WEBVTT FILE 1 00:00:05.120 --> 00:00:09.450 You're going into environment that's completely unforgiving. The temperatures 2 00:00:09.450 --> 00:00:12.450 that we're seeing on the spacecraft or have not been seen by any other 3 00:00:12.450 --> 00:00:17.849 spacecraft ever before. The scariest thing about the Sun is the unknown. We 4 00:00:17.849 --> 00:00:22.259 see it every day but we see it from 93 million miles away. 5 00:00:22.259 --> 00:00:26.699 This first perihelion were going into we have very minimal contact - all we can 6 00:00:26.699 --> 00:00:31.499 get is a tone. I'm going to be waiting on the edge of my seat for those beacon 7 00:00:31.499 --> 00:00:38.300 tones. The Sun facing side will be exposed to in excess of 2,500 degrees Fahrenheit 8 00:00:38.300 --> 00:00:38.800 We're gonna go closer to the Sun than any other spacecraft has gone before. We're 9 00:00:43.110 --> 00:00:46.800 not going to do that once we're not gonna do it twice - we're gonna do that 24 10 00:00:46.800 --> 00:00:53.820 times - and that is terrifying. We really don't know what we're gonna find until we get 11 00:00:53.820 --> 00:01:00.260 there. In 1958 Gene Parker had an idea that the 12 00:01:00.260 --> 00:01:07.040 area around the Sun would behave in a certain way. There are two really 13 00:01:07.040 --> 00:01:12.620 overarching mysteries that we have always wanted to study: why is the corona 14 00:01:12.620 --> 00:01:16.550 hotter than the surface of the Sun? Why is the solar wind continuously 15 00:01:16.550 --> 00:01:23.360 accelerated? We are now in what we call our encounter attitude the TPS is pointed 16 00:01:23.360 --> 00:01:27.800 at the Sun and we will not leave that attitude until we get back around the 17 00:01:27.800 --> 00:01:32.060 backside of the Sun. So we keep the thermal shield between the spacecraft 18 00:01:32.060 --> 00:01:37.070 body and the Sun. We have designed the spacecraft to be able to do the right 19 00:01:37.070 --> 00:01:41.180 thing no matter what it sees. You can't do Parker Solar Probe unless you're 20 00:01:41.180 --> 00:01:43.910 willing to build a spacecraft that could take care of 21 00:01:43.910 --> 00:01:46.400 itself; you can't build Parker Solar Probe 22 00:01:46.400 --> 00:01:50.390 unless you can build a shield that could withstand the thermal environment; you 23 00:01:50.390 --> 00:01:54.290 can't do Parker Solar Probe unless you can keep the power generation cool - and 24 00:01:54.290 --> 00:01:57.790 all these things contain some level of risk. 25 00:01:57.790 --> 00:02:02.270 The Sun is a wideband radio source so any spacecraft is either in front of the 26 00:02:02.270 --> 00:02:06.920 Sun behind the Sun or near the Sun you can't talk to it. Parker Solar Probe is 27 00:02:06.920 --> 00:02:11.030 designed to transmit four different kinds of beacon tones A is a good beacon, 28 00:02:11.030 --> 00:02:13.850 the fault management system is reporting that all systems are nominal. 29 00:02:13.850 --> 00:02:18.410 The other three tones mean that some type of fault has occurred on board. We 30 00:02:18.410 --> 00:02:22.130 will be mostly out of contact with the spacecraft through encounter so the only 31 00:02:22.130 --> 00:02:28.790 thing we will have is those beacon tones. We will be all waiting for the call: "APL, 32 00:02:28.790 --> 00:02:35.090 APL - I am Parker Solar Probe. I'm doing well, and I have surprises for you. The fear 33 00:02:35.090 --> 00:02:41.220 and tension and stress is all going to be focused on those last few minutes. 34 00:02:41.220 --> 00:02:47.679 This truly is a mission of discovery.