The Science of Pluto: Great Expectations (Part 3)

An artist's rendering of Pluto's surface, with Charon looming large on the horizon. The double-planet Pluto-Charon system, represent the last unexplored frontier of the Solar System, which will be unveiled in all its glory in just a few days from now. Image Credit: National Space Society

An artist’s rendering of Pluto’s surface, with Charon looming large on the horizon. The double-planet Pluto-Charon system, represent the last unexplored frontier of the Solar System, which will be unveiled in all its glory in just a few days from now. Image Credit: National Space Society

“We are living through a remarkably privileged era,
when certain deep truths about the Cosmos
are still within reach of the human spirit of exploration”

– Brian Greene, American theoretical physicist, TEDxTalk (2012)

 

Having been launched more than nine years ago in January 2006, NASA’s New Horizons spacecraft is in the very final stages of its approach to Pluto, tasked with conducting the first ever fly by in human history of the distant dwarf planet and its moons. A secondary objective of its mission is the reconnaissance of the vast area that lays beyond as well: the frozen realm of minor bodies at the very edges of our Solar System, better known as the Kuiper Belt. In order to carry out this mission as planned, the intrepid robotic explorer is equipped with some of the most advanced instruments ever to have flown on a planetary science mission, creating an aura of great expectations among the science community and the public at large regarding the exploration of the Solar System’s last unexplored frontier.

Having traversed more than 5 billion km of interplanetary space following its launch in 2006 and after a successful and highly productive six-month-long, long-range reconnaissance of Pluto which started in January of this year, New Horizons is now ready to begin its close-encounter science observations of the Pluto system on July 12, just two days before closest approach. Ever since the mission entered its third approach phase to Pluto on June 23, the spacecraft has been conducting daily observations of the entire Pluto system, while returning hundreds of tantalising images of the distant dwarf planet that are becoming more detailed with each passing day. Just as the spacecraft will enter the encounter phase of its mission on July 12, it will start transmitting most of the data that will have been already collected, back to Earth, including optical navigation images and most of the close-up images of Pluto up to that point. The purpose for this data downlink will be two-fold, on one hand ensuring that most of the images of Pluto and Charon that will have been already taken will make it back to Earth and allowing the spacecraft to empty its data recorders on the other hand for the intense brief period of closest approach two days later.

New Horizons' trajectory through the Pluto system during the day of closest approach on July 14. All hours are in UTC. Image Credit: Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute (JHUAPL/SwRI)

New Horizons’ trajectory through the Pluto system during the day of closest approach on July 14. All hours are in UTC. Image Credit: Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute (JHUAPL/SwRI)

At the day of closest approach, and having already been cleared to follow its ‘optimal science’ trajectory through the Pluto system, New Horizons will fly past Pluto at a distance of just 13,700 km and 29,500 km from Charon, allowing it to return images of the pair’s surfaces with a resolution of up to 0.4 km/pixel. This level of detail will provide scientists with truly spectacular images of both celestial bodies in order to meet the mission’s science objectives. These include the close-up geologic and color imaging of Pluto and its system of moons, the detailed surface mapping of both Pluto and Charon, as well as the study of Pluto’s atmosphere and its possible interaction with Charon. In addition, the mission’s science team wants to address a series of long-standing open questions about the interiors of both bodies and their dynamical and geologic evolution through time.

The time of closest approach will not mark the end of the mission’s reconnaissance of Pluto however. Following its flyover of the distant planet’s surface, New Horizons will be positioned in such a way that it will be able to observe Pluto occult the distant Sun, allowing scientists to study the planet’s night-time surface and atmospheric temperatures, and search for any additional rings. New Horizon’s departure from the Pluto system has been divided into three phases by the mission’s science teams, which will span the remainder of the year from July to December, during which the spacecraft will conduct remote sensing of Pluto’s moons until it reaches the limits of its imaging systems’ resolution, as it will gradually recede away.

Worthy of note, is that contrary to popular belief, at the day of closest approach day on July 14, New Horizons will not be sending any data back to Earth, because it will be busy collecting data during the Pluto flyby. All everyone will be able to do during these intense 24 hours, will be to wait for the spacecraft to send a brief tone which will indicate that it has passed through the Pluto system successfully. Travelling at the speed of light, this brief signal is expected to be received by ground controllers on July 14 at 21:09 EDT, a full 4.5 hours after closest approach itself. Even then, the spacecraft will have to wait until the morning hours of July 15 before it can start transmitting its first batch of ‘browse’ black-and-white images of the Pluto system. One of the reasons that are causing these delays, is the agonizingly slow data rates of 1 kilobit per second with which the spacecraft transmits its data back to Earth. At its current distance of more than 5 billion km away, New Horizons’ signals are so weak that can only be picked up by the largest, 70-m-wide antennas of NASA’s Deep Space Network in the U.S., Spain, and Australia. Nevertheless, the mission’s science teams are planning to have the images available for the public within the first 48 hours after they have been received, in order to make everyone participate in the historic event of humanity’s first close fly by of Pluto. “On the actual closest approach day, we will not be bringing back any imaging data,” says Cathy Olkin, deputy project scientist for New Horizons, at the Southwest Research Institute, in Boulder, Co. “We need to keep our sights on Pluto. We need to train our instruments on Pluto and that means we’ll not be taking time to send data back down to Earth, and so on closest approach day we’re all gonna have to be patient while New Horizons is exploring Pluto.”

The timeline of the New Horizons mission, from the start of the long-range reconnaissance of Pluto in January 2015 to the end of all of its data downlink to Earth in October 2016. Image Credit:  Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute (JHUAPL/SwRI)

The timeline of the New Horizons mission, from the start of the long-range reconnaissance of Pluto in January 2015 to the end of all of its data downlink to Earth in October 2016. Image Credit: Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute (JHUAPL/SwRI)

Even though New Horizons fly by of Pluto will only take the better part of a day to be complete, the spacecraft will accumulate a treasure trove of more than 60 gigabits, or more than 7 gigabytes of science data. Due to its long distance from Earth and the slow data rates with which the spacecraft will be communicating with ground controllers, all of these data will take approximately a year and a half in order to be downloaded in its entirety. New Horizons will start beaming up the lower-resolution, thumbnail-type images of the Pluto encounter first in mid-September, while the full data set of the high-resolution ones will have to wait until October 2016 before they will be downloaded in its entirety. “In the middle of September we’re gonna have a one-week time period, when we’ll bring down selected high-priority data sets, explains Olkin. ‘These are things that we really want to get to the ground to help fill out our early studies of what Pluto, Charon and its moons look like. Then, starting in late September or early October, we will be bringing down what we call our ‘browse’ data set. This is all of our observations but at a lower resolution, so we can get them down more quickly. Then finally, in late November, we will start our full-resolution playback…It’s those 60 gigabits of data that we will be filling [New Horizons] data recorders with and that will be played back all through 2016…We’re gonna have surprises and discoveries over the next year and a half, as Pluto reveals itself with each and every Deep Space Network pass.”

Far from being just a one-day mission, New Horizons will keep scientists and the public alike busy for a long time, as new worlds will be slowly revealed to us for the first time. “This is a real moment in time for you to watch us turn a point of light into a planet,” says Dr. Alan Stern, principal investigator for New Horizons, at the Southwest Research Institute.

This moment in time begins just under a week from now.

 

You can read Part 1 and Part 2, here and here.

 

Stay with AmericaSpace for regular updates and LIVE COVERAGE of New Horizons’ approach and flyby of the Pluto system.

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1 comment to The Science of Pluto: Great Expectations (Part 3)

  • Brian Greene’s comment that we live in a privileged era where cosmic truths are within the human spirit of exploration is a profound statement that will reverberate for generations to come. It is also a testament to the hard work, dedication and the pure genius of those who made this mission possible. I would rank New Horizons as one of the most significant events of the space age.