1 00:00:09,509 --> 00:00:14,009 Herald: Our next speaker has studied in Bielefeld, 2 00:00:14,009 --> 00:00:18,649 and he studied... *laughter**clapping* 3 00:00:18,649 --> 00:00:21,230 what he did is: He studied laser physics. 4 00:00:21,230 --> 00:00:26,309 And now he is working at the Max Planck Institute for extraterrestrial physics. 5 00:00:26,309 --> 00:00:28,250 And today he will explain you 6 00:00:28,250 --> 00:00:31,199 how it is possible to use laser light 7 00:00:31,199 --> 00:00:33,160 to enhance distorted images 8 00:00:33,160 --> 00:00:34,649 that were take from the earth 9 00:00:34,649 --> 00:00:36,899 of stars and galaxies and nebulars. 10 00:00:36,899 --> 00:00:39,270 So I want to hear a 11 00:00:39,270 --> 00:00:40,739 really loud and warm applaus 12 00:00:40,739 --> 00:00:42,489 for Peter Buschkamp with 13 00:00:42,489 --> 00:00:43,760 "Shooting lasers into space - 14 00:00:43,760 --> 00:00:49,859 For science"! *applause* 15 00:00:49,859 --> 00:00:58,109 All right! Thank you for the nice introduction 16 00:00:58,109 --> 00:01:00,120 Thank you, for coming here 17 00:01:00,120 --> 00:01:00,709 this evening. 18 00:01:00,709 --> 00:01:01,969 I'm very excited 19 00:01:01,969 --> 00:01:04,839 to speak at the conference. 20 00:01:04,839 --> 00:01:05,560 Finally I find a talk 21 00:01:05,560 --> 00:01:08,400 where I can contribute 22 00:01:08,400 --> 00:01:09,630 after all those years. 23 00:01:09,630 --> 00:01:11,590 I'm not going to talk about Bielefeld. 24 00:01:11,590 --> 00:01:13,190 You might want to hear something about that. 25 00:01:13,190 --> 00:01:17,210 I'm not allowed to tell you... right? 26 00:01:17,210 --> 00:01:20,750 Okay, so today I'm going to talk about 27 00:01:20,750 --> 00:01:23,400 a bit what is in my field 28 00:01:23,400 --> 00:01:27,780 of experties. 29 00:01:27,780 --> 00:01:29,210 If there is one thing 30 00:01:29,210 --> 00:01:31,030 I want to bring across to you 31 00:01:31,030 --> 00:01:31,900 then it is 32 00:01:31,900 --> 00:01:33,610 It's not about a single person 33 00:01:33,610 --> 00:01:37,320 showing this to you this evening. 34 00:01:37,320 --> 00:01:41,770 This is a team effort and a real team effort. 35 00:01:41,770 --> 00:01:43,210 So most of the images are done by 36 00:01:43,210 --> 00:01:45,980 a college of mine Julian Ziegeleder. 37 00:01:45,980 --> 00:01:47,880 And the PI of the project, 38 00:01:47,880 --> 00:01:48,740 so the leader of the project 39 00:01:48,740 --> 00:01:50,550 Sebastian Rabien 40 00:01:50,550 --> 00:01:53,000 has contributed some slides. 41 00:01:53,000 --> 00:01:54,540 And I wouldn't be standing here today 42 00:01:54,540 --> 00:01:59,920 and showing you these images 43 00:01:59,920 --> 00:02:01,600 if it wasn't for a huge team 44 00:02:01,600 --> 00:02:03,090 and many people. 45 00:02:03,090 --> 00:02:06,060 I hope this is reasonably complete, 46 00:02:06,060 --> 00:02:08,119 but I think there were even more. 47 00:02:08,119 --> 00:02:12,610 Many people have tributed most and 48 00:02:12,610 --> 00:02:16,129 long years of there career into such a project. 49 00:02:16,129 --> 00:02:18,180 So this is never about something 50 00:02:18,180 --> 00:02:19,450 which a single person does 51 00:02:19,450 --> 00:02:21,629 and he or she finds something very cool 52 00:02:21,629 --> 00:02:22,799 and then saves the world. 53 00:02:22,799 --> 00:02:27,670 No, it's always a big, big team! 54 00:02:27,670 --> 00:02:29,489 But before we actually see the lasers 55 00:02:29,489 --> 00:02:34,879 then in working, we have of course to clarify 56 00:02:34,879 --> 00:02:36,170 why we do this. 57 00:02:36,170 --> 00:02:38,290 This is not just because we can. 58 00:02:38,290 --> 00:02:41,639 We can! But there is a reason for that, 59 00:02:41,639 --> 00:02:43,200 because if you want to get funding, 60 00:02:43,200 --> 00:02:47,189 you have to write a reason and a reasonable reason. 61 00:02:47,189 --> 00:02:50,260 Not just because "We want to!" 62 00:02:50,260 --> 00:02:51,159 So in the first part 63 00:02:51,159 --> 00:02:53,810 I will introduce you 64 00:02:53,810 --> 00:02:54,519 to the whole thing 65 00:02:54,519 --> 00:02:57,469 and we talk about bit... about the problem 66 00:02:57,469 --> 00:02:59,450 which we want to tackle 67 00:02:59,450 --> 00:03:03,109 with this kind of technique. 68 00:03:03,109 --> 00:03:06,670 I will mostly present only diagrams 69 00:03:06,670 --> 00:03:09,370 not actual hardware blocks or relays. 70 00:03:09,370 --> 00:03:12,290 So you get the basic concept. 71 00:03:12,290 --> 00:03:14,579 So when we do astronomy 72 00:03:14,579 --> 00:03:15,980 we do two types of things. 73 00:03:15,980 --> 00:03:18,139 We either do imaging, 74 00:03:18,139 --> 00:03:20,349 which is: We maybe produce a nice image 75 00:03:20,349 --> 00:03:23,919 of a star - so that's the blop over there - 76 00:03:23,919 --> 00:03:25,650 or we take this image, 77 00:03:25,650 --> 00:03:28,349 maybe this little blop over there, 78 00:03:28,349 --> 00:03:30,510 and make it into a spectrum, 79 00:03:30,510 --> 00:03:32,060 so disperse the light, 80 00:03:32,060 --> 00:03:36,689 and then we look at the differential intensity 81 00:03:36,689 --> 00:03:38,599 between the diverse colors 82 00:03:38,599 --> 00:03:39,959 or are there maybe 83 00:03:39,959 --> 00:03:42,799 - for example you see black lines in there - 84 00:03:42,799 --> 00:03:46,260 absorption bands and so on. 85 00:03:46,260 --> 00:03:49,799 To do such a thing you need a spectrograph 86 00:03:49,799 --> 00:03:50,819 and in a spectrograph 87 00:03:50,819 --> 00:03:53,969 there is a thing called an entrance slit. 88 00:03:53,969 --> 00:03:55,430 So this slit you have to 89 00:03:55,430 --> 00:03:56,779 put over your objects, 90 00:03:56,779 --> 00:04:00,459 so you don't get light from left or right next to the object 91 00:04:00,459 --> 00:04:03,150 to what you want to observe or analyse 92 00:04:03,150 --> 00:04:06,779 so that you only get light from where you wanted. 93 00:04:06,779 --> 00:04:08,290 The thing is now 94 00:04:08,290 --> 00:04:11,029 this slit can not be made 95 00:04:11,029 --> 00:04:14,079 arbitrarily wide or small, 96 00:04:14,079 --> 00:04:18,139 because the width of the slit directly 97 00:04:18,139 --> 00:04:20,380 determines what kind of resolution 98 00:04:20,380 --> 00:04:22,220 you have in such a spectrometer. 99 00:04:22,220 --> 00:04:24,500 as it's called. This is a quantity 100 00:04:24,500 --> 00:04:26,410 Which needs to be above a certain value 101 00:04:26,410 --> 00:04:28,880 when you want to do certain kinds of analyses. 102 00:04:28,880 --> 00:04:31,530 So it has fixed width. 103 00:04:31,530 --> 00:04:34,370 So now if we look at an image produced 104 00:04:34,370 --> 00:04:36,620 of one of the most capable telescopes 105 00:04:36,620 --> 00:04:38,330 on this planet 106 00:04:38,330 --> 00:04:41,780 and we put a representation for this slit 107 00:04:41,780 --> 00:04:42,360 over the star 108 00:04:42,360 --> 00:04:45,540 - okay now its white, let's make this black - 109 00:04:45,540 --> 00:04:47,310 then you see if you want to go 110 00:04:47,310 --> 00:04:48,610 for that star over there, 111 00:04:48,610 --> 00:04:50,650 you do have a problem already. 112 00:04:50,650 --> 00:04:52,820 As said, you can't make this slit wider, 113 00:04:52,820 --> 00:04:56,370 but the star is actually larger than the slit, 114 00:04:56,370 --> 00:04:57,790 meaning that you lose light. 115 00:04:57,790 --> 00:04:59,970 "Well you lose some light...." No! 116 00:04:59,970 --> 00:05:02,110 If you want to quantitative measurements 117 00:05:02,110 --> 00:05:03,700 you want to have all the lights 118 00:05:03,700 --> 00:05:05,690 and all the pixels. 119 00:05:05,690 --> 00:05:07,100 So you can't get rid of them 120 00:05:07,100 --> 00:05:09,840 and just throwing something away. 121 00:05:09,840 --> 00:05:13,420 So, but our image is looking like that. 122 00:05:13,420 --> 00:05:17,730 It's maybe nice, so but can we do better? 123 00:05:17,730 --> 00:05:19,540 Yes, we can! 124 00:05:19,540 --> 00:05:21,010 And this is what we can achieve with 125 00:05:21,010 --> 00:05:22,320 adaptive optics. 126 00:05:22,320 --> 00:05:23,980 This is an image that has been produce 127 00:05:23,980 --> 00:05:25,820 with adaptive optics with a 128 00:05:25,820 --> 00:05:29,170 LASER AO assisted system. 129 00:05:29,170 --> 00:05:31,530 And if I flip back and forth you see 130 00:05:31,530 --> 00:05:34,850 there is a difference! 131 00:05:34,850 --> 00:05:40,720 All right! So why is that? 132 00:05:40,720 --> 00:05:45,090 Why don't we get this ideal images? 133 00:05:45,090 --> 00:05:47,560 The reason is because there is the atmosphere. 134 00:05:47,560 --> 00:05:50,830 The atmosphere is great for breathing. 135 00:05:50,830 --> 00:05:53,050 It's not that great for astronomy. 136 00:05:53,050 --> 00:05:55,120 So if you have a star up there somewhere 137 00:05:55,120 --> 00:05:55,890 in outer space 138 00:05:55,890 --> 00:05:58,530 - can be very far away - so the photon 139 00:05:58,530 --> 00:06:01,300 have travelled for 11 Billion years 140 00:06:01,300 --> 00:06:03,080 and now they finally hit the atmosphere 141 00:06:03,080 --> 00:06:04,330 and then something happens 142 00:06:04,330 --> 00:06:05,720 which you do not want. 143 00:06:05,720 --> 00:06:07,420 Okay, first they travel freely. 144 00:06:07,420 --> 00:06:09,940 There is a nice planar wavefront. 145 00:06:09,940 --> 00:06:12,000 So it's not disturbed by anything, 146 00:06:12,000 --> 00:06:14,400 maybe something but that's not the 147 00:06:14,400 --> 00:06:18,220 scope of this evening. It's planar, it's nice! 148 00:06:18,220 --> 00:06:20,180 And if you actually have a satellite, 149 00:06:20,180 --> 00:06:21,170 it's very cool. 150 00:06:21,170 --> 00:06:23,440 Because then you can directly record this 151 00:06:23,440 --> 00:06:25,000 undisturbed light. 152 00:06:25,000 --> 00:06:27,400 If you have something on the ground, 153 00:06:27,400 --> 00:06:30,820 well, you do get a problem, 154 00:06:30,820 --> 00:06:33,080 because the atmosphere introduces turbulence, 155 00:06:33,080 --> 00:06:36,570 because, well, the air wobbles a bit. 156 00:06:36,570 --> 00:06:38,470 There are stream coming from all directions. 157 00:06:38,470 --> 00:06:40,270 There are temperature gradients in there. 158 00:06:40,270 --> 00:06:42,520 And these all work together 159 00:06:42,520 --> 00:06:44,420 and make from this nice planar wave front 160 00:06:44,420 --> 00:06:46,530 a crumbled one. 161 00:06:46,530 --> 00:06:49,450 If you have a perfect image 162 00:06:49,450 --> 00:06:50,150 which you create 163 00:06:50,150 --> 00:06:51,510 - This is called "diffraction limit". 164 00:06:51,510 --> 00:06:53,310 This is just limited by the size 165 00:06:53,310 --> 00:06:54,780 of your optics. 166 00:06:54,780 --> 00:06:56,700 So the wider your optics is, 167 00:06:56,700 --> 00:06:59,400 the nicer your resolution is of your image. 168 00:06:59,400 --> 00:07:01,090 If you then build a large facility with 169 00:07:01,090 --> 00:07:04,150 maybe two 8 meter mirrors on the ground, 170 00:07:04,150 --> 00:07:08,550 well, you only get your seeing limited image. 171 00:07:08,550 --> 00:07:10,250 Seeing limited. The Seeing is this wobbling 172 00:07:10,250 --> 00:07:12,830 of the atmosphere as it's called. 173 00:07:12,830 --> 00:07:13,530 And that's about it. 174 00:07:13,530 --> 00:07:15,430 You can make it arbitrarily large. 175 00:07:15,430 --> 00:07:17,750 You won't get a better resolution 176 00:07:17,750 --> 00:07:18,990 then a backyard telescope 177 00:07:18,990 --> 00:07:22,170 of having 20cm in diameter. 178 00:07:22,170 --> 00:07:24,680 So yeah... 179 00:07:24,680 --> 00:07:28,070 What to do? 180 00:07:28,070 --> 00:07:30,890 There have been people, of course, 181 00:07:30,890 --> 00:07:33,580 thinking about this problem longer. 182 00:07:33,580 --> 00:07:38,130 And the first idea came up in 1953. 183 00:07:38,130 --> 00:07:40,870 And some guy Palomar Observatory 184 00:07:40,870 --> 00:07:44,380 in California said: "Well, if we have 185 00:07:44,380 --> 00:07:46,390 the means of continuously measuring 186 00:07:46,390 --> 00:07:48,560 the deviation of rays from all parts 187 00:07:48,560 --> 00:07:52,140 of the mirror and amplifying and feedback 188 00:07:52,140 --> 00:07:55,310 this information so as to correct locally 189 00:07:55,310 --> 00:07:56,450 the figure of the mirror 190 00:07:56,450 --> 00:07:58,370 in response to schlieren pattern, 191 00:07:58,370 --> 00:08:00,870 we could expect to compensate both 192 00:08:00,870 --> 00:08:03,760 for the seeing and for the inherent imperfections 193 00:08:03,760 --> 00:08:04,850 in the optical figure." 194 00:08:04,850 --> 00:08:07,450 Ehhh... what? 195 00:08:07,450 --> 00:08:11,750 So if we could somehow get rid of this wobbling 196 00:08:11,750 --> 00:08:13,240 or conteract that, 197 00:08:13,240 --> 00:08:15,490 then we could get this perfect 198 00:08:15,490 --> 00:08:17,980 diffraction limited imaging we get in space 199 00:08:17,980 --> 00:08:20,480 also on the ground. 200 00:08:20,480 --> 00:08:22,210 In the 1970s the US military started 201 00:08:22,210 --> 00:08:23,420 to experiment on that. 202 00:08:23,420 --> 00:08:25,280 Well, I guess the Russians too, 203 00:08:25,280 --> 00:08:29,240 but it's not... it's known that the US started 204 00:08:29,240 --> 00:08:31,889 at Starfire Optical Range. 205 00:08:31,889 --> 00:08:35,320 In 1982 they build the first AO system, 206 00:08:35,320 --> 00:08:37,950 adaptive optics system. 207 00:08:37,950 --> 00:08:39,940 The "Compensated Imaging System" on Hawaii. 208 00:08:39,940 --> 00:08:44,029 And in the late 80s the first astronomical use, 209 00:08:44,029 --> 00:08:45,870 adaptive optics system "COME-ON" 210 00:08:45,870 --> 00:08:48,270 as it was called was installed at the 211 00:08:48,270 --> 00:08:50,640 Observatoire Haute-Provence 212 00:08:50,640 --> 00:08:53,560 and at ESO at La Silla. 213 00:08:53,560 --> 00:09:01,000 That's the European Space Observatory. 214 00:09:01,000 --> 00:09:03,240 All right so that was: 215 00:09:03,240 --> 00:09:06,510 Yeah, we get for we found that this 216 00:09:06,510 --> 00:09:08,090 fussy blob is actually not a fussy blob, 217 00:09:08,090 --> 00:09:10,070 but two fussy blobs. 218 00:09:10,070 --> 00:09:11,890 *laughter* 219 00:09:11,890 --> 00:09:15,710 Well it's a binary system as I would say 220 00:09:15,710 --> 00:09:19,230 if this was at an astronomical conference. 221 00:09:19,230 --> 00:09:23,830 But yeah, you disentangle things 222 00:09:23,830 --> 00:09:26,540 you could not see before. 223 00:09:26,540 --> 00:09:30,950 Okay! How does this AO system look like in principle? 224 00:09:30,950 --> 00:09:33,330 So again we have this star somewhere, 225 00:09:33,330 --> 00:09:34,430 we've learned already that 226 00:09:34,430 --> 00:09:37,230 we do have... - actually you see this slight 227 00:09:37,230 --> 00:09:38,650 schlieren pattern in the air 228 00:09:38,650 --> 00:09:41,650 for the warm and the exhaust from the... 229 00:09:41,650 --> 00:09:45,440 Yes, there is a bit flimmering in the background. 230 00:09:45,440 --> 00:09:47,830 That's seeing. Okay? 231 00:09:47,830 --> 00:09:49,390 So the image is not as sharp here as 232 00:09:49,390 --> 00:09:52,290 it comes from the projector. 233 00:09:52,290 --> 00:09:55,410 Okay, that comes from somewhere 234 00:09:55,410 --> 00:09:57,050 and then we need a system 235 00:09:57,050 --> 00:09:59,690 which has three components. 236 00:09:59,690 --> 00:10:02,360 One is a deformable mirror, 237 00:10:02,360 --> 00:10:04,500 the other is a wave front sensor 238 00:10:04,500 --> 00:10:07,440 and the third one is a real time computer. 239 00:10:07,440 --> 00:10:09,320 We need something to actually measure 240 00:10:09,320 --> 00:10:11,110 what is going on. 241 00:10:11,110 --> 00:10:14,270 Then we need to take this measurement 242 00:10:14,270 --> 00:10:16,320 and extract some information from 243 00:10:16,320 --> 00:10:20,170 this measurement 244 00:10:20,170 --> 00:10:21,089 and then we need something 245 00:10:21,089 --> 00:10:23,920 which can correct this wave front, 246 00:10:23,920 --> 00:10:24,770 straighten it out so to speak, 247 00:10:24,770 --> 00:10:27,560 'cause we want to have it straight again. 248 00:10:27,560 --> 00:10:31,529 So the wave front sensor sends some information 249 00:10:31,529 --> 00:10:32,930 to the real time computer. 250 00:10:32,930 --> 00:10:35,130 This some information namely is: 251 00:10:35,130 --> 00:10:36,630 What is the curvature? 252 00:10:36,630 --> 00:10:39,070 How does this wiggled thingy look like? 253 00:10:39,070 --> 00:10:40,570 - The wavefront - 254 00:10:40,570 --> 00:10:42,860 And that real time computer computes 255 00:10:42,860 --> 00:10:44,550 then information that goes 256 00:10:44,550 --> 00:10:46,000 to the deformable mirror 257 00:10:46,000 --> 00:10:47,700 and that in real time shaped 258 00:10:47,700 --> 00:10:49,500 in an arbitrary shape 259 00:10:49,500 --> 00:10:54,440 conteracting that incoming wave front 260 00:10:54,440 --> 00:10:55,870 and then straightening it out. 261 00:10:55,870 --> 00:10:58,150 So we do have a light path like this. 262 00:10:58,150 --> 00:11:00,150 First it goes on the deformable mirror, 263 00:11:00,150 --> 00:11:01,360 goes on something else, 264 00:11:01,360 --> 00:11:02,930 which I will come to in a minute, 265 00:11:02,930 --> 00:11:04,860 and then this wave front sensor. 266 00:11:04,860 --> 00:11:08,830 And of course this means if you run it 267 00:11:08,830 --> 00:11:12,710 you do have a control loop, 268 00:11:12,710 --> 00:11:14,170 meaning measure something here, 269 00:11:14,170 --> 00:11:14,790 the wavefront, 270 00:11:14,790 --> 00:11:16,710 you put the information into there feeding 271 00:11:16,710 --> 00:11:18,570 that into the deformable mirror, 272 00:11:18,570 --> 00:11:20,880 that deforms somehow, 273 00:11:20,880 --> 00:11:24,440 modifies this wave front that comes 274 00:11:24,440 --> 00:11:26,170 from above and then of course 275 00:11:26,170 --> 00:11:28,490 you want to have a feedback loop: 276 00:11:28,490 --> 00:11:30,029 Is that what I did enough? 277 00:11:30,029 --> 00:11:31,250 Do I have to do more? 278 00:11:31,250 --> 00:11:35,240 And also: Of course in the next second 279 00:11:35,240 --> 00:11:36,920 or split second this pattern 280 00:11:36,920 --> 00:11:38,020 will have changed, 281 00:11:38,020 --> 00:11:39,420 because the atmosphere is dynamic. 282 00:11:39,420 --> 00:11:41,240 If it wasn't dynamic we don't need 283 00:11:41,240 --> 00:11:42,480 to do this in real time, 284 00:11:42,480 --> 00:11:44,050 but we have to do it in real time. 285 00:11:44,050 --> 00:11:46,420 Real time meaning we have to do this correction 286 00:11:46,420 --> 00:11:50,080 and calculation and sensing at a rate of 287 00:11:50,080 --> 00:11:54,390 about 1 kHz, so a 1000 times a second. 288 00:11:54,390 --> 00:11:55,600 Then we have a scientific instrument 289 00:11:55,600 --> 00:11:58,650 because actually we do want to see 290 00:11:58,650 --> 00:11:59,440 what is in there. 291 00:11:59,440 --> 00:12:00,680 And so this thing in the middle 292 00:12:00,680 --> 00:12:02,440 is a beam splitter. 293 00:12:02,440 --> 00:12:03,830 It takes some of the light, 294 00:12:03,830 --> 00:12:04,899 puts it to the wave front sensor 295 00:12:04,899 --> 00:12:07,420 not all, because most of it should go into 296 00:12:07,420 --> 00:12:08,800 the scientific instrument 297 00:12:08,800 --> 00:12:10,540 and there, as you see here, 298 00:12:10,540 --> 00:12:12,080 then the wave front is straightened out 299 00:12:12,080 --> 00:12:13,950 again and then I can focus it 300 00:12:13,950 --> 00:12:17,430 into my instrument. 301 00:12:17,430 --> 00:12:18,839 To do actually that 302 00:12:18,839 --> 00:12:19,550 I have to do... 303 00:12:19,550 --> 00:12:21,630 - This is the one slide in this talk 304 00:12:21,630 --> 00:12:26,539 with a Greek symbol - 305 00:12:26,539 --> 00:12:30,510 You have to this incoming wave front 306 00:12:30,510 --> 00:12:31,950 which is shown in orange 307 00:12:31,950 --> 00:12:33,960 and then you do a piecewise linear fit 308 00:12:33,960 --> 00:12:35,649 which is an approximation 309 00:12:35,649 --> 00:12:36,690 of the slope. 310 00:12:36,690 --> 00:12:38,390 Of it actually how it looks like. 311 00:12:38,390 --> 00:12:43,380 It's put into linear pieces. 312 00:12:43,380 --> 00:12:46,010 And the size of what is normally 313 00:12:46,010 --> 00:12:49,320 can be taken als a linear fit 314 00:12:49,320 --> 00:12:51,860 Piece is roughly 10 - 15 cm 315 00:12:51,860 --> 00:12:53,600 for good observation sites 316 00:12:53,600 --> 00:12:55,290 while this thingy here 317 00:12:55,290 --> 00:12:57,649 so this is the primary mirror of the telescope 318 00:12:57,649 --> 00:12:58,860 which collects all the light 319 00:12:58,860 --> 00:13:01,310 that comes from outer space 320 00:13:01,310 --> 00:13:04,339 is usually for the big telescopes 321 00:13:04,339 --> 00:13:06,990 at this point 8 to 10 meters 322 00:13:06,990 --> 00:13:13,730 Okay, but how do we get this slope? 323 00:13:13,730 --> 00:13:15,980 Now we know that we can approximate it 324 00:13:15,980 --> 00:13:18,000 in pieces, but how do we get 325 00:13:18,000 --> 00:13:19,960 the slope? 326 00:13:19,960 --> 00:13:22,140 Because we need theses slopes of course 327 00:13:22,140 --> 00:13:25,220 fed into this deformable mirror 328 00:13:25,220 --> 00:13:25,710 to maybe okay: 329 00:13:25,710 --> 00:13:27,560 If it comes like this, I go like this 330 00:13:27,560 --> 00:13:29,620 and it comes in nicely 331 00:13:29,620 --> 00:13:30,960 or comes out nicely. 332 00:13:30,960 --> 00:13:33,649 So is where the sensor comes in. 333 00:13:33,649 --> 00:13:36,290 There are different types of these sensors, 334 00:13:36,290 --> 00:13:37,470 but the one we are using 335 00:13:37,470 --> 00:13:40,910 is a so called Shack-Hartmann-Sensor. 336 00:13:40,910 --> 00:13:43,640 And it looks like this. 337 00:13:43,640 --> 00:13:45,850 We have... this is the ideal case of course. 338 00:13:45,850 --> 00:13:48,060 So we have an incoming planar wave front 339 00:13:48,060 --> 00:13:49,560 - straight on. 340 00:13:49,560 --> 00:13:51,690 And we do have an array of lenses, 341 00:13:51,690 --> 00:13:57,020 so it's just 1.. 2.. 3.. 4.. lenses 342 00:13:57,020 --> 00:14:00,050 and then in an array like 4 by 4. 343 00:14:00,050 --> 00:14:02,300 And they all focus what is coming in 344 00:14:02,300 --> 00:14:05,500 into onto a detector and this wave front 345 00:14:05,500 --> 00:14:07,350 that is coming in is planar 346 00:14:07,350 --> 00:14:09,220 like this on the left. 347 00:14:09,220 --> 00:14:11,709 Then you do get a regular spaced grid 348 00:14:11,709 --> 00:14:15,420 of focus points, in this case 4 times 4 349 00:14:15,420 --> 00:14:17,630 so 16. 350 00:14:17,630 --> 00:14:19,430 If now this incoming wave front 351 00:14:19,430 --> 00:14:24,399 is no planar it looks like this. 352 00:14:24,399 --> 00:14:26,970 So the focus points do move a bit, 353 00:14:26,970 --> 00:14:28,670 because, well, it came in like this, 354 00:14:28,670 --> 00:14:29,959 so the focus is offset. 355 00:14:29,959 --> 00:14:33,730 I will flip it back and forth again. 356 00:14:33,730 --> 00:14:36,540 So it's looking like this and you see 357 00:14:36,540 --> 00:14:39,240 of course you do know what is perfect 358 00:14:39,240 --> 00:14:43,100 meaning they are at their designated grid points. 359 00:14:43,100 --> 00:14:47,480 If its imperfect, well, then just measure 360 00:14:47,480 --> 00:14:50,450 the deviation from their zero position 361 00:14:50,450 --> 00:14:51,270 so to speak 362 00:14:51,270 --> 00:14:55,720 and then you do have a proxy for the slope. 363 00:14:55,720 --> 00:14:57,570 Of course it's a bit more complicated than that. 364 00:14:57,570 --> 00:15:00,300 There are matrices involved which are not 365 00:15:00,300 --> 00:15:04,790 necessarily in a square form 366 00:15:04,790 --> 00:15:05,890 and you have to invert them 367 00:15:05,890 --> 00:15:10,970 and if you don't... yeah... ... 368 00:15:10,970 --> 00:15:12,660 There are pretty clever people 369 00:15:12,660 --> 00:15:15,610 and programmers working on this type of 370 00:15:15,610 --> 00:15:16,870 problems. 371 00:15:16,870 --> 00:15:19,030 And this is actual current research. 372 00:15:19,030 --> 00:15:23,650 This is far from done, this field. 373 00:15:23,650 --> 00:15:27,520 Okay, so suppose we do have the slopes. 374 00:15:27,520 --> 00:15:29,430 Then we take a deformable mirror 375 00:15:29,430 --> 00:15:32,580 and this is the zeros order approximation 376 00:15:32,580 --> 00:15:33,950 of a deformable mirror. 377 00:15:33,950 --> 00:15:35,640 Let's say the wave front looks like that, 378 00:15:35,640 --> 00:15:37,630 well, then take just a mirror which is 379 00:15:37,630 --> 00:15:39,649 maybe reset a bit in the middle 380 00:15:39,649 --> 00:15:41,470 the other tipped forward. 381 00:15:41,470 --> 00:15:43,450 It bounces on this mirror 382 00:15:43,450 --> 00:15:45,820 and because there is something sticking out there 383 00:15:45,820 --> 00:15:46,680 and in there 384 00:15:46,680 --> 00:15:49,430 well if this approaches there goes back 385 00:15:49,430 --> 00:15:50,790 and in the end the whole thing 386 00:15:50,790 --> 00:15:54,510 when it has been reflected is planar again. 387 00:15:54,510 --> 00:15:57,170 Okay, that as said, 388 00:15:57,170 --> 00:15:58,910 that is the easiest order approximation 389 00:15:58,910 --> 00:16:01,029 for that. It's a bit more complicated. 390 00:16:01,029 --> 00:16:03,930 Your incoming wave front doesn't look like that 391 00:16:03,930 --> 00:16:08,680 It's normally a bit more complex. 392 00:16:08,680 --> 00:16:10,850 And that means you do have to have 393 00:16:10,850 --> 00:16:17,170 more wobbling in your deformable mirror. 394 00:16:17,170 --> 00:16:18,279 You could do this. 395 00:16:18,279 --> 00:16:21,399 That's in the upper diagram. 396 00:16:21,399 --> 00:16:22,899 You could do this with a membran 397 00:16:22,899 --> 00:16:24,200 which is continues 398 00:16:24,200 --> 00:16:27,730 or maybe it's also in pieces 399 00:16:27,730 --> 00:16:29,580 and this segments are driven up and down 400 00:16:29,580 --> 00:16:32,450 or maybe tilted by piezo stages 401 00:16:32,450 --> 00:16:35,140 that are put underneath. 402 00:16:35,140 --> 00:16:36,540 Remember they have to do like 403 00:16:36,540 --> 00:16:38,759 a thousand times a second 404 00:16:38,759 --> 00:16:40,220 or you could do something like 405 00:16:40,220 --> 00:16:43,720 you take a two piezo electric wafers 406 00:16:43,720 --> 00:16:45,399 they have opposite polarizations 407 00:16:45,399 --> 00:16:47,110 put electrodes inbetween 408 00:16:47,110 --> 00:16:49,060 and then when you apply a voltage to this blue 409 00:16:49,060 --> 00:16:51,350 electrodes then you have local bending. 410 00:16:51,350 --> 00:16:52,950 So the one thing will bend up, 411 00:16:52,950 --> 00:16:55,990 the other ones will bend in the opposite direction. 412 00:16:55,990 --> 00:16:58,080 And then you do have changing curvature 413 00:16:58,080 --> 00:17:00,560 on this whole thing. 414 00:17:00,560 --> 00:17:04,260 It's not that easy of course in reality, 415 00:17:04,260 --> 00:17:07,510 because they are not completely independent 416 00:17:07,510 --> 00:17:09,429 one cell will influence the other 417 00:17:09,429 --> 00:17:11,519 and yes... 418 00:17:11,519 --> 00:17:14,320 But this is the basic principle. 419 00:17:14,320 --> 00:17:18,369 Okay, now you have seen 420 00:17:18,369 --> 00:17:19,970 there was this beam splitter. 421 00:17:19,970 --> 00:17:22,150 So most of the thing goes into the 422 00:17:22,150 --> 00:17:23,099 science instrument 423 00:17:23,099 --> 00:17:26,270 and some goes to our wave front sensor 424 00:17:26,270 --> 00:17:27,760 of the light. 425 00:17:27,760 --> 00:17:30,549 If the object we want to record like 426 00:17:30,549 --> 00:17:34,670 a galaxy that is 11 Billion lightyears away 427 00:17:34,670 --> 00:17:36,190 then this galaxy is to faint. 428 00:17:36,190 --> 00:17:38,860 We can't analyse it's light. 429 00:17:38,860 --> 00:17:41,140 So what do we do? 430 00:17:41,140 --> 00:17:43,230 We need maybe a star that is nearby. 431 00:17:43,230 --> 00:17:45,030 So our galaxy, which we actually do want 432 00:17:45,030 --> 00:17:47,160 to observe, is the red thingy 433 00:17:47,160 --> 00:17:49,030 the bright star is the yellow one 434 00:17:49,030 --> 00:17:50,789 and if there are reasonably close together 435 00:17:50,789 --> 00:17:52,500 - reasonably close meaning 436 00:17:52,500 --> 00:17:56,280 about 10-20 arcseconds. 437 00:17:56,280 --> 00:17:58,350 If you stretch your arm and look at 438 00:17:58,350 --> 00:18:01,750 your little finger at the finger nail, 439 00:18:01,750 --> 00:18:06,120 this is about 30 arcminutes. 440 00:18:06,120 --> 00:18:08,950 1 arcminute has 60 arcseconds so it's 441 00:18:08,950 --> 00:18:09,900 very close! 442 00:18:09,900 --> 00:18:11,080 It's not like the galaxy is there 443 00:18:11,080 --> 00:18:13,500 and the star is there. No! 444 00:18:13,500 --> 00:18:15,550 It's there! 445 00:18:15,550 --> 00:18:18,460 Because if you have a large separation 446 00:18:18,460 --> 00:18:22,140 then they do sense different turbulence. 447 00:18:22,140 --> 00:18:27,330 Simple as that. 448 00:18:27,330 --> 00:18:28,530 Now the thing is 449 00:18:28,530 --> 00:18:31,080 that less than 10% of the objects 450 00:18:31,080 --> 00:18:31,660 you have on sky 451 00:18:31,660 --> 00:18:33,110 which you are normally interested 452 00:18:33,110 --> 00:18:36,390 do have a sufficiently close and bright star 453 00:18:36,390 --> 00:18:37,160 nearby. 454 00:18:37,160 --> 00:18:38,230 So what to do? 455 00:18:38,230 --> 00:18:45,290 And now we come to the lasers. *laughter* 456 00:18:45,290 --> 00:18:48,270 Because if don't have your.... 457 00:18:48,270 --> 00:18:49,750 If the don't wanna play nicely 458 00:18:49,750 --> 00:18:54,750 build your own themepark with yes ... you know. 459 00:18:54,750 --> 00:18:57,929 So make your own star! 460 00:18:57,929 --> 00:18:59,610 This is what we do. 461 00:18:59,610 --> 00:19:02,680 Because if the star is not nearby, 462 00:19:02,680 --> 00:19:04,799 a sufficiently bright one, 463 00:19:04,799 --> 00:19:07,830 well, why has it to be sufficiently bright? 464 00:19:07,830 --> 00:19:09,620 Because if you want to do this computation 465 00:19:09,620 --> 00:19:12,120 a thousand times a second, well, 466 00:19:12,120 --> 00:19:19,470 then the time for your CCD when you record this image 467 00:19:19,470 --> 00:19:23,820 for your wavefront is a thousands of a second. 468 00:19:23,820 --> 00:19:25,280 And if you don't have enough photons 469 00:19:25,280 --> 00:19:26,799 in a thousands of a second, well, 470 00:19:26,799 --> 00:19:29,299 then there is no computation of this offset 471 00:19:29,299 --> 00:19:31,640 of this little green dots on that grid. 472 00:19:31,640 --> 00:19:33,490 So you need a lot of photons. 473 00:19:33,490 --> 00:19:36,549 So let's get enough photons! 474 00:19:36,549 --> 00:19:37,580 And there are actually two things 475 00:19:37,580 --> 00:19:38,799 what you can do. 476 00:19:38,799 --> 00:19:42,480 There is a conveniently placed sodium layer 477 00:19:42,480 --> 00:19:44,280 in the upper atmosphere. 478 00:19:44,280 --> 00:19:45,620 *laughing* 479 00:19:45,620 --> 00:19:47,530 It's 19 km above ground 480 00:19:47,530 --> 00:19:49,990 and there is a sodium layer. 481 00:19:49,990 --> 00:19:52,070 And what you actually can do is 482 00:19:52,070 --> 00:19:54,870 you can take a laser on ground here, 483 00:19:54,870 --> 00:19:58,179 and then shot laser which corresponds 484 00:19:58,179 --> 00:20:02,630 to the energy transition of this sodium atoms 485 00:20:02,630 --> 00:20:07,610 which is 589.2 nm. It's orange. 486 00:20:07,610 --> 00:20:09,179 And excited those atoms up there 487 00:20:09,179 --> 00:20:09,960 in the atmosphere and they will 488 00:20:09,960 --> 00:20:10,620 start to glow. 489 00:20:10,620 --> 00:20:12,010 And if you have a focus, 490 00:20:12,010 --> 00:20:13,250 if you focus it in there, 491 00:20:13,250 --> 00:20:17,400 and than you have a blob of sodium atoms 492 00:20:17,400 --> 00:20:19,270 lighting up in the upper atmosphere, 493 00:20:19,270 --> 00:20:21,669 maybe... what ever some hundred meters long 494 00:20:21,669 --> 00:20:26,640 and some meters wide as big as your focus is there. 495 00:20:26,640 --> 00:20:30,440 This can be done with a continuous laser. 496 00:20:30,440 --> 00:20:31,559 This has been done in the past. 497 00:20:31,559 --> 00:20:33,750 Yes, of course. 498 00:20:33,750 --> 00:20:37,100 And actually the first instruments 499 00:20:37,100 --> 00:20:39,360 were build like that. 500 00:20:39,360 --> 00:20:40,240 The thing is 501 00:20:40,240 --> 00:20:42,720 in those days they were very, very expensive. 502 00:20:42,720 --> 00:20:44,799 There is no sodium laser. 503 00:20:44,799 --> 00:20:50,260 There are only Di LASERs and they are messy 504 00:20:50,260 --> 00:20:52,030 and expensive. 505 00:20:52,030 --> 00:20:55,100 Nowadays we can build this as fibre laser 506 00:20:55,100 --> 00:20:57,730 but not ten 10 years ago or 15 years ago. 507 00:20:57,730 --> 00:21:00,070 An other solution is to actually 508 00:21:00,070 --> 00:21:03,470 use Rayleigh scattering in the atmosphere. 509 00:21:03,470 --> 00:21:06,220 You use a Nd-YAG LASER 510 00:21:06,220 --> 00:21:08,900 which is 532nm. It's green. 511 00:21:08,900 --> 00:21:10,650 It's easily available, it's cheap 512 00:21:10,650 --> 00:21:12,540 compared to the other one. 513 00:21:12,540 --> 00:21:15,860 And then you focus it in the atmosphere. 514 00:21:15,860 --> 00:21:17,820 The only thing is: 515 00:21:17,820 --> 00:21:19,770 You will do have backscatter of photons 516 00:21:19,770 --> 00:21:21,179 all along the way. 517 00:21:21,179 --> 00:21:22,410 So you have to think about 518 00:21:22,410 --> 00:21:24,620 how can I only record light from 519 00:21:24,620 --> 00:21:26,720 a certain height above ground? 520 00:21:26,720 --> 00:21:28,890 Because otherwise I don't have a spot, 521 00:21:28,890 --> 00:21:31,210 I have a ...ehhh... a laser beam column 522 00:21:31,210 --> 00:21:33,120 somewhere there. 523 00:21:33,120 --> 00:21:34,400 Okay! 524 00:21:34,400 --> 00:21:35,990 How do this things look like? 525 00:21:35,990 --> 00:21:37,960 Can we dim these lights actually a bit? 526 00:21:37,960 --> 00:21:40,000 Or is it only an off switch? 527 00:21:40,000 --> 00:21:45,169 Can you check on this? Let's check on there... 528 00:21:45,169 --> 00:21:49,040 Just push the button... come on... 529 00:21:49,040 --> 00:21:54,780 No? No. No! 530 00:21:54,780 --> 00:21:57,800 laughing 531 00:21:57,800 --> 00:22:06,380 Nooo! 532 00:22:06,380 --> 00:22:07,700 It's still on here... 533 00:22:07,700 --> 00:22:12,530 *gasp* 534 00:22:12,530 --> 00:22:16,540 All right, it's looking like this. 535 00:22:16,540 --> 00:22:19,380 Who has been at the camp? 536 00:22:19,380 --> 00:22:21,150 There was an astronomy talk at the camp 537 00:22:21,150 --> 00:22:24,910 from Liz. 538 00:22:24,910 --> 00:22:27,890 Actually if this talk had been tomorrow 539 00:22:27,890 --> 00:22:29,429 we would had have a live conference 540 00:22:29,429 --> 00:22:31,720 to that side because Liz is right now here 541 00:22:31,720 --> 00:22:35,050 and she send me that picture 542 00:22:35,050 --> 00:22:36,070 just some hours ago. 543 00:22:36,070 --> 00:22:38,520 That is how the just do things on 544 00:22:38,520 --> 00:22:41,059 Paranal in Chile. 545 00:22:41,059 --> 00:22:42,309 The thing I will talk about 546 00:22:42,309 --> 00:22:44,900 is the green one to the right. 547 00:22:44,900 --> 00:22:49,640 That's the thing I have been involved with. 548 00:22:49,640 --> 00:22:52,600 Yea, let's look into that. 549 00:22:52,600 --> 00:22:55,980 So if you shoot the laser into the atmosphere 550 00:22:55,980 --> 00:22:57,490 of course you do have problem. 551 00:22:57,490 --> 00:22:58,860 The star is very far away, 552 00:22:58,860 --> 00:23:00,790 it's infinitely far away. 553 00:23:00,790 --> 00:23:01,960 And the light that comes down 554 00:23:01,960 --> 00:23:05,100 is in a cylinder. 555 00:23:05,100 --> 00:23:08,660 And if you shoot a laser up, it's a cone. 556 00:23:08,660 --> 00:23:10,940 So you only probe the green region. 557 00:23:10,940 --> 00:23:15,580 The unsampled volume of turbulence is to the side. 558 00:23:15,580 --> 00:23:18,650 That is a problem with our laser AO. 559 00:23:18,650 --> 00:23:26,200 An other problem we face is this one. 560 00:23:26,200 --> 00:23:30,140 When we take a star to measure the wave front 561 00:23:30,140 --> 00:23:33,380 then it passes only once through the atmosphere. 562 00:23:33,380 --> 00:23:35,530 The laser beam goes up and down. 563 00:23:35,530 --> 00:23:36,630 And so there is a component 564 00:23:36,630 --> 00:23:37,760 called tip tilt component 565 00:23:37,760 --> 00:23:40,870 which is actually just the thing moving around 566 00:23:40,870 --> 00:23:43,799 It's not just the phase 567 00:23:43,799 --> 00:23:45,929 that gets disturbance introduced 568 00:23:45,929 --> 00:23:48,600 in the wave front but this moving around. 569 00:23:48,600 --> 00:23:54,630 So not the bright and more or less bright twinkling 570 00:23:54,630 --> 00:23:56,539 little star thingy, 571 00:23:56,539 --> 00:23:58,289 but the moving around. 572 00:23:58,289 --> 00:24:00,400 And that can not be sensed with a laser guild star. 573 00:24:00,400 --> 00:24:02,549 So when ever we do laser AO 574 00:24:02,549 --> 00:24:04,570 We do need an other star 575 00:24:04,570 --> 00:24:05,600 to get this component. 576 00:24:05,600 --> 00:24:08,080 But this star can be a bit further away, 577 00:24:08,080 --> 00:24:11,669 like an arcminute or 2 arcminutes or so. 578 00:24:11,669 --> 00:24:17,150 So it's that... is wide. There are enough. 579 00:24:17,150 --> 00:24:18,490 And then we should think about 580 00:24:18,490 --> 00:24:20,220 actually what we have to correct and so 581 00:24:20,220 --> 00:24:23,789 we should make a profile of the turbulence 582 00:24:23,789 --> 00:24:25,100 above ground. 583 00:24:25,100 --> 00:24:27,059 And this is how it looks like. 584 00:24:27,059 --> 00:24:29,390 And for example for the side 585 00:24:29,390 --> 00:24:32,370 where we are there in Arizona 586 00:24:32,370 --> 00:24:34,450 we see that most of the turbulence 587 00:24:34,450 --> 00:24:37,400 is actually just above the ground. 588 00:24:37,400 --> 00:24:39,360 So we maybe should care mostly 589 00:24:39,360 --> 00:24:41,220 about the ground layer. 590 00:24:41,220 --> 00:24:44,559 It's not so much about the high altitude things. 591 00:24:44,559 --> 00:24:47,230 So and then what we do is: 592 00:24:47,230 --> 00:24:48,580 Well we want to sample 593 00:24:48,580 --> 00:24:50,660 the ground stuff nicely 594 00:24:50,660 --> 00:24:54,679 so we don't take one but 3 lasers. 595 00:24:54,679 --> 00:24:58,039 So to fill this area nicely. 596 00:24:58,039 --> 00:25:00,210 And yes, of course, we can also combine this 597 00:25:00,210 --> 00:25:03,410 and this looks like that. 598 00:25:03,410 --> 00:25:05,630 This combination we will not talk about today. 599 00:25:05,630 --> 00:25:09,809 We will only talk about that. 600 00:25:09,809 --> 00:25:11,080 This is how it looks like. 601 00:25:11,080 --> 00:25:13,110 So this is our telescope, the primary mirror 602 00:25:13,110 --> 00:25:16,590 which receives the light from outer space 603 00:25:16,590 --> 00:25:19,460 it then deflects on the secondary, tertiary 604 00:25:19,460 --> 00:25:20,600 and than somewhere here. 605 00:25:20,600 --> 00:25:22,610 But first we need to have to shoot the laser up. 606 00:25:22,610 --> 00:25:25,539 And it's launched from a laser box 607 00:25:25,539 --> 00:25:28,940 onto a mirror behind that secondary mirror 608 00:25:28,940 --> 00:25:30,530 over there into the atmosphere 609 00:25:30,530 --> 00:25:33,400 and after 40 microseconds it reaches 610 00:25:33,400 --> 00:25:36,200 an altitude of 12 km. 611 00:25:36,200 --> 00:25:37,620 And then of course it comes back. 612 00:25:37,620 --> 00:25:40,220 After 80 microseconds it's here 613 00:25:40,220 --> 00:25:41,419 in our detector again. 614 00:25:41,419 --> 00:25:43,730 So the star then lights up, 615 00:25:43,730 --> 00:25:46,050 has this cone, get's focused there, focus, 616 00:25:46,050 --> 00:25:48,460 reflected to here 617 00:25:48,460 --> 00:25:53,820 and we do have our signal in our detector after 80 ms 618 00:25:53,820 --> 00:25:55,429 and as said, because of course 619 00:25:55,429 --> 00:25:59,070 the laser has scattering all along its path, 620 00:25:59,070 --> 00:26:03,350 you want to gate this information to 12 km 621 00:26:03,350 --> 00:26:05,539 and well then you just -just- look at 622 00:26:05,539 --> 00:26:06,880 when your laser pulse started 623 00:26:06,880 --> 00:26:09,419 wait. wait. wait. wait. wait. 624 00:26:09,419 --> 00:26:11,500 open the shutter for the detector 625 00:26:11,500 --> 00:26:14,980 for short time after 80ms, 626 00:26:14,980 --> 00:26:16,350 close it again and then analyse 627 00:26:16,350 --> 00:26:18,699 and read out what you just did. 628 00:26:18,699 --> 00:26:19,960 Easy, huh? 629 00:26:19,960 --> 00:26:21,520 So we are done. 630 00:26:21,520 --> 00:26:23,390 Thank you for coming to my talk 631 00:26:23,390 --> 00:26:26,400 and now go out and build your own lasers 632 00:26:26,400 --> 00:26:28,799 with... to... 633 00:26:28,799 --> 00:26:30,980 *laughing* 634 00:26:30,980 --> 00:26:34,309 Now we are going to look at this thing 635 00:26:34,309 --> 00:26:37,370 which is actually build and which works. 636 00:26:37,370 --> 00:26:39,650 So this is called ARGOS. 637 00:26:39,650 --> 00:26:41,250 It's a ground layer AO system. 638 00:26:41,250 --> 00:26:42,570 That's what we want to build. 639 00:26:42,570 --> 00:26:44,210 It has wide field corrections. 640 00:26:44,210 --> 00:26:46,110 That means you can not correct 641 00:26:46,110 --> 00:26:49,559 just a tiny patch on sky but for for astronomical use 642 00:26:49,559 --> 00:26:52,190 a huge area, meaning it's not just 643 00:26:52,190 --> 00:26:54,070 a circle of 10 arcseconds but 644 00:26:54,070 --> 00:26:56,850 this thing can correct 4 by 4 arcminutes 645 00:26:56,850 --> 00:26:58,230 which is huge, 646 00:26:58,230 --> 00:27:01,559 so all the objects that are in there. 647 00:27:01,559 --> 00:27:03,669 We have a multi-laser constellation. 648 00:27:03,669 --> 00:27:05,140 We have seen that why we need this, 649 00:27:05,140 --> 00:27:05,850 because we want to fill 650 00:27:05,850 --> 00:27:06,940 the complete ground layer. 651 00:27:06,940 --> 00:27:10,289 So we have 3 laser guild stars per eye. 652 00:27:10,289 --> 00:27:11,480 Why per eye? 653 00:27:11,480 --> 00:27:14,070 This will be clear in minute. 654 00:27:14,070 --> 00:27:17,419 And we use high power pulse green lasers. 655 00:27:17,419 --> 00:27:20,710 And this deformable mirror is actually 656 00:27:20,710 --> 00:27:22,970 build in the telescope system already. 657 00:27:22,970 --> 00:27:25,299 The secondary mirror is the deformable mirror 658 00:27:25,299 --> 00:27:26,960 which is very convenient, 659 00:27:26,960 --> 00:27:29,320 because then all the instruments, 660 00:27:29,320 --> 00:27:31,020 that sit on the telescope can benefit from 661 00:27:31,020 --> 00:27:33,980 this system. 662 00:27:33,980 --> 00:27:36,270 It's installed at this telescope. 663 00:27:36,270 --> 00:27:38,240 Look's pretty odd. Yes, I admit that. 664 00:27:38,240 --> 00:27:39,780 That's the Large Binocular Telescope. 665 00:27:39,780 --> 00:27:41,850 It's two telescopes on one mount. 666 00:27:41,850 --> 00:27:44,299 One primary, two primaries. 667 00:27:44,299 --> 00:27:47,570 It's roughly 23 by 25 by 12 meters. 668 00:27:47,570 --> 00:27:50,789 It sits on Mont Graham in Arizona. 669 00:27:50,789 --> 00:27:52,470 And it has an adaptive secondary mirror 670 00:27:52,470 --> 00:27:58,159 which is this violette coloured thingy 671 00:27:58,159 --> 00:28:00,630 up there in the middle on top. 672 00:28:00,630 --> 00:28:04,760 This is how it looks like. 673 00:28:04,760 --> 00:28:05,720 This is the control room 674 00:28:05,720 --> 00:28:06,800 where you sit. 675 00:28:06,800 --> 00:28:09,470 This stays fixed. 676 00:28:09,470 --> 00:28:11,890 All this shiny part rotates. 677 00:28:11,890 --> 00:28:12,860 That's the actual telescope, 678 00:28:12,860 --> 00:28:14,500 the red thing that moves up and down. 679 00:28:14,500 --> 00:28:17,169 So the whole building rotates and it moves 680 00:28:17,169 --> 00:28:19,210 up and down. 681 00:28:19,210 --> 00:28:27,419 It's from ceiling... the ceiling is at level 11. 682 00:28:27,419 --> 00:28:30,990 So when you actually sit there, 683 00:28:30,990 --> 00:28:34,779 you can watch around a bit 684 00:28:34,779 --> 00:28:39,960 ... this is outside... it's winter... yuh!... let's see... 685 00:28:39,960 --> 00:28:41,940 There is a ladder... 686 00:28:41,940 --> 00:28:46,070 Yes, this thing is huge...eh.. nice.. cool 687 00:28:46,070 --> 00:28:47,960 Okay, that's what it's looks like 688 00:28:47,960 --> 00:28:53,740 when you are actually there. 689 00:28:53,740 --> 00:28:56,870 Okay, our system layout is like this. 690 00:28:56,870 --> 00:28:59,789 We have this adaptive secondary mirror 691 00:28:59,789 --> 00:29:02,820 which is the deformable mirror. 692 00:29:02,820 --> 00:29:05,580 We have the primary, tertiary. 693 00:29:05,580 --> 00:29:06,900 That is clear already. 694 00:29:06,900 --> 00:29:11,520 So we have a laser box. 695 00:29:11,520 --> 00:29:15,240 The green things is the lasers themselfs. 696 00:29:15,240 --> 00:29:16,299 So that's how it looks like. 697 00:29:16,299 --> 00:29:18,179 We produce some laser beams. 698 00:29:18,179 --> 00:29:19,970 We have steering mirrors in there 699 00:29:19,970 --> 00:29:22,190 to get them into the right pattern on sky 700 00:29:22,190 --> 00:29:22,980 of course. 701 00:29:22,980 --> 00:29:24,330 We do have control cameras, 702 00:29:24,330 --> 00:29:25,870 if : Is the focus right? 703 00:29:25,870 --> 00:29:27,059 Is the position right? 704 00:29:27,059 --> 00:29:28,280 This is one control loop 705 00:29:28,280 --> 00:29:30,039 another control loop, another control loop 706 00:29:30,039 --> 00:29:31,590 an other control loop. 707 00:29:31,590 --> 00:29:33,140 The black thing is the shutter. 708 00:29:33,140 --> 00:29:35,030 Because we have to close this whole thing, 709 00:29:35,030 --> 00:29:36,870 when aircrafts are overhead, 710 00:29:36,870 --> 00:29:38,500 when satellites are overhead. 711 00:29:38,500 --> 00:29:40,120 So if you want to use this system, 712 00:29:40,120 --> 00:29:43,100 you have to, 6 weeks in advance, you have to 713 00:29:43,100 --> 00:29:45,809 put out your list of observable targets 714 00:29:45,809 --> 00:29:47,230 to some military agency. 715 00:29:47,230 --> 00:29:49,309 And they will tell you: Okay! Not Okay! 716 00:29:49,309 --> 00:29:51,840 Okay! Not Okay! Not Okay! Not Okay! Okay! 717 00:29:51,840 --> 00:29:54,600 Not Okay, meaning something is passing overhead. 718 00:29:54,600 --> 00:29:56,710 Hmm... what could this be? 719 00:29:56,710 --> 00:30:03,460 *laughing* 720 00:30:03,460 --> 00:30:04,950 Of course, at some point the lasers 721 00:30:04,950 --> 00:30:07,360 come down again in this cone shape. 722 00:30:07,360 --> 00:30:11,039 They will reach the primary mirror 723 00:30:11,039 --> 00:30:14,110 and ultimately it will end up 724 00:30:14,110 --> 00:30:15,210 in the wave front sensor 725 00:30:15,210 --> 00:30:18,270 which is much more complex than just this box. 726 00:30:18,270 --> 00:30:21,929 I showed you before. 727 00:30:21,929 --> 00:30:23,220 So there are aquisition cameras 728 00:30:23,220 --> 00:30:25,409 which detect are we at the right spot. 729 00:30:25,409 --> 00:30:27,990 Do the spots get onto the detector 730 00:30:27,990 --> 00:30:29,789 in a nice fashion. 731 00:30:29,789 --> 00:30:31,659 We do have to do this gating, remember? 732 00:30:31,659 --> 00:30:33,020 We have to open this shutter 733 00:30:33,020 --> 00:30:36,570 for the CCD when we want to record the light. 734 00:30:36,570 --> 00:30:39,659 This tiny fraction after 80ms. 735 00:30:39,659 --> 00:30:43,510 After the laser pulse has been launched. 736 00:30:43,510 --> 00:30:44,250 It's done in here. 737 00:30:44,250 --> 00:30:45,179 These are Pockel Cells. 738 00:30:45,179 --> 00:30:49,320 So its an electro optical effect. 739 00:30:49,320 --> 00:30:53,980 And then there is also something 740 00:30:53,980 --> 00:30:55,940 in addition because I said 741 00:30:55,940 --> 00:30:58,549 we can't do without the tip tilt 742 00:30:58,549 --> 00:31:00,049 and there is another unit in here 743 00:31:00,049 --> 00:31:03,059 that sits right in front of the science instrument 744 00:31:03,059 --> 00:31:04,799 that detects this tip tilt star, 745 00:31:04,799 --> 00:31:08,140 this additional star. 746 00:31:08,140 --> 00:31:11,020 So you have the laser wave front light, 747 00:31:11,020 --> 00:31:13,970 the green one, you do have this tip tilt light, 748 00:31:13,970 --> 00:31:15,049 the blue one, 749 00:31:15,049 --> 00:31:17,080 and you do have the actual science light 750 00:31:17,080 --> 00:31:20,250 from the object you want to observe on sky. 751 00:31:20,250 --> 00:31:22,799 That goes directly into this scientific instrument 752 00:31:22,799 --> 00:31:25,250 in the end. 753 00:31:25,250 --> 00:31:28,020 And then you have a lot of control things. 754 00:31:28,020 --> 00:31:29,929 Of course, you do need a common clock 755 00:31:29,929 --> 00:31:33,470 for this synchronization of all this pulses 756 00:31:33,470 --> 00:31:35,760 and the gating and what not. 757 00:31:35,760 --> 00:31:37,260 And of course you need the information 758 00:31:37,260 --> 00:31:40,260 for the tip tilt component and for the wave front 759 00:31:40,260 --> 00:31:41,440 into this computer 760 00:31:41,440 --> 00:31:44,110 which sends then all the slops 761 00:31:44,110 --> 00:31:45,760 - you remember we have to do this 762 00:31:45,760 --> 00:31:48,760 linear approximation pieces wise, yes - 763 00:31:48,760 --> 00:31:49,929 into the secondary mirror 764 00:31:49,929 --> 00:31:52,880 which than deforms in real time. 765 00:31:52,880 --> 00:31:57,120 And does this a thousand times a second. 766 00:31:57,120 --> 00:31:59,470 This is how it looks like. 767 00:31:59,470 --> 00:32:05,210 So when I am there I am roughly that tall. 768 00:32:05,210 --> 00:32:08,000 The two black tubes right in the middle, 769 00:32:08,000 --> 00:32:11,960 those are the two tubes which go up. 770 00:32:11,960 --> 00:32:14,710 Looks like this. 771 00:32:14,710 --> 00:32:17,529 So, this is how the components are distributed 772 00:32:17,529 --> 00:32:21,460 over the telescope... once back.. okay 773 00:32:21,460 --> 00:32:24,220 primary mirror, primary mirror, 774 00:32:24,220 --> 00:32:26,390 some instruments in the middle, 775 00:32:26,390 --> 00:32:28,409 some tertiary mirror, 776 00:32:28,409 --> 00:32:31,839 the secondaries, the adaptive ones up there. 777 00:32:31,839 --> 00:32:37,900 Yes, I hate to use this laser pointers. 778 00:32:37,900 --> 00:32:39,440 *laughing* 779 00:32:39,440 --> 00:32:40,690 Because I am always going like this... eee 780 00:32:40,690 --> 00:32:44,520 (green laser pointer on the slides) 781 00:32:44,520 --> 00:32:48,610 *laughing* 782 00:32:48,610 --> 00:32:52,939 That's my man! *laughing* 783 00:32:52,939 --> 00:32:54,650 So okay! 784 00:32:54,650 --> 00:32:58,440 So we do have the adaptive secondary 785 00:32:58,440 --> 00:33:00,940 up there and then it goes back on the 786 00:33:00,940 --> 00:33:02,860 tertiary down there and then it goes over 787 00:33:02,860 --> 00:33:04,580 into the science instrument, 788 00:33:04,580 --> 00:33:11,999 all the wave front sensors and what not. 789 00:33:11,999 --> 00:33:14,879 Again, we do have a laser system. 790 00:33:14,879 --> 00:33:16,760 We have to place somewhere a launch system 791 00:33:16,760 --> 00:33:19,700 for the laser, a dichroic to separate 792 00:33:19,700 --> 00:33:23,480 between the laser light, the tip tilt light and the science light. 793 00:33:23,480 --> 00:33:25,460 We do have to have a wave front sensor 794 00:33:25,460 --> 00:33:27,529 to check how the wave front looks like. 795 00:33:27,529 --> 00:33:29,039 We do have to have this tip tilt control. 796 00:33:29,039 --> 00:33:29,890 We have calibration source. 797 00:33:29,890 --> 00:33:31,240 A calibration source would be nice 798 00:33:31,240 --> 00:33:33,510 to calibrate the system during daytime, 799 00:33:33,510 --> 00:33:38,260 aircraft detection, yes, satellite avoidance, 800 00:33:38,260 --> 00:33:41,279 -also an issue here- and a control software. 801 00:33:41,279 --> 00:33:43,840 There are many people just writing... 802 00:33:43,840 --> 00:33:45,830 ...just haha... writing software for this. 803 00:33:45,830 --> 00:33:51,350 And this is really hard. 804 00:33:51,350 --> 00:33:53,179 Some are also on the conference. 805 00:33:53,179 --> 00:33:54,370 They don't want to be pointed out 806 00:33:54,370 --> 00:33:56,200 as I learned, but you will find them 807 00:33:56,200 --> 00:34:01,059 at the conference, if you look at the right places. 808 00:34:01,059 --> 00:34:05,700 That's where the laser box is located. 809 00:34:05,700 --> 00:34:09,449 Just next to it is the electronics rack. 810 00:34:09,449 --> 00:34:10,839 How does this thing look like? 811 00:34:10,839 --> 00:34:12,730 So that is one of our lasers. 812 00:34:12,730 --> 00:34:17,839 It's about 20 W. Don't get your finger in there. 813 00:34:17,839 --> 00:34:19,099 *laughing* 814 00:34:19,099 --> 00:34:20,940 It really hurts. 815 00:34:20,940 --> 00:34:25,329 (Did you try?) No! 816 00:34:25,329 --> 00:34:30,260 There is a mandatory annual laser training of course. 817 00:34:30,260 --> 00:34:34,679 Yes, if you want to have something like this at home, 818 00:34:34,679 --> 00:34:37,280 you do need a huge refrigerator next to it 819 00:34:37,280 --> 00:34:38,940 just for the cooling of that thing. 820 00:34:38,940 --> 00:34:41,580 This is nothing you want to have at home. 821 00:34:41,580 --> 00:34:46,418 Just because it's... that bulky... no..it's not.. 822 00:34:46,418 --> 00:34:47,818 but actually when you do 823 00:34:47,818 --> 00:34:49,379 this green laser pointer thingy 824 00:34:49,379 --> 00:34:50,790 then there is always this always this: 825 00:34:50,790 --> 00:34:52,770 "Don't use this for more than 10 seconds." 826 00:34:52,770 --> 00:34:54,429 Because why? Because the crystal inside 827 00:34:54,429 --> 00:34:55,429 heats up. 828 00:34:55,429 --> 00:34:56,980 And if you can't dissipate that heat 829 00:34:56,980 --> 00:34:58,770 the crystal at some point breaks 830 00:34:58,770 --> 00:35:00,710 and then your laser pointer is broken. 831 00:35:00,710 --> 00:35:02,990 This thing gets continuously cooled. 832 00:35:02,990 --> 00:35:06,510 So, therefore it's a bit more expensive. 833 00:35:06,510 --> 00:35:08,960 *laughing* 834 00:35:08,960 --> 00:35:10,250 If you than put it up, 835 00:35:10,250 --> 00:35:12,190 so this is still on the lab table 836 00:35:12,190 --> 00:35:13,589 when it was integrated and tested 837 00:35:13,589 --> 00:35:15,530 and than at some point it gets put all 838 00:35:15,530 --> 00:35:17,820 in a box with all this control mirrors 839 00:35:17,820 --> 00:35:20,020 and cameras and what not. 840 00:35:20,020 --> 00:35:22,030 But finally you see in the middle 841 00:35:22,030 --> 00:35:23,520 on this picture there is 842 00:35:23,520 --> 00:35:26,010 a focusing lens and then you see 843 00:35:26,010 --> 00:35:29,300 these 3 tiny little beam coming out of there 844 00:35:29,300 --> 00:35:32,359 which than expand on sky in size 845 00:35:32,359 --> 00:35:36,089 of course when they are in 12 km height 846 00:35:36,089 --> 00:35:38,730 but that's how they come out of it. 847 00:35:38,730 --> 00:35:41,339 And if you install this in the telescope, 848 00:35:41,339 --> 00:35:42,869 you actually have to tilt the telescope, 849 00:35:42,869 --> 00:35:44,280 because otherwise you can't reach it. 850 00:35:44,280 --> 00:35:48,880 And then you need your climbing gear. 851 00:35:48,880 --> 00:35:50,520 So once you have produced the lasers, 852 00:35:50,520 --> 00:35:52,310 you need to propagate them to a through 853 00:35:52,310 --> 00:35:57,849 a dust tube onto a launch mirror, 854 00:35:57,849 --> 00:36:00,369 a folding mirror and from there to 855 00:36:00,369 --> 00:36:02,960 a launch mirror. 856 00:36:02,960 --> 00:36:06,460 Yes and then it looks like this! 857 00:36:06,460 --> 00:36:09,730 Okay, so the lasers come from here into that 858 00:36:09,730 --> 00:36:11,690 and then over to the other side 859 00:36:11,690 --> 00:36:14,859 over the secondary mirror and then 860 00:36:14,859 --> 00:36:17,920 being shot right up into space 861 00:36:17,920 --> 00:36:20,450 like this. 862 00:36:20,450 --> 00:36:23,950 Okay, so if you want to have that at home, 863 00:36:23,950 --> 00:36:27,020 .... eh... but I can tell you the whole facility 864 00:36:27,020 --> 00:36:31,980 does cost less than one fully equipped Eurofighter 865 00:36:31,980 --> 00:36:44,750 *laughing* *applause* 866 00:36:44,750 --> 00:36:48,470 Thank you for taking the hint. 867 00:36:48,470 --> 00:36:50,339 Yeah, that's how it looks like. 868 00:36:50,339 --> 00:36:53,260 It's.... yes it's... *laughing* ... yeah... 869 00:36:53,260 --> 00:36:56,620 *laughing**applause* Okay? 870 00:36:56,620 --> 00:36:59,960 okay... I have to admit this are a bit longer exposers. 871 00:36:59,960 --> 00:37:01,420 It's not that bright and green 872 00:37:01,420 --> 00:37:04,450 when you are actually at the telescope up there. 873 00:37:04,450 --> 00:37:07,510 But if you have been in the dark long enough 874 00:37:07,510 --> 00:37:11,460 around ten minutes, then I really becomes bright. 875 00:37:11,460 --> 00:37:13,640 There is a little telescope that observes, 876 00:37:13,640 --> 00:37:15,859 where actually the spots are on sky. 877 00:37:15,859 --> 00:37:17,089 And if we have clear sky, 878 00:37:17,089 --> 00:37:19,260 then we have this constellation on the right. 879 00:37:19,260 --> 00:37:21,830 So that is how the lasers come up. 880 00:37:21,830 --> 00:37:25,330 As I said you do see them all the way up, 881 00:37:25,330 --> 00:37:26,990 but we are interested in the little dots 882 00:37:26,990 --> 00:37:27,490 at the end. 883 00:37:27,490 --> 00:37:28,910 You can barely see them. 884 00:37:28,910 --> 00:37:30,190 If there are high clouds, 885 00:37:30,190 --> 00:37:36,080 well than we produce something like this. 886 00:37:36,080 --> 00:37:39,000 We have the dichroic when the light comes back down 887 00:37:39,000 --> 00:37:39,930 as said. 888 00:37:39,930 --> 00:37:42,349 Which separates the science light in red 889 00:37:42,349 --> 00:37:44,320 and the laser light in green. 890 00:37:44,320 --> 00:37:46,030 This is how it looks like. 891 00:37:46,030 --> 00:37:49,890 Actually the dichroic is right in front of Sebatian there 892 00:37:49,890 --> 00:37:51,930 and from there it gets then reflected 893 00:37:51,930 --> 00:37:55,220 on a reflector and then up into the 894 00:37:55,220 --> 00:37:59,310 wave front sensing unit. 895 00:37:59,310 --> 00:38:03,990 So there is the dichroic, there is the reflector, 896 00:38:03,990 --> 00:38:06,420 and it goes over in this unit 897 00:38:06,420 --> 00:38:11,300 which is the wave front sensing unit 898 00:38:11,300 --> 00:38:13,349 which sits there, at the side. 899 00:38:13,349 --> 00:38:20,150 That's how it looks, when it gets installed. 900 00:38:20,150 --> 00:38:22,359 And that is how it looks inside. 901 00:38:22,359 --> 00:38:24,160 So you have the 3 laser beams coming 902 00:38:24,160 --> 00:38:26,619 from the side, from the sky, of course. 903 00:38:26,619 --> 00:38:27,720 You have patrol cameras 904 00:38:27,720 --> 00:38:30,030 which monitor where are these? 905 00:38:30,030 --> 00:38:32,570 Are they at the right spot? 906 00:38:32,570 --> 00:38:36,330 Do we have to steer the lasers a bit? 907 00:38:36,330 --> 00:38:42,160 Than we have some control for the position 908 00:38:42,160 --> 00:38:45,760 of the laser spots and the field. 909 00:38:45,760 --> 00:38:47,310 The Pockel cells are the ones 910 00:38:47,310 --> 00:38:49,520 that do this opening and closing in front 911 00:38:49,520 --> 00:38:50,230 of the shutter. 912 00:38:50,230 --> 00:38:52,089 You can't use a mechanic shutter in front 913 00:38:52,089 --> 00:38:52,890 of the CCD. 914 00:38:52,890 --> 00:38:55,280 We have to do this electro optically 915 00:38:55,280 --> 00:38:59,970 So you have a polarization of the laserbeams. 916 00:38:59,970 --> 00:39:03,440 And you have a polarizer... a cross polarizer 917 00:39:03,440 --> 00:39:05,420 and then you just turn the polarisation 918 00:39:05,420 --> 00:39:06,740 of the crystals. 919 00:39:06,740 --> 00:39:08,410 It's an electro optical effect 920 00:39:08,410 --> 00:39:10,700 and then it gets passed through 921 00:39:10,700 --> 00:39:12,700 or it gets blocked. 922 00:39:12,700 --> 00:39:15,540 Then you also of course have this lens slit arrays 923 00:39:15,540 --> 00:39:19,080 in there and then the CCD 924 00:39:19,080 --> 00:39:21,599 which actually records this dot pattern. 925 00:39:21,599 --> 00:39:23,470 You remember, this 4 by 4... 926 00:39:23,470 --> 00:39:25,540 well it's not 4 by 4 in our case we do 927 00:39:25,540 --> 00:39:28,660 have a bit more resolution. 928 00:39:28,660 --> 00:39:32,339 The sensory looks like this. 929 00:39:32,339 --> 00:39:35,589 This is actually a custom build CCD. 930 00:39:35,589 --> 00:39:37,170 Very special. 931 00:39:37,170 --> 00:39:38,599 The imaging area is in the middle 932 00:39:38,599 --> 00:39:40,990 and when you read out the thing, 933 00:39:40,990 --> 00:39:43,250 you split the image in half, 934 00:39:43,250 --> 00:39:44,720 you transfer it to the sides 935 00:39:44,720 --> 00:39:46,960 to the frame store area and than read it out. 936 00:39:46,960 --> 00:39:49,210 'Cause read out is slow, transfer is fast. 937 00:39:49,210 --> 00:39:51,380 And you have to do this a thousand times 938 00:39:51,380 --> 00:39:54,190 a second at very low read out noise, 939 00:39:54,190 --> 00:39:58,560 which is only 4 electron read out noise. 940 00:39:58,560 --> 00:40:01,109 For the experts here in the audience, 941 00:40:01,109 --> 00:40:05,030 this is very good. 942 00:40:05,030 --> 00:40:08,280 It's not many pixels but it's more than enough for us. 943 00:40:08,280 --> 00:40:09,730 So how does this look like? 944 00:40:09,730 --> 00:40:11,030 It looks like that! 945 00:40:11,030 --> 00:40:13,380 So there you have your pattern again, 946 00:40:13,380 --> 00:40:15,130 regularly spaces pattern of course 947 00:40:15,130 --> 00:40:19,310 from 3 laser guild stars you get 3 patterns 948 00:40:19,310 --> 00:40:21,900 and then you analyse, well, the position, 949 00:40:21,900 --> 00:40:24,230 the relative position, the absolute position 950 00:40:24,230 --> 00:40:26,490 of those stars on their grid, 951 00:40:26,490 --> 00:40:29,530 and somehow compute this slopes 952 00:40:29,530 --> 00:40:33,070 from there feed them back, compute then 953 00:40:33,070 --> 00:40:35,530 actually electrical information from them 954 00:40:35,530 --> 00:40:37,450 which you can than feed into your 955 00:40:37,450 --> 00:40:39,240 deformable mirror again 956 00:40:39,240 --> 00:40:42,950 which sits on top of the telescope 957 00:40:42,950 --> 00:40:47,180 and then hopefully everything works. 958 00:40:47,180 --> 00:40:49,780 This you can digest at home. *laughing* 959 00:40:49,780 --> 00:40:52,220 It's in the stream now so it will be 960 00:40:52,220 --> 00:40:54,329 saved for all eternity 961 00:40:54,329 --> 00:40:55,240 and all the aliens 962 00:40:55,240 --> 00:40:57,940 which record all the electromagnetic field 963 00:40:57,940 --> 00:41:00,790 from Bielefeld... (mumbling) 964 00:41:00,790 --> 00:41:02,050 *laughing* 965 00:41:02,050 --> 00:41:05,579 Anyway, so, just in short. 966 00:41:05,579 --> 00:41:08,550 There is down in green there is this thing 967 00:41:08,550 --> 00:41:12,140 that goes up from the lasers through 968 00:41:12,140 --> 00:41:14,660 some steering mirrors. 969 00:41:14,660 --> 00:41:19,710 We have diagnostics, then we got to focus 970 00:41:19,710 --> 00:41:21,530 check launch mirror one and launch mirror two 971 00:41:21,530 --> 00:41:24,579 onto sky and then we go back 972 00:41:24,579 --> 00:41:27,000 up there N1 is the primary mirror. 973 00:41:27,000 --> 00:41:29,099 And then we go through this whole chain 974 00:41:29,099 --> 00:41:31,740 and there are various control loops 975 00:41:31,740 --> 00:41:35,109 sitting in there. 976 00:41:35,109 --> 00:41:37,070 And all this things have to talk together 977 00:41:37,070 --> 00:41:40,720 on very high rates. 978 00:41:40,720 --> 00:41:44,579 Sometimes you see 1 kHz other things are a bit slower. 979 00:41:44,579 --> 00:41:50,030 This all needs highly sophisticated control software. 980 00:41:50,030 --> 00:41:51,950 And the programmers can be real proud 981 00:41:51,950 --> 00:41:54,050 of what they did in the past 982 00:41:54,050 --> 00:41:56,990 with all this control loops. 983 00:41:56,990 --> 00:42:00,200 The tip tilt is very... much much much easier, 984 00:42:00,200 --> 00:42:00,829 because all the... 985 00:42:00,829 --> 00:42:01,960 you remember this tip tilt 986 00:42:01,960 --> 00:42:03,400 so this all is moving around. 987 00:42:03,400 --> 00:42:06,030 So you have 4 quadrants at a little cell 988 00:42:06,030 --> 00:42:08,390 and it moves to somewhere up, down, 989 00:42:08,390 --> 00:42:09,060 left, right. 990 00:42:09,060 --> 00:42:10,760 You can easily detect that. 991 00:42:10,760 --> 00:42:14,280 That is feed into an array 992 00:42:14,280 --> 00:42:17,470 of 4 Avalanche Photon Diodes 993 00:42:17,470 --> 00:42:20,020 to actually record this and for that 994 00:42:20,020 --> 00:42:22,119 we don't need many photons. 995 00:42:22,119 --> 00:42:24,180 So this tip tilt star can comparably... 996 00:42:24,180 --> 00:42:28,130 be comparably dim. 997 00:42:28,130 --> 00:42:30,680 The calibration unit for the daytime calibration 998 00:42:30,680 --> 00:42:32,130 can be put into the beam, 999 00:42:32,130 --> 00:42:34,150 so this arms can swing over, 1000 00:42:34,150 --> 00:42:35,750 over the primary mirror and then we can 1001 00:42:35,750 --> 00:42:40,910 inject artificial stars via a hologram 1002 00:42:40,910 --> 00:42:42,890 into the whole unit during daytime 1003 00:42:42,890 --> 00:42:44,510 and calibrate this whole thing. 1004 00:42:44,510 --> 00:42:48,560 And than yes, we are back here. 1005 00:42:48,560 --> 00:42:52,210 This is how we look like. 1006 00:42:52,210 --> 00:42:57,460 Maybe concentrate on this two areas first. 1007 00:42:57,460 --> 00:43:00,750 I will flip back an forth many times. 1008 00:43:00,750 --> 00:43:02,260 But, yeah, what is this? 1009 00:43:02,260 --> 00:43:04,400 Are this two stars which are just fuzzy 1010 00:43:04,400 --> 00:43:05,700 and dim? 1011 00:43:05,700 --> 00:43:07,510 Or is this an extended object? 1012 00:43:07,510 --> 00:43:09,480 The upper one may be a galaxy because it's 1013 00:43:09,480 --> 00:43:11,030 elongated. 1014 00:43:11,030 --> 00:43:13,970 Okay, concentrate on that. 1015 00:43:13,970 --> 00:43:24,450 Well, it actually just a bunch of stars. 1016 00:43:24,450 --> 00:43:26,099 And this is over a huge field. 1017 00:43:26,099 --> 00:43:28,170 So the correction is not just in the middle 1018 00:43:28,170 --> 00:43:30,570 but you can see also at the very edges 1019 00:43:30,570 --> 00:43:33,040 of this image, we do see this improvement 1020 00:43:33,040 --> 00:43:34,540 in image quality. 1021 00:43:34,540 --> 00:43:39,480 Of course you can have the diagram, if you want. 1022 00:43:39,480 --> 00:43:43,190 So the blue line is without the thing beam activated, 1023 00:43:43,190 --> 00:43:44,300 open loop, 1024 00:43:44,300 --> 00:43:46,349 and if we close the control loop, to do 1025 00:43:46,349 --> 00:43:49,040 this measurement and correction in real time 1026 00:43:49,040 --> 00:43:53,589 we do squeeze all the energy into a few pixels 1027 00:43:53,589 --> 00:43:54,800 which of course also means 1028 00:43:54,800 --> 00:43:57,730 our signal to noise level in a single pixel 1029 00:43:57,730 --> 00:43:59,140 goes up tremendously. 1030 00:43:59,140 --> 00:44:00,460 Meaning you can decrease 1031 00:44:00,460 --> 00:44:03,320 your exposer time. 1032 00:44:03,320 --> 00:44:06,200 Which is important if you want to observe galaxies 1033 00:44:06,200 --> 00:44:09,349 at this telescopes 1034 00:44:09,349 --> 00:44:12,480 it's 200 Dollars a minute. 1035 00:44:12,480 --> 00:44:16,460 *laughing* 1036 00:44:16,460 --> 00:44:18,370 It's not cheap. 1037 00:44:18,370 --> 00:44:23,920 Okay, good so... the thing... 1038 00:44:23,920 --> 00:44:27,520 just last week there was another commissioning run 1039 00:44:27,520 --> 00:44:30,339 testing commissioning run for this system. 1040 00:44:30,339 --> 00:44:34,420 And my colleges José Borelli and Lorenzo Busoni 1041 00:44:34,420 --> 00:44:36,450 have done a nice video. 1042 00:44:36,450 --> 00:44:38,810 The music btw. "hallo gamer" 1043 00:44:38,810 --> 00:44:42,599 it's royalty for ears... 1044 00:44:42,599 --> 00:44:46,040 If it was now darker therefore I asked, 1045 00:44:46,040 --> 00:44:47,880 this would come up nicer, 1046 00:44:47,880 --> 00:44:49,060 but let's see! 1047 00:44:49,060 --> 00:44:50,880 There is sound hopefully, 1048 00:44:50,880 --> 00:44:53,260 so the sound guys, let's see! 1049 00:46:40,720 --> 00:47:00,020 *applause* 1050 00:47:00,020 --> 00:47:02,540 Of course this a longer exposure. 1051 00:47:02,540 --> 00:47:07,089 It's not that starwars like 1052 00:47:07,089 --> 00:47:09,810 I would have loved to use some starwars 1053 00:47:09,810 --> 00:47:13,349 tones along those. But you know, all those rights 1054 00:47:13,349 --> 00:47:16,640 and... what not... yes... anyway! 1055 00:47:16,640 --> 00:47:17,770 That's how it looks like. 1056 00:47:17,770 --> 00:47:22,559 So you have 3 laser beams per eye. 1057 00:47:22,559 --> 00:47:24,910 Remember, we have 2 telescopes on one mount. 1058 00:47:24,910 --> 00:47:26,490 They look roughly in the same direction 1059 00:47:26,490 --> 00:47:28,630 but still... 1060 00:47:28,630 --> 00:47:31,460 So if you observe two telescopes 1061 00:47:31,460 --> 00:47:39,640 at the same time it's only 100 dollars a minute. 1062 00:47:39,640 --> 00:47:44,270 Yea, This is not so much the shiny part 1063 00:47:44,270 --> 00:47:47,130 on the dome itself, but if you actually 1064 00:47:47,130 --> 00:47:49,240 do stand on the mountain during night 1065 00:47:49,240 --> 00:47:50,859 and are a bit dark adapted, 1066 00:47:50,859 --> 00:47:54,800 you see the laser beams like that. 1067 00:47:54,800 --> 00:47:57,230 And don't be fooled! 1068 00:47:57,230 --> 00:47:59,770 If you are at the valley, 1069 00:47:59,770 --> 00:48:02,560 or very far away you hardly see them. 1070 00:48:02,560 --> 00:48:03,829 You don't see them at all. 1071 00:48:03,829 --> 00:48:04,990 You see them there. 1072 00:48:04,990 --> 00:48:08,079 If you are two kilometers off side already, 1073 00:48:08,079 --> 00:48:10,650 it's merely a dim greenish something. 1074 00:48:10,650 --> 00:48:13,390 If you are down in the valley 10 km off, 1075 00:48:13,390 --> 00:48:14,640 you don't see them any more. 1076 00:48:14,640 --> 00:48:17,460 If you take a camera, 5 minutes exposer, yes! 1077 00:48:17,460 --> 00:48:18,919 But otherwise, No! 1078 00:48:18,919 --> 00:48:20,180 There is no such thing as 1079 00:48:20,180 --> 00:48:22,690 "The people in the valley down can see like 1080 00:48:22,690 --> 00:48:29,350 these lasers pew pew every night.".. and no. 1081 00:48:29,350 --> 00:48:37,330 Ok, which gets me to the last part. 1082 00:48:37,330 --> 00:48:40,089 How, do you become 1083 00:48:40,089 --> 00:48:45,949 and how do you work as a laser rocket scientist? 1084 00:48:45,949 --> 00:48:48,099 Yes, I put this in the talk directly, 1085 00:48:48,099 --> 00:48:50,660 because I do get this question in the Q&A, normally, 1086 00:48:50,660 --> 00:48:52,690 when I talk about these things, 1087 00:48:52,690 --> 00:48:53,670 and it's always like: 1088 00:48:53,670 --> 00:48:58,659 "What do I need to do if I want to do this?" 1089 00:48:58,659 --> 00:49:01,520 Maybe you have already an idea about this 1090 00:49:01,520 --> 00:49:05,119 because you have seen how complex this thing is. 1091 00:49:05,119 --> 00:49:12,859 And, there are so many things to do in these kind of projects 1092 00:49:12,859 --> 00:49:16,150 and on various levels, also in the administration, 1093 00:49:16,150 --> 00:49:22,450 also for senior people, new people, maybe master thesis works on that 1094 00:49:22,450 --> 00:49:28,819 or bachelor, or PHD or then as a post-doc. 1095 00:49:28,819 --> 00:49:30,160 It's very complex. 1096 00:49:30,160 --> 00:49:34,150 Yes, and it's not only about just shooting lasers in the end. 1097 00:49:34,150 --> 00:49:39,250 Sometimes it's just about checking the cables 1098 00:49:39,250 --> 00:49:41,020 It needs to be done. 1099 00:49:41,020 --> 00:49:45,690 There is a tremendous amount of electronics and electrics involved. 1100 00:49:45,690 --> 00:49:52,240 There are all the mechanical components in such a system are custom built. 1101 00:49:52,240 --> 00:49:55,579 Either the institutes built it themselves 1102 00:49:55,579 --> 00:49:59,210 or they give it out of house. 1103 00:49:59,210 --> 00:50:01,319 There are these real time computers, for example. 1104 00:50:01,319 --> 00:50:02,829 this is by the way our real time computer 1105 00:50:02,829 --> 00:50:05,880 from micrograde, if you want to look that up. 1106 00:50:05,880 --> 00:50:08,460 it's company. It builds these things. 1107 00:50:08,460 --> 00:50:10,650 They need to be programmed. 1108 00:50:10,650 --> 00:50:13,579 Oh, if actually somebody is here in the audience 1109 00:50:13,579 --> 00:50:15,599 with real hard core experience on 1110 00:50:15,599 --> 00:50:18,750 real time computing, coding and such things, 1111 00:50:18,750 --> 00:50:20,590 do talk to me! 1112 00:50:20,590 --> 00:50:23,540 *laughing* 1113 00:50:23,540 --> 00:50:26,540 Yeah, this is how our software system looks like. 1114 00:50:26,540 --> 00:50:31,839 A very small part of the GUIs. It's a lot of code 1115 00:50:31,839 --> 00:50:35,010 and a lot of work and a lot of sleepless nights 1116 00:50:35,010 --> 00:50:38,760 in front of these computers and just testing it and testing it 1117 00:50:38,760 --> 00:50:41,829 and then testing some more, and testing even more. 1118 00:50:41,829 --> 00:50:44,859 And, to be involved in these kind of projects, 1119 00:50:44,859 --> 00:50:48,560 you don't need to be a laser physicist, 1120 00:50:48,560 --> 00:50:51,479 because there is no one thing. 1121 00:50:51,479 --> 00:50:54,890 If you want to take 3 messages out of this, it's: 1122 00:50:54,890 --> 00:50:57,060 it's a team effort, there are many tasks, 1123 00:50:57,060 --> 00:51:01,499 and there are many jobs, and you have to pick one. 1124 00:51:01,499 --> 00:51:04,170 Because in this one job you do in these projects 1125 00:51:04,170 --> 00:51:06,500 you have to be very, very, very good. 1126 00:51:06,500 --> 00:51:09,750 Because there are other people that are very, very, very good. 1127 00:51:09,750 --> 00:51:13,650 If you work in these kind of projects, if you meet a new person for the first time 1128 00:51:13,650 --> 00:51:17,359 just assume that he or she knows everything about this 1129 00:51:17,359 --> 00:51:18,940 and you know nothing. 1130 00:51:18,940 --> 00:51:24,130 You will quickly realize if that is true. 1131 00:51:24,130 --> 00:51:26,319 But otherwise, if you assume it the other way round, 1132 00:51:26,319 --> 00:51:28,730 you just make a fool of yourself, okay? 1133 00:51:28,730 --> 00:51:29,849 Don't do that. 1134 00:51:29,849 --> 00:51:34,170 People in science, second most important thing if you really want go into this, 1135 00:51:34,170 --> 00:51:38,740 people in science are just like people outside science 1136 00:51:38,740 --> 00:51:42,429 meaning you will meet nice people and you will meet..... 1137 00:51:42,429 --> 00:51:44,800 *laughing* 1138 00:51:44,800 --> 00:51:47,480 just like in life. 1139 00:51:47,480 --> 00:51:52,470 It's not that these things are spheres where people are, you know 1140 00:51:52,470 --> 00:51:57,180 floating above the lab surface and nice coloured. 1141 00:51:57,180 --> 00:52:00,819 No, it's hard work. 1142 00:52:00,819 --> 00:52:04,829 And if you actually go into this like study physics 1143 00:52:04,829 --> 00:52:08,640 or maybe if you want to construct this, 1144 00:52:08,640 --> 00:52:10,480 of course all the drawings are done by 1145 00:52:10,480 --> 00:52:13,339 people how have learned this in there studies, 1146 00:52:13,339 --> 00:52:16,810 so "Maschinenbau" what ever... 1147 00:52:16,810 --> 00:52:18,210 Go for that one. 1148 00:52:18,210 --> 00:52:21,079 Building optics needs optics experience. 1149 00:52:21,079 --> 00:52:23,520 If you want to actually build stuff, 1150 00:52:23,520 --> 00:52:26,079 well, there are many people in this institutes 1151 00:52:26,079 --> 00:52:28,099 or universities who work 1152 00:52:28,099 --> 00:52:30,500 in the mechanical fabrication departments 1153 00:52:30,500 --> 00:52:31,609 or electronics departments. 1154 00:52:31,609 --> 00:52:35,460 They just do PCB layouting all the time. 1155 00:52:35,460 --> 00:52:38,369 But this things do need sophisticated electronics 1156 00:52:38,369 --> 00:52:40,140 and this all custom built. 1157 00:52:40,140 --> 00:52:42,160 This is nothing you can buy of the shelf. 1158 00:52:42,160 --> 00:52:45,300 Nothing of it! Almost nothing. 1159 00:52:45,300 --> 00:52:46,500 And this means you might end up 1160 00:52:46,500 --> 00:52:48,819 with something equally cool. 1161 00:52:48,819 --> 00:52:51,099 It's not that you can have this one thing 1162 00:52:51,099 --> 00:52:53,829 and then BAM ten years later you will be 1163 00:52:53,829 --> 00:52:56,829 the laser-rocket scientist. You won't! 1164 00:52:56,829 --> 00:52:58,740 You might become one 1165 00:52:58,740 --> 00:53:01,819 and then even after 10 years, 1166 00:53:01,819 --> 00:53:04,010 you might realize this is not the thing 1167 00:53:04,010 --> 00:53:07,660 you want to do forever. 1168 00:53:07,660 --> 00:53:09,380 So I have to correct 1169 00:53:09,380 --> 00:53:10,900 the introduction in one point: 1170 00:53:10,900 --> 00:53:12,750 I'm no longer working there. 1171 00:53:12,750 --> 00:53:14,819 I recently left. 1172 00:53:14,819 --> 00:53:17,849 I'm now have my own company. 1173 00:53:17,849 --> 00:53:19,270 I'm still involved in these things. 1174 00:53:19,270 --> 00:53:21,710 I do calculations for this kinds of things, 1175 00:53:21,710 --> 00:53:23,520 but I'm not at an institute any more, 1176 00:53:23,520 --> 00:53:25,900 because I decided for example for me 1177 00:53:25,900 --> 00:53:29,190 that the contract conditions in this type 1178 00:53:29,190 --> 00:53:33,440 of scientific work are not of the type, 1179 00:53:33,440 --> 00:53:38,400 which I want to live with any more. 1180 00:53:38,400 --> 00:53:40,500 Like one year contracts. 1181 00:53:40,500 --> 00:53:49,220 *applause* 1182 00:53:49,220 --> 00:53:51,760 And so there are many ways of being involved in this 1183 00:53:51,760 --> 00:53:53,970 and don't just... don't just focus on the this! 1184 00:53:53,970 --> 00:53:56,710 Focus on what you really want to do and 1185 00:53:56,710 --> 00:53:59,440 you might end up in this 1186 00:53:59,440 --> 00:54:00,650 and if you don't, 1187 00:54:00,650 --> 00:54:03,563 well you do something equally cool. 1188 00:55:52,879 --> 00:55:56,730 All right! Questions? 1189 00:55:56,730 --> 00:56:04,800 *applause* 1190 00:56:04,800 --> 00:56:06,839 Herald: Okay, first of all 1191 00:56:06,839 --> 00:56:10,450 thank you for our daily dosis of lasers. 1192 00:56:10,450 --> 00:56:13,730 I have said... Ich hab keine Zeit... 1193 00:56:13,730 --> 00:56:16,589 cause we have really not much time left for Q&A, 1194 00:56:16,589 --> 00:56:19,530 so I'm first asking the signal angel, 1195 00:56:19,530 --> 00:56:21,410 if there are any questions from the internet, 1196 00:56:21,410 --> 00:56:25,880 because... was that a 2? 2! ok. 1197 00:56:25,880 --> 00:56:28,670 because this people can't ask questions afterwards, soo... 1198 00:56:28,670 --> 00:56:31,329 Peter: I'll be all congress and if you want to reach me 1199 00:56:31,329 --> 00:56:35,699 directly 7319 is this telephone. 1200 00:56:35,699 --> 00:56:39,030 Herald: Ok, the signal angel questions. 1201 00:56:39,030 --> 00:56:41,130 Signal A.: Yeah, the first question from the internet was: 1202 00:56:41,130 --> 00:56:43,559 How strong the laser actually is 1203 00:56:43,559 --> 00:56:45,509 or if it could be any danger for something 1204 00:56:45,509 --> 00:56:47,380 in the vicinity? 1205 00:56:47,380 --> 00:56:48,440 Peter: Actually, no! 1206 00:56:48,440 --> 00:56:51,210 So we shoot up around 15 to 20 W 1207 00:56:51,210 --> 00:56:53,290 per laser beam. 1208 00:56:53,290 --> 00:56:55,579 If there was actually a plane flying through 1209 00:56:55,579 --> 00:56:58,410 our laser beam, 1210 00:56:58,410 --> 00:57:01,380 then nothing happens to the pilots. 1211 00:57:01,380 --> 00:57:03,040 They don't get blinded or what not, 1212 00:57:03,040 --> 00:57:06,290 because it's di... the beamsize at that altitude 1213 00:57:06,290 --> 00:57:09,069 is so big already.. they will of course look like: 1214 00:57:09,069 --> 00:57:10,710 "Errr what is this?" 1215 00:57:10,710 --> 00:57:12,720 And that's what we do not want, 1216 00:57:12,720 --> 00:57:14,470 because then they might push some other buttons 1217 00:57:14,470 --> 00:57:16,660 which they are not suppose to push. 1218 00:57:16,660 --> 00:57:17,750 *laughing* 1219 00:57:17,750 --> 00:57:20,270 If you of course work directly at the system, 1220 00:57:20,270 --> 00:57:21,200 you have to maintain it, 1221 00:57:21,200 --> 00:57:24,140 you open it, you have to align the lasers 1222 00:57:24,140 --> 00:57:27,559 and what not beyond there self aligning capabilities, 1223 00:57:27,559 --> 00:57:29,619 you do have to wear all this protective laser goggles 1224 00:57:29,619 --> 00:57:32,140 and what not, because if you do... 1225 00:57:32,140 --> 00:57:35,359 if you don't you do have instant eye damage. 1226 00:57:35,359 --> 00:57:39,189 It is not... no its instant. 1227 00:57:39,189 --> 00:57:41,400 You might not see it instantly. 1228 00:57:41,400 --> 00:57:45,160 But the instant... it's there instantly, period. 1229 00:57:45,160 --> 00:57:48,290 So really, folks, don't experiment on this 1230 00:57:48,290 --> 00:57:49,589 laser stuff at home, 1231 00:57:49,589 --> 00:57:53,319 if you are not following basic laser safety rules. 1232 00:57:53,319 --> 00:57:56,290 Not prying this things from the DVD burners 1233 00:57:56,290 --> 00:58:00,540 or no blue ray thingys "uuh does it really work?" 1234 00:58:00,540 --> 00:58:02,030 Just, just don't! 1235 00:58:02,030 --> 00:58:05,329 Your eyesight is not worth it. period. 1236 00:58:05,329 --> 00:58:08,080 It's not! 1237 00:58:08,080 --> 00:58:10,849 Herald: Please remember to cover your still working eye! 1238 00:58:10,849 --> 00:58:13,500 Peter: Yeah... only look into the laser beam 1239 00:58:13,500 --> 00:58:16,130 with your remaining eye. 1240 00:58:16,130 --> 00:58:17,489 Herald: The other question? 1241 00:58:17,489 --> 00:58:20,040 Signal A. :And the second question from the internet 1242 00:58:20,040 --> 00:58:21,940 was... It's actually commenting that, 1243 00:58:21,940 --> 00:58:24,230 this was a very cool concept already been used 1244 00:58:24,230 --> 00:58:26,520 and where do you see this going 1245 00:58:26,520 --> 00:58:28,849 in the next 10 years, so what's the outlook 1246 00:58:28,849 --> 00:58:31,820 for observation from the Earth's surface 1247 00:58:31,820 --> 00:58:33,250 in the next 10 years? 1248 00:58:33,250 --> 00:58:34,569 Peter: Oh, of course 1249 00:58:34,569 --> 00:58:36,089 the telescopes will get bigger and bigger. 1250 00:58:36,089 --> 00:58:38,170 The next generation of the telescope is coming up 1251 00:58:38,170 --> 00:58:39,660 in the 2020s. 1252 00:58:39,660 --> 00:58:41,369 The European Extremely Large Telescope 1253 00:58:41,369 --> 00:58:45,200 will be about roughly around 40 meters in diameter. 1254 00:58:45,200 --> 00:58:47,220 These are so huge they can't work in 1255 00:58:47,220 --> 00:58:49,250 seeing limited operation any more. 1256 00:58:49,250 --> 00:58:54,030 They do have to have laser AO all the time. 1257 00:58:54,030 --> 00:58:55,609 It will look similar to this. 1258 00:58:55,609 --> 00:58:57,349 So this is in that sense also 1259 00:58:57,349 --> 00:58:58,650 a technology demonstrator. 1260 00:58:58,650 --> 00:59:01,910 There will be a combined thing. 1261 00:59:01,910 --> 00:59:03,850 You may remember this diagram 1262 00:59:03,850 --> 00:59:06,260 with the one sodium laser in the middle 1263 00:59:06,260 --> 00:59:07,740 and the others outside. 1264 00:59:07,740 --> 00:59:09,319 So these combined things. 1265 00:59:09,319 --> 00:59:12,240 And then you can also imagine something, 1266 00:59:12,240 --> 00:59:13,869 that you probe different heights 1267 00:59:13,869 --> 00:59:14,910 in the atmosphere, 1268 00:59:14,910 --> 00:59:18,130 because you do have different turbulence layers 1269 00:59:18,130 --> 00:59:22,480 and all of these then have their own 1270 00:59:22,480 --> 00:59:23,750 deformable mirror. 1271 00:59:23,750 --> 00:59:25,660 So it's a very comp... gets a very complex set, 1272 00:59:25,660 --> 00:59:29,460 a multi conjugate AO as it's called. 1273 00:59:29,460 --> 00:59:30,700 And then there are of course 1274 00:59:30,700 --> 00:59:33,940 new... there is research being done on 1275 00:59:33,940 --> 00:59:36,950 how to detect this wave front 1276 00:59:36,950 --> 00:59:38,089 most efficently. 1277 00:59:38,089 --> 00:59:40,380 And there is a so called thing called 1278 00:59:40,380 --> 00:59:42,410 the pyramid sensor. 1279 00:59:42,410 --> 00:59:44,230 You can look for that, also 1280 00:59:44,230 --> 00:59:46,220 we do have one in our system. 1281 00:59:46,220 --> 00:59:47,730 And this is very efficient. 1282 00:59:47,730 --> 00:59:49,680 So it takes much less photons 1283 00:59:49,680 --> 00:59:52,750 to get to the same signal to noise level. 1284 00:59:52,750 --> 00:59:55,740 This is active research and... well... 1285 00:59:55,740 --> 00:59:58,140 Every major telescope of course now has this. 1286 00:59:58,140 --> 01:00:00,400 And every big telescopes in the future 1287 01:00:00,400 --> 01:00:04,870 will have this all over the place. 1288 01:00:04,870 --> 01:00:09,270 Herald: Okay, we're completely out of time. Again. 1289 01:00:09,270 --> 01:00:10,580 Again, so thank you very much. 1290 01:00:10,580 --> 01:00:12,070 Peter: Thank you! 1291 01:00:12,070 --> 01:00:17,809 *applause*