The Interstellar Age (4 page)

The missions that have come since
Voyager
, such as the Jupiter orbiter
Galileo
and the Saturn orbiter
Cassini
, have revealed those worlds and their rings and moons anew, with more powerful senses, at higher resolution, and over extended periods of time. The time spent by these spacecraft in the Jupiter and Saturn systems has allowed us, for the first time, to see those worlds
in motion
, active and
evolving—by nature a difficult task for a flyby mission like
Voyager
. These worlds are dynamic, a fact easy to forget when all you get is a short movie of the approach or a few still snapshots of a place apparently frozen in time. The more extensive time-lapse movies that we now have of these worlds from orbiting spacecraft have brought them to life. We can close our eyes and see the colossal storms raging on Jupiter as they morph into reality. Closer to home, rovers like
Spirit
,
Opportunity
, and
Curiosity
and the orbiters high above them are helping us unlock the secrets of ancient, Earthlike Mars, while orbiters circle and map Mercury, Venus, the moon, asteroids, and comets (as well as our own planet!) to help put the story of our origins together. Space exploration used to be dominated by the United States and the USSR, but now it has expanded into a truly global enterprise with significant contributions from Europe, Canada, Japan, China, India, and others. We are in the midst of a golden age of the exploration of space by people across our planet. About thirty active robotic missions are out there plying the ocean of space on our behalf, poised to make some of the most profound discoveries of all time. These missions let us vicariously see and hear and taste and touch the dirt and wind and ice of other worlds, following in the footsteps of the most grand and far-flung of them all, the
Voyagers.

VOYAGER
AND ME

We first crossed paths professionally, me and
Voyager
, when I was a college student in the 1980s, searching for a way to make a career out of my childhood dreams of astronomy and space. I applied for and—to my amazement—was accepted by both MIT and Caltech
to study astronomy (as my friend Bill Nye would joke about his own acceptance by his beloved Cornell, “There must have been a clerical error of some kind”). Against the wishes of family and friends (most of whom had never heard of the place), I chose Caltech, partly because I needed to spread my wings and explore firsthand the things I was hearing about this strange new world called California, and partly because I knew that Caltech was intimately connected to JPL, the epicenter of planetary exploration in the United States.

The smell of the olive trees the first day I walked onto the campus of the California Institute of Technology in the fall of 1983 was the smell of
newness
and
change
. It turned out I had traded an insular, small town and small-state family life for an insular, small dorm and small-campus nerdy life. I had never been so challenged academically (the professors are notoriously merciless there, since many have either invented the field they are teaching and written the textbooks themselves, or they are busily distracted by, and actively working on, the cutting edge of whatever was being taught). I failed Math 1 and so they put me and a small group of other struggling students in a “special” math class called Math 0.9—just slightly less than Math 1.

One day, I saw a small ad posted on one of the bulletin boards that I would frequently peruse on my job search around campus (remember: no Internet!), looking for a student to help analyze some ultraviolet measurements of Jupiter.

That sounds like astronomy, I thought to myself. Why not check it out?

The ad was posted by Mark Allen, a Caltech/JPL research faculty member. He grilled me in his strong New York accent about my background and previous experience during the interview. Despite
consistently hearing myself answer “no,” “none,” or “I don’t know what that means” to his questions, I felt good about him. Up to that point, my life’s work experience had consisted of picking car parts in my father’s junkyard, plotting chemical assay results in a metal refinery lab run by the father of one of my high school friends, and taking out the trash along with other odd jobs in a mall clothing store for large women. Incredibly, Mark offered me the job anyway. Maybe it was the plotting experience (that’s mostly what the work he needed turned out to be about). Or maybe it was a clerical error. Whatever the reason, it changed my life.

Working every day in South Mudd, Caltech’s building that houses its Division of Geological and Planetary Sciences, was an absolute delight for a young space junkie. There were posters and murals and space paraphernalia all over the place, and the halls and offices were lousy with famous (to me, at least) faculty, staff, grad students, and postdocs who were working on missions like
Voyager
and
Viking.
I would faithfully print and analyze plots for Mark, but while waiting for my plots to print or for my computer job to process (I was low on the priority totem pole), I would wander the halls and daydream about the far-off places the people around me were exploring. It was
much
more fun than classes and homework and exams, and so my grades continued to suffer. I kept my head
just
above the waterline and was lucky not to “flame out” like some of my other fellow Math 0.9 friends—but it was close.

I grew up thinking that astronomers studied everything: stars, galaxies, planets, moons, whatever. It’s all in space, right? But it turns out they’re compartmentalized, balkanized, self-segregated by distance, and then by energy: solar system, galactic, extragalactic, cosmologic, and then from microwave/infrared (low energy) to
UV and gamma rays (high energy) within each of those realms. At a party with these people, you would not want to confuse a high-energy extragalactic cosmologist with a near-Earth asteroid hunter, believe me! But I also learned that there are
different
kinds of
solar system
researchers out there who are
not astronomers
but who are geologists, or chemists, or physicists, or meteorologists
.
They happen to study nearby solar system objects (or maybe meteorite samples of them) rather than astronomical objects, and at Caltech at the time, most of them didn’t use telescopes but instead used images and other data taken by robotic space missions to do their science. Many of them were designing or flying their own cameras and other instruments in space. I had found my tribe! It turned out that the particular flavor of astronomy, space mission, and hands-on engineering experience that I was looking for had a name: planetary science. And at Caltech, I could actually get a
degree
in planetary science! I switched my major.

The halls of South Mudd are where I first met G. Edward Danielson Jr., or just “Ed,” as he liked to be called. A cheerful, big, sometimes shy gentleman, Ed was a member of the Caltech/JPL technical staff who specialized in designing, building, and operating cameras in space, for missions like
Mariners 6
,
7
, and
10
,
Viking
, and the Hubble Space Telescope. He was also a member of
Voyager
’s imaging team and spent a lot of time looking at and analyzing the incredible images sent back from Jupiter and Saturn just a few years earlier. I would run into Ed at the printer, where I would often have to sheepishly hand him back his printout—which I was holding and admiring—of some amazing
Voyager
image of Saturn or
Viking
image from Mars that had printed out before my plot. He started getting into the habit of giving them back to me, saying something
like “Oh, that’s the wrong one” or “Oh, the contrast is wrong in this one” or some such. But I was onto him—he knew how much I treasured each of those printouts, even the underexposed or oversaturated ones. It was a fun little game, and soon I felt comfortable enough to talk with him about what he was doing. That’s how Ed turned me on to a new and growing field called
image processing
.

While I was too inexperienced and naïve to know it at the time, I later came to realize that at his core Ed was really a tinkerer, more of an engineer and a
science enabler
than a pure scientist. He cared about helping to make science discoveries from the
Voyager
images, for sure, but he cared more about how the cameras were working
,
so that he could help make sure that they were taking the best possible photos that could be taken. For a flyby mission, you get only one shot—so you want to make sure the cameras are pointed in the right direction, and you have to make sure that the exposures are at the right level. Point toward empty space or set the exposure time too short: all-black image. Point in the right direction but take too long an exposure: all-white image, or at least lots of uncorrectable saturation. Accidentally point at the sun: fry the camera. The stakes were high, and so guys like Ed who were responsible for getting it right
had to get it right.
I had never encountered that kind of pressure among scientists or engineers before.

As Mark Allen’s project was finishing up, it turned out Ed Danielson was looking for some help processing images from the
Voyager 2
flyby of Saturn so that they could understand how the camera was changing over time, as it got older and farther away from the sun, to help the team prepare to
get it right
for the flyby of Uranus the following year. I will never know if Ed really needed a student to do that work or if he made the job up for me to keep me around. I
was delighted and jumped at the chance. It was like hitching another ride on the
Voyagers
.

Back in the day, image processing was done on
the
(single) computer used by each faculty group (it was, conveniently, located near
the
printer), and it was a pretty competitive ordeal to get time to run programs and analyze images. As an undergraduate working among a group of active and productive faculty, postdocs, and grad students, I was the last guy in the queue, and so to get time on the image-processing computer, I often had to come in to work during the graveyard shift, catching Ed at either the end of his workday or the beginning of the next. Those nights were ghostly quiet, with just the hum of the nearby computer fans or the distant whine of the janitor’s vacuum cleaner to keep me company. As I gazed upon image after image from
Voyager
’s close flyby of Saturn, my thoughts would sometimes wander. I’d imagine myself as a passenger on that ship, imagine the gasps my fellow travelers and I would make as we passed through the flat disk of Saturn’s glorious, gossamer rings. And flat indeed! Although the main rings span the width of more than twenty Earths, they are only about thirty feet thick! If Saturn’s rings were a DVD, that DVD would only be about ten
atoms
thick, or about 100,000 times thinner than a human hair. The cool thing was that no one knew exactly why they were so thin, but I figured the answer was probably right there among the images I was working with.

I used to tell my friends that I was working at the edge of space. That’s because my job was to pore over the
Voyager
images and, literally, find the edges of space—the pixels where the planet ended and space began. Many of
Voyager
’s images, especially the ones taken when the spacecraft was really close to Saturn, have parts of the
planet’s edge (called the
limb
) or the rings’ edges gracefully arcing through the photos. I would identify those parts of the image, and using some special software that Ed and others on the
Voyager
team had devised, I would try to fit a smooth mathematical curve to those edges. The curve was an estimate of how the edge of the planet
should
be curved when viewed from
Voyager
at the time and place that each photo was taken, if
Voyager
were precisely where it was predicted to be and if the camera were behaving exactly as predicted. But the spacecraft was
never
precisely where it was predicted to be, because of the slight push and pull of the gravity of Saturn and its moons, and the cameras
never
behaved exactly as predicted, because of the strange ways that the cold temperatures or the intense radiation from the magnetic fields close to Saturn itself could introduce artifacts into
Voyager
’s old-style vidicon camera system (which, unlike a modern digital image detector, would capture images using a cathode ray tube and electron scanning gun, like in old TV sets). So my lovely curves would never fit perfectly the first time, and I’d have to go back and fine-tune them a little to get a better curve to fit the limb, nudging the inferred position of the spacecraft a little, or tweaking some aspect of the lens distortion.

It was interesting work but it was painstakingly slow. Just to
display
an 800 x 800–pixel
Voyager
image on Ed’s screen could sometimes take thirty seconds to a minute (depending on who else was using the computer’s processor), as the pixels slowly scrolled down onto the screen like thick paint dripping down a wall. To run the limb-fitting program, I had to submit the program as a “job” to the computer, and that job could be in a queue with other jobs for hours. I had to give my job a priority: low numbers like 1 to 5 were highest priority, and high numbers like 15 to 20 were lowest priority. I could
see who else was running jobs on the computer—many professors and students would submit big complex calculation jobs in the 15-to-20 range at the end of the day so they could run overnight. If I was there at night working alone, I’d often give my jobs high priorities, a 3 to 5 maybe, so they’d run quicker (maybe a half hour per limb fit, if I was lucky). A couple of times I messed up, though, leaving my high-priority job caught in some infinite mathematical loop and still accidentally running during normal daytime hours. I’d get some dirty looks in the halls when I returned later in the day. I suspect Ed got chewed out over my screwups more than once.