Twenty-some hours later, after an epic inter-
stellar journey, this rippling wave will reach
Earth. By the time the ping gets here, its strength
has dramatically diminished—down to about
0.1 billion-billionth of a watt. The signal’s trip
across our solar system is over, but its voyage has
just begun. The challenge now is greater than
crossing our corner of the galaxy; it is to hear and
make sense of the information within the mes-
sage, the most distant whisper of our own creation.
Capturing this tiny sliver of nearly nothing takes
highly trained and technical ears. Several of them.
For Voyagers I and II, they take the shape of three
21-story-tall dishes—each with a diameter of 230
feet and a heft of nearly 3,000 tons—positioned
evenly across the globe. Constructed specifically
for deep-space listening, they turn skyward, ready
to receive the probes’ daily status reports.
One of the dishes, dubbed DSS-14, looms over
a lonely patch of Southern California’s Mojave
Desert, approximately 60 miles from the near-
est highway. It nestles in a small valley, between
low craggy mountains—the remnants of long-
dead volcanoes. To get anywhere near it, you pass
through two layers of security gates at Fort Irwin
military base. An extensive briefing introduces
you to the neighbors, which include unexploded
ordnance, three species of rattlesnake, camel spi-
ders, scorpions, and packs of feral donkeys, which
have a yen to gallop up and bite a chunk out of an
unsuspecting visitor just for the hell of it.
DSS-14 appears around a bend in the road,
standing like a sentinel, casting a long, warped
shadow on the bright desert floor. Overhead, tur-
key vultures ride the wind by its rim. All is silent,apart from the gusts and the crunch, crunch, crunch
of footsteps on the sand. But there is another sound
too, somewhere far beyond all human hearing,
mixed in with the hum of the rest of the universe.
The Fort Irwin-based complex—which NASA’s
Jet Propulsion Laboratory named Goldstone after
a long-abandoned mining town—houses about a
dozen smaller dishes too, the first of which went
online in 1958. (A decommissioned Apollo an-
tenna still haunts the scrubby ground.) There are
similar fields in the Australian bush, outside Can-
berra, and in Robledo de Chavela, near Madrid,
which were established in 1965. DSS-14 and its
international copies went up in the 1960s and
’70s. Since the Mercury IV mission in 1964, these
three arrays have linked us with every craft we’ve
sent above low Earth orbit.
The positioning of the gargantuan ears is key.
The three sites are spaced by longitude (120 de-
grees apart for full 360 coverage) and united in
proximity. Proximity to approximately nothing.
Isolation prevents the high- powered space signals
and earthly communications—like chatter from air-
traffic control— from interfering with one another.
The three facilities and their antennas comprise
the Deep Space Network, a program run out of JPL
headquarters near Pasadena, California. The sys-
tem constantly listens for pings from and sends
commands to about 40 probes, spacecraft, satel-
lites, and rovers. Some are as close as the moon.
Others are way afield, like Juno whizzing around
Jupiter, and New Horizons, which in mid-2015
buzzed Pluto. And, of course, Voyagers I and II,
both of which launched in 1977 to study Jupiter
and Saturn. They’re the oldest and farthest-flung
missions NASA or JPL—or anyone—oversees.
Downloads from the two Voyagers deliver in-
sights about the rarefied world of interstellar
space: observations about low-energy charged
particles, magnetic fields, and the plasma that ac-
counts for the majority of our universe. The data
rides the waveform as strings of ones and zeros, at
a rate of 160 bits per second (that’s one-fifteenth
the info of the slowest fax-machine connection).
Studying it has helped physicists do things like
outline the contours of the heliosphere—the mag-
netic bubble that surrounds our solar system—and
determine the speed of the sun’s wind.
At a time when NASA is experimenting with
faster, denser light-based communication sys-
tems, it’s easy to assume radio will fade away. Yet
one will never eclipse the other. As the Voyager
probes push the technology to its outer limits, they
provide a reminder of all the unique insights radio
waves collect along their flight path. The noise theLook up. Somewhere beyond
our solar system, where it’s
well below zero, pitch-dark,
and the next-nearest star
is a 400-century ride away,
an electrical charge sparks
a radio signal. The blip is
faint, some 22 watts, no
more power than a typical
refrigerator bulb needs. The
source is Voyager I. Its
12-foot antenna is calling
home from the blackness.POPSCI.COM -- WINTER 2019 PG -- 68