The New Horizons spacecraft will fly by Pluto in 2015, with the closest approach happening on July 14. New Horizons will be making observations for months leading up to the closest approach and for some time after. The New Horizons encounter with Pluto presents a once-in-a-lifetime opportunity to directly link our Earth-based view of Pluto with ‘ground truth’ provided by in situ measurements.
To support the New Horizons encounter, our Campaign Goal is straightforward: Establish an extensive measurement context using Earth-based telescopes (on the ground and in orbit) for the state of the Pluto system at the time of the flyby, including evolving trends in the system for at least one year prior- and post-flyby.
While "simultaneous" measurements at the time of the July 14, 2015 flyby are of obvious importance for calibration and context, the need for pre- and post-flyby observations are equally important. Pluto is known to be a constantly changing world due to the solar energy being received decreasing by ~2% per year on account of its eccentric orbit now carrying it rapidly away from perihelion. What’s more, the orientation of Pluto's spin axis the sub-solar latitude by (the height of the "midday Sun") to change more than 1 degree per Earth year, bringing 100,000 square kilometers of new surface area into sunlight for the first time in a century (while casting an equal and opposite polar area into a century long arctic winter). These orbit-related effects on the atmosphere and surface of Pluto are on top of the well-known longitudinal variations measurable over the course Pluto’s 6.387 day rotation.