WEBVTT FILE 1 00:00:00.060 --> 00:00:05.009 The SWEAP investigation consists of three separate instruments and a central 2 00:00:05.009 --> 00:00:09.840 electronics box most of the instruments within sweep sit on either side of the 3 00:00:09.840 --> 00:00:14.130 spacecraft stare out over the entire sky and make maps of all the different 4 00:00:14.130 --> 00:00:17.940 particles and what energies they're moving at what types of particles they 5 00:00:17.940 --> 00:00:23.070 are the purpose of sweep is to measure the bulk of the solar wind and a solar 6 00:00:23.070 --> 00:00:26.670 atmosphere one of the biggest questions we want to resolve with Solar Probe is 7 00:00:26.670 --> 00:00:29.670 how the corona in the solar wind are heated in order to do that we need to 8 00:00:29.670 --> 00:00:34.350 see if there are waves that are coming from the Sun and depositing energy 9 00:00:34.350 --> 00:00:38.700 within the solar atmosphere in the solar wind so we have a series of sensors 10 00:00:38.700 --> 00:00:44.579 across the spacecraft that will collect individual particles electrons fully 11 00:00:44.579 --> 00:00:48.719 ionized hydrogen helium which we call protons and alphas and other minor ions 12 00:00:48.719 --> 00:00:54.030 and make maps of the number of particles as a function of their speed and energy 13 00:00:54.030 --> 00:00:59.070 and type we take those maps on the ground and we can interpret them to 14 00:00:59.070 --> 00:01:03.539 figure out the temperature the density the pressure of the solar wind and the 15 00:01:03.539 --> 00:01:07.530 solar atmosphere on the RAM side of the spacecraft so that's in the shadow of 16 00:01:07.530 --> 00:01:11.580 the heat field in the direction that Solar Probe is moving around the Sun we 17 00:01:11.580 --> 00:01:17.159 have Span A. Span A looks ahead of the spacecraft it has an electron and an ion 18 00:01:17.159 --> 00:01:21.840 instrument and they can see the entire sky on that side of the spacecraft on 19 00:01:21.840 --> 00:01:26.640 the other side the anti ram side of the spacecraft we have Span B which 20 00:01:26.640 --> 00:01:31.710 basically looks behind our direction of motion Span a and Span B are each able 21 00:01:31.710 --> 00:01:35.909 to take an inventory of electrons coming from any direction in the sky their 22 00:01:35.909 --> 00:01:40.530 fields of view stitch together like the seams on a baseball the spans combined 23 00:01:40.530 --> 00:01:44.610 to give us a field of view that covers nearly the entire sky and we have one 24 00:01:44.610 --> 00:01:47.759 large gap in our field of view and it's produced by the heat shield at the front 25 00:01:47.759 --> 00:01:50.640 of the spacecraft so we have the Solar Probe Cup is the 26 00:01:50.640 --> 00:01:54.869 final instrument within SWEAP. The Solar Probe cups sits on a strut it looks 27 00:01:54.869 --> 00:01:58.950 around the heat shield and faces directly into the Sun when our solar 28 00:01:58.950 --> 00:02:02.280 wind or solar atmosphere comes blowing into the cup 29 00:02:02.280 --> 00:02:06.390 if those particles which are charged don't have enough energy they get 30 00:02:06.390 --> 00:02:10.289 reflected out by that electric field we've set up the particles with enough 31 00:02:10.289 --> 00:02:13.530 energy to make it past the could feel come in and strike a plate 32 00:02:13.530 --> 00:02:18.480 and we record the current all we have to do in an individual measurement is sweep 33 00:02:18.480 --> 00:02:22.110 in voltage and measure the number of particles that can make it in as a 34 00:02:22.110 --> 00:02:25.890 function of the voltage that's sweep when we interpret it lets us figure out 35 00:02:25.890 --> 00:02:30.840 the average speed direction energy temperature density of individual 36 00:02:30.840 --> 00:02:35.770 populations of particles