P-1 day: Navigating Pluto


Where? 1.2 million kilometers to go at 1.2 million kilometers per day, as of 7:49 AM this morning of July 13th in Baltimore, almost exactly one day before the blessed event. Pluto is about 400 pixels across in the LORRI camera, but to the naked eye it’s still only 23 percent the size of the full moon. Over the next 24 hours that image will blow up, far overflowing the boundaries of LORRI, requiring that mosaics be done to cover more than the camera’s tiny footprint on the surface.

Where to? Pluto! At 7:48:45 in Como, North Carolina, 11:48:45 GMT, plus or minus 36 seconds or so.

Where from? The over-crowded planet that we all adore.

Today is the Navigators’ well-deserved day off while the rest of the project works its collective fingers to the bone. Our last delivery, Crit 37, is delivered. From here on, the laws of physics solely guide the spacecraft and nothing more can be done except to enjoy the ride. The pressure is off and decompression begins.

For your entertainment, here’s an excerpt from The Darkest Side of Saturn. It’s a few days before the Voyager (Nomad in the story) encounter with Neptune. Harris Mitchel does a radio interview with an obnoxious host about the upcoming event. As for the Pluto flyby, the Neptune event also has dual occultations explained in the story, with the main difference that Neptune’s gravity flings Nomad through occultations with the planet and its big moon Triton, while for the much weaker gravity of Pluto, the flinging is more like a very gentle, almost unnoticeable bending of the trajectory.


Navigating Neptune

The next morning as Harris drove to work along the surface streets between San Marino and the Lab, he tuned his radio to K-N-E-E, a low-powered downtown AM station. Reception was poor and he had to strain to hear through the static. Finally he found what he was listening for.

It was sobering to hear the host, James Conland, announce, “In the next segment, we’re talking to Harris Mitchel who wrote an article in last Sunday’s Times about spaceship Nomad’s encounter with Neptune. That’s up in fifteen minutes.”

Me! Fifteen minutes! And he was running late. He jogged left off New York Drive onto North Lake Avenue, then immediately right on Woodbury Road and drove as fast as he dared.

“. . . and the segment after that, we’ll take calls on how to bash liberals with the facts. Just remember, my friends, James Conland is your Truth Meister, believe me. The truth is putty in my hands!”

Uh-oh. A warning claxon went off in Harris’s brain. A right-wing whacko. What have I gotten into?

Woodbury Road became Oak Grove Drive, and as he sped into the final curve leading toward the entrance of ATL Harris saw, off to his right across the arroyo, the large motley collection of buildings that constituted the Lab growing out of the foothills of the San Gabriel mountains. Three minutes later he drove past the sign that announced “NASA Advanced Technology Laboratory.” He turned left just before the guard island and zipped along Mesa Road to the west parking lot.

Vacant parking spaces were filling rapidly, even at 7:20 in the morning. The impending encounter attracted a lot of visitors to the Lab—scientists, engineers, and media people—from all over the world. To the considerable irritation of the regulars who parked there, the security guards sent the overflow visitors traffic into the regular parking areas. Harris pulled into a spot near the far end of a row and alternately trotted and walked the two hundred yards to the main guard shack, attaché case swinging by his side. He noticed a large CNN TV van parked along the side of Oak Grove Drive, thick black cables spilling out of the back doors and snaking across the sidewalk through the fence to the auditorium. There’s the first one. There’ll be more in another day or two.

He flashed his ID card into the window of the guard shack as he went by and walked into the pleasant tree-shaded, grass-lined mall that served as a vestibule to the rest of the Lab. It looks more like a sleepy college campus than a laboratory, he thought to himself for the umpteenth time. An ornamental concrete pond that had lain empty for years to impress the earnest frugality of the Lab onto visiting congressmen and other federal budgeters was filled again with water, and fountains spurted merrily on both sides of the footbridge running across it. The water ran down a concrete creek bed lined on both sides by banks of luxurious grass and pine trees.

Harris paced briskly across the mall to the spacecraft operations building. He took the steps three at a time to the second floor and walked into his office at 7:27 precisely, sweating and breathing hard, but with time to spare!

None of his office mates were in yet. He scribbled a note across a piece of scratch paper, “Please do not disturb. Radio interview in progress,” and taped it to the front of the door. He sat down at his desk, pulled out the crib sheet filled with Nomad and Neptune “gee-whiz” facts that he’d constructed the night before, and waited for the phone to ring.

Neptune. A tiny blue dot almost three billion miles from Earth. It’s a cold, impersonal place—a speck of a planet through even the largest telescope, but an enormous gas giant full of mysterious wonders when seen up close.

Next week we’re going to experience it up close, you and I. We will see it through the eyes of a solar diplomat: a traveler, explorer, adventurer, and representative of the human race; a large metal-plastic-silicon representative named Nomad . . .

That’s the way his article had started. Apparently it had been syndicated in newspapers across the country; even though it had been out less than a week, he’d already received letters from Michigan, North Dakota, and New York.

Neptune. In seven more days, when Nomad II dove over Neptune’s north pole and intercepted Triton on the other side, the planet and its large moon would become as real to Harris as Saturn and its rings had been nine years earlier. Already the planet loomed enormously, a body whose light powder blue atmosphere streaked with white clouds and a large oval dot strained to spill over the framed confines of Nomad’s narrow angle camera into the more bountiful space of the wide-angle camera.

The phone rang at 7:31.

“Mister Mitchel?”


“Hi, I’m Polly Marx at K-N-E-E. How are you this morning?”

“Hi Polly. I need a coffee transfusion. Other than that, I’m ready.” He made his voice a lot more confident than he felt.

“Great! We’ve got two more commercials to go and then you’re on. Will you hold?”


“Ummm . . .” There was a pause.


“I read your article and really liked it.”


“I know this is going to sound awfully forward, and you don’t know me at all, so I hope you won’t misconstrue, but I wonder if you’d like to do lunch sometime?”

“Hmmm. Well, maybe.”

“Think about it, please. I’ve always been interested in the space program and I’d love to talk to somebody like you who’s actually in it. And I could give you a tour of the station, here.” She giggled. “Besides, your article gave me the goose bumps and I want to see what you look like.”

Harris laughed. He got her phone number.

“Bye, now,” she said in a soft voice. “Hope I hear from you.”

I wonder if she looks like her voice sounds.

Polly’s sexy voice was replaced by a jingle about the awesome flavor of Puddy-Do Wiener Dogs (“Pud-dy-Do, the on-ly Wien-ner Dog for you, Pud-dy-do!”), followed by a frenetic pitch by Long John’s Body Shop in Long Beach, (“Drop by and get your body adjusted.”), followed by an advertisement for Trash (“The movie that trashes your preconceptions about bad taste.”), followed by a pitch from Get Rich Investments, Inc. (“The gold market is ex-ploding today.”), followed by . . .

That’s FIVE commercials, Harris thought just as an unctuously self-assured voice interrupted and smoothly rumbled into his ear, “Hello, Mister Mitchel, how are you this morning, and how’s Uranus . . . I mean Neptune, heh-heh?”

“Oh, Neptune’s fine, and my anus is, too. How’s yours?”

“Good, good. Oh, what a relief it’s going to be to talk to a real person instead of a nerd.”

“Thank you.”

“We’re on in twenty seconds, so I’ll do a quick intro and we’ll talk, okay?”


The last commercial resumed and ended. Conland’s voice came back.

“Now for a little something about one of the only things the federal government has any business doing, and that’s the space program. Space! The final frontier! We need space to grow. We need it for our real estate developers on Mars—new lands to exploit without having to put up with the environmental freaks. In a week we’re going to look at some of that potential new real estate with our Nomad spacecraft. It’s about to send a report back on the planet Neptune and its stupendously big moon Triton. On the line we have Harris Mitchel whose poetic article on the Nomad encounter with Neptune ran in the Times editorial pages last Sunday. Believe me, I normally choke on the word poetic, but when an article is about the free human spirit and Yankee ingenuity on the new American frontier, what other word do you use? How are you, Harris, and how’s the quest for Neptune?”

“Hello, Mister Conland. I’m fine. I’m afraid we’re going to have a problem developing the real estate on Neptune though, since there’s no place to lay cornerstones. It’s full of gas and maybe liquids right down to the core, totally un-usable. Maybe you’d do a little better on Triton, but you’d better bring your parka since it gets nine hundred times less light from the Sun. We’re pretty sure we’ll find either liquid or frozen nitrogen there.”

“Then I’ll bring my fur-lined mittens and bunny slippers, too. What’s your job on the Nomad project, Mister Mitchel? Are you one of the scientists?”

“Actually no, I’m an interplanetary navigator, and we . . .”

“If somebody told me that on the street I’d call for the boys in white jackets, but in your case it’s actually true.”

“Right. I’m one of the people more concerned with the journey than the destination. We’re the ones who make Nomad go where she’s supposed to go.”

“She, huh? It’s hard to guide a woman, isn’t it? Real estate aside, why are we going to Neptune, Mister Mitchel? Why are we spending our hard-earned money on a planet three gazillion miles away? What does Mister American Taxpayer get out of this?”

“He gets the same thing that every man, woman, and child in the rest of the world gets, Mister Conland: a lift in his spirits and a feel-good feeling. He gets a bright shiny future to think about, instead of a crusty dismal past full of wars and crime and hatred and other depressing things. He gets to look outward toward a new world instead of inward at an old one. That’s what he gets out of Neptune. I think it’s worth it. Don’t you?”

. . . The science at Neptune is important, but think also about the voyage, the adventure. Knowledge is good for the human mind, but travel is food for the psyche. And Nomad’s travels have been and will be prodigious. It has been on its way from Earth since 1977, wending a crooked path through the outer solar system. Now, in a handful of days, Nomad makes its final rendezvous, a close brush and embrace with Neptune before flying out of the solar system to begin an odyssey through the Milky Way galaxy, an unattended lonely voyage that may last billions of years . . .

“How do you navigate to a planet three billion miles away?”

Harris explained that he and his teammates collected Doppler and ranging data from the Deep Space Network stations that tracked Nomad. They collected images from Nomad’s telemetry—pictures of Triton and Nereid and the newly discovered satellites.

They dumped the tracking data into a large black cast-iron pot, metaphorically speaking—actually the pot was a large computer—along with other ingredients such as data calibrations and planet and satellite ephemerides. They stirred vigorously. They incanted techno-babble and tasted frequently, adding spices, a priori covariances, and toad tongues now and again until the brew was complete and the answer was apparent: they knew where the spacecraft was and where it was going well enough to plan the last maneuver that Nomad would ever do.

In three more days they would execute TCM20 (Trajectory Change Maneuver number 20), and four days later Nomad would go skimming—actually sizzling at twenty-seven kilometers per second— just above Neptune’s atmosphere. The giant’s gravitational hand would grab her, wind up and swing her in a tight arc and pitch her downward at a steep angle toward Triton on the far side of its tilted orbit about Neptune.

“You’re not going to hit Triton, are you? Splat! End of Nomad, end of project.”

“No, no, we’re aiming about forty thousand kilometers behind it, trying to pass through the dual occultation zone.”

“That sounds doubly occult to me, Mister Mitchel. Is this a sinister liberal plot?”

Harris laughed. He was beginning to relax. “Well, it’s true that I’m a liberal . . .”

“I’m amazed, you sound so reasonable, but I’ll try not to hold it against you.”

“. . . but there’s nothing at all sinister about me or the dual occultation. We want to make Nomad pass behind Triton as seen from both the Earth and the Sun. That way we get information about Triton’s atmosphere and surface by Earth tracking Nomad until it disappears, and Nomad watching the Sun until it disappears.”

“Is it hard to hit this zone? Is it as hard to hit as a homeless person at two hundred yards with an AK-47?”

“It’s about as hard as finding kindness in a right-wing conservative’s soul, which is harder than starting an ice-cream franchise on the sun.”

“Ouch. Heh-heh.”

“It’s hard, Mister Conland, because Triton is so far away on the other side of Neptune and the zone is so small. We have our last chance to target it with our final maneuver in a few days. After that the laws of physics take over and it’s completely out of our hands. Nomad passes over Neptune really deep in its gravitational well, and any errors left over from the maneuver get magnified on the rest of the trip to Triton. I’ll give you an analogy: imagine you’re a planet sized baseball pitcher standing on Neptune’s north pole like it was a pitcher’s mound . . .”

“And my feet are freezing because they’re in that cold atmosphere, right?”

“Yeah, and maybe your cleats are dug into methane icebergs. Anyhow, even though the zone we want to hit is fourteen hundred kilometers wide, at the scale of this planet-sized pitcher, Triton’s dual occultation zone looks like it’s about three times smaller than the strike zone at home plate. You have to throw a perfect strike over a six inch wide home plate to get a dual occultation.”

“Gee, Mister Wizard, space navigation is hard! And what if I don’t get a strike? Do I get pelted with beer bottles by the fans? What’s the consequence?”

Harris suppressed a sudden impulse to say, I have to run naked through the streets.

“You’re totally humiliated because you said you could do this and you didn’t. As a consequence, you lose all your credibility and live the rest of you life in shame and degradation and never get invited on a radio talk show again.”

“That’s the worst of all.”

“Oh yeah, and you get pelted by the scientists. They throw outdated textbooks at your head because you lost a science opportunity, probably the only opportunity in our lifetime to accurately measure the components of Triton’s atmosphere.”

“So you’re letting it all hang out here, Mister Mitchel? This is your career on the line?”

“It’s a tough, dirty job, Mister Conland, but somebody has to do it.”

Conland wound down the interview. They’d been going almost thirty minutes.

“Bring it home for me, Mister Mitchel. What’s in store for Nomad? What happens after Neptune?”

. . . Even though Nomad will go blind and deaf after a few tens of years; even though she will die an electronic death, she will still have the germ of human creativity and daring incorporated into her very structure.

She will carry two messages—an explicit one in the form of a golden record, and an implicit one stated by her profoundly improbable existence. And both messages will say to the finder, in essence, “I am from planet Earth. I am of the human race. We are small and insignificant but our souls are large because we have set out on a journey to know the universe.

“Well said, Mister Mitchel. Not bad for a mush-brained liberal and an engineer to boot. If you hit the occultation zone, you can come back on our program. If you miss, we’re gonna tell Congress to kick your butt and cut off your funding.”

“Thanks, Mister Conland. It’s been a challenge and a pleasure educating a right-wing fruitcake, and I hope I have a chance to do it again. Meanwhile, don’t shoot too many welfare mothers.”

“You sure know how to hurt a guy, Mister Mitchel . . .”

“So do you.”

“. . . but seriously, it’s been a pleasure.”

“And seriously, Mister Conland, I’ve enjoyed it.”


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