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NASA sets goals on New Horizons

- Joshua Johnson

On Jan. 19, 2006, NASA's New Horizons probe launched from Cape Canaveral Air Force Base in Florida. Thirteen hours later, the spacecraft flew past the orbit of the Moon on a more than three billion-mile and nine year journey bound for Pluto and the Kuiper belt in the outermost regions of our solar system. The spacecraft weighing just over 1,000 pounds launched from the top of an Atlas V-551 rocket at 2:00 pm local time.

The launch of New Horizons was plagued by delays and setbacks for two days before a successful launch could be completed. The launch was scrubbed on the first day of its launch window, Jan. 17 due to high winds in Florida. A power outage at the mission control center at Johns Hopkins University's Applied Physics Laboratory caused the mission to be set back again on Jan. 18.

At liftoff, the rocket's main engine and five solid rocket boosters provided a thrust of almost 2.5 million pounds of thrust. New Horizons now holds the record of being the fastest spacecraft ever launched. With the help of a Centaur second stage and the Star 48B third stage, the tiny spacecraft is currently in route to a fly-by and gravity assist from Jupiter in 13 months at an approximate speed of 36,000 miles per hour (10 miles per second). The probe will improve on that record when it receives a boost from Jupiter's gravity and speeds towards Pluto at 47,000 miles per hour.

New Horizons will be the first probe to ever reach and study Pluto and its large moon, Charon. Sometimes known as a "double planet system" due to Charon's large size compared to Pluto (Charon's diameter is roughly 50% of Pluto's), the two bodies are shrouded in mystery. Very little is known about the ninth planet; all current information has been taken from ground-based telescopes. Even the Hubble Space Telescope cannot make out much more than fuzzy details of the tiny planet's surface.

Heightening the need for further exploration of Pluto was the discovery of two smaller moons last summer. Tentatively named "P1" and "P2", these moons are so small (40 and 125 miles in diameter, respectively) that they cannot be studied from Earth. In addition, recently scientists have discovered that Pluto has a very thin atmosphere comprised of nitrogen and methane that condenses to the planet's surface during its winter months, and then evaporates to reform an atmosphere as the planet gets closer to the sun. Currently the atmospheric pressure at the surface of Pluto is estimated to be 100,000 times less than Earth's.

After exploring Pluto and Charon, New Horizons is slated for an extended mission to the band of comets, asteroids, and other stellar material known as the Kuiper Belt. There is much current debate on whether Pluto should be classified as a planet or a Kuiper Belt Object (KBO).

Just before encountering our ninth planet, mission planners will select a KBO to steer the craft to after the probe's main mission. Approximately five years after flying past Pluto, New Horizons will perform a very similar mission on the selected KBO.

The $700 million probe will be powered by 24 pounds of plutonium dioxide in its radioisotope thermoelectric generator (RTG) producing about 200 watts of both electricity and thermal energy at the time New Horizons reaches Pluto. An RTG was selected by NASA because at 4 billion miles from Earth, the Sun is little more than a bright star, making solar panels useless.

The "brains" of New Horizons lie in a Mongoose V processor operating at 12-megahertz to reduce power consumption. The probe has two solid-state recorders of 8 gigabytes each of data storage (one primary and one backup system). Initially, the probe will be capable of a data transfer rate of 38,000 bits per second. Once transmitting data about its encounter with Pluto, however, due to the extreme distance, the probe will be transmitting between 600 and 1,200 bits per second. The entire data set compiled by the probe's sensors will take nine months to fully download to scientists on Earth.

Data and images will be taken of the Pluto system beginning five months before then. Samples of the planet's weak atmosphere, along with dust particles in space will be analyzed by the probe. At its closest approach to Pluto, New Horizons will capture images that distinguish features as small as 25 meters in size on the planet's surface.

According to NASA, the expected closest approach of New Horizons at Pluto will be on Jul. 15, 2015.

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