[slate]
Hi my name is Tom Statler and I work at NASA Headquarters
in Washington, D.C. where I am the Program Scientist for the DART mission.
[slate]
The DART mission is humanity’s first
attempt to change the motion of a celestial body. And the reason
we’re doing this is to test our ability to protect the Earth
from an impact by an asteroid if we should ever discover in the future
an asteroid that is heading on a collision course for Earth. [slate]
[slate]
Planetary defense is about making sure that a rock from space
doesn’t send us back to the Stone Age. And the key parts of planetary defense
are first of all finding the asteroids that are potentially
hazardous to the Earth. And we understand where about
40 percent of those asteroids are. We know that no
known asteroid is a danger to the Earth right now. But the
concern is about the asteroids we don’t know about yet. And if we
should ever discover an asteroid that’s on a collision course with Earth, we want to
be able to discover this years in advance so that we can give the asteroid
a push - not to destroy it - we probably wouldn’t be able to do that anyway.
But just to prevent that collision. And the DART mission - the Double Asteroid
Redirection Test is our first test of one way of doing that.
[slate]
DART’s going to a binary asteroid - a double
asteroid for two really good reasons. The little asteroid
Dimorphos which is in orbit around the big asteroid Didymos,
that asteroid is about the size of object
that we would tend to be concerned about. The most abundant asteroids are the small ones
and this one about 160 meters across, or about the size of a football stadium,
is large enough that it really would cause severe damage
if it struck the Earth. Now by impacting, by
doing our experiment, a kinetic experiment on the small moonlet asteroid
we’re able to measure our effectiveness in deflecting
the asteroid by watching the change in the orbit of the little asteroid around the
big one. It makes measurement a lot more precise and a lot easier to do
with telescopes on Earth. The other reason we’re doing it is that the presence of the
large asteroid there keeps the little one in orbit around it as the pair
go around the sun. So that means that this asteroid which is
not a danger to Earth now, will never become a danger to the Earth
because of anything that we do in the DART mission. [slate]
[slate]
No asteroid that we know of now is a danger
to the Earth. And the Didymos asteroid that DART is going to,
that also is not a danger to the Earth and there’s nothing that we could do to it that will
make it a danger to the Earth. But the possibility of
an asteroid large enough that it could affect huge numbers of people
the likelihood of that happening during our lifetimes
is there. It’s not a high probability, but
we take precautions about low-probability events all the time. It’s a
low probability that your house will burn down for example, but you take precautions
to make sure that doesn’t happen and you have fire insurance.
[slate]
Anyone who wants to know about
DART can follow on social media by using the hashtag #DARTMission
or by looking at nasa.gov/dartmission.
[slate]
[slate] At the
moment of impact with Dimorphos, DART will be moving at about
4 miles per second, that’s about 15,000 miles an hour.
[slate]
[slate] The important thing isn’t how
far we move the asteroid, it’s how much we change its speed by.
So we’re going to change the speed of the asteroid by only a few
millimeters per second. It’s far far smaller than walking speed.
But the idea in planetary defense is that if there is a
hazardous asteroid, a dangerous asteroid, and we discover it years in advance,
then a change in its velocity that tiny given time to
add up, given time to work, can make the difference between
an impact on Earth and a safe miss. [slate]
[slate]
NASA’s planetary defense strategy is to do
several things at the same time. The most important one is to
search for asteroids because we only know about
40 percent of the populations of asteroids that could be dangerous
and we need to find that other 60 percent - track them, establish
their orbits around the Sun and figure out which ones could be
dangerous to us now or in the future. Also like in the DART
mission, we want to develop the technologies for deflecting asteroids,
mitigating the effects of the asteroid hazard
and then we want to be working with other federal agencies, state and local
governments, and governments world-wide to
understand how the world-wide community can deal with
this issue of planetary defense and protect the entire world.
Share information, transmit information up the chain
to the decision-makers, do what’s necessary to respond to an actual asteroid
danger if there ever is one.
[slate]
DART is carrying a small
CUBESat, it's called LICIACube, it was contributed by the Italian Space Agency and it
job basically is to watch the impact from a little distance away.
It’s riding along on the DART spacecraft and it’s going to be deployed
a few days before the kinetic impact. It’s going to maneuver
and offset itself to the side so that it doesn’t run into the same
asteroid that DART is running into, and it’s got two cameras on it that are going to
try to first catch the actual impact of DART on camera,
but then more importantly see the
ejecta, the plume of material that’s blown off the surface of the asteroid and how that
develops. If we’re fortunate, we’ll be able to see the impact crater
newly formed by the DART impact.
And then LICIACube will do something that DART can’t do that is fly past
the asteroid, look back, and get the full three dimensional shape
of the object that we hit which we won’t know until we actually get there.
[slate]
One of my favorite things about DART is the name. It’s the Double Asteroid Redirection
Test and we’re going to a double asteroid. It’s a binary
asteroid, but we’re also doing a double test. DART is a test
of our ability to actually execute a kinetic impact. Build a spacecraft
that can autonomously direct itself
to a collision with an asteroid. But also we have to test
how a real asteroid responds to that deflection attempt.
Because it’s one thing to take a very expensive spacecraft
and smash it to bits on the surface of an asteroid, but really the question we want to
answer is how effectively do we move an asteroid when we do that.
So DART is a double test on a double asteroid.