Getting a closer look at Pluto

On February 4, 2010, NASA released a set of images that were the most detailed ever taken until then of the distant dwarf planet Pluto. Before the New Horizons spacecraft explored Pluto, getting a closer look at it was no easy task. A.S.Ganesh tells you how scientists managed it nevertheless…

Come February 18, and it will be 94 years since we’ve known of the existence of Pluto. Pluto has enjoyed popularity with the public throughout its known existence. Right from the time it was discovered in 1930 and hailed as the ninth planet, through to 2006 when it was demoted to the status of a dwarf planet, and since, Pluto has held the imagination of the masses.

Pluto takes nearly 248 years to orbit around the sun and its elongated orbit ensures that it is about 7.3 billion kilometres from the sun at its farthest and gets closest when it is about 4.4 billion kilometres from it! With its closest distance to the sun in itself being very very far, this Kuiper belt object is naturally very distant from Earth as well.

So far, in fact, that trying to see and resolve the surface of Pluto from Earth is akin to trying to see the print on a ball when the ball is placed over 50 km away! Pluto’s disk is so small that it can’t be resolved from beneath the Earth’s atmosphere. We are not just talking about plain viewing, but also using the most powerful ground-based telescopes.

It was a space-based telescope in the form of the Hubble Space Telescope that enabled the first unobstructed viewing of Pluto. Tasked with observing and imaging the planet in June-July 1994 (remember that it was still a planet back then), it was put together and released for public consumption on March 7, 1996.

The Hubble Space Telescope was tasked with snapping Pluto again in 2002-2003. Astronomers had installed in it a new camera called the Advanced Camera for Surveys (ACS). This new camera was equipped with an operating mode called the High-Resolution Camera (HRC). The ACS/HRC system produced 384 images of Pluto – the most detailed set of observations made of Pluto until then.

These raw images were then worked on by scientists and engineers for years on end before they were eventually released to the public on February 4, 2010. This set of images were, until then, the most detailed ever of Pluto.

“This has taken four years and 20 computers operating continuously and simultaneously to accomplish,” said lead investigator Mark Buie of the Southwest Research Institute in Boulder, Colorado at a NASA press conference on that day. Even though Buie, who had developed special algorithms to sharpen the Hubble data, put it across in just a statement at the press conference, he went into more details when writing about this research project for his website.