82 00:03:39,590 --> 00:03:41,539 It's going to be about laser sensing, 83 00:03:41,540 --> 00:03:44,599 which is routinely employed every day. 84 00:03:44,600 --> 00:03:46,309 If you look up the weather on your 85 00:03:46,310 --> 00:03:48,799 smartphones, there's a 86 00:03:48,800 --> 00:03:50,959 fair chance that you will be looking at 87 00:03:50,960 --> 00:03:53,059 some refined laser data that has 88 00:03:53,060 --> 00:03:55,189 been taken either from ground into 89 00:03:55,190 --> 00:03:56,930 space or from space to ground. 90 00:03:58,010 --> 00:04:00,109 And to 91 00:04:00,110 --> 00:04:02,299 finish, we'll talk a bit about laser 92 00:04:02,300 --> 00:04:03,809 communication. 93 00:04:03,810 --> 00:04:05,719 Of course, this is something a lot of 94 00:04:05,720 --> 00:04:07,099 people here in the audience are also 95 00:04:07,100 --> 00:04:08,749 interested in. 96 00:04:08,750 --> 00:04:10,429 It's the chaos communication Congress, 97 00:04:10,430 --> 00:04:12,559 after all, and this is 98 00:04:12,560 --> 00:04:14,419 something that takes place above our 99 00:04:14,420 --> 00:04:16,849 heads, is being built right now 100 00:04:16,850 --> 00:04:18,679 and is actually pretty exciting. 101 00:04:20,480 --> 00:04:21,949 So first, let's talk about laser 102 00:04:21,950 --> 00:04:22,950 propulsion. 103 00:04:23,960 --> 00:04:26,089 Laser propulsion is a 104 00:04:26,090 --> 00:04:28,279 method of pushing something 105 00:04:28,280 --> 00:04:29,899 forward with just light. 106 00:04:29,900 --> 00:04:31,489 How does this work? 107 00:04:31,490 --> 00:04:33,439 Well, I mean, photons are not just there 108 00:04:33,440 --> 00:04:35,629 to illuminate things, which 109 00:04:35,630 --> 00:04:37,159 they do a pretty great job. 110 00:04:37,160 --> 00:04:39,340 And they also, of course, carry momentum. 111 00:04:40,430 --> 00:04:41,629 It's just a tiny bit. 112 00:04:41,630 --> 00:04:43,699 It's the energy divided by the 113 00:04:44,840 --> 00:04:46,189 speed of light. 114 00:04:46,190 --> 00:04:48,379 But still, there is a bit 115 00:04:48,380 --> 00:04:50,059 of momentum being transferred from a 116 00:04:50,060 --> 00:04:52,160 photon when it hits some surface. 117 00:04:53,480 --> 00:04:55,579 To get a rough idea how much this 118 00:04:55,580 --> 00:04:57,589 is, if you are in Earth orbit, 119 00:04:58,880 --> 00:04:59,880 you get 120 00:05:01,400 --> 00:05:03,619 the amount of photons from the Sun, which 121 00:05:03,620 --> 00:05:05,209 is equivalent to the so-called solar 122 00:05:05,210 --> 00:05:07,579 constant, which is one thousand 123 00:05:07,580 --> 00:05:09,679 three hundred sixty one, 124 00:05:09,680 --> 00:05:12,349 I guess if I remember correctly, 125 00:05:12,350 --> 00:05:14,279 watts per square meter. 126 00:05:15,650 --> 00:05:18,739 This translates then if you have a 127 00:05:18,740 --> 00:05:20,839 solar cell which you 128 00:05:20,840 --> 00:05:22,909 put into Earth orbit and just 129 00:05:22,910 --> 00:05:24,679 let the photons from the Sun push it 130 00:05:24,680 --> 00:05:26,929 forward, which is equivalent 131 00:05:26,930 --> 00:05:28,489 to well, it depends a bit on your 132 00:05:28,490 --> 00:05:29,929 orientation of the scale. 133 00:05:29,930 --> 00:05:31,939 And if it's a black cell of photons get 134 00:05:31,940 --> 00:05:34,489 absorbed or they get ideally reflected 135 00:05:34,490 --> 00:05:36,529 if you have. So that means if you have an 136 00:05:36,530 --> 00:05:38,209 inelastic collision on an elastic 137 00:05:38,210 --> 00:05:40,249 collision for the physicists in the room, 138 00:05:41,330 --> 00:05:43,699 but roughly you get around seven 139 00:05:43,700 --> 00:05:44,899 micron Newton, 140 00:05:46,040 --> 00:05:46,969 that's not much. 141 00:05:46,970 --> 00:05:48,559 Of course that's not much. 142 00:05:48,560 --> 00:05:50,659 Well, you can say a scale 143 00:05:50,660 --> 00:05:52,279 up our yossele. 144 00:05:52,280 --> 00:05:53,599 It's not just one square meter. 145 00:05:53,600 --> 00:05:55,279 Maybe it's 100 by 100 meters 146 00:05:56,390 --> 00:05:58,939 that the point is it may be just 147 00:05:58,940 --> 00:06:01,249 a very tiny fraction from each 148 00:06:01,250 --> 00:06:03,859 photons, but there are a lot of photons 149 00:06:03,860 --> 00:06:05,569 and this is for free. 150 00:06:05,570 --> 00:06:07,429 So if you maybe have a mission, which you 151 00:06:07,430 --> 00:06:09,439 just want to push far away and you have 152 00:06:09,440 --> 00:06:11,209 time on your hands, maybe this is 153 00:06:11,210 --> 00:06:13,009 something you want to do because this is 154 00:06:13,010 --> 00:06:14,249 constant. 155 00:06:14,250 --> 00:06:16,699 It's not like a chemical which burns 156 00:06:16,700 --> 00:06:17,929 off after some time. 157 00:06:17,930 --> 00:06:20,179 You don't have to bring huge amounts 158 00:06:20,180 --> 00:06:22,639 of propellant into space for that. 159 00:06:22,640 --> 00:06:24,139 This may be an option. 160 00:06:24,140 --> 00:06:26,569 Is this pure science fiction right now? 161 00:06:26,570 --> 00:06:28,279 No, actually not. 162 00:06:28,280 --> 00:06:29,280 Um, 163 00:06:30,410 --> 00:06:33,079 this is a representation 164 00:06:33,080 --> 00:06:35,179 of a test solar 165 00:06:35,180 --> 00:06:37,279 sail satellite from the 166 00:06:37,280 --> 00:06:39,619 Japanese Space Agency, 167 00:06:39,620 --> 00:06:41,869 which has been launched in 2010. 168 00:06:41,870 --> 00:06:43,159 It's called EQUASS. 169 00:06:43,160 --> 00:06:45,329 And then you get a rough idea 170 00:06:45,330 --> 00:06:47,149 of what this is actually looks like, 171 00:06:47,150 --> 00:06:49,069 because if you just let this is just a 172 00:06:49,070 --> 00:06:51,049 sail with something in the middle. 173 00:06:51,050 --> 00:06:52,999 But, yeah, this is actually flying right 174 00:06:53,000 --> 00:06:55,669 now. They hope to they last communicated 175 00:06:55,670 --> 00:06:57,739 with it in 2014 and they 176 00:06:57,740 --> 00:06:59,300 hope to communicate 177 00:07:00,470 --> 00:07:02,209 in the next year with it again. 178 00:07:02,210 --> 00:07:04,339 And what you see here is in the middle, 179 00:07:04,340 --> 00:07:06,559 for example, there is the little payload. 180 00:07:06,560 --> 00:07:09,289 So some experiments, 181 00:07:09,290 --> 00:07:11,569 a little transmitter to communicate back 182 00:07:11,570 --> 00:07:13,729 to Earth. And these blue 183 00:07:13,730 --> 00:07:15,619 stripes you see around the middle, these 184 00:07:15,620 --> 00:07:17,209 are actually solar cells, which then 185 00:07:17,210 --> 00:07:19,099 produce the electricity for the 186 00:07:19,100 --> 00:07:21,199 experiments on board 187 00:07:21,200 --> 00:07:23,539 because this thing is 40 meters by 40 188 00:07:23,540 --> 00:07:25,609 meters. So this is not much, but it's 189 00:07:25,610 --> 00:07:28,699 a nice technical demonstration platform. 190 00:07:28,700 --> 00:07:31,459 Of course, if you want to go really 191 00:07:31,460 --> 00:07:33,889 into serious propulsion 192 00:07:33,890 --> 00:07:36,019 with that, you'd rather look 193 00:07:36,020 --> 00:07:38,629 maybe at sales, which one hundred meters 194 00:07:38,630 --> 00:07:39,559 by 100 meters. 195 00:07:39,560 --> 00:07:41,749 Or even a kilometer, we don't have 196 00:07:41,750 --> 00:07:43,819 a real clue yet how to make them how to 197 00:07:43,820 --> 00:07:46,039 bring them into space, what to use 198 00:07:46,040 --> 00:07:48,229 actually as the sailing material, how 199 00:07:48,230 --> 00:07:50,089 to unfold it properly, but will 200 00:07:50,090 --> 00:07:51,090 eventually get them. 201 00:07:54,170 --> 00:07:56,959 Another thing you could be thinking of 202 00:07:56,960 --> 00:07:59,149 is, of course, not the sun, but of 203 00:07:59,150 --> 00:08:01,249 course, to shine a big 204 00:08:01,250 --> 00:08:03,499 laser on this, maybe a ground 205 00:08:03,500 --> 00:08:05,899 based laser, maybe a space based laser 206 00:08:05,900 --> 00:08:08,419 that is, of course, project star shot. 207 00:08:08,420 --> 00:08:10,459 It's going through the media all over the 208 00:08:10,460 --> 00:08:12,319 place right now. 209 00:08:12,320 --> 00:08:14,419 This is a very interesting concept which 210 00:08:14,420 --> 00:08:16,999 uses a ground based or maybe space 211 00:08:17,000 --> 00:08:17,899 based laser. 212 00:08:17,900 --> 00:08:20,899 And of course, there you have targeted 213 00:08:20,900 --> 00:08:22,669 and directed laser light. 214 00:08:22,670 --> 00:08:23,690 So you don't have the 215 00:08:24,770 --> 00:08:27,559 the one over R-squared 216 00:08:27,560 --> 00:08:29,629 problem from the for the when you get far 217 00:08:29,630 --> 00:08:30,920 away from the from the sun. 218 00:08:32,030 --> 00:08:34,249 This is an option, another option. 219 00:08:34,250 --> 00:08:36,739 Using lasers in a in 220 00:08:36,740 --> 00:08:39,048 a in a 221 00:08:39,049 --> 00:08:41,269 similar manner is not to just 222 00:08:41,270 --> 00:08:44,089 push the sail forward with your 223 00:08:44,090 --> 00:08:46,129 laser but to use the laser actually to 224 00:08:46,130 --> 00:08:48,979 transfer energy to your spacecraft 225 00:08:48,980 --> 00:08:51,739 and these so-called laser energized 226 00:08:51,740 --> 00:08:53,119 laser based propulsion. 227 00:08:53,120 --> 00:08:55,249 This is nothing like a sail, 228 00:08:55,250 --> 00:08:57,709 although this might be look like it. 229 00:08:57,710 --> 00:09:00,019 I like these 60s and 70s space 230 00:09:00,020 --> 00:09:01,219 and so on. 231 00:09:01,220 --> 00:09:03,439 The very on the very left, you see 232 00:09:03,440 --> 00:09:06,229 a laser array here in some, uh, 233 00:09:06,230 --> 00:09:09,039 um, orbit around 234 00:09:09,040 --> 00:09:10,579 one of the moons of Jupiter. 235 00:09:10,580 --> 00:09:12,409 I think it should be either because of 236 00:09:12,410 --> 00:09:14,359 the guys down there anyway. 237 00:09:14,360 --> 00:09:16,789 So this is sending out a powerful 238 00:09:16,790 --> 00:09:19,639 laser beam to one of these reflectors 239 00:09:19,640 --> 00:09:21,829 on the spacecraft itself in 240 00:09:21,830 --> 00:09:23,839 the front. Again, that's the payload at 241 00:09:23,840 --> 00:09:26,299 the very real again, that's the engine 242 00:09:26,300 --> 00:09:28,609 in the middle. There's everything else. 243 00:09:28,610 --> 00:09:30,709 And so what we do here is we 244 00:09:30,710 --> 00:09:33,199 do have propellant on board. 245 00:09:33,200 --> 00:09:35,329 Um, but unlike in the 246 00:09:35,330 --> 00:09:36,889 chemical rocket where we use the 247 00:09:36,890 --> 00:09:39,199 propellant for the for the energy 248 00:09:39,200 --> 00:09:41,329 and also the debris from the 249 00:09:41,330 --> 00:09:44,059 propellant, the dust and the 250 00:09:44,060 --> 00:09:45,859 after the what comes out after the 251 00:09:45,860 --> 00:09:48,829 reaction for the thrust here, 252 00:09:48,830 --> 00:09:51,319 we use some external means of energy 253 00:09:51,320 --> 00:09:53,569 transfer on a propellant which gets 254 00:09:53,570 --> 00:09:56,089 then pushed out of the 255 00:09:56,090 --> 00:09:58,339 of the nozzle of our 256 00:09:58,340 --> 00:10:00,259 propulsion system and then pushes the 257 00:10:00,260 --> 00:10:01,249 whole thing forward. 258 00:10:01,250 --> 00:10:04,219 If you think of a normal jet engine, 259 00:10:04,220 --> 00:10:06,559 it's the same you use it's the medium 260 00:10:06,560 --> 00:10:09,229 and you use kerosene as the 261 00:10:09,230 --> 00:10:10,549 as the energy 262 00:10:12,020 --> 00:10:13,669 to actually drive the engine. 263 00:10:15,500 --> 00:10:17,869 Um, another very 264 00:10:17,870 --> 00:10:20,209 interesting thing which is 265 00:10:20,210 --> 00:10:22,969 being discussed in the 266 00:10:22,970 --> 00:10:25,039 scientific literature right now is 267 00:10:25,040 --> 00:10:27,769 the so-called photonic laser thruster. 268 00:10:27,770 --> 00:10:30,619 Um, and for some applications 269 00:10:30,620 --> 00:10:32,689 also in military application, 270 00:10:32,690 --> 00:10:34,969 there is the the great wish for 271 00:10:34,970 --> 00:10:37,039 having formation 272 00:10:37,040 --> 00:10:39,259 flying satellites, which 273 00:10:39,260 --> 00:10:41,629 also maybe are flying together like this, 274 00:10:41,630 --> 00:10:43,309 and then they expand into a nice 275 00:10:43,310 --> 00:10:45,439 formation and have a nice long bass 276 00:10:45,440 --> 00:10:47,689 line between them and they should get 277 00:10:47,690 --> 00:10:49,849 together again, um, 278 00:10:49,850 --> 00:10:52,639 for some radar, for some interferometry 279 00:10:52,640 --> 00:10:54,859 of radar on the ground to see where, 280 00:10:54,860 --> 00:10:55,999 you know, uh, yeah. 281 00:10:56,000 --> 00:10:57,509 All this kind of stuff. 282 00:10:57,510 --> 00:11:00,049 Um, this can be done with 283 00:11:00,050 --> 00:11:02,239 teachers to just have 284 00:11:02,240 --> 00:11:03,319 a rope between those. 285 00:11:03,320 --> 00:11:06,769 But if you have small satellites, 286 00:11:06,770 --> 00:11:08,869 um, you maybe want to 287 00:11:08,870 --> 00:11:10,519 think about something else and this is 288 00:11:10,520 --> 00:11:11,639 then what you do. 289 00:11:11,640 --> 00:11:13,909 So you have a laser between those two 290 00:11:13,910 --> 00:11:15,409 vehicles. The mission vehicle and the 291 00:11:15,410 --> 00:11:17,539 resource vehicle can also be 292 00:11:17,540 --> 00:11:18,559 of comparable size. 293 00:11:18,560 --> 00:11:20,479 Doesn't matter. The interesting thing is 294 00:11:20,480 --> 00:11:22,819 here you do reduce the photons. 295 00:11:22,820 --> 00:11:25,069 It's not just that you shine them on a 296 00:11:25,070 --> 00:11:27,169 reflecting surface, like on a sale 297 00:11:27,170 --> 00:11:29,269 or as we've seen 298 00:11:29,270 --> 00:11:30,889 in the in the other case. 299 00:11:30,890 --> 00:11:33,079 But you have them actually enter 300 00:11:33,080 --> 00:11:34,159 like a laser cavity. 301 00:11:34,160 --> 00:11:36,559 They are mirrors to each side of this. 302 00:11:36,560 --> 00:11:38,659 And so you reduce the photons. 303 00:11:38,660 --> 00:11:40,879 And this is very efficient in pushing two 304 00:11:40,880 --> 00:11:42,619 small masses out of each other. 305 00:11:42,620 --> 00:11:44,269 And then if you just switch it off, they 306 00:11:44,270 --> 00:11:46,339 will gravitate together again. 307 00:11:46,340 --> 00:11:48,619 This is a very nice thing to 308 00:11:48,620 --> 00:11:50,119 have formation of light, at least as 309 00:11:50,120 --> 00:11:52,129 proposed. It's not yet demonstrated in 310 00:11:52,130 --> 00:11:54,439 space, but we'll soon will see 311 00:11:54,440 --> 00:11:55,440 this. 312 00:11:58,640 --> 00:11:59,640 Laser brooms, 313 00:12:01,100 --> 00:12:03,289 if you look at the earth from far 314 00:12:03,290 --> 00:12:05,419 away, or maybe not even so far away 315 00:12:05,420 --> 00:12:06,889 within the orbit 316 00:12:07,940 --> 00:12:10,139 of our moon, around the 317 00:12:10,140 --> 00:12:12,319 Earth, and if you exaggerate a bit, this 318 00:12:12,320 --> 00:12:14,779 is how it looks like Earth is enshrouded 319 00:12:14,780 --> 00:12:16,279 by junk right now. 320 00:12:16,280 --> 00:12:18,679 This junk has been put there 321 00:12:18,680 --> 00:12:19,819 by us. 322 00:12:19,820 --> 00:12:22,549 We are 50 years of space exploration, 323 00:12:22,550 --> 00:12:25,639 upper stages of rockets having collided, 324 00:12:25,640 --> 00:12:27,409 tanks being ripped off, 325 00:12:28,760 --> 00:12:29,989 satellites. 326 00:12:29,990 --> 00:12:31,579 We have collided. 327 00:12:31,580 --> 00:12:33,949 And this makes up a huge amount 328 00:12:33,950 --> 00:12:35,659 of space debris, as it is called. 329 00:12:36,770 --> 00:12:38,869 There are around 30000 330 00:12:38,870 --> 00:12:41,119 objects of the size of 10 centimeters 331 00:12:41,120 --> 00:12:43,549 in space around Earth, about 332 00:12:43,550 --> 00:12:45,169 several hundred thousand of the size of 333 00:12:45,170 --> 00:12:47,629 one centimeter. So some thumb size 334 00:12:47,630 --> 00:12:50,449 and over almost 200 millions 335 00:12:50,450 --> 00:12:52,579 of them smaller than 336 00:12:52,580 --> 00:12:54,649 one millimeter. So the ring you see here 337 00:12:54,650 --> 00:12:57,229 is the, of course, the geosynchronous 338 00:12:57,230 --> 00:12:59,359 orbit. And in low earth orbit, 339 00:12:59,360 --> 00:13:00,109 you also see this. 340 00:13:00,110 --> 00:13:01,789 Is this a problem? Yes, this is a 341 00:13:01,790 --> 00:13:02,790 problem. 342 00:13:03,290 --> 00:13:05,419 Here you see a nice image from ESA 343 00:13:06,620 --> 00:13:08,599 at the end, I think it was in this 344 00:13:08,600 --> 00:13:10,729 September. Twenty sixteen 345 00:13:10,730 --> 00:13:12,799 Sentinel one A is one 346 00:13:12,800 --> 00:13:14,569 of the new class Earth observation 347 00:13:14,570 --> 00:13:16,009 satellites from ESA. 348 00:13:16,010 --> 00:13:18,169 And actually on the left you see how 349 00:13:18,170 --> 00:13:19,939 the one of the solar panels looked like 350 00:13:19,940 --> 00:13:21,049 before the impact. 351 00:13:21,050 --> 00:13:22,489 And then on the right you'll see, yeah, 352 00:13:22,490 --> 00:13:24,709 there was some space 353 00:13:24,710 --> 00:13:26,749 debris hitting the satellite and that's 354 00:13:26,750 --> 00:13:28,909 about 40 centimeters in 355 00:13:28,910 --> 00:13:30,619 diameter damage on one of the solar 356 00:13:30,620 --> 00:13:31,429 panels. 357 00:13:31,430 --> 00:13:33,679 And this roughly corresponds to 358 00:13:33,680 --> 00:13:36,019 some space debris, junk piece 359 00:13:36,020 --> 00:13:38,869 of around five millimeters or 360 00:13:38,870 --> 00:13:40,219 even less. 361 00:13:40,220 --> 00:13:43,519 So we have to think about if 362 00:13:43,520 --> 00:13:45,589 now space traffic is 363 00:13:45,590 --> 00:13:47,719 increasing and how to how to get 364 00:13:47,720 --> 00:13:48,969 rid of this. 365 00:13:48,970 --> 00:13:51,169 Um, one concept is to 366 00:13:51,170 --> 00:13:53,479 actually shoot up this from the ground. 367 00:13:55,430 --> 00:13:57,679 Of course, not in a matter 368 00:13:57,680 --> 00:13:59,989 that you now destroy these 369 00:13:59,990 --> 00:14:02,089 pieces and just split them up and even 370 00:14:02,090 --> 00:14:03,169 smaller pieces. 371 00:14:03,170 --> 00:14:04,619 This is not what we want to do. 372 00:14:04,620 --> 00:14:06,679 Of course not, because we want to reduce 373 00:14:06,680 --> 00:14:08,389 the size. How do we reduce the size of 374 00:14:08,390 --> 00:14:09,529 these things? 375 00:14:09,530 --> 00:14:11,629 Well, if we get them 376 00:14:11,630 --> 00:14:13,759 into an orbit, that they will just 377 00:14:13,760 --> 00:14:16,039 gradually go down in Earth's atmosphere 378 00:14:16,040 --> 00:14:17,689 and just burn up in the Earth's 379 00:14:17,690 --> 00:14:19,879 atmosphere. Problem solved. 380 00:14:19,880 --> 00:14:22,249 And this is actually what we what is 381 00:14:22,250 --> 00:14:24,469 being proposed right 382 00:14:24,470 --> 00:14:26,599 now. And if you take a 383 00:14:26,600 --> 00:14:27,619 commercial 384 00:14:28,850 --> 00:14:31,039 high power laser at around five to 10 385 00:14:31,040 --> 00:14:33,229 kilowatt, which you can buy and put 386 00:14:33,230 --> 00:14:35,809 it on a decent telescope, 387 00:14:35,810 --> 00:14:36,810 you could 388 00:14:38,600 --> 00:14:40,969 move the orbits or the orbital 389 00:14:40,970 --> 00:14:43,249 velocity of space 390 00:14:43,250 --> 00:14:45,409 debris of around one to 391 00:14:45,410 --> 00:14:47,449 10 centimeters by one millimeter per 392 00:14:47,450 --> 00:14:49,519 second in 393 00:14:49,520 --> 00:14:51,589 only shining your laser 394 00:14:51,590 --> 00:14:53,779 at it again, it's like a solar sail. 395 00:14:53,780 --> 00:14:56,809 It's just pushing the stuff with photons. 396 00:14:56,810 --> 00:14:58,909 So it would it will have 397 00:14:58,910 --> 00:15:00,409 a slightly different orbit. 398 00:15:00,410 --> 00:15:02,149 It will then go into Earth's atmosphere 399 00:15:02,150 --> 00:15:03,530 and then just burn up. 400 00:15:05,240 --> 00:15:07,639 Of course, this has also been proposed 401 00:15:07,640 --> 00:15:09,109 from space. 402 00:15:09,110 --> 00:15:11,179 Actually, this is the same guy who 403 00:15:11,180 --> 00:15:13,399 is now in this project started 404 00:15:13,400 --> 00:15:15,679 a project looking 405 00:15:15,680 --> 00:15:17,879 at all that and at all 406 00:15:17,880 --> 00:15:19,939 despite two thousand and fifteen, 407 00:15:19,940 --> 00:15:21,529 if you want to look up those papers, that 408 00:15:21,530 --> 00:15:22,849 quite interesting reads. 409 00:15:22,850 --> 00:15:24,859 And for example, this is a proposed 410 00:15:24,860 --> 00:15:26,899 satellite that flies 411 00:15:28,340 --> 00:15:30,199 now in deeper space. 412 00:15:30,200 --> 00:15:32,839 They did not just think about 413 00:15:32,840 --> 00:15:34,939 deflecting space debris, 414 00:15:34,940 --> 00:15:37,519 but also here targeting 415 00:15:37,520 --> 00:15:40,009 asteroids. So this is a 416 00:15:40,010 --> 00:15:42,349 platform which has big arrays 417 00:15:42,350 --> 00:15:44,389 of solar cells to power the onboard 418 00:15:44,390 --> 00:15:46,459 lasers. And then we just 419 00:15:46,460 --> 00:15:49,399 shine this laser at the asteroid 420 00:15:49,400 --> 00:15:51,039 for quite some time. 421 00:15:51,040 --> 00:15:52,669 It could be a year. It could be maybe 10 422 00:15:52,670 --> 00:15:54,829 years. If we identify the threat to 423 00:15:54,830 --> 00:15:56,299 Earth early enough. 424 00:15:56,300 --> 00:15:57,259 This is easy. 425 00:15:57,260 --> 00:15:59,209 Also, by the way, if you're interested in 426 00:15:59,210 --> 00:16:01,519 this stuff, there is a 427 00:16:01,520 --> 00:16:03,859 conference about planetary defense 428 00:16:03,860 --> 00:16:05,119 conference. 429 00:16:05,120 --> 00:16:06,890 Just look it up so you can take part. 430 00:16:08,150 --> 00:16:10,579 This is people are discussing seriously 431 00:16:10,580 --> 00:16:11,580 about this. 432 00:16:12,290 --> 00:16:14,599 Um, what you do then is not 433 00:16:14,600 --> 00:16:16,609 to just push the asteroid with your 434 00:16:16,610 --> 00:16:18,799 photons, but here 435 00:16:18,800 --> 00:16:19,800 asteroids. 436 00:16:21,500 --> 00:16:24,709 Very often contain frozen 437 00:16:24,710 --> 00:16:26,899 frozen material, frozen gases, 438 00:16:26,900 --> 00:16:29,149 so you sublimate those gases 439 00:16:29,150 --> 00:16:31,249 and actually while the gas 440 00:16:31,250 --> 00:16:33,529 sublimates from the from the asteroid 441 00:16:33,530 --> 00:16:35,359 itself, it creates a bit of thrust. 442 00:16:35,360 --> 00:16:37,459 Of course, it's 443 00:16:37,460 --> 00:16:39,319 just like a little chemical rockets 444 00:16:39,320 --> 00:16:41,809 thruster and that gradually 445 00:16:41,810 --> 00:16:43,279 pushes things out of the way. 446 00:16:44,690 --> 00:16:47,629 This is the so-called Starlight 447 00:16:47,630 --> 00:16:48,889 Mission, as it's called. 448 00:16:48,890 --> 00:16:50,719 There's also a disaster which then 449 00:16:50,720 --> 00:16:53,389 proposes to have a dedicated 450 00:16:53,390 --> 00:16:55,549 shown on the left, a a platform with 451 00:16:55,550 --> 00:16:57,739 even more powerful lasers and then 452 00:16:57,740 --> 00:16:59,029 have an array of 453 00:17:00,290 --> 00:17:02,689 mirrors somewhere in space to direct 454 00:17:02,690 --> 00:17:04,909 this, for example, to an asteroid. 455 00:17:04,910 --> 00:17:07,189 Maybe this just needs half, half 456 00:17:07,190 --> 00:17:09,289 a day each each day for 457 00:17:09,290 --> 00:17:10,969 four or five years to be deflected. 458 00:17:10,970 --> 00:17:13,219 So it will not hit us in 30 459 00:17:13,220 --> 00:17:15,469 years from now. And then we turn this 460 00:17:15,470 --> 00:17:16,858 mirror in another direction. 461 00:17:16,859 --> 00:17:19,009 And just to push a bit, our spacecraft, 462 00:17:19,010 --> 00:17:21,108 our solar sail spacecraft, like the 463 00:17:21,109 --> 00:17:23,179 project star 464 00:17:23,180 --> 00:17:25,338 thingy, which we want to push through 465 00:17:25,339 --> 00:17:27,899 space. This could be done. 466 00:17:27,900 --> 00:17:30,349 It's shown here in detail how 467 00:17:30,350 --> 00:17:32,629 you would do this with an asteroid as 468 00:17:32,630 --> 00:17:33,630 a set. You just, 469 00:17:35,840 --> 00:17:37,969 uh, sublimate the the 470 00:17:37,970 --> 00:17:40,759 gases there and use them as thrusters. 471 00:17:40,760 --> 00:17:43,099 This is, of course, not what we do 472 00:17:43,100 --> 00:17:44,659 have in space right now. 473 00:17:44,660 --> 00:17:45,709 It's being proposed. 474 00:17:45,710 --> 00:17:48,319 What we do have in space right now 475 00:17:48,320 --> 00:17:49,579 is laser sensing, 476 00:17:52,250 --> 00:17:54,319 laser sensing, so-called light 477 00:17:54,320 --> 00:17:56,659 on its light detection and ranging 478 00:17:56,660 --> 00:17:57,679 like radar. 479 00:17:57,680 --> 00:17:59,989 And what we do is we do have 480 00:17:59,990 --> 00:18:02,419 a transmitter on a spacecraft. 481 00:18:02,420 --> 00:18:04,489 Um, it shines down into the 482 00:18:04,490 --> 00:18:07,129 atmosphere. It's a pulsed laser, 483 00:18:07,130 --> 00:18:09,229 just like the laser in last year's talk, 484 00:18:09,230 --> 00:18:10,429 which we shoot upwards. 485 00:18:10,430 --> 00:18:12,589 So we know exactly when 486 00:18:12,590 --> 00:18:14,509 we started the pulse and where it is 487 00:18:14,510 --> 00:18:17,449 after a given time. 488 00:18:17,450 --> 00:18:19,489 So if the pulse travels down into the 489 00:18:19,490 --> 00:18:21,799 atmosphere, it will, of course, 490 00:18:21,800 --> 00:18:23,629 traverse different parts of the 491 00:18:23,630 --> 00:18:24,630 atmosphere 492 00:18:25,700 --> 00:18:27,619 and thereby probe different layers, maybe 493 00:18:27,620 --> 00:18:29,959 high clouds, high winds, more lower 494 00:18:29,960 --> 00:18:31,789 winds or something like that. 495 00:18:31,790 --> 00:18:33,259 And it will back scatter. 496 00:18:33,260 --> 00:18:35,269 And we, of course, know the time the 497 00:18:35,270 --> 00:18:37,339 light travels downward and upward. 498 00:18:37,340 --> 00:18:39,529 And so if you make a graph of the signal 499 00:18:39,530 --> 00:18:41,809 intensity versus time, we can learn 500 00:18:41,810 --> 00:18:43,369 about the different heights in the 501 00:18:43,370 --> 00:18:44,370 atmosphere. 502 00:18:45,290 --> 00:18:46,939 We cannot just do this with one leg so we 503 00:18:46,940 --> 00:18:48,469 can maybe do it with two lasers 504 00:18:49,760 --> 00:18:52,489 and therefore use different wavelength. 505 00:18:52,490 --> 00:18:54,589 That means looking at how the 506 00:18:54,590 --> 00:18:56,839 one wavelength is 507 00:18:56,840 --> 00:18:58,909 absorbed by the atmosphere and then 508 00:18:58,910 --> 00:19:00,890 looking at how the other wavelength is 509 00:19:02,450 --> 00:19:04,519 absorbed by the atmosphere and then 510 00:19:04,520 --> 00:19:06,589 correlate this and then maybe even learn 511 00:19:06,590 --> 00:19:08,499 something about the chemical, 512 00:19:09,520 --> 00:19:11,839 uh, chemical composition 513 00:19:11,840 --> 00:19:14,089 of the Earth in our line 514 00:19:14,090 --> 00:19:15,090 of sight. 515 00:19:15,740 --> 00:19:18,049 Or we do something like Doppler shift 516 00:19:18,050 --> 00:19:20,059 measurements. And they are we can learn 517 00:19:20,060 --> 00:19:22,909 about, for example, how wind is 518 00:19:22,910 --> 00:19:24,439 blowing in the atmosphere. 519 00:19:24,440 --> 00:19:26,689 So our timeline is essentially a set 520 00:19:26,690 --> 00:19:28,699 the distance from our spacecraft, which 521 00:19:28,700 --> 00:19:31,329 then translates to altitude so short 522 00:19:31,330 --> 00:19:33,289 it just means it's near to me. 523 00:19:33,290 --> 00:19:35,479 It's the high atmosphere and the far 524 00:19:35,480 --> 00:19:37,579 away time signal is, 525 00:19:37,580 --> 00:19:39,349 of course, then the grantly are maybe 526 00:19:40,370 --> 00:19:42,739 this is hopefully being launched 527 00:19:42,740 --> 00:19:43,369 next year. 528 00:19:43,370 --> 00:19:45,889 This mission has been on the menu 529 00:19:45,890 --> 00:19:47,809 a bit longer. It was a bit delayed. 530 00:19:47,810 --> 00:19:50,089 This is Isa's new satellite 531 00:19:50,090 --> 00:19:52,339 for just profiling the wind. 532 00:19:52,340 --> 00:19:54,289 And you'll see an artist's description on 533 00:19:54,290 --> 00:19:55,399 the on the right. 534 00:19:55,400 --> 00:19:57,319 The only actual instrument on this on the 535 00:19:57,320 --> 00:20:00,199 satellite will be this wind glider. 536 00:20:00,200 --> 00:20:01,759 And it would probe down into the 537 00:20:01,760 --> 00:20:04,129 atmosphere and give you exact 538 00:20:04,130 --> 00:20:05,579 measurements how the wind is blowing. 539 00:20:05,580 --> 00:20:08,299 So this will then use this Doppler 540 00:20:08,300 --> 00:20:10,849 method where you send out 541 00:20:10,850 --> 00:20:13,149 a signal and just measure, um, 542 00:20:13,150 --> 00:20:15,259 the, um, the 543 00:20:15,260 --> 00:20:17,599 shift in frequency from the return 544 00:20:17,600 --> 00:20:19,549 signal, which is then influenced by if 545 00:20:19,550 --> 00:20:21,469 you have maybe hit something that is 546 00:20:21,470 --> 00:20:23,689 receding from you or coming towards you, 547 00:20:23,690 --> 00:20:25,129 of course, you have to calculate out the 548 00:20:25,130 --> 00:20:27,169 satellite motions itself and earth motion 549 00:20:27,170 --> 00:20:28,669 at double-blind, whatnot. 550 00:20:28,670 --> 00:20:30,979 So this is hugely complicated. 551 00:20:30,980 --> 00:20:32,689 And if you want to have a look at the 552 00:20:32,690 --> 00:20:34,909 instrument, it's looking like this. 553 00:20:34,910 --> 00:20:37,069 And this is another lesson. 554 00:20:37,070 --> 00:20:39,919 We had this in in the talk before. 555 00:20:39,920 --> 00:20:42,079 Space technology is really, 556 00:20:42,080 --> 00:20:43,519 really hard. I'm not saying it's not 557 00:20:43,520 --> 00:20:44,599 possible. It is possible. 558 00:20:44,600 --> 00:20:46,519 It's it is being built. 559 00:20:46,520 --> 00:20:48,619 But it's not just you don't just 560 00:20:48,620 --> 00:20:49,819 fumble something together. 561 00:20:49,820 --> 00:20:50,899 And who has ever 562 00:20:52,340 --> 00:20:54,499 put a I mean, we 563 00:20:54,500 --> 00:20:56,629 have heard by Andre's talk 564 00:20:56,630 --> 00:20:58,819 about the the microscopes and how to 565 00:20:58,820 --> 00:21:01,039 build your own microscopes for 566 00:21:01,040 --> 00:21:02,040 for maybe 567 00:21:03,200 --> 00:21:05,989 doing laser microscopes 568 00:21:05,990 --> 00:21:08,119 to to enhance the resolution and 569 00:21:08,120 --> 00:21:10,429 how to build them on a on 570 00:21:10,430 --> 00:21:12,649 a on a on a typical optical 571 00:21:12,650 --> 00:21:13,650 lab bench 572 00:21:14,960 --> 00:21:17,059 here. You do it essentially the 573 00:21:17,060 --> 00:21:19,219 same, but also you have to launch this 574 00:21:19,220 --> 00:21:20,739 thing and actually. 575 00:21:20,740 --> 00:21:22,299 This is the most critical part because 576 00:21:22,300 --> 00:21:23,619 this would be shaken like hell, and 577 00:21:23,620 --> 00:21:25,689 whoever has just had a laser ready 578 00:21:25,690 --> 00:21:26,740 resonator alone 579 00:21:28,420 --> 00:21:30,579 mostly is not a fan of. 580 00:21:30,580 --> 00:21:32,379 Yeah, just come into my lap and kick my 581 00:21:32,380 --> 00:21:34,539 table a couple of times and let's see 582 00:21:34,540 --> 00:21:35,619 if it's still working. 583 00:21:35,620 --> 00:21:37,749 This will be happening during launch. 584 00:21:37,750 --> 00:21:40,179 And so you have to really make it perfect 585 00:21:40,180 --> 00:21:41,889 and tested and tested and tested and 586 00:21:41,890 --> 00:21:43,659 tested and tested and tested again. 587 00:21:43,660 --> 00:21:45,219 And when you think you have not done 588 00:21:45,220 --> 00:21:46,149 enough testing your test. 589 00:21:46,150 --> 00:21:47,150 No. 590 00:21:48,470 --> 00:21:50,659 Um, another thing, of course, 591 00:21:50,660 --> 00:21:52,349 you can make distance measurements, this 592 00:21:52,350 --> 00:21:54,469 is used on the, uh, on the 593 00:21:54,470 --> 00:21:57,019 European Autonomous 594 00:21:57,020 --> 00:21:59,509 Autonomous Transfer Vehicle, the ATV 595 00:21:59,510 --> 00:22:01,639 that docked to the International Space 596 00:22:01,640 --> 00:22:02,989 Station. 597 00:22:02,990 --> 00:22:04,099 This is how it looks like. 598 00:22:04,100 --> 00:22:06,049 And there's a little lighter interface on 599 00:22:06,050 --> 00:22:08,119 the side and it 600 00:22:08,120 --> 00:22:10,249 sees the International Space Station then 601 00:22:10,250 --> 00:22:12,379 in falls colors, which mean 602 00:22:12,380 --> 00:22:14,509 this green stuff is very 603 00:22:14,510 --> 00:22:16,699 new to me. This it's the French 604 00:22:16,700 --> 00:22:17,839 way I have to dock. 605 00:22:17,840 --> 00:22:19,489 And the red part is then 606 00:22:20,720 --> 00:22:22,069 at the very back. This is the truss 607 00:22:22,070 --> 00:22:23,689 structure of the International Space 608 00:22:23,690 --> 00:22:25,189 Station. And the whitish thing in the 609 00:22:25,190 --> 00:22:27,349 middle is one of the Soyuz capsules that 610 00:22:27,350 --> 00:22:30,229 is right now docking on the International 611 00:22:30,230 --> 00:22:31,339 Space Station. 612 00:22:31,340 --> 00:22:33,679 So this is being used routinely 613 00:22:33,680 --> 00:22:36,019 now in space and said 614 00:22:36,020 --> 00:22:38,809 you can maybe see it in your 615 00:22:38,810 --> 00:22:41,089 weather app on your smartphone every day. 616 00:22:41,090 --> 00:22:42,739 I'm not talking about this one. 617 00:22:42,740 --> 00:22:44,629 This will be in the later, actually, 618 00:22:44,630 --> 00:22:45,949 maybe in the next talk. 619 00:22:45,950 --> 00:22:48,499 You can also do gravitational waves 620 00:22:48,500 --> 00:22:51,019 and then you have to communicate between 621 00:22:51,020 --> 00:22:53,089 different satellites, not 622 00:22:53,090 --> 00:22:55,129 in terms of just exchanging data, but 623 00:22:55,130 --> 00:22:58,129 you're actually flying a Michelsen 624 00:22:58,130 --> 00:23:00,289 interferometer in space and measure 625 00:23:00,290 --> 00:23:02,569 the relative distances between 626 00:23:02,570 --> 00:23:05,029 three satellites separated by 627 00:23:06,950 --> 00:23:08,989 thousands of kilometers in space to 628 00:23:08,990 --> 00:23:10,549 detect gravitational waves. 629 00:23:10,550 --> 00:23:12,229 We'll learn about this in the next talk, 630 00:23:13,310 --> 00:23:14,929 some of the remaining time. 631 00:23:14,930 --> 00:23:17,389 Let me briefly 632 00:23:17,390 --> 00:23:19,699 give you an overview of how 633 00:23:19,700 --> 00:23:23,299 our communication is actually affected 634 00:23:23,300 --> 00:23:25,699 by lasers in Sky. 635 00:23:27,050 --> 00:23:29,359 This is mostly developing right now. 636 00:23:29,360 --> 00:23:31,429 So the first satellites 637 00:23:31,430 --> 00:23:33,859 who employ this on commercial platforms 638 00:23:33,860 --> 00:23:35,779 are already in space. 639 00:23:35,780 --> 00:23:37,879 The next will be launched next year and 640 00:23:37,880 --> 00:23:38,880 the years after that. 641 00:23:40,760 --> 00:23:43,129 Why do we want to do this 642 00:23:43,130 --> 00:23:44,089 laser communication? 643 00:23:44,090 --> 00:23:46,369 I mean, can we just do the normal 644 00:23:46,370 --> 00:23:47,599 KNU or Cuban 645 00:23:48,740 --> 00:23:50,809 radio frequencies, which we are 646 00:23:50,810 --> 00:23:52,999 using? I mean, satellite TV, it's 647 00:23:53,000 --> 00:23:54,589 working fine. 648 00:23:54,590 --> 00:23:56,239 The thing is, of course, with the laser 649 00:23:56,240 --> 00:23:58,099 communications, you do have a much higher 650 00:23:58,100 --> 00:24:00,199 bandwidth and that means you 651 00:24:00,200 --> 00:24:02,269 have several tens of gigabits per 652 00:24:02,270 --> 00:24:03,679 second per channel. 653 00:24:03,680 --> 00:24:05,210 It's very, very efficient. 654 00:24:06,220 --> 00:24:08,209 And this is actually interesting for 655 00:24:08,210 --> 00:24:10,279 space. And again, because have learned in 656 00:24:10,280 --> 00:24:12,799 the previous talks that each 657 00:24:12,800 --> 00:24:14,959 kilogram you want to put into space 658 00:24:14,960 --> 00:24:17,089 costs you a real a lot 659 00:24:18,860 --> 00:24:20,179 of euros. 660 00:24:20,180 --> 00:24:23,089 And so if you look at radio frequency, 661 00:24:23,090 --> 00:24:25,309 you get about a point 662 00:24:25,310 --> 00:24:27,619 five megabits per second per 663 00:24:27,620 --> 00:24:30,049 watt. So electrical 664 00:24:30,050 --> 00:24:32,179 consumption and kilogram, if you're 665 00:24:32,180 --> 00:24:34,249 using it as a tool, if you're looking 666 00:24:34,250 --> 00:24:36,349 at a laser communication system, it's 667 00:24:36,350 --> 00:24:38,419 more in the range of five 668 00:24:38,420 --> 00:24:41,419 megabits per watt and kg. 669 00:24:41,420 --> 00:24:43,669 Um, the communication terminals are 670 00:24:43,670 --> 00:24:46,519 smaller and they are. 671 00:24:46,520 --> 00:24:48,589 And if you, for example, have a satellite 672 00:24:48,590 --> 00:24:50,749 pointing just down on earth 673 00:24:50,750 --> 00:24:52,729 with its radio footprint, the radio 674 00:24:52,730 --> 00:24:54,739 footprint is really, really large. 675 00:24:54,740 --> 00:24:56,839 If you do laser communications, 676 00:24:56,840 --> 00:24:58,039 you can get down. 677 00:24:58,040 --> 00:25:00,409 You are even with a small telescope 678 00:25:00,410 --> 00:25:02,539 of about 20 centimeter size in 679 00:25:02,540 --> 00:25:05,209 diameter on you on your spacecraft. 680 00:25:05,210 --> 00:25:06,920 You can get down your footprint 681 00:25:08,000 --> 00:25:10,069 on the Earth to about six 682 00:25:10,070 --> 00:25:12,019 kilometers. So this is a very, very tiny 683 00:25:12,020 --> 00:25:13,819 spot. So if you're the only one who sits 684 00:25:13,820 --> 00:25:15,679 in the middle of the desert observing the 685 00:25:15,680 --> 00:25:17,509 signal, so nobody is going to be 686 00:25:17,510 --> 00:25:18,799 eavesdropping on you. 687 00:25:18,800 --> 00:25:21,079 Also, there are some ideas 688 00:25:21,080 --> 00:25:23,059 how to do this interferer metrically. 689 00:25:23,060 --> 00:25:25,069 And then if you actually were to 690 00:25:25,070 --> 00:25:26,659 intercept the signal, you would destroy 691 00:25:26,660 --> 00:25:27,799 the interference pattern. 692 00:25:27,800 --> 00:25:29,210 And this is not going to work on 693 00:25:30,290 --> 00:25:32,419 this is how roughly looks like what we 694 00:25:32,420 --> 00:25:34,189 want to do. So this is what we have right 695 00:25:34,190 --> 00:25:35,959 now. It's the radio link between a ground 696 00:25:35,960 --> 00:25:38,149 station, also called ground segment 697 00:25:38,150 --> 00:25:40,699 in, uh, in space lingo. 698 00:25:40,700 --> 00:25:42,709 And this is the satellite bus up there. 699 00:25:42,710 --> 00:25:44,599 Yeah, it's called satellite bus. 700 00:25:44,600 --> 00:25:46,729 Don't be uh, it's 701 00:25:46,730 --> 00:25:49,399 just called, um, 702 00:25:49,400 --> 00:25:50,899 and it has the payload on top. 703 00:25:50,900 --> 00:25:52,939 So if you ever payload on satellite by 704 00:25:52,940 --> 00:25:54,739 satellite, but the satellite and payload 705 00:25:54,740 --> 00:25:56,449 is the stuff you put on them to do the 706 00:25:56,450 --> 00:25:58,159 actual thing you want to do. 707 00:25:58,160 --> 00:26:00,589 Um, this is for example, in geostationary 708 00:26:00,590 --> 00:26:02,759 orbit for satellite TV. 709 00:26:02,760 --> 00:26:05,089 Um, but there are other things also 710 00:26:05,090 --> 00:26:07,309 flying around in geostationary orbit 711 00:26:07,310 --> 00:26:09,379 or in low earth orbit and in low 712 00:26:09,380 --> 00:26:12,169 Earth orbit. You see that the orbit 713 00:26:12,170 --> 00:26:14,299 just vanishes behind the 714 00:26:14,300 --> 00:26:16,519 horizon there. So if you have maybe 715 00:26:16,520 --> 00:26:19,429 a satellite that looks at 716 00:26:19,430 --> 00:26:22,219 Earth like probing of the wind 717 00:26:22,220 --> 00:26:24,139 like we've seen before, it is only 718 00:26:24,140 --> 00:26:26,269 visible from your ground segment from 719 00:26:26,270 --> 00:26:28,399 your ground station for a brief period 720 00:26:28,400 --> 00:26:31,219 of time. Who has done 721 00:26:31,220 --> 00:26:33,469 SDR radio on 722 00:26:33,470 --> 00:26:34,399 the no satellites. 723 00:26:34,400 --> 00:26:35,849 Anyone? 724 00:26:35,850 --> 00:26:38,009 Oh, yeah. OK, so those people 725 00:26:38,010 --> 00:26:40,109 do know what I'm talking about, so you 726 00:26:40,110 --> 00:26:42,359 have about 10, 20 minutes 727 00:26:42,360 --> 00:26:43,740 if you have a real nice 728 00:26:44,910 --> 00:26:47,159 position where you can see the satellite, 729 00:26:47,160 --> 00:26:49,289 where you can record the weather 730 00:26:49,290 --> 00:26:51,419 image that gets transmitted from the but 731 00:26:51,420 --> 00:26:53,339 after then nothing. 732 00:26:53,340 --> 00:26:55,199 So it would be nice, for example, to have 733 00:26:55,200 --> 00:26:57,719 an optical link, high data rates 734 00:26:57,720 --> 00:26:59,579 said to one of the geostationary 735 00:26:59,580 --> 00:27:01,919 satellites and then have them maybe 736 00:27:01,920 --> 00:27:04,230 over, then talk to your 737 00:27:05,250 --> 00:27:07,079 low Earth orbit, maybe then over other 738 00:27:07,080 --> 00:27:08,789 hubs when it gets out of the reach of the 739 00:27:08,790 --> 00:27:11,039 one geostationary satellite and so 740 00:27:11,040 --> 00:27:13,229 on. So this could be really interesting. 741 00:27:13,230 --> 00:27:15,299 Again, yes, maybe radio also, but 742 00:27:15,300 --> 00:27:17,639 ESET high data rates 743 00:27:17,640 --> 00:27:18,640 and all the 744 00:27:20,430 --> 00:27:22,430 pluses that come with the lasers. 745 00:27:24,390 --> 00:27:26,699 So for the technically inclined 746 00:27:26,700 --> 00:27:28,739 in this audience, it's 747 00:27:30,360 --> 00:27:32,189 how do we communicate? 748 00:27:32,190 --> 00:27:33,929 We have three different types of 749 00:27:33,930 --> 00:27:36,239 modulation. This is the one off keying 750 00:27:36,240 --> 00:27:38,339 the OK, that just means you 751 00:27:38,340 --> 00:27:39,989 just switch your laser on and off 752 00:27:39,990 --> 00:27:40,949 Marsing. 753 00:27:40,950 --> 00:27:42,489 It's what you have in your fiber line 754 00:27:42,490 --> 00:27:43,499 cut. Maybe at home 755 00:27:45,780 --> 00:27:47,909 it's what you do from ground to space. 756 00:27:47,910 --> 00:27:49,509 You have postposition modulation. 757 00:27:49,510 --> 00:27:51,180 This is what you have in your TV remote 758 00:27:53,460 --> 00:27:54,510 and actually. 759 00:28:11,530 --> 00:28:14,179 Jump, jump, jump, jump, jump, jump, 760 00:28:14,180 --> 00:28:15,180 jump, jump. 761 00:28:17,680 --> 00:28:18,680 Perfect. 762 00:28:29,610 --> 00:28:30,610 So this is what you do. 763 00:28:33,810 --> 00:28:35,129 All right. 764 00:28:35,130 --> 00:28:37,079 This is what you do from ground to space, 765 00:28:37,080 --> 00:28:38,670 because this is very, 766 00:28:39,960 --> 00:28:42,089 very immune to 767 00:28:42,090 --> 00:28:43,679 disturbances by the atmosphere. 768 00:28:43,680 --> 00:28:44,609 You still have to look through the 769 00:28:44,610 --> 00:28:45,610 atmosphere. 770 00:28:46,470 --> 00:28:48,539 If you have nothing in your line of 771 00:28:48,540 --> 00:28:50,259 sight, you can, of course, go to nice 772 00:28:50,260 --> 00:28:52,469 modulation principles 773 00:28:52,470 --> 00:28:55,229 like a binary face shifting 774 00:28:55,230 --> 00:28:57,329 or higher 775 00:28:57,330 --> 00:28:58,619 modulation schemes. 776 00:28:58,620 --> 00:29:01,079 But this means that if you modulate 777 00:29:01,080 --> 00:29:02,909 the phase that you do not want to have a 778 00:29:02,910 --> 00:29:04,709 medium in between, which is disturbing 779 00:29:04,710 --> 00:29:06,899 your your face and this is the 780 00:29:06,900 --> 00:29:08,609 atmosphere. So this is only used for 781 00:29:08,610 --> 00:29:10,229 space to space links. 782 00:29:10,230 --> 00:29:12,179 This is how a laser communications 783 00:29:12,180 --> 00:29:14,159 terminal looks like. 784 00:29:14,160 --> 00:29:16,649 You have the laser and everything down 785 00:29:16,650 --> 00:29:18,059 there somewhere at the bottom, you have 786 00:29:18,060 --> 00:29:20,309 two mirrors 787 00:29:20,310 --> 00:29:23,219 reflecting it. Then out of the central 788 00:29:23,220 --> 00:29:25,299 aperture at the very front, 789 00:29:25,300 --> 00:29:27,959 it's about 13 centimeters usually. 790 00:29:27,960 --> 00:29:29,459 And this is how it looks inside. 791 00:29:29,460 --> 00:29:31,479 So the laser is at the very bottom there. 792 00:29:31,480 --> 00:29:33,179 And then you have diverse mirrors in 793 00:29:33,180 --> 00:29:35,789 there to get actually the laser out 794 00:29:35,790 --> 00:29:38,219 set. Different modulation 795 00:29:38,220 --> 00:29:39,809 schemes are being used, different 796 00:29:39,810 --> 00:29:41,819 frequencies are being used. 797 00:29:41,820 --> 00:29:44,099 Typically, if you want to reuse 798 00:29:44,100 --> 00:29:46,229 telecommunication equipment 799 00:29:46,230 --> 00:29:48,119 off the shelf, if you use one thousand 800 00:29:48,120 --> 00:29:49,949 five hundred fifty nanometers, you get 801 00:29:49,950 --> 00:29:51,779 this in the normal telecommunications 802 00:29:51,780 --> 00:29:53,909 industry. If you want to, 803 00:29:53,910 --> 00:29:56,519 for example, imply a new Dunja laser, 804 00:29:56,520 --> 00:29:59,219 the infrared part, you go for the 805 00:29:59,220 --> 00:30:00,499 10 64 nanometer 806 00:30:01,770 --> 00:30:03,899 and people are working together in 807 00:30:03,900 --> 00:30:05,609 space. So, for example, here it's the 808 00:30:05,610 --> 00:30:07,769 lunar laser communication demonstrator 809 00:30:07,770 --> 00:30:09,929 from from NASA talking to as 810 00:30:09,930 --> 00:30:12,509 ground station in Teneriffe. 811 00:30:12,510 --> 00:30:14,579 And this is how it looks like from space. 812 00:30:14,580 --> 00:30:16,739 Actually, there's no video online. 813 00:30:16,740 --> 00:30:19,319 But yeah, um, 814 00:30:19,320 --> 00:30:20,999 if you look at the communications unit, 815 00:30:21,000 --> 00:30:23,029 that is the optical module, this is just 816 00:30:23,030 --> 00:30:25,019 laser. But of course, internally you need 817 00:30:25,020 --> 00:30:28,469 controller electronics, you need a modem. 818 00:30:28,470 --> 00:30:30,689 But the nice thing about is 819 00:30:30,690 --> 00:30:32,969 if you if 820 00:30:32,970 --> 00:30:35,039 you do this standardized, you don't have 821 00:30:35,040 --> 00:30:36,689 this complicated set up yet. 822 00:30:36,690 --> 00:30:39,449 For example, seen in the experiment 823 00:30:39,450 --> 00:30:41,939 for the wind measurements with the Leida 824 00:30:41,940 --> 00:30:44,519 looking down here, you just take 825 00:30:44,520 --> 00:30:46,649 a commercial off the shelf units from 826 00:30:46,650 --> 00:30:48,749 telecommunication industry, slap it 827 00:30:48,750 --> 00:30:50,160 together and you're got to go. 828 00:30:51,390 --> 00:30:52,889 You can also do this for deep space 829 00:30:52,890 --> 00:30:54,689 communication. This was a mission 830 00:30:54,690 --> 00:30:57,329 proposed by NASA, said it was canceled 831 00:30:57,330 --> 00:30:59,339 to do this up to Mars. 832 00:30:59,340 --> 00:31:01,019 You can do this from satellite to 833 00:31:01,020 --> 00:31:01,589 satellite. 834 00:31:01,590 --> 00:31:03,359 This has been done with the Terraza 835 00:31:03,360 --> 00:31:06,419 satellite from ESA and the NASA 836 00:31:06,420 --> 00:31:09,119 and via satellite. 837 00:31:09,120 --> 00:31:11,519 And right now, the Europeans building a 838 00:31:11,520 --> 00:31:13,259 data relay system around Earth. 839 00:31:13,260 --> 00:31:15,329 It's called the DRC, the European data 840 00:31:15,330 --> 00:31:16,709 relay system. 841 00:31:16,710 --> 00:31:19,079 Um, it's hosted on a commercial 842 00:31:19,080 --> 00:31:21,659 satellite from that and 843 00:31:21,660 --> 00:31:23,069 a dedicated satellite that will be 844 00:31:23,070 --> 00:31:24,299 launched later. 845 00:31:24,300 --> 00:31:25,859 And you'll see here the laser links, for 846 00:31:25,860 --> 00:31:27,719 example, in red between the satellites or 847 00:31:27,720 --> 00:31:29,189 in green to the International Space 848 00:31:29,190 --> 00:31:31,079 Station. And then they have also radio 849 00:31:31,080 --> 00:31:32,609 frequency links down. 850 00:31:32,610 --> 00:31:35,039 The next step is already 851 00:31:35,040 --> 00:31:37,739 in the works. It will be the so-called 852 00:31:37,740 --> 00:31:38,879 gluconate. 853 00:31:38,880 --> 00:31:41,399 So position various 854 00:31:41,400 --> 00:31:43,529 satellites on a 855 00:31:43,530 --> 00:31:45,719 geostationary orbit around Earth, 856 00:31:45,720 --> 00:31:47,819 having intercommunication from satellite 857 00:31:47,820 --> 00:31:50,279 to satellite on laser based. 858 00:31:50,280 --> 00:31:52,409 And of course, the next step 859 00:31:52,410 --> 00:31:53,410 will be this one. 860 00:31:54,870 --> 00:31:55,870 And 861 00:31:57,090 --> 00:31:59,009 my personal interest would be then to 862 00:31:59,010 --> 00:32:00,010 have this one. 863 00:32:08,610 --> 00:32:10,979 Is there anything else? 864 00:32:10,980 --> 00:32:13,619 Yes, I know that in the abstract 865 00:32:13,620 --> 00:32:15,000 I did mention. 866 00:32:17,040 --> 00:32:18,040 We had stuff, 867 00:32:20,380 --> 00:32:23,019 communication, laser based 868 00:32:23,020 --> 00:32:25,360 from submerged submarines. 869 00:32:27,010 --> 00:32:29,169 Two satellites in space, 870 00:32:29,170 --> 00:32:30,700 yes, this is being done. 871 00:32:33,160 --> 00:32:36,039 Downside is you will not find any 872 00:32:36,040 --> 00:32:38,589 open access publications 873 00:32:38,590 --> 00:32:40,899 which you can show, which can be streamed 874 00:32:40,900 --> 00:32:42,759 into the Internet. Just Google for it. 875 00:32:42,760 --> 00:32:44,739 You will find really nice sets of 876 00:32:44,740 --> 00:32:45,740 information there. 877 00:32:46,720 --> 00:32:49,659 It is that for certain frequencies 878 00:32:49,660 --> 00:32:51,909 in the blue and in the green, actually, 879 00:32:51,910 --> 00:32:54,079 the ocean is pretty transparent to this 880 00:32:54,080 --> 00:32:55,329 laser wavelength. 881 00:32:55,330 --> 00:32:57,429 And so you don't need some, 882 00:32:57,430 --> 00:32:59,499 uh, some something floating on 883 00:32:59,500 --> 00:33:01,149 the surface of the ocean and then maybe 884 00:33:01,150 --> 00:33:03,669 have a fiber line down to your submarine 885 00:33:03,670 --> 00:33:04,759 and then. No, no, no, no, no. 886 00:33:04,760 --> 00:33:06,729 You just shine the laser at the ocean 887 00:33:07,840 --> 00:33:09,910 and this is the other way around to 888 00:33:11,650 --> 00:33:13,479 just look it up. It's pretty interesting. 889 00:33:13,480 --> 00:33:15,729 Some of the stuff has been declassified. 890 00:33:15,730 --> 00:33:17,319 Well, actually, that's the only source 891 00:33:17,320 --> 00:33:19,449 which I also have because I don't work in 892 00:33:19,450 --> 00:33:21,069 this kind of stuff. 893 00:33:21,070 --> 00:33:23,079 And if I did, I couldn't tell you. 894 00:33:27,060 --> 00:33:29,429 Yeah, so there's a lot of stuff going 895 00:33:29,430 --> 00:33:31,649 on in space above our heads right now 896 00:33:31,650 --> 00:33:34,349 and in the near future, 897 00:33:34,350 --> 00:33:36,419 just watch out with your spaceship if you 898 00:33:36,420 --> 00:33:37,420 do the asteroids. 899 00:33:38,520 --> 00:33:39,520 We don't want to see that. 900 00:33:40,720 --> 00:33:42,300 OK, next. OK, thank you. 901 00:33:56,760 --> 00:33:58,969 Thank you very much for this amazing 902 00:33:58,970 --> 00:33:59,970 talk. 903 00:34:00,560 --> 00:34:02,899 We perhaps have time for 904 00:34:02,900 --> 00:34:05,029 one short question, a really 905 00:34:05,030 --> 00:34:06,409 short question. 906 00:34:06,410 --> 00:34:08,359 So somebody's already on the microscope. 907 00:34:08,360 --> 00:34:09,919 He's driving. How do you get a shot? 908 00:34:09,920 --> 00:34:10,920 Question number two. 909 00:34:11,900 --> 00:34:14,089 Yeah, try OK. 910 00:34:14,090 --> 00:34:16,279 It's just about how far the 911 00:34:16,280 --> 00:34:18,169 weather affects communication. 912 00:34:18,170 --> 00:34:20,419 We had a company that had two 913 00:34:20,420 --> 00:34:22,039 locations and tried to do laser 914 00:34:22,040 --> 00:34:24,379 communication and it turned out focus, 915 00:34:24,380 --> 00:34:26,209 even snow, even more evil. 916 00:34:26,210 --> 00:34:28,819 So how is it from 917 00:34:28,820 --> 00:34:29,769 space to earth? 918 00:34:29,770 --> 00:34:32,149 Yeah, you do have these problems, 919 00:34:32,150 --> 00:34:33,150 of course, too. 920 00:34:33,889 --> 00:34:36,169 You do have the only 921 00:34:36,170 --> 00:34:38,209 thing you can do is maybe use modulation, 922 00:34:38,210 --> 00:34:40,399 which is more immune to 923 00:34:40,400 --> 00:34:42,019 it. Otherwise, if you have really dense 924 00:34:42,020 --> 00:34:44,718 fog at some point just out 925 00:34:44,719 --> 00:34:47,539 and therefore the Groundling 926 00:34:47,540 --> 00:34:49,609 segments are often still 927 00:34:49,610 --> 00:34:51,379 you've seen, for example, in the Globe 928 00:34:51,380 --> 00:34:53,599 Net in the European data relay system, 929 00:34:53,600 --> 00:34:55,849 the Groundlings are all always at least 930 00:34:55,850 --> 00:34:57,110 back up with radio links. 931 00:34:59,440 --> 00:35:01,629 So it's also getting a little too 932 00:35:01,630 --> 00:35:03,819 loud here to answer questions, really, 933 00:35:03,820 --> 00:35:06,069 so if you have any more questions, 934 00:35:06,070 --> 00:35:08,049 just come here to the front and ask Peter 935 00:35:08,050 --> 00:35:08,979 directly. 936 00:35:08,980 --> 00:35:11,499 And now we want to end with 937 00:35:11,500 --> 00:35:13,719 a last big round of 938 00:35:13,720 --> 00:35:16,209 applause to thank our speaker, 939 00:35:16,210 --> 00:35:17,210 Peter.