Last Stop in the So­lar Sys­tem

Nine years af­ter leav­ing Earth, New Hori­zons sets its sights on Pluto, and what­ever lies be­yond.

Air & Space Smithsonian - - Front Page - BY AN­DREW CHAIKIN

This July, from three bil­lion miles away, a space­craft will send the first close-ups ever seen of Pluto.

THIS JULY 14,

at around 9 p.m. East­ern time, a burst of ra­dio teleme­try will com­plete a three-bil­lion-mile trek to ar­rive at one of the huge dish an­ten­nas of NASA’S Deep Space Net­work. The sig­nal will make its way to a com­mand cen­ter in Mary­land, where plan­e­tary sci­en­tist Alan Stern will be wait­ing. If the sig­nal ar­rives as planned, he will know that the re­con­nais­sance of Pluto he spent the last 25 years work­ing to­ward has suc­ceeded.

Thir­teen hours ear­lier, the 1,100-pound, grand-pi­ano-size probe called New Hori­zons will have sped past the dwarf planet and its ret­inue of moons, gath­er­ing close-up im­ages and other data that Stern ex­pects will “rewrite the text­books.” That is, if New Hori­zons man­ages to avoid col­lid­ing with par­ti­cles of dust and ice, which—at a flyby speed of 31,000 mph—could de­stroy the craft be­fore it has a chance to trans­mit its find­ings to Earth. Stern, who is based at the South­west Re­search In­sti­tute in Boul­der, Colorado, says, “That should be a nail-biter.” He says it al­most cheer­fully, as if he wel­comes the or­deal. By now, as the mis­sion’s prin­ci­pal in­ves­ti­ga­tor and the driv­ing force be­hind its creation, Stern is used to ten­sion. Al­most ev­ery­thing about get­ting to Pluto has been a strug­gle.

Twenty-five years ago, when he be­gan his Pluto quest, plan­e­tary sci­en­tists were still an­tic­i­pat­ing the con­clu­sion of the Grand Tour of the outer so­lar sys­tem by the twin Voy­ager space­craft, launched in 1977. At one time plan­ners had con­sid­ered in­clud­ing Pluto on Voy­ager 1’s itin­er­ary, but in­stead chose a flight path that would al­low close fly­bys of more al­lur­ing tar­gets like Saturn’s moon Ti­tan. And so, af­ter pass­ing Saturn in 1980, Voy­ager 1 headed off to­ward in­ter­stel­lar space, and the Grand Tour ended with Voy­ager 2’s flyby of Nep­tune in Au­gust 1989. Most sci­en­tists were un­trou­bled that Pluto had been left out. Not Alan Stern. To him, the ex­plo­ration of the so­lar sys­tem was un­fin­ished. By the spring of 1989, with a new PH.D. in as­tro­physics and plan­e­tary sci­ence, Stern was al­ready think­ing about how to get NASA to send a mis­sion to the ninth planet. He started talk­ing up the idea. “I was a young guy,” he re­calls, “and se­nior guys in the field, guys that were in their 50s then, would say to me, ‘Are you kid­ding me? Ev­ery­one will be dead by the time we get there.’ Mean­ing they would be dead. It’s hu­man na­ture.”

Stern ral­lied sev­eral young sci­en­tists, and even a few older ones, to take up the cause. The idea be­came even more ap­peal­ing af­ter Voy­ager 2’s Nep­tune flyby, when sci­en­tists got their first good look at the icy moon Tri­ton, thought to be a close cousin of Pluto. Voy­ager’s im­ages re­vealed weird, con­torted ter­rains and, to ev­ery­one’s amaze­ment, gey­sers of frozen ni­tro­gen. There was rea­son to think Pluto might be just as strange and ex­cit­ing.

Dis­cov­ered in 1930 af­ter a nearly year-long tele­scopic search by a young ob­ser­va­tory as­sis­tant named Clyde Tom­baugh, Pluto is so faint and so dis­tant—its 248-year or­bit av­er­ages 3.7 bil­lion

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