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How Atomic Clock Will Get Humans To Mars On Time



NASA navigators
are helping build a future where spacecraft could safely and autonomously fly themselves
to destinations like the Moon and Mars.

Navigators today
tell a spacecraft where to go by calculating its position from Earth and mission
the location data to space in a two-way relay system that can take anywhere
from minutes to hours to deliver directions. This method of navigation means that
No matter how missionary travels through the solar system, our spacecraft
are still tethered to the ground, waiting for commands from our planet.

That limitation
poses obvious problems for a future crewed mission to another planet. How can
astronauts navigate far from Earth if they don't have immediate control over
where are they going? And how can they accurately land on another planet when
There is a communication delay that affects how quickly they can adjust

NASA's Deep
Space Atomic Clock is a toaster-size device that aims to answer those questions.
It's the first GPS-like instrument small and stable enough to fly on a
spacecraft. The technology demonstration enables the spacecraft to know where
it is without needing to rely on that data from Earth. In late June, the clock
will launch on the SpaceX Falcon Heavy rocket into Earth's orbit for one year,
where it will test whether it can help spacecraft locate itself in space.

If the Deep
Space Atomic Clock is a year in space goes well, it could pave the way for a
future of one-way navigation in which astronauts are guided by a GPS-like
system over the surface of the Moon or can safely fly their own missions to
Mars and beyond.

"Everybody
spacecraft exploring deep space is steered by navigators here on Earth. Deep
Space Atomic Clock will change that by enabling onboard autonomous navigation,
or self-driving spacecraft, "said Jill Seubert, the deputy principal
investigator.

There's no GPS in Deep Space

Atomic clocks
in space aren't new. Every GPS device and smartphone determines its location via
atomic clocks on satellites orbiting Earth. The satellites send signals from
space, and the receiver triangulates your position by measuring how long it is
signals take to reach your GPS.

Currently,
spacecraft flying beyond Earth's orbit don't have a GPS to find their way
through space. Atomic clocks on GPS satellites aren't accurate enough to send
directions to spacecraft, when being off at even less than a second could mean
missing a planet by miles.

Instead, navigators
use giant antennas on Earth to send a signal to the spacecraft, which bounces
it back to Earth. Extremely precise clocks on the ground measure how long it is
takes the signal to make this two-way journey. The amount of time tells them
how far away the spacecraft is and how fast it is going. Only then can
navigators send directions to the spacecraft, count it where to go.

"It's the
same exact concept as an echo, "said Seubert." If I'm standing in front of a
mountain and I shout, the longer it takes for the echo to come back to me, the
farther away the mountain is. "

Two-way navigation
means that no matter how deep into space a mission goes, it still has to wait
for a signal carrying commands to cross the fixed distances between planets. it's
a process made famous by Mars landings like Curiosity, when the world waited 1

4
long minutes with mission control for the rover to send the message that it
landed safely. The delay is an average wait time
Mars is in their orbits, it can take anywhere from 4 to 20 minutes for a
one-way signal to travel between planets.

It's a slow,
laborious way to navigate in deep space, one that ties up the giant antennas or
NASA's Deep
Space Network
like a busy phone line. During this exchange, a spacecraft
flying at tens of thousands of miles per hour could be in an entirely different

A Better Way to Navigate

An atomic clock
Small enough to fly on a mission but precise enough to give accurate directions
could eliminate the need for this two-way system. Future navigators would send
a signal from Earth to a spacecraft. Like its Earthly cousins, the Deep Space Atomic
Clock onboard would measure the amount of time it took that signal to reach it.
The spacecraft could then calculate its own position and trajectory,
essentially giving itself directions.

"Having
a clock onboard would enable onboard radio navigation and, when combined with
optical navigation, make for more accurate and safe way for astronauts
able to navigate themselves, "said Deep Space Atomic Clock Principal
Investigator Todd Ely.

This one-way navigation
has applications for Mars and beyond. DSN antennas would be able to communicate
with multiple missions at a time by broadcasting one signal into space. The new
Technology can improve the accuracy of GPS on Earth. And multiple spacecraft
With Deep Space Atomic Clocks could be orbit Mars, creating a GPS-like network
that would give directions to robots and humans on the surface.

"The Deep
Space Atomic Clock will have the ability to aid in navigation, not just locally
but in other planets as well. One way to think of it as if we had GPS at other
planets, "said Eric Burt, the ion clock development lead.

Burt and fellow
JPL clock physicists Robert Tjoelker and John Prestage created a mercury ion
clock, which maintains its stability in space in the same way as
refrigerator-size atomic clocks on Earth. In lab tests, the Deep Space Atomic
Clock proved to be 50 times more accurate than GPS clocks. That's an error of 1
second every 10 million years.

The clock's demonstration
a space will determine whether it can remain stable in orbit. If it does, a
Deep Space Atomic Clock could fly on a mission as early as the 2030s. The first
step toward self-driving spacecraft that could one day carry humans to other
worlds

The Deep Space
Atomic Clock is hosted on a spacecraft provided by General Atomics
Electromagnetic Systems of Englewood, Colorado. It is sponsored by the Technology
Demonstration Mission Program
within NASA's Space Technology
Mission Directorate and the Space
Communications and Navigation program
within NASA's Human
Exploration and Operations Mission Directorate. JPL manages the project

Here's five
things to know about NASA's Deep Space Atomic Clock:

https://www.nasa.gov/feature/jpl/five-things-to-know-about-nasas-deep-space-atomic-clock

Learn about the
Other NASA missions on the SpaceX Falcon Heavy launch that's carrying the Deep
Space Atomic Clock

https://www.nasa.gov/spacex

News Media Contact

Arielle Samuelson
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-0307
arielle.a.samuelson@jpl.nasa.gov

2019-116


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