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Guided By Starlight, New Horizons Speeds Toward Pluto

“Second star to the right, and straight on ‘til morning,” Peter Pan told Wendy as they sailed toward Neverland. Though the story is a fairytale, navigating by starlight is a tried-and-true method for crossing oceans on Earth as well as the vast cosmic sea.

Like Peter Pan and millennia of humans, NASA’s New Horizons spacecraft is flying by the light of the stars. As it sails toward its July 14 rendezvous with Pluto, the spacecraft is keeping a close eye on thousands of pinpricks of light. Not only do the stars help tell the spacecraft exactly where it needs to go, they tell the spacecraft where to point its instruments as it meets up with Pluto.

“The stars are always the key factor in determining that,” says Gabe Rogers, New Horizons’ lead guidance and control engineer.

Seeing Stars

Riding aboard New Horizons are two star cameras, each aimed in a different direction.

“They’re used for determining which direction the spacecraft is pointed in, or where all the cameras and instruments are oriented,” Rogers says.

Ten times each second, the cameras snap images of their starfields. They compare those images with an onboard map of more than 10,000 stars. Based on that information, the spacecraft can figure out if it’s tipped up or down, or slightly swiveled.

“All you need is about three or four stars,” Rogers says.

If something is amiss, the spacecraft will automatically adjust its pointing. This piece of the puzzle is crucial for Tuesday’s Pluto encounter, when the spacecraft will have one chance to make hundreds of observations as it speeds through the Pluto system. Of course, none of that can happen if it ends up looking in the wrong place. (Learn more about the historic mission to Pluto on the National Geographic Channel.)



There’s another way stars are helping New Horizons plot its course, and it has to do with finding Pluto itself. It might seem as though this should be simple, but it’s not. Pluto was discovered in 1930 – just 85 years ago. A full Pluto-year is the equivalent of 248 Earth-years, so we haven’t actually seen it complete a full orbit around the sun. As such, we’re not exactly sure how that path unfolds.

“We don’t really know its distance very well,” Rogers says.

Up until today, the spacecraft’s Long-Range Reconnaissance Imager (LORRI) was snapping photos used for optical navigation. These images include the starfield behind Pluto and its moons. Two teams, one at California-based KinetX Aerospace and the other The Johns Hopkins University’s Applied Physics Lab, have been reviewing the navigation images and using them to adjust New Horizons’ course heading.

“They look at those images and compare them to the known starfields, and come up with where we are in space,” Rogers says. “I can happily say that as of Saturday morning, in the last set of optical navigation images, Pluto is right where it’s supposed to be.”

But just how far away is Pluto? We know it’s on the order of 3 billion miles away. Yet New Horizons is traveling at more than 30,000 miles per hour, and at that speed, flying by Pluto will only take around three minutes. In other words, the spacecraft needs to deploy its instruments at exactly the right times to get all the data it’s tasked with collecting. So, New Horizons needs to know how far from Pluto it is, with much greater precision than simply a few thousand miles, give or take.

Figuring out that precise distance is something the team is constantly working on. In fact, there have been daily updates over the last few weeks – and there will be two more updates today (Sunday). The second of these, scheduled for late tonight, will offer the last opportunity to perform a trajectory correction, if needed, Rogers says. “Then we’re just sort of cruising to Pluto.”

One-Hour Special Mission Pluto hosted by Jason Silva premieres Tuesday, July 14 at 9/8c on National Geographic Channel.

9 thoughts on “Guided By Starlight, New Horizons Speeds Toward Pluto

  1. Is it no possible to put the spacecraft in orbit around Pluto instead of passing by?

    ND: Hi, Kevin! We’ve answered this question here. Essentially, Pluto’s gravity is so weak that any orbiting spacecraft needs to be going slowly. It would take too much fuel for New Horizons to slow down and pull into Pluto-orbit — you’d have to undo all of that velocity gained during the original rocket launch (plus the gravity assist at Jupiter), and that requires a rather heavy load of additional fuel. Too heavy, in fact, to realistically launch out of Earth-orbit. The alternative at this point is to just go really slowly, but then we’d still be waiting…and waiting…and waiting…and waiting…for New Horizons to arrive at the Pluto system.

  2. I have been interested in the stars and planets since I was 6yrs old I’m now 68yrs soon to be 69yrs I am totally intrigued with all planets and anything that to do with them or the stars. I am so unhappy not to find out more about Pluto as far as the circles go

  3. The Moon was born from the Earth in the early live days of the two. The proof of such assertion is shown in the part I USM http://www.kanevuniverse.com where is calculated the centripetal acceleration on the Moon’s surface which exactly coincides with the experimental one, through the following newly found out rule there: To distinguish the planets from other objects in the solar system, there it isn’t enough to estimate the form of orbit (elliptic or more-less circuit one) and the mass of object, but also to calculate the own centripetal acceleration via the field formula: g=V.C/R.ln(1+V/C), where R – is the distance between the planet and the Sun, V=w.R, where w – is the angular velocity of the equatorial area of the Sun. See USM part I http://www.kanevuniverse.com If obtained result coincides with the same acceleration estimated by the low: g=G(M/r.r), then the observing object is planet…if it isn’t then this is asteroid or some another alien object! The same formula is applies to calculate the centripetal acceleration of the Moon, where R is the distance between the Earth and the Moon and (w) is the angular velocity of the equatorial plane of the Earth. The coincidence is remarkable. The same is in force about all (I repeat all) moons of all planets in the solar system, which means that all moons of the planets also was born from respectively planets. G.Kanev

  4. Very nice accomplishment for a people who are about to go bankrupt and experience hyper inflation. I guess we won’t be able to do THIS again for at least a few hundred years when we finally dig out from all this debt.

  5. Excellent work! Thank all involved. Your hard work,commitment, and visions has definitely educated the world, you’re teachers to all, who doesn’t want to see and hear all you’ve achieved?… No one.

  6. Amazing work! As this hurting world is struggling, your efforts to explore give us hope. We need that hope here. Just by the fact that man wants to explore the beyond, I believe that desire is saving us. Don’t listen to negative comments about this work. This work is essential to man,and the money put into it is small in comparison to
    the knowledge we gain by exploring the next frontier!

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