Tag Archives: New Horizons

P-0 days: Navigating Pluto

Where are we?


Closest approach was at 7:49 AM this Tuesday morning, July 14th in Baltimore. Pluto—12,500 kilometers away—was about 22 times the size of the Moon seen by the naked eye. Image mosaics are underway. The next event, occultations of the Sun and Earth by Pluto, begins at 8:45. After that, the same occultations by Charon begin at 10:15.

Of course, we have no way of knowing any of these things really happened until information travels at the leisurely speed of light for 4 hours and 25 minutes to get to Earth. Unfortunately, at this red-hot moment, the spacecraft is too busy with pictures and other observations to turn the antenna towards us to send that information. We have to wait until later this evening when the antenna centers on Earth and sends a radio postcard.

Where are we going?

The outer environs of the solar system, deeper into the Kuiper Belt for another encounter with one of a couple of recently discovered heavenly bodies (if NASA approves a mission extension), thence to the Oort Cloud and onward into the Milky Way.

Where are we from?

Solar System
Milky Way Galaxy
Universe, Zip 18395782886253402871-981294673.23

This is my last post of the Navigation countdown. We’re seeing Pluto up close and personal—we hope, unless the spacecraft has run into a piece of random debris, in which case we’ll never hear from it again and all those pictures will be lost. We’ll know for sure tonight.

Pluto. Been there, done that. Remember, this is about the voyage, not the destination. We Navigators almost always get you there, and in this case we most definitely got you there, whether the spacecraft is healthy and intact or in tatters. Onward to the next body. Onward with the next mission, to the next dream hatching in our restless souls. It is a never-ending journey.

What’s the point of this exploration? Will any of us ever live on any of these new worlds we’ve paid lots of money to get to? I think not. I think that the era of solar and extra-solar settlement is far beyond the horizon of our lifetimes. We have a lot of wars to fight and disasters to recover from before our evolved descendants ever colonize another world in this solar system or beyond. It will happen, but not soon, not until we’ve evolved the mean-streak and stupidity out of ourselves.

Will we wipe ourselves out? No. The human race is hardy and some will survive the worst disasters, be it nuclear war, devastating climate change, or a random asteroid strike. Some will survive and begin the climb back to civilization and the next disaster, just as it happens in Walter Miller’s A Canticle for Leibowitz. Read that book if you want a chilling yet poignant depiction of our future. Science fiction writers are the long-term Navigators of our species.

My message, if it’s not clear, is that we have little need to be optimistic in the short run—I think we’ll have a series of disasters and recoveries—but the future is very bright indeed over the long haul of centuries, millennia, or even millions of years. After all, we’ve only been around as a species for a couple of million years on Earth; think what we’ll be like in a couple more!

Meanwhile, life presses on, full of struggle and despair but sometimes with a glimmer of hope on the horizon. The hope is that we learn a little more today than we knew yesterday. The hope is the beginning of the next adventure. Onward to the Kuiper Belt and the outermost reaches of our solar system.

Why go? I think I said it best myself as Voyager finished Neptune a long time ago and headed out toward the deeps of the galaxy. The very fact of her improbable existence cruising among the stars for billions of years to come say this to any potential finders:

I am from the 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.


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.”


P-2 days: Navigating Pluto

Microsoft PowerPointScreenSnapz001

The Target Plane (aka B-Plane) & Arrival Time History

Where? 2.8 million kilometers to go, shuffling along at 1.2 million kilometers every day as of midnight this morning, July 12th, in Virginia Beach, Virginia. Sunday. Pluto is about 170 pixels across in the LORRI camera, but to the naked eye it’s around 10 percent the size of the full moon.

Where to? Pluto! At 7:48:54 AM, July 14th Washington D.C. time, (11:48:54 GMT), plus or minus 37 seconds or so.

Where from? The blue-green planet with the high albedo and lots of salty liquid water on the surface.

6:00 AM: The Sun rises at our hotel overlooking beautiful Lake Kittamaqundi in Columbia, Maryland. In a half-hour Jan will drive me to APL about 15 minutes south from here.

This will be our busiest day. Today we’ll nail down the arrival time (we hope), so I may not get much written. My plan is to add snatches of commentary as time allows. Watch this space …

7:19 AM: Jan drops me off at the APL back entrance and drives back to the hotel for breakfast. I come into the lab, elevate to the fifth floor of our building, and walk into the “Bullpen” where doughnut holes and coffee await. The Bullpen is a large-ish room where the Navigators and some of the Science folk hang out.

There’s an email from Jeremy saying the new radiometric tracking data is ready. Jeremy, Chris, and Dale are prime for generating solutions today, and they’re busy getting their computer runs set up. Coralie and Derek just now walk in from where they’ve been working on the optical data since zero-dark-thirty this morning in a conference room down the hall. They’ve finished ahead of schedule …

7:50 AM: We finish our daily huddle outlining what we’re up to today. There are two OpNav deliveries, Crit 36 and Crit 37, and two corresponding “OD” (Orbit Determination) deliveries combining the radiometric and OpNav data sets. At this late date, OpNav rules. It’s much more powerful than the radiometric, nailing down both our location in the target plane and our arrival time. The first solution is due at 10:06, we’ll have an hour from then to prepare a presentation for the informal “OD Conclave” meeting at 11:06, and then a formal Mission Management Meeting at 2:36 pm for announcing our delivery to the project at large.

Processing for the second OD delivery, Crit 37, starts at 11:36, and gets wrapped up in the final formal meeting ending at 12:26 tomorrow morning. We’re hoping the solution will be so non-controversial that it can be finalized earlier, around 7 PM this evening, so we can take the rest of the day off.

Dale, Chris, and Jeremy are prime for the OD solutions today. Bobby and Fred run the show, put together the slides, and give the presentations. Ken works on generating Monte Carlo statistics for the slides. Coralie and Derek (and Philip back at home base in California) get a little rest before starting the Crit 37 optical data. I watch all, absorbing sponge-like as much as I can to write omnisciently on this page, pretending to know what I’m doing, but it’s hard to keep up. I’ll tackle my own OD processing in a few minutes, shadowing Dale or Jeremy probably, but in truth I’m slow at this process, not nearly as nimble at the keyboard as the younger whippersnappers, so I mostly provide reality checks here and there as I can.

Coralie emailed us late images of Pluto and Charon, with a single comment in her text: “:)”. Craters begin to pop out.

INAV (Independent Nav) from JPL works on the other end of the Bullpen from us, being as independent as ever they can be, their job being to shadow us with their own processes and software to provide yet another reality check …

3:15 PM: The Crit 36 delivery was made. Not much movement in the target plane, but  the arrival time drifted a little earlier by about 6 seconds with a uncertainty of about plus or minus 36. Although the Navigation Team recommends that an onboard update be done, we’ll be neither surprised nor disappointed if it isn’t approved, since most of the possible trajectories (from the Monte Carlo analysis) still fit in the desired design space.

Microsoft PowerPointScreenSnapz002

Target Plane & Arrival Time: Crit 36 & Friends

The Crit 37 OpNav data was delivered a little over an hour ago, and the OD Navigators are working on the next set of solutions. So far, no surprises and none expected. All is well.

6:40 PM: It is done! The Crit 37 solution, which is the last one before the flyby, is finished and delivered. It’s close enough to the last one that there’s no reason to risk a failure by updating the onboard sequence. The late night meeting is cancelled. There is no update, New Horizons flies on, and Pluto looms ahead.

There is nothing more that can be done. Time for the Navigators to take a deep breath and enjoy the rest of the show!



P-3 days: Navigating Pluto

Where? 4.0 million kilometers out, getting 1.2 million kilometers closer each day, as of midnight this Saturday morning of July 11th in Columbia, Maryland. Pluto is about 120 pixels across in the LORRI camera, but to the naked eye it’s only 7 percent the size of the full moon.

Where to? Pluto! At 7:49:02 AM, July 14th Columbia time, plus or minus 47 seconds or so.

Where from? Earth.

Yesterday afternoon the Navigators recommended to the project that an update to the onboard sequence be made, since the current solution location in the target plane (think of it as the throw of a dart) and its corresponding cloud of uncertainty has drifted towards the top center of the 65 x 130 kilometer box that represents the acceptable region for the flyby.

It’s actually a cube rather than a box, since there’s also a limit to the acceptable arrival time of 200 seconds centered on 7:49:49 AM Columbia, Maryland time. If the trajectory goes through that box and the spacecraft closest approach is within 100 seconds of the desired time, all is well and the current design is good. If it goes outside that box/cube, then either some science data may be lost, or the sequence will need tweaking to make the observations optimal again.

The Navigation Team recommendation was to upload a tweak to the canned-in spacecraft sequence design to guard against a drifting solution, essentially re-centering the cube around the current solution. The independent Navigation Team agreed. The Science Team agreed. The Mission Operations Team agreed.

The mission leader didn’t agree. Alan Sterns’ reasoning was that there’s too much risk of missing the whole flyby if the spacecraft should go into safe mode again, like it did on July 4th, an unanticipated event. If that happened, it’s quiet possible that the spacecraft couldn’t be returned to normal operation in time for the flyby, resulting in a loss of almost all of the mission objectives. Better to risk some suboptimal science observations than the whole mission.

Nobody wants that, not the scientists, not the engineers, and not the Navigators, so there has not been any grumbling about the decision. It was justified.

Today we processed Crit 35 optical navigation data.

The good news is that the mild solution drift we’ve seen in the last few days in both the target plane and the arrival time seems to have abated, and the error bounds continue to shrink up around the solution.

There is no bad news.

My wife just landed in Baltimore.

Life is good!


P-4 days: Navigating Pluto

We are the Navigators. We say where we are and where we’re going.

Where are we? As of midnight this morning, July 10th, we were 5.2 million kilometers away, eating up those remaining kilometers at the rate of 1.2 million a day.

Where are we going? Pluto! To 12,550 kilometers above the surface, plus or minus a few, at the closest approach time of 7:48:49, July 14th, on the US east coast, plus or minus around 54 seconds or so (1-sigma). Of course we couldn’t know that for sure until the radio signal hits the ground about four-and-a-half hours later … if there were a radio signal. There won’t be because New Horizons will be looking at satellite Charon at that red-hot moment, with the antenna pointed away from Earth.

Where were we? That’s in the past, we don’t particularly care. The most important thing is not where we’ve been but where we’re headed. And that’s the future, not the past. But if you have to know, we are from Earth, we are of the human race.

Politicians should also be Navigators. They should tell us where the human race is, and where it’s going. But they don’t. Are we headed into a long-term presence in space, leading to colonies in the solar system and beyond? Or are we slouching toward overpopulation disasters like pollution, climate change, and nuclear Armageddon? They can’t tell us that because nobody knows. We are a chaotic, unorganized civilization with no Navigators to point the way, and little guidance to correct our trajectory.

Meanwhile, back here on Earth, we have Crit 34 to worry about: Critical delivery number 34 of optical navigation data has just been delivered to us, hot from the spacecraft through the DSN (Deep Space Network), through a maze of data pipelines to our very own Optical Navigators in our big room at APL (the Applied Physics Laboratory) that we call The Bullpen. Our Optical Navigators have just finished calculating the centers of 2 Hydra, 3 Pluto, 3 Charon, and 2 Nix images taken yesterday, and now we, the rest of the Navigators on the team are going to combine that information with the rest of the Doppler and ranging data from the DSN and come up with an answer: When do we get to Pluto?

The solution will shift by X seconds, with an uncertainty of Y, and we’ll report that to the project at large. Then the decision will be made: Will we tweak the already loaded sequence to accommodate the new results? The betting is that we will, since recent solutions have moved us earlier than the nominal arrival, and the error bars are shrinking down around those answers. We’ll know by the end of today.



See Voyager at Neptune for the previous deepest space adventure of the far, far past.

P-5 days: Navigating Pluto

Midnight beginning Thursday, July 9th on the U.S. east coast: New Horizons is 6.5 million kilometers from it’s destination, still doing 1.2 kilometers per day.

Seen from the spacecraft, Pluto is only two-hundredths of a degree across. To put that in perspective, that’s only 4 percent of the diameter of the full moon seen from your back yard. However, to the LORRI camera, that amounts to 74 pixels, which is starting to be a respectable size in terms of picking up the hitherto unseen Plutonian details. It will continue to get much better as we continue this high-speed approach.

But I digress; this is about the trip, not the destination. Today we’ll process Crit 33 OpNav data. That’s short for the critical 33rd delivery of the precious images used for optical navigation. It’s the images of Pluto, Charon, and the rest of the satellites against a starry background.

It’s critical for a couple of reasons. First, image files are big, even after data compression, and there’s a lot to download for each critical delivery from a spacecraft 4.8 billion kilometers from Earth. It takes a long time to download the images at the low data rate. Second, the arrival time is still unknown by about a minute, and that doesn’t get knocked down to the few-second level until the last few days, beginning now. The time pressure on all the spacecraft teams, especially the Navigators, is high. Every new delivery of optical navigation data is critical to determining the encounter timing so that the onboard sequence can be adjusted by that improved timing knowledge. Image mosaics are already planned and onboard the spacecraft, but they may need tweaking by whatever amount of time change we get from the OpNav data.

As I write, several hours have flown by since the previous sentence and we’ve processed the OpNav data, merged it with the radiometric tracking data, and gotten multiple solutions. It looks like we’re arriving early by roughly a minute, but we have to be cautious about that because the uncertainty is still almost the same size as the time shift, meaning that the shift is only barely significant.

For that reason, we’re not going to take the chance of tweaking the onboard sequence yet for fear of inadvertently screwing up something else in the spacecraft computer. Editing data on the computer on your desk is one thing—editing data on a spacecraft 4.8 billion kilometers from Earth is quite another. A little fat-fingered “oops” on your laptop won’t cost much to fix compared to the hundreds of millions of dollars spent on this spacecraft and the fact that this is probably the only time in our lives for this opportunity.

This is history, and a little oops that might turn the antenna away from Earth, never to be turned back again, never to be heard from again, never to send back those first-time detailed pictures from the last planet of our traditional solar system … well, that would be a disaster of the first magnitude. We don’t want to take the least unnecessary risk of that happening, and while the timing uncertainties are still large, that’s an unnecessary risk.

Tomorrow we tackle Crit 34 to see if we can improve on the arrival time even more.

Meanwhile, why do we make this extraordinary effort to explore this tiny, almost insignificant body at the edge of our solar system?

Because we have to. Because it defines us. Because billions of years of evolution have shaped us into the curious, never-satisfied beings that we are.

Because it is part of our souls.


P–7 days: Navigating Pluto

As of the first instant of this morning, July 7th on the US east coast, the little spacecraft was about 8.7 million kilometers from Pluto, getting 1.2 kilometers closer each day.

We’re almost completely recovered from the hiccup that happened July 4th when New Horizons took on a little too much multitasking trying to simultaneously compress data for downlink and load up the sequence of activities for the flyby at the same time. This caused the equivalent of a brain freeze, and the spacecraft went into a defensive fetal position, spinning up to 5 rpm to provide stability for its earth-pointed dish antenna, then dropping off into a light midsummer night’s snooze. We have to wonder, when spacecraft sleep do they dream of electric sheep? (With a nod to Philip K. Dick.)

We lost some tracking and science data, but it’s not a vital loss that won’t be made up in the following days with much more powerful information on where we are and what Pluto looks like. Pluto currently spans about one percent of the field of view of our long-range camera, covering about 55 pixels. You can’t see a lot of detail in an image only 55 pixels across, you can only be taunted and tantalized by vague shapes and shadows. Those shapeless, shifty features will begin to stabilize and fill out in exquisite detail over the next few days.

Our last maneuver is behind us—several days ago—and we have delivered the spacecraft from our capable hands into those of Misters Newton and Einstein whose inviolable laws of physics will guide New Horizons the rest of the way in. Nothing more can be done about where it is and what time it gets there, but we can do a series of Knowledge Updates to better inform us on where to point the cameras and other instruments. That’s what the Navigators get into today, delayed by the little snooze, as the first new tracking data comes down from the now revived and presumably refreshed, spacecraft. Here is where the rubber meets the road in a series of tightly coordinated and time limited interactions between the Navigators and the rest of the project teams. The spacecraft may get its snoozes now and then, but the Navigators are headed into some sleepless days and nights.


I don’t know if I’ll be able to continue these posts while things get hectic, so for interim entertainment here’s some filler about Voyager’s encounter with Neptune in 1989 from a Navigator’s perspective. There are a lot of similarities with the current Pluto adventure, and differences too. The excerpt is from the chapter titled “Neptune” from my novel The Darkest Side of Saturn. The spacecraft is named Nomad, but don’t be fooled, it’s really Voyager. There are some fictionalized versions of real events that happened during that wondrous time, but the rest is full of lies. Your task, dear reader, is to separate the wheat from the chaff.

Navigating Neptune

The party started in the Navigation Team’s operations area an hour before midnight, two hours before the Neptune closest approach time. They fished drinks out of a metal washtub filled with ice, beer, juice, and sodas. They cut slices of brie and slabs of pâté from paper plates between the computer terminals lining long tables on both sides of the room. They spread their fare on stout crackers and delicate wafers, popped olives into their mouths, and poured wine from bottles and jugs into plastic cups.

They were very happy, all nineteen members belonging to the Navigation Team functional groups: Radiometric Data Conditioning, Maneuver and Trajectory, Optical Navigation, and Orbit Determination. Harris, the newest of the new and lowest of the low on the navigation totem pole, was perhaps happiest of all. After working nearly twenty-four hours straight, their job was finished. Nomad was nearly on course. The new camera pointing commands had been uplinked across four hours and seventeen minutes of light travel time to the spacecraft. Now the laws of physics ruled supreme. There was nothing more to do, nothing more that could be done. Eat, drink, and be merry, for in a few more hours we either bathe in glory or go splat!

They pitched darts at Neptune. On the far wall of the navigation operations area was a large bulletin board. Tacked onto the center of it was a square of graph paper three feet on each side with tick marks annotating every ten kilometers of the divisions. This was the navigation target plane for Neptune, although Neptune was not on it. At this scale, Neptune would have been represented as an enormous circle whose closest edge was a few feet down and to the right—off the chart.

Dozens of small multicolored paste-on dots sprinkled the chart—yellow, blue, green, brown, black, and red ones. A red one near the center, larger than the others, was labeled “TCM20 aimpoint.” Because of the inevitable maneuver errors, this was where Nomad certainly would not go, although it shouldn’t be far away. The smaller colored dots, representing solutions vying with each other to show where Nomad was actually headed, had meandered away from the aimpoint as new data came in after the maneuver.

They were throws of the navigator’s darts, almost literally. Each dot represented an experiment to test the sensitivity of the trajectory to the ubiquitous errors in every source of information. No two solutions were exactly the same except that they tended to cluster in places. There was a cluster of green dots for solutions that used optical data of Triton and a blue grouping about thirty kilometers away accounting for data that included optical observations of the temporarily named N1—first of the new satellites discovered by Nomad.

For the latest solution—they were loathe to call it final; there was always just one more data point to include, just one more computer run to make—they’d placed a red dot and labeled it NAV3, the name for their ultimate delivery of knowledge. Nevertheless, it was final, the last delivery that could affect the success or failure of the encounter, delivered to the sequence designers so that Nomad’s camera angles could undergo a last-minute shift and she would send back pictures of things like satellites and cloud features instead of nothings in empty space.

Knowledge and control were the two halves of the navigator’s function. Gather the data to determine Where are we and where are we going?, then use the knowledge to apply the control: Burn the engine! Change the trajectory! Finally, when it’s too late in the game to burn the engine, when it’s too late to control the trajectory, all you can do is improve the knowledge to point the instruments, whose purpose is . . . to gain more knowledge.

Job done, the party navigators pitched darts while the rest of the Nomad engineers and scientists labored away over hot computers in rooms upstairs. They watched the Lab TV news report as Nomad approached the ring plane crossing at midnight, or rather, as the downlink data containing that event approached Earth, because the event had already happened over four hours earlier. Either Nomad had already splattered against a random rock just outside the visible ring, in which case the signal would come to an abrupt halt in a few minutes, or it had not. The navigators, including Harris, were well into some serious beer drinking.

At six minutes after one o’clock in the morning, as Nomad skimmed over the top of Neptune and Carl Sagan’s face graced the TV, Harris ambled to one of the several phones scattered over the operations tables and punched a number.

“Hello?” Diana answered.

“Hi. Whatcha doin’?”

“Oh, nothing much right now.” She seemed distracted.

“Why don’t you-all come on down here to our party?”

“Why thanks, Harris. I believe I will.”

Minutes after they talked, as Harris lifted his fifth can of beer for the evening, Diana walked through the door of the navigation area trailing a TV crew carrying lights, sound equipment, and a camera. They taped her even as she walked. As one of the few female scientists on the project, and a good-looking one at that, she was in heavy media demand.

Uh oh. Harris discreetly parked the beer can on the table behind a stack of printouts as she walked straight up to him. Drinking at the Lab was forbidden; getting caught on television was certain career death. He tried not to wobble as she shook his hand.

“Congratulations,” she said formally for the camera. “Looks like it’s going to be successful.”

“Congrad . . . grajlations to you too. It’s a good encounter, huh? Good stuff, you know what I mean? I mean we’re doin’ good.”

“Loosen up,” the director said. “You’re like statues.”

At the director’s suggestion they linked elbows—beautiful young female scientist and intrepid male engineer—and faced the camera with silly grins on their faces.

“No no. Too posed. How about a toast.”

Somebody brought them plastic glasses filled with orange juice. Harris and Diana held them high and clicked them together.

“Here’s to science,” Diana toasted and smiled.

“Here’s to engineering,” Harris answered.

“Here’s to knowledge,” she said.

“And here’s to control and a dual occultation.”

“May we be so lucky.” Diana’s smile began to crack. “Here’s to wisdom.”

“And good ol’ ingenuity.”

They chugged their orange juices, the navigators clapped, and the director was mollified. A few minutes later another network TV crew stole Diana away for an interview.