Monday July 13, 2015

Media Monday: Pluto and Charon

Pluto

















By now you may have heard about New Horizons, a NASA spacecraft that will fly by Pluto and its moon Charon tomorrow. New Horizons will have its closest approach to Pluto at a distance of 12,500 km on July 14th, 2015 at 7:49 AM EDT. However, you may not want to risk being late to work to see the highest resolution image yet of Pluto come in - the best encounter-period image should be downlinked around 11:07 PM EDT by the Deep Space Network this evening, but it may not be released until the Phone Home briefing at 8:53 PM EDT tomorrow evening when New Horizons sends us a signal to let us know it survived the encounter. 

During the approach itself, New Horizons will be focused on collecting scientific data from its instrument payload, including three optical instruments, two plasma instruments, a dust sensor, and a radio science receiver. That said, the highest resolution images of Pluto at .4 km/pixel won't be returned until next Monday. In fact, during the encounter-period, only 1% of the science data that the probe acquires will be downlinked to Earth. The rest will have to be patiently obtained during the months after the flyby. The reason why it takes so long is that Pluto is very far away - more than 30 times Earth's distance from the sun (see this cool scale model of the solar system if our moon was one pixel in size. Be prepared to be scrolling for awhile to get to Pluto). This immense distance that data has to travel means New Horizons' radio signal is about 1 kilobit per second. One high resolution image of Pluto is 1024 pixels square, which can be compressed losslessly to 2.5 megabits. One 2.5 megabit image at 1 kilobit per second means it takes 42 minutes to return one image. Images are important, but the spacecraft is also designed to collect scientific data. This means that two periods during the approach, New Horizons will focus solely on collecting data from its other scientific instruments to be returned at a later time while the cameras get a break. 

The mission thus far has not been without its challenges. On July 4th, the spacecraft's signal was lost in what the Principal Investigator Alan Stern calls New Horizons's "Apollo 13" moment. The main computer had been asked two computationally intensive tasks at once due to a hard-to-detect flaw in the command sequence. New Horizons performed as it was programmed to do: switch to the backup computer, enter safe mode, stop science, and ask Earth for help. The team quickly identified the problem and had the spacecraft back up and working on July 7th

New Horizons has already provided us with valuable scientific information about the last-to-be explored body in our solar system. Alan Stern revealed in a press briefing today that Pluto is officially larger than Eris, known to many as the dwarf planet that killed Pluto's planet status. The first compositional measurements have revealed that Pluto has a polar cap composed of methane and nitrogen ices. And no longer is Mars the sole red body in the solar system - Pluto is also a red-orange color with several significant dark and bright spots. 

The best way to stay up to date with New Horizons updates is social media, especially Twitter. People to follow include Emily Lakdawalla (@elakdawalla), a planetary scientist and senior editor for The Planetary Scientist; Popular Science's Amy Shira Teitel as @astVintageSpace; Dr. Katie Mack (@AstroKatie), a cosmologist; The Bad Astronomer Dr. Phil Plait (@BadAstronomer), New Horizons' Principal Investigator, Alan Stern (@AlanStern), and of course, the  official New Horizons account: @NewHorizons2015. 

New Horizons was launched in 2006 when Hubble provided us with the best picture of Pluto (left image) and MySpace was the most popular website in the world and iPhones didn't exist. Tomorrow we will have images several hundred times sharper than the right-side image, taken yesterday and processed by the New Horizons team. We will finally see the surface geology, learn the atmospheric properties, and have a clearer understanding of this eagerly anticipated planet. 

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