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New Horizons closes in on Pluto

Jenny Winder, News Writer
Apr 12, 2015, 3:15 UTC

Sen—With less than a hundred days until closest approach, NASA's New Horizons spacecraft has begun a series of observations, including the first colour and spectral observations of Pluto and its moons as the mission closes in on its goal.

Since New Horizons launched nine years ago on Jan. 19, 2006, scientists have had a very long wait finally to get close-up views of their target.

New Horizons is currently about 4.79 billion km (3 billion miles) from Earth and speeding towards Pluto, which now lies less than 111 million km (69 million miles) away, at approximately 50,000 km (over 31,000 miles) per hour. 

Since January this year, when New Horizons officially began its science mission, the images the spacecraft has taken have comprised a few pixels and primarily been used to navigate the spacecraft toward Pluto while the instruments on board have been sampling the surrounding environment.


Pluto and Charon, seen Jan. 25 and 27, 2015, through the telescopic Long-Range Reconnaissance Imager (LORRI). Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Now the mission is in what is called Approach Phase 2 (AP2) which aims to get a more detailed picture of the Pluto system, which has five known moons.

From now until mid June the spacecraft will take long-exposure images looking for any additional moons or rings or any other hazards New Horizons could face as it passes between Pluto and its largest moon Charon.

The spacecraft will also take the first ultraviolet observation of the surface and atmosphere of Pluto and Charon.

Alan Stern, the mission's principal investigator from Southwest Research Institute, told Sen: “AP2 is when New Horizons moves from environmental characterization of the region where Pluto orbits to specific observations of the Pluto system itself.

"In the coming weeks we will train all our imagers on Pluto, and its moons, as they emerge from dots to spinning worlds viewed by mid-AP2 at better resolution than any previous imagery ever taken.

"We’ll also continue environmental modeling of the dust and plasma environment in AP2, and we’ll start to take initial ultraviolet and infrared spectra of Pluto. AP2 is where the exploration of Pluto by humankind begins."

The New Horizons science payload consists of seven instruments, two plasma instruments to study solar wind interactions and atmospheric escape from Pluto, a dust sensor and radio science receiver/radiometer and three optical instruments.

The optical instruments include Alice, a sensitive ultraviolet imaging spectrometer which studies atmospheric composition and structure. Ralph studies surface composition and creates surface temperature maps, while the Long Range Reconnaissance Imager (LORRI) will provide the highest-resolution images.

By mid-May LORRI should be sending back images that surpass Hubble-quality resolution, showing Pluto in detail never seen before. However we may have to wait until June or July before the we see details of surface features. 

"The best images we have today still show Pluto and its moons as dots in the distance, but by the time AP2 ends in June, we'll see Pluto like never seen before," said Stern in a statement. "This is the time when Pluto transforms from a planetary astronomer's world—spied only through telescopes with just the slightest detail—to a planetary science target of the most capable flyby spacecraft ever sent on a first reconnaissance mission."

Mission Project Manager Glen Fountain, of Johns Hopkins University Applied Physics Laboratory (APL), said in a statement: "As the year started, we said New Horizons was on Pluto's doorstep.

"Now we're opening that door, getting closer and closer to our first real look at these mysterious worlds on the edge of the planetary frontier. This is pure exploration, and it's amazing to be a part of it."