STAR STRUCK - The Voyager Missions:
Taking Us on a Grand Tour of the Planets


Written by Phil Konstantin and Robyn Mellon
Photos courtesy of NASA




On May 5, 1989, the United States resumed its interplanetary
missions with the launch of the space shuttle Atlantis, whose crew
then set free the $550 million Magellan spacecraft for its voyage
to Venus. Magellan will reach Earth's nearest planetary neighbor
on August 10, 1990, for an eight-month orbital picture-taking sesson 
and sophisticated radar "look" at Venus.

But Americans won't have to wait until next year to learn more
about another of our planetary sisters. This August 5, NASA's Voyager II, 
which was launched in 1977, has a date with Neptune and
will pass within 2,700 miles of that planet. At that time, Neptune
will be approximately 2.8 billion miles from Earth, but the photographs 
are expected to be dramatically revealing.

Back in 1977, Voyagers I and II were launched on unmanned rockets and 
on different trajectories so that each could maximize its grand
tour of our solar system. Voyager I flew by Jupiter and Saturn before
heading out of our galaxy. Voyager II also approached those two planets, 
but at a different angle, as well as Uranus before heading for its
rendezvous with Neptune this summer.

California facilities have been the backbone of the Voyager missions, 
with the Jet Propulsion Laboratory (JPL) in Pasadena controlling each 
mission, and the Goldstone Radiotelescope in the Mojave Desert transmitting 
instructions and receiving the gathered observations and data. Both 
spacecraft contain 11 sophisticated instrument packages that allow them 
to carry out investigative experiments in many diverse fields of study 
such as plasma waves, ultraviolet spectroscopy and photopolarimetry.

It took over seven years and the combined efforts of hundreds of
scientists and technicians to develop the sophisticated and complex on-board 
systems. The computer system (actually two independent computers) that 
controls and guides the spacecraft is so well designed that it is capable
of making its own decisions when Earth-based instructions would
take too long to cross the vast distances involved.

Each Voyager has two video cameras which have been transmitting
the images that have captivated the public's imagination. In fact, it
was Voyager I that took the famous (and first!) photo of the moon and
the Earth together from outer space.

Through the two spacecraft, numerous discoveries have been made. Jupiter 
alone provided a veritable treasure trove of new information in 1979. It 
was found to have a previously unknown ring system over 3,600 miles wide!
Before Voyager's trip, only Saturn's and Uranus' rings were discernable to 
astronomers. Also, by piecing together a series of photos of
the mysterious Red Spot of Jupiter, scientists were able to make a
movie of it, thus revealing the Spot's motion. This 300-year-old
storm, which is as large as several Earths, now viewed "in motion"
has helped experts understand more about the violent storms in
Jupiter's upper atmosphere. Also, enormous magnetic and radiation
fields have been discovered by the Voyagers' sensitive instruments,
some of which are active in the audio ranges — Jupiter is actually
making its own "music"!

The two spacecraft provided numerous close-ups of the major
moons of Jupiter, which has 16 (although there is evidence suggesting there 
are more). Ganymeade, the largest of Jupiter's moons and larger than the 
planet Mercury, was dotted with vast mountain ranges and valleys deeper 
than our Grand Canyon. Europa looked like a billiard ball with
painted-on cracks. lo proved to be loaded with active volcanos — the
only body in the solar system, other than Earth, discovered so far
to have volcanic activity. lo, also the nearest of the major moons to
Jupiter, was found to be losing about a ton of its surface every day
due to the strength of the electromagnetic and radiation fields of
its "parent" planet.

Almost two years later, both Voyagers visited Saturn as they moved
farther away from Earth. Saturn, with its rings visible to even the
ancient astronomers, has fascinated mankind for centuries. And
they were no disappointment to the scientists involved in the Voyager missions.

Previously, it was thought that Saturn's rings were several separate 
bands possibly comprised of planetary debris. As the cameras 
sent back closer and closer images of the rings, however, and as other
instrument packages probed their energy spectrums, the "rings" dissolved 
into one enormous layer of fist-sized particles. Scientists now
believe that Saturn's moons are continually reshaping the "rings"
by their gravitational fields, which cause different density levels that
give the "rings" their separated appearance.

Saturn's largest moon is Titan and is the only moon with an
appreciable atmosphere. This methane-based environment seems
to have many of the same chemical components that experts feel
were present on Earth when life began developing here. However,
due to both the extreme cold and weak sunlight reaching Titan, the
chance of life as we know it developing there (a photosynthetic-based 
organism) is highly unlikely.

Early in 1986, Voyager II flew by Uranus, revealing even more 
information. Several new rings were discovered (nine were known 
previously) as well as 10 new smaller moons, bringing the total to 15.
Uranus has proved to be highly unusual in other ways, too. The
angle at which the planet rotates is almost horizontal (compared to
Earth's nearly verticle rotation), and its magnetic field was found
to be 60° different than its rotation and offset from the center as
well, making it the most unusual planet in the solar system so far.
While much smaller than Jupiter, it seems to be much denser, and it
has a thin atmosphere which shines with an ultraviolet glow.

Larry Soderblom, a member of the Voyager Imaging Science team,
describes Uranus' innermost major moon, Miranda, as "... the most
exotic body in the solar system. It's as if geological terrains were
stolen from throughout the solar system and assembled in one object." 
Miranda has mountains with cliffs 16 miles high! If you were to
drop a rock off the top of one of these cliffs, it would take nine
minutes for it to hit the ground. Viewing the photos of Miranda,
you can see it is truly an extraordinary satellite.

The Voyager II has traveled tremendously vast distances, and very
large numbers are needed to represent them. And yet, some parts of
the Voyager mission will be accomplished on an almost microscopic scale.

Voyager broadcasts its signal back to Earth at 22 watts of power,
compared to a normal AM radio station which broadcasts at 5,000
watts. But, due to the enormous distance that the radio wave will
have to travel from Neptune, it will reach us here on Earth as a
faint signal of less than one billionth of a millionth of a watt
(.000,000,000,000,001).

JPL scientists have had to redesign Voyager II's programming
(from Earth) to take full advantage of its limited computer 
data-storage system and its now-feeble broadcast capabilities. Because the
available sunlight on Neptune is only one-fourth that of Uranus
(which wasn't that much), new programming had to be designed with
instructions for longer exposures. This additional exposure time
would normally mean fewer photos could be taken, so engineers and
programmers also redesigned the storage/retrieval/broadcast systems 
in such a way that, while less data is sent to Earth, we will see
the same results as the earlier photos. This will allow Voyager to
take and transmit more photos than it would have with the previous 
programming. So, in many ways, it is a better spacecraft now
than it was when it was launched over a decade ago. There have been
some mechanical failures, but the craft has survived the extreme cold
and innumerable hazards of deep space remarkably well.

As Voyager II swoops down toward Neptune's surface, some scientists 
expect to find frozen water at -300°F, which would make it as hard 
as steel. Others speculate Voyager will discover an atmosphere of 
methane and other gases, but only time will tell. Neptune's largest 
moon, Triton, should also provide many new wonders for modern 
civilization to puzzle over.

Voyagers I and II have sent back to Earth an enormous array of photo 
images and scientific data, both answering and generating hundreds 
of questions about the many properties of our solar system. If that 
achievement were not grand enough by itself, consider also that they 
were sending information about Earth and mankind out to the stars. 
Attached to each Voyager craft is a record, made of gold to withstand 
the severe radiation and other hazards of deep space, containing 116 
digitized photographs of Earth scenes and 87 1/2 minutes of music. 
The music ranges from the songs of the humpback whales to Senegal 
percussion to Peruvian pan-pipes to Bach, Mozart and even Chuck Berry.

Astronomers Carl Sagan and Timothy Ferris were two of the experts 
who decided what items (photos, music, etc.) would be selected as 
our introduction to any intelligent extraterrestrials who might find 
one of the Voyagers. Timothy Ferris told me, "Earth may be one of many 
worlds, but it also contains many worlds." Thus a wide variety of 
sights and sounds were sent into space to tell whoever or whatever is 
out there who we are, where we are and what we were like in our 21st 
century.

Although it may take millions of years before any "E.T.s" find the 
Voyagers and their records of us, we will continue to reap the benefits 
of the knowledge our spacecraft send us, enabling us to understand 
our physical universe that much better. However, should "aliens" happen 
across our craft, and assuming they will be successful in deciphering 
its codes, what will they think of Earth? And what kind of message 
would they send us back? Perhaps, "Send more Chuck Berry!" 



June 1989