54 AUSTRALIAN AVIATION
F
ar away, 13 billion miles from
Earth, there is a tiny man-made
spacecraft drifting away from
Earth and everything that we
know. This spacecraft, Voyager 1, has
travelled further than anything else
humans have made, learning about the
deepest parts of our solar system and
now beyond. It is our first foray into
interstellar space, with the spacecraft
having left the comfort of our solar
system.
We sent Voyager 1 off on its
journey 40 years ago for an important
mission. It visited and studied the
biggest planets of our solar system and
their moons for the first time. Then,
the spacecraft was to travel further
and faster than any other human
spacecraft.
So far in fact that the Voyager
team collaborated with Carl Sagan to
include a special disk that described
mankind in case intelligent life was to
stumble across the spacecraft in outer
space – we were venturing into the
unknown and didn’t know who was
going to join us. The disk is made of
gold, and it includes images of a man
and a woman, the atomic structure
of water and carbon, and a pictorial
description of where we are in the
solar system. The disk is also a record
which includes samples of languages
from around the world and some
of the most memorable music from
across history.
Reaching true space means that
Voyager 1 is our first opportunity to
discover and learn about the true
space environment without our Sun
affecting the results. We’ve never
had a chance to look at what the
emptiness of space looks like without
the Sun’s magnetic field, winds and
other solar events playing a role in the
environment.
The mission of Voyager 1 does not
stop with reaching interstellar status,
there is a wealth of knowledge and
scientific discoveries to come from the
next leg of the mission in the vastness
of space.
We have been in communication
with it the entire journey, using its
radio antennae and a set of small
devices called thrusters to orient itself.
These thrusters fire in tiny pulses, or
‘puffs’, lasting mere milliseconds, to
subtly rotate the spacecraft so that its
antenna points at our planet. Since
2014, NASA scientists have faced
the challenge that these thrusters
have started to degrade and that we
faced losing communications with
Voyager 1.
We were going to lose contact witha very important human relic.
But the Voyager team at NASA
was able to successfully fire up the
spacecraft’s backup thrusters that have
been unused, dormant and collecting
‘space dust’ since 1980.
The Voyager team assembled
a group of propulsion experts at
NASA’s Jet Propulsion Laboratory
(JPL), Pasadena, California to study
the problem. Chris Jones, Robert
Shotwell, Carl Guernsey and Todd
Barber analysed options and predicted
how the spacecraft would respond in
different scenarios. They agreed on an
unusual solution: Try giving the job
of orientation to a set of thrusters that
had been asleep for 37 years.
“With these thrusters that are still
functional after 37 years without use,
we will be able to extend the life of the
Voyager 1 spacecraft by two to three
years,” said Suzanne Dodd, project
manager for Voyager at JPL.“The Voyager flight team dug
up decades-old data and examined
the software that was coded in an
outdated assembler language, to make
sure we could safely test the thrusters,”
said JPL’s Chris Jones.
The backup thrusters are identical
in size and functionality to the
currently degraded ones, they just
had a different purpose and are in a
different place on the spacecraft. The
backup thrusters were originally used
to control the spacecraft’s trajectory
as it flew by Jupiter, Saturn, and
important moons of each. They were
needed to accurately fly by and point
the spacecraft’s instruments at a
smorgasbord of targets, with engineers
using them to control the trajectory of
the spacecraft.
But because Voyager 1’s last
planetary encounter was Saturn, the
Voyager team hadn’t needed to use
the thrusters since November 8 1980.
Back then, the thrusters were used in
a more continuous firing mode; they
had never been used in the brief bursts
necessary to orient the spacecraft.
On Tuesday, November 28 2017,
Voyager engineers fired up the
four backup thrusters for the first
time in 37 years and tested their
ability to orient the spacecraft using
10-millisecond pulses. The team
waited eagerly as the test results
travelled through space, taking 19
hours and 35 minutes to reach an
antenna in Goldstone, California
that is part of NASA’s Deep Space
Network.
Lo and behold, on Wednesday,
November 29, they learned the
thrusters had worked perfectly – and
just as well as the original orientation
control thrusters.
“The Voyager team got more
excited each time with each milestone
in the thruster test. The mood wasVoyager 1’s gold disc describes
mankind (and features
music recording) in case it is
discovered by intelligent life in a
distant future.JPL/NASAVoyager 1 is launched atop
its Titan/Centaur-6 launch
vehicle from the Kennedy
Space Center, Florida on
September 5 1977.NASA‘We sent
Voyager 1 off
on its journey
40 years ago.’
Voyager