NASA’s New Horizons Spacecraft Getting Closer to Pluto



The morning of January 19th, 2006 started much like any other morning; I had my coffee, read the newspaper, then browsed the internet to see what was new in the world.  As soon as I noticed a small news item announcing the launch of the New Horizons mission that morning, I clicked the link to the story.  It was the first I had ever heard of New Horizons, so I had no idea what it was all about.  When I read that New Horizons was lifting off that day to start it’s journey to Pluto, I wanted to turn cartwheels; of all the planets in the solar system, Pluto was the only one remaining that had received no attention from a NASA mission.

Pluto was a mystery; the best resolution we could get from the Hubble Space Telescope was still nothing more than a tiny, unresolved disc.  Compared to the rest of the planets, we knew nearly nothing about it.  We still don’t, for that matter.  At least not as much as, say, Jupiter, Saturn, or Mars.

It’s a sure bet that Pluto is a small, bitterly cold and dead world.  At Pluto’s distance, the sun appears in the sky as a bright star, so there’s little or no actual daylight anywhere on the surface.  That doesn’t make it any less attractive as a target for a mission, though.  I had often wondered what it’s like on Pluto.  I suppose for me the appeal and the mystery of Pluto is that it’s so far away from the earth, in the remote outer reaches of the solar system.  So far, in fact, that New Horizons has been hurtling through space at breakneck speed – as I write this, something over nine miles per second – and after eight and a half years it still isn’t there yet.  Ah, but only one more year to wait, you see, because it’s due to arrive July 14th, 2015.

Therein lies the only thing I don’t like about the mission; it’s not actually going to arrive at Pluto, but instead it will do a close flyby, snap some photos, take all the measurements it can while zipping by the planet, and continue on without so much as slowing down one iota.  I don’t like it, but I understand it.  At the speed New Horizons is traveling, it would take much more fuel than it could carry onboard to slow it enough to go into orbit for an extended study of the planet.  (Yes, I know Pluto is no longer classed as a planet, but when I was in school, it was.  Sorry, old habits die hard, so it’s still a planet to me.)  Another reason for the quick flyby is that Pluto reached it’s perigee, or closest point to the sun in 1989 and has been moving farther away since then.  As it continues to get more distant from the sun, it’s getting colder.  The time will soon come when the thin atmosphere of Pluto will condense into ice and precipitate to the surface as frost – and it won’t become a gaseous atmosphere again for more than 200 years, when Pluto finally comes back around to perigee.  Slowing the spacecraft would take time, and the transit time would have been substantially increased, increasing the risk of getting there after it’s gotten too cold at the surface.

It was obviously for this reason that after New Horizons was launched, it wasted no time getting on its way to Pluto.  Actually, the scientists and technicians in control of the spacecraft floored the gas pedal, so to speak, and just eight and a half hours after take-off, New Horizons was waving goodbye to the Moon.  Just over two months later, it sped past the orbit of Mars.  It still wasn’t headed for Pluto, though, but a mere thirteen months after launch, in February 2007, New Horizons whipped closely around Jupiter, using the slingshot effect to give it a boost to a whopping speed of over fourteen miles per second* in the direction of Pluto.

The spacecraft is carrying seven instruments onboard, which despite their cute names, will carry out some interesting observations:

Ralph is an imager that will take visible and infrared photos.

Alice (ah, lovely Alice) is an ultraviolet imaging spectrometer that will analyze the composition of Pluto’s atmosphere.  It will also be used to look for an atmosphere around Pluto’s largest moon Charon, as well as its other four moons: Nix, Hydra, Styx, and Kerberos.

REX, which stands for Radio science EXperiment, will measure atmospheric composition and temperature.

LORRI, which is a LOng Range Reconnaissance Imager, will employ a telescopic camera that will be used to map Pluto’s far side and generally provide high resolution geologic images and data.

SWAP, which stands for Solar Wind Around Pluto, will measure the atmospheric escape rate and the solar wind around Pluto.

PEPSSI, which is the Pluto Energetic Particle Spectrometer Science Investigation, will measure the composition and density of plasma escaping from Pluto’s atmosphere.

SDC, or the Student Dust Counter, is so named because it was built and is being operated by students.  It’s measuring the space dust New Horizons encounters on its way across the solar system.

All in all, there will hopefully be some good data gathered from the Plutonian system.  I just hope the instruments are all in good working order so that the single flyby will produce some good data.  If any of them aren’t, it will be a missed opportunity, for there will be no second chance.

From Pluto, New Horizons will continue on into the the largely unexplored outer parts of the Solar System, where it will hopefully encounter objects in the Kuiper Belt.  If so, given the relative young age of the spacecraft, it should be able to send back the same sort of data it will be transmitting from Pluto.  But I still wonder if it was worth it to risk it all on a high-speed, once-only flyby.  Known Kuiper Belt objects such as Sedna and Quaoar are presently too distant from the direction toward which New Horizons is moving, and no other specific objects are mentioned for observation.  I suppose there is the hope that one or more will be encountered, but so far as I can determine, there is no guarantee.

Still, I’m glad the mission is well underway, and I look forward to seeing the photos and information that comes back from a planet that has intrigued me since I was a boy.  One other thing I might note here – Clyde Tombaugh, who discovered Pluto in 1930, will be the first man in the vicinity of Pluto, and the first man to leave our Solar System.  His ashes are aboard New Horizons.


* Fourteen miles per second would please me to no end if it were the muzzle velocity of a round fired from my rifle, but there are obviously problems with the physics of this – at that speed, it would turn meteorite almost immediately, and burn up in the air before it hit its target.  At least I think it would.  On the other hand, at that speed it still might hit, but by that time it would be the hottest tracer round ever fired and really light up my target.  But then, I’m not a physicist… just a dreamer.




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