New Horizons is a flyby mission. That is, in order to reach Pluto in a reasonable amount of time (it was launched in 2006, time-to-Pluto will have been nine years), it launched with a high speed which was further boosted by gravitational assist from Jupiter. It's not carrying fuel to brake this speed, nor is Pluto massive enough to be used for gravitational assist to slow it (which is how other Gas Giant orbital missions have slowed sufficiently to be captured in orbit).
From Wikipedia: "New Horizons is intended to fly within 10,000 km (6,200 mi) of Pluto. New Horizons will have a relative velocity of 13.78 km/s (49,600 km/h; 30,800 mph) at closest approach, and will come as close as 27,000 km (17,000 mi) to Charon" (Pluto's moon).
The nearest approaches can still be adjusted depending on mission parameters as the probe approaches Pluto. Some consideration is given to the post-Pluto mission, with other Kuiper belt objects being targeted for study.
In the roughly four hours it takes for radio signals from the flyby to reach Earth, New Horizons will have travelled half the distance between the Earth and Moon. Which is to say, it won't be hanging around Pluto very long.
By contrast in the case of Mars we have multiple probes in orbit around Mars, including the Mars Reconnaissance Orbiter (MRO), which through a combination of thruster fire and aerobraking (dipping into Mars's atmosphere to slow its velocity) has been orbiting Mars at an altitude of 300 km, allowing for both photography and other sensor observations, since 2006. The result is a vast wealth of close-in imagery with a resolution of up to 18 meters.
So: yes, if all goes well we should get some high-quality imagery of Pluto, from as close as 10,000 km -- 33 times the distance of the MRO from Mars. But it's going to be a once-through pass, at high speed, and with no options for retargeting sensors from Earth to reexamine interesting objects.
I wonder whether Neptune or Uranus could be used to 'aerobreak' in order to get a probe into an orbit around Pluto. I'm guessing with Pluto's eccentric path there should be points in time where it is close to one of these planets, but it is probably a window that only opens up on a timescale of hundreds of years?
That's a possibility, but the bigger problem is simply the size of the solar system.
Uranus is 2.88 billion km from the Sun.
Neptune is 4.5 billion km from the Sun. Nearly twice as far as Uranus.
Pluto is 5.9 billion km from the Sun on average. It varies a lot, from inside the orbit of Neptune to nearly double the distance - 4.4 to 7.3 billion km. New Horizons will be reaching it at one of its nearer approaches. Pluto is also significantly inclined to the solar plane, unlike the planets.
By contrast Jupiter is less than 1 billion km away: 0.779 billion km.
Saturn is 1.4 billion km -- twice as far as Jupiter.
Note that if you managed to slow yourself down at Neptune on your way out to Pluto, you'd still have the distance from the Sun to Saturn to traverse. Say you cut half your speed -- it would take you nearly six and a half years to reach Pluto, rather than the 3.2 of the current mission trajectory. You're trading speed and time here.
And you'd still have to lose some 20,000 km/h of velocity when you arrived.
Space is big. Really big. You won't believe just how vastly, hugely, mind bogglingly big it is.
Then there's the orbital periods. Neptune's year is nearly 165 Earth years, Uranus is 84 years, Pluto's is nearly 248 years. This means that Pluto, discovered in 1930, won't have completed a full orbit of the Sun until 2177. Neptune, discovered in 1846, completed its first full orbit since only in 2010.
That's what I meant with eccentric path though: As far as I know Pluto is not always that far out, there are points in time where it's closer to the sun than Neptune - which should be a good moment when either Uranus or Neptune could be used to aerobreak.
Edit: but only when they also line up correctly, which is why I think it would take hundreds of years of waiting.
Edit2: After watching the linked video, Uranus would be out, since Pluto is never close to it, but Neptune might work at some point in time when these planets are close.
The Neptune-Pluto alignment is one that might be interesting to explore on a solar system simulator. I suspect you might have to wait a fair fraction of a thousand years for that though, at a minimum.
New Horizons is a flyby mission. That is, in order to reach Pluto in a reasonable amount of time (it was launched in 2006, time-to-Pluto will have been nine years), it launched with a high speed which was further boosted by gravitational assist from Jupiter. It's not carrying fuel to brake this speed, nor is Pluto massive enough to be used for gravitational assist to slow it (which is how other Gas Giant orbital missions have slowed sufficiently to be captured in orbit).
From Wikipedia: "New Horizons is intended to fly within 10,000 km (6,200 mi) of Pluto. New Horizons will have a relative velocity of 13.78 km/s (49,600 km/h; 30,800 mph) at closest approach, and will come as close as 27,000 km (17,000 mi) to Charon" (Pluto's moon).
http://en.wikipedia.org/wiki/New_Horizons#Pluto_approach
The nearest approaches can still be adjusted depending on mission parameters as the probe approaches Pluto. Some consideration is given to the post-Pluto mission, with other Kuiper belt objects being targeted for study.
In the roughly four hours it takes for radio signals from the flyby to reach Earth, New Horizons will have travelled half the distance between the Earth and Moon. Which is to say, it won't be hanging around Pluto very long.
By contrast in the case of Mars we have multiple probes in orbit around Mars, including the Mars Reconnaissance Orbiter (MRO), which through a combination of thruster fire and aerobraking (dipping into Mars's atmosphere to slow its velocity) has been orbiting Mars at an altitude of 300 km, allowing for both photography and other sensor observations, since 2006. The result is a vast wealth of close-in imagery with a resolution of up to 18 meters.
http://en.wikipedia.org/wiki/Mars_Reconnaissance_Orbiter
So: yes, if all goes well we should get some high-quality imagery of Pluto, from as close as 10,000 km -- 33 times the distance of the MRO from Mars. But it's going to be a once-through pass, at high speed, and with no options for retargeting sensors from Earth to reexamine interesting objects.