WEBVTT FILE 1 00:00:00.290 --> 00:00:04.330 [Music] 2 00:00:04.350 --> 00:00:08.710 [Music] 3 00:00:08.730 --> 00:00:12.850 [Music] 4 00:00:12.870 --> 00:00:16.900 Ira Thorpe: LISA Pathfinder is a mission led by the European Space Agency 5 00:00:16.920 --> 00:00:21.050 to demonstrate technologies for a future space-based gravitational wave observatory. 6 00:00:21.070 --> 00:00:25.270 We've just had a very historic event with the 7 00:00:25.290 --> 00:00:29.430 successful detection of gravitational waves from the ground, and that was using these instruments called LIGO. 8 00:00:29.450 --> 00:00:33.530 For detecting gravitational waves in space you need a slightly different kind of detector, 9 00:00:33.550 --> 00:00:37.690 and the detector that we all are working towards has a name LISA, for Laser 10 00:00:37.710 --> 00:00:41.870 Interferometer Space Antenna. So that's where we get the name LISA Pathfinder. 11 00:00:41.890 --> 00:00:45.910 So basically it demonstrates some of the technologies that we will use on LISA 12 00:00:45.930 --> 00:00:50.110 to eventually build a space-based gravitational wave detector. You're looking for these very 13 00:00:50.130 --> 00:00:54.170 small distortions in space and time, and so you need to have some object 14 00:00:54.190 --> 00:00:58.200 that you can use to reference space and time, basically something that's falling. 15 00:00:58.220 --> 00:01:02.230 And any object in space, in principle it's sort of just falling, it's just feeling gravity. 16 00:01:02.250 --> 00:01:06.420 But when you look at very exquisite detail you find there's other forces that are pushing 17 00:01:06.440 --> 00:01:10.480 that object around, and so this technology called drag-free control was developed, 18 00:01:10.500 --> 00:01:14.520 where the test mass actually sits inside the satellite, and the satellite's 19 00:01:14.540 --> 00:01:18.550 flying around it like a flying shield. And so we needed to demonstrate this technology 20 00:01:18.570 --> 00:01:22.600 and show that we could really place that test mass in absolutely perfect free fall, 21 00:01:22.620 --> 00:01:26.790 and that's what we've done. The test was incredibly successful. The level that's been measured 22 00:01:26.810 --> 00:01:30.900 you know, not only meets our requirement for LISA Pathfinder, but actually approaches 23 00:01:30.920 --> 00:01:34.920 the requirement for doing the full-scale detector, for LISA, and so we're just absolutely thrilled 24 00:01:34.940 --> 00:01:39.100 What that will allow us to do when we build the full scale detector is 25 00:01:39.120 --> 00:01:43.150 detect gravitational waves from things like merging supermassive black holes at the edge of the 26 00:01:43.170 --> 00:01:47.220 universe. What's shown 27 00:01:47.240 --> 00:01:51.300 in the graph here is basically how imperfect this test mass 28 00:01:51.320 --> 00:01:55.390 is in free fall. Right? So we'd like it to be perfect, it's not quite perfect, 29 00:01:55.410 --> 00:01:59.500 and we're measuring the imperfection. This is directly what we measure with the 30 00:01:59.520 --> 00:02:03.630 instrument and the very exciting thing is that it's far below the LISA Pathfinder 31 00:02:03.650 --> 00:02:07.780 requirements. The first thing we noticed was at the very lowest frequencies 32 00:02:07.800 --> 00:02:11.960 we had this increase in noise. This was actually due to the fact that the 33 00:02:11.980 --> 00:02:15.990 spacecraft is jittering about in angle. And we can actually measure how the spacecraft jitters 34 00:02:16.010 --> 00:02:20.070 and we can subtract it. The final thing we did was 35 00:02:20.090 --> 00:02:24.110 we looked at the noise in this middle-frequency band here, and we determined that this is actually due to 36 00:02:24.130 --> 00:02:28.170 some sort of subtle imperfections in the construction of the instrument. 37 00:02:28.190 --> 00:02:32.240 And so we can fit these, and subtract them from the data, and we get down to this next line. 38 00:02:32.260 --> 00:02:36.320 And this is exactly what we'd expect from a gravitational wave detector and tells 39 00:02:36.340 --> 00:02:40.450 us that we're getting a very good understanding of our instrument. 40 00:02:40.470 --> 00:02:44.570 The really exciting thing is if we place on this graph the requirement for the full-scale 41 00:02:44.590 --> 00:02:48.730 detector, for the LISA detector. And you'll see that although we weren't these 42 00:02:48.750 --> 00:02:52.760 requirements, we very nearly made these requirements. Here, essentially, we, you know, 43 00:02:52.780 --> 00:02:56.860 turned it on out of the box and it just worked. If you were to take the performance of 44 00:02:56.880 --> 00:03:00.890 LISA Pathfinder today and just build LISA with that same performance, you would get 45 00:03:00.910 --> 00:03:04.950 the vast majority of the science that we've all been going after for all this time. 46 00:03:04.970 --> 00:03:08.980 And, you know, this idea, the idea for LISA, the space-based gravitational wave detector, dates back 47 00:03:09.000 --> 00:03:13.030 you know, more than 40 years, it's older than I am. And, you know, we haven't flown 48 00:03:13.050 --> 00:03:17.090 the full mission yet, but we've flown a mission, you know, LISA Pathfinder, that's shown this is possible, 49 00:03:17.110 --> 00:03:21.180 that you can actually do this. And, you know, some of these people that invested, you know, the past several 50 00:03:21.200 --> 00:03:25.290 decades of their lives, you know, developing this mission and to see it work, it was just 51 00:03:25.310 --> 00:03:29.320 totally inspiring. [Music] 52 00:03:29.340 --> 00:03:33.340 [Music] 53 00:03:33.360 --> 00:03:46.239 [Beeping]