1
00:00:00,260 --> 00:00:05,550
[David McComas] ISIS, the Integrated Science Investigation of the Sun, is an experiment which looks at

2
00:00:05,550 --> 00:00:10,290
energetic particles over a broad range of
energies, from tens of thousands of electron

3
00:00:10,290 --> 00:00:14,019
volts up to about a hundred million electron volts.

4
00:00:14,019 --> 00:00:17,140
The ISIS instrument is based on solid state detectors.

5
00:00:17,140 --> 00:00:22,340
Those are detectors that when a particle passes
through them, energy’s deposited and you

6
00:00:22,340 --> 00:00:26,800
can measure that energy and you can measure
that the particle has actually passed through.

7
00:00:26,800 --> 00:00:31,230
So there’s the solar wind, which is this
continuous flow of lower-energy particles,

8
00:00:31,230 --> 00:00:36,129
and then there are much more sporadic and
episodic events like solar flares that spew

9
00:00:36,129 --> 00:00:39,350
out great numbers of these much more energetic
particles.

10
00:00:39,350 --> 00:00:43,499
in our higher-energy instrument, we have a
whole set of layers of these detectors so

11
00:00:43,499 --> 00:00:47,589
when a particle passes through those layers
it leaves energy in each and every one of

12
00:00:47,589 --> 00:00:49,139
those detectors.

13
00:00:49,139 --> 00:00:53,420
Those detectors are also segmented in pieces
like a pie and so when a particle comes through

14
00:00:53,420 --> 00:00:57,649
from a particular direction you can tell both
the direction the particle came through at

15
00:00:57,649 --> 00:01:02,389
and you can tell the energy and species of
that particle by looking at all the different

16
00:01:02,389 --> 00:01:04,129
energy depositions.

17
00:01:04,129 --> 00:01:08,720
In our lower-energy instrument, we also have
the same sort of solid state detectors, but

18
00:01:08,720 --> 00:01:12,461
in addition to that we use an extra trick,
which is when a particle passes through a

19
00:01:12,461 --> 00:01:17,230
very thin foil it ejects an electron, we’re
able to detect that, and that gives us the

20
00:01:17,230 --> 00:01:18,690
start timing for the particle.

21
00:01:18,690 --> 00:01:23,810
One of the big issues for ISIS is to understand
the difference between solar energetic particles

22
00:01:23,810 --> 00:01:28,000
that just come from the Sun with a certain
energy and those that are energized in interplanetary

23
00:01:28,000 --> 00:01:29,720
space as they move outward.

24
00:01:29,720 --> 00:01:34,700
By the time they get out to the Earth’s
orbit, that’s all so messed up, mangled

25
00:01:34,700 --> 00:01:38,390
up, that it’s kind of hard to tell the difference
between those, but as we get in closer and

26
00:01:38,390 --> 00:01:42,470
closer to the Sun, we’ll be able to differentiate
those two types of sources, which will be

27
00:01:42,470 --> 00:01:48,220
really important for understanding the fundamentals
of energetic particles in the solar system.

28
00:01:48,220 --> 00:01:52,320
By going in close and measuring the detailed
distributions of these energetic particles,

29
00:01:52,320 --> 00:01:56,340
their energies, directions, and their species,
we’re going to learn things that we couldn’t

30
00:01:56,340 --> 00:01:59,280
possibly learn by looking forever from a remote
distance.

31
00:01:59,280 --> 00:02:03,090
And by understanding our Sun in detail, we
can understand lots of other stars in much

32
00:02:03,090 --> 00:02:03,680
greater detail.