How a miniaturized atomic clock could revolutionize space exploration Jill Seubert
Transcriber: Joseph Geni
Reviewer: Camille Martínez
Six months ago,
I watched with bated breath
as NASA’s InSight lander
descended towards the surface of Mars.
Two hundred meters,
80 meters,
60, 40, 20, 17 meters.
Receiving confirmation
of successful touchdown
was one of the most
ecstatic moments of my life.
And hearing that news was possible
because of two small cube sets
that went along to Mars with InSight.
Those two cube sets essentially
livestreamed InSight’s telemetry
back to Earth,
so that we could watch in near-real time
as that InSight lander went screaming
towards the surface of the red planet,
hitting the atmosphere of Mars
at a top speed of about
12,000 miles per hour.
Now, that event was livestreamed to us
from over 90 million miles away.
It was livestreamed from Mars.
Meanwhile,
the two Voyager spacecraft –
now, these are these two
almost unbelievably intrepid explorers.
They were launched
the same year that all of us here
were being introduced to Han Solo
for the first time.
And they are still sending back data
from interstellar space
over 40 years later.
We are sending more spacecraft
further into deep space
than ever before.
But every one of those
spacecraft out there
depends on its navigation being performed
right here at Earth
to tell it where it is
and, far more importantly,
where it is going.
And we have to do that navigation
here on Earth for one simple reason:
spacecraft are really bad
at telling the time.
But if we can change that,
we can revolutionize
the way we explore deep space.
Now, I am a deep space navigator,
and I know you’re probably
thinking, “What is that job?”
Well, it is an extremely unique
and also very fun job.
I steer spacecraft,
from the moment they separate
from their launch vehicle
to when they reach
their destination in space.
And these destinations –
say Mars for example, or Jupiter –
they are really far away.
To put my job in context for you:
it’s like me standing here in Los Angeles
and shooting an arrow,
and with that arrow, I hit a target
that’s the size of a quarter,
and that target the size of a quarter
is sitting in Times Square, New York.
Now, I have the opportunity
to adjust the course of my spacecraft
a few times along that trajectory,
but in order to do that,
I need to know where it is.
And tracking a spacecraft
as it travels through deep space
is fundamentally a problem
of measuring time.
You see, I can’t just pull out my ruler
and measure how far away my spacecraft is.
But I can measure
how long it takes a signal
to get there and back again.
And the concept is exactly
the same as an echo.
If I stand in front of
a mountain and I shout,
the longer it takes for me
to hear my echo back at me,
the further away that mountain is.
So we measure that signal time
very, very accurately,
because getting it wrong
by just a tiny fraction of a second
might mean the difference between
your spacecraft safely and gently landing
on the surface of another planet
or creating yet another
crater on that surface.
Just a tiny fraction of a second,
and it can be the difference
between a mission’s life or death.
So we measure that signal time
very, very accurately here on Earth,
down to better than
one-billionth of a second.
But it has to be measured here on Earth.
There’s this great imbalance of scale
when it comes to deep space exploration.
Historically, we have been able to send
smallish things extremely far away,
thanks to very large things
here on our home planet.
As an example, this is the size
of a satellite dish
that we use to talk
to these spacecraft in deep space.
And the atomic clocks that we use
for navigation are also large.
The clocks and all of their
supporting hardware
can be up to the size of a refrigerator.
Now, if we even want to talk about
sending that capability into deep space,
that refrigerator needs to shrink down
into something that can fit
inside the produce drawer.
So why does this matter?
Well, let’s revisit one of our
intrepid explorers, Voyager 1.
Voyager 1 is just over
13 billion miles away right now.
As you know, it took
over 40 years to get there,
and it takes a signal traveling
at the speed of light over 40 hours
to get there and back again.
And here’s the thing
about these spacecraft:
they move really fast.
And Voyager 1 doesn’t stop and wait
for us to send directions from Earth.
Voyager 1 keeps moving.
In that 40 hours that we are waiting
to hear that echo signal
here on the Earth,
Voyager 1 has moved on
by about 1.5 million miles.
It’s 1.5 million miles further
into largely uncharted territory.
So it would be great
if we could measure that signal time
directly at the spacecraft.
But the miniaturization
of atomic clock technology is …
well, it’s difficult.
Not only does the clock technology
and all the supporting hardware
need to shrink down,
but you also need to make it work.
Space is an exceptionally
harsh environment,
and if one piece breaks
on this instrument,
it’s not like we can just send
a technician out to replace the piece
and continue on our way.
The journeys that these spacecraft take
can last months, years,
even decades.
And designing and building a precision
instrument that can support that
is as much an art as it is
a science and an engineering.
But there is good news: we are making
some amazing progress,
and we’re about to take
our very first baby steps
into a new age of atomic space clocks.
Soon we will be launching
an ion-based atomic clock
that is space-suitable.
And this clock has the potential
to completely flip the way we navigate.
This clock is so stable,
it measures time so well,
that if I put it right here
and I turned it on,
and I walked away,
I would have to come back
nine million years later
for that clock’s measurement
to be off by one second.
So what can we do with a clock like this?
Well, instead of doing
all of the spacecraft navigation
here on the Earth,
what if we let the spacecraft
navigate themselves?
Onboard autonomous navigation,
or a self-driving spacecraft, if you will,
is one of the top technologies needed
if we are going to survive
in deep space.
When we inevitably send humans
to Mars or even further,
we need to be navigating
that ship in real time,
not waiting for directions
to come from Earth.
And measuring that time wrong
by just a tiny fraction of a second
can mean the difference between
a mission’s life or death,
which is bad enough for a robotic mission,
but just think about the consequences
if there was a human crew on board.
But let’s assume that we can
get our astronauts
safely to the surface
of their destination.
Once they’re there, I imagine they’d like
a way to find their way around.
Well, with this clock technology,
we can now build
GPS-like navigation systems
at other planets and moons.
Imagine having GPS on the Moon or Mars.
Can you see an astronaut
standing on the surface of Mars
with Olympus Mons rising
in the background,
and she’s looking down
at her Google Maps Mars Edition
to see where she is
and to chart a course to get
where she needs to go?
Allow me to dream for a moment,
and let’s talk about something
far, far in the future,
when we are sending humans to places
much further away than Mars,
places where waiting for a signal
from the Earth in order to navigate
is just not realistic.
Imagine in this scenario
that we can have a constellation,
a network of communication satellites
scattered throughout deep space
broadcasting navigation signals,
and any spacecraft picking up that signal
can travel from destination
to destination to destination
with no direct tie to the Earth at all.
The ability to accurately
measure time in deep space
can forever change the way we navigate.
But it also has the potential
to give us some pretty cool science.
You see, that same signal
that we use for navigation
tells us something
about where it came from
and the journey that it took
as it traveled from antenna to antenna.
And that journey, that gives us data,
data to build better models,
better models of planetary atmospheres
throughout our solar system.
We can detect subsurface oceans
on far-off icy moons,
maybe even detect tiny ripples in space
due to relativistic gravity.
Onboard autonomous navigation
means we can support more spacecraft,
more sensors to explore the universe,
and it also frees up navigators –
people like me –
to work on finding the answers
to other questions.
And we still have
a lot of questions to answer.
We know such precious little
about this universe around us.
In recent years, we have discovered
nearly 3,000 planetary systems
outside of our own solar system,
and those systems are home
to almost 4,000 exoplanets.
To put that number in context for you:
when I was learning about planets
for the first time as a child,
there were nine,
or eight if you didn’t count Pluto.
But now there are 4,000.
It is estimated that dark matter
makes up about 96 percent of our universe,
and we don’t even know what it is.
All of the science returned
from all of our deep space
missions combined
is just this single drop of knowledge
in a vast ocean of questions.
And if we want to learn more,
to discover more, to understand more,
then we need to explore more.
The ability to accurately
keep time in deep space
will revolutionize the way
that we can explore this universe,
and it might just be one of the keys
to unlocking some of those secrets
that she holds so dear.
Thank you.
(Applause)