As a kid, I poured over diagrams in Popular Science magazine describing possible Grand Tours of the outer solar system (Jupiter, Saturn, Uranus, Neptune, and Pluto) made possible by a rare alignment of the planets. Unfortunately, budget cuts reduced the Grand Tour to the Voyager missions to Jupiter and Saturn. While Voyager 2’s mission was ultimately extended to fly by Uranus and Neptune, Voyager 1 was deflected out of the ecliptic (plane of the solar system) by close fly-bys of Saturn and its planet-size moon Titan to obtain breathtaking and unprecedented photographs of Saturn’s rings from above, but thereby sacrificing its opportunity to visit Pluto.
After an intense public relations campaign, of which I was a small part, NASA launched New Horizons in 2006 with the highest launch speed of any spacecraft, crossing the moon’s orbit in under half a day. Powered by the radioactive decay of 11 kg of Pu-238 and carrying an ounce of Pluto discoverer Clyde Tombaugh’s ashes, New Horizons will fly by Pluto and its large moon Charon this July. I expect both Pluto and Charon to be complex worlds, possibly including phenomena like exotic snows and cyrovolcanism.
New Horizons will transmit a few highly-compressed closeup images of Pluto and Charon just after the fly-by but will transmit most of the fly-by data over the next year. (For fixed spacecraft transmission power, Earth reception power decreases like the inverse square of the distance, which is about 4.5 light-hours at Pluto. The spacecraft compensates by reducing the data rate to allow the receiver to integrate the incoming signal, thereby increasing the signal-to-noise ratio.)
This week, images from New Horizons will exceed the resolution of the Hubble Space Telescope. Already images from April suggest surface features, including a polar cap. The long awaited unveiling of Pluto has begun.