Sky and Telescope - March 2018 - 84

FOCAL POINT by Jane Green

A Brief Eternity

It seems ages since we launched the Voyagers. But in the grand scheme, it's but a moment ago.

electronics and navigational knowledge, could they build machines that
could last in space for at least 10 years?
Would planet-aided gravity assists really
reduce travel time? Could the spacecraft
survive crossing the asteroid belt and
Jupiter's intense radiation ﬁeld? Could
we receive the data transmitted by these
spacecraft across billions of kilometers
of space?

Where in that flow of Time
and Space will humankind's continuum lie?
To their everlasting credit, the scientists and engineers ﬁgured it out. In the
early 1970s they dispatched two lesselaborate probes, Pioneers 10 and 11, as
scouts to reconnoiter the way. Learning
vital lessons from them, NASA personnel hurriedly redesigned both Voyagers
and fortiﬁed the Deep Space Network to
enable the all-important transfer of data.
The Voyagers pushed the very limits
of our science and engineering. But we
prevailed, and in a comparative tick of

Artist's concept of Voyager 1 entering interstellar space

M A RCH 2 018 * SK Y & TELESCOPE

cosmic time. In the coming decades,
that tick generated wide-spreading
reverberations across the solar system:
roving on Mars, orbiting Jupiter and
Saturn, landing on Titan, ﬂying by
Pluto, and landing on a comet, to share
but a few.
Now, as Voyager 2 punches the
heliosheath to join Voyager 1 in interstellar space, these hoary spacecraft are
nearing the end of their scientiﬁc lifetimes. And so, alas, are their creators,
who were at the height of their careers
when the Voyagers launched.
Aerospace engineer Gary Flandro,
who calculated the rare planetary alignment underlying the entire adventure, is
now reaching his mature years. Voyager
chief scientist Ed Stone and imagingteam head Brad Smith - the same.
James Van Allen, Carl Sagan, and former Jet Propulsion Laboratory director
Bruce Murray are sadly no longer with
us, their energies extinguished even as
their contributions continue to inﬂuence the scientiﬁc continuum.
We humans wish we could anchor
ourselves for a longer stay, but each of
us is merely a drop in Thoreau's ceaseless stream, as ephemeral as a drop of
dew on a sunny morning. What will
the next drop or ripple produce? Who
will contribute and for how long? What
will we learn about the cosmos? Where
in that ﬂow of Time and Space will
humankind's continuum lie?
Watching The Planets, I realized more
poignantly than ever before how everything we have ever known, or ever will
know, is but a single breath in the life
of the grandest continuum of all: the
universe itself.
¢ JANE GREEN, a Fellow of the Royal
Astronomical Society, is an author,
lecturer, and broadcaster from Sussex,
England.

N ASA / JPL- CA LTECH

INSPIRED BY THE VOYAGER mission's 40th anniversary last summer, I
recently watched a 1999 BBC series, The
Planets. In particular I savored Episode
Three, which focused on the giant
planets and the Voyager spacecraft. The
episode recalled those heady days in the
mid-1960s when NASA's deep thinkers envisioned dispatching probes on a
"Grand Tour" of all the outer planets.
I was quickly reminded how space
exploration then remained in its
infancy. In those days, unmanned
craft had ventured no farther than to
Venus and Mars. For the Grand Tour to
be successful, scientists would have to
overcome many mission "impossibles."
But I was even more struck by how
the series had captured brevity. Henry
Thoreau's maxim, "Time is but the
stream I go a-ﬁshing in," came to mind.
Despite being our longest-lived spacecraft, Voyagers 1 and 2 constitute but a
ripple in the endless current of Time.
In the decade-plus that saw the
canceling of the Grand Tour program
and the launching of its replacement,
the Voyagers, in 1977, scientists shared
their fears: Constrained by limited

Sky and Telescope - March 2018

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