Today the New Horizons space probe is performing its Pluto flyby

Pluto  and Charon photographed by the New Horizon space probe on July 11, 2015 (Photo NASA-JHUAPL-SWRI)
Pluto and Charon photographed by the New Horizon space probe on July 11, 2015 (Photo NASA-JHUAPL-SWRI)

Today, NASA’s New Horizons space probe will carry out the much anticipated Pluto flyby. When at NASA’s mission control center it’s early morning, it will pass at a distance that will reach a minimum of 12,500 kilometers (about 7,800 miles) from the dwarf planet. All New Horizons’ instruments will be used to analyze Pluto as ever before but some time will be devoted also to its moons, particularly Charon.

This flyby is the culmination of a mission that began in January 2006 with the launch of the New Horizons space probe but since February 2015 it’s been sending photographs with increasing details of Pluto and Charon. Coincidentally, this time comes on the 50th anniversary of the Mars flyby of the Mariner 4 space probe, the first success in that kind of mission.

The New Horizons spacecraft was supposed to investigate the last planet of the solar system after the other eight had been observed by other probes. Ironically, a few months after its launch, Pluto was downgraded to a dwarf planet. This doesn’t detract from this mission’s value, in fact in some ways it’s even more important because after this flyby, New Horizons will continue its journey to the boundaries of the solar system of which we know really little.

In October 2014, NASA announced three possible candidates among the Kuiper Belt objects observed for the New Horizons space probe’s second mission. It’s already conducting its first mission at billions of kilometers from Earth, in 2018 or 2019 it will reach an object that we struggle to see with our best instruments.

It may seem strange that a mission that costs $723 million doesn’t it entering Pluto’s orbit for a longer study. The problem is that the New Horizons space probe is traveling at approximately 14 km/s and to brake it would have to carry a considerable amount of extra fuel. This would mean an enormous increase in costs because more fuel means a much greater mass and the need for a much more powerful rocket for its launch.

The period of close study of Pluto is short but the results are already extraordinary because the data already obtained are much better than those available before the New Horizons mission. Now the study of Pluto and Charon’s geology can begin and we can hope to know something more about the smaller moons.

It’s already been possible to measure the diameter of Pluto more accurately than ever. It’s approximately 2,370 kilometers (1,473 miles), a little more than was previously measured. This makes it a bit larger than the dwarf planet Eris. Charon’s diameter was easier to measure because it has no atmosphere to disturb the instruments and was confirmed at about 1,208 km (751 miles).

NASA TV will cover the event during the day but there will be no images or other data live. The problem isn’t the four and a half hours necessary for New Horizons’ signals  to reach the Earth but the fact that the probe can’t communicate during its flyby.

New Horizons’ antenna is fixed so the probe must be oriented towards the Earth to communicate. However, during the flyby, the spacecraft will be oriented towards its targets. Only after a few hours, it will be directed to the Earth again and will start sending the collected data. Given the slowness in communications, it will take a very long time but it’s worth being patient because very interesting photographs and other data will slowly arrive.

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