What Will New Horizons See — and When?

In his third "insider blog" about the New Horizons mission, principal investigator Alan Stern offers a look at the timetable for getting results from the historic flyby.

It sounds like science fiction, but it’s not: NASA’s New Horizons spacecraft is on final approach to the Pluto system! After 113 months in flight, the fastest spacecraft ever launched is now barely 30 days from its destination. Closest approach of the flyby occurs on July 14th at 11:50 Universal Time.

I’m writing a series of insider blogs about the mission for Sky & Telescope, and in this third one, I want to give you a feel for what images and other data sets we’ll be receiving on the ground during the encounter.

As background to that, I should explain first that New Horizons was built to be very, very effective at taking and storing large amounts of data as it zips past Pluto and its five moons at 13.8 km (8.6 miles) per second. This was accomplished by providing the capability for up to five of the seven science instruments to be operating at any one time, and by providing two large recorders for data storage during encounter. As a result of these and other design features, New Horizons will take about 100 times as much data during the flyby as it can send back on a typical day. Given this, and given that we have to share NASA’s Deep Space Network of communications stations with other missions, getting all of the Pluto system observations back on Earth will take the rest of 2015 and most of 2016.

That in turn means that New Horizons, long after it's passed by Pluto, will continue to return new data and discoveries — to you — and to our science team, for a very long time — almost as if it were still at the planet, gathering data.

But even though we'll be receiving a steady stream of images, spectra, and other data for some 16 months after July’s flyby, many images and other observations will be returned during the close-approach operations spanning July 4th to July 20th.

The table below shows you just the images (and their expected resolutions) that we expect to receive each day during that 2½-week-long window. Keep in mind that Pluto’s diameter is almost 2,400 km (1,500 miles), so for example, a 40-km/pixel image should put about 3,000 pixels on Pluto's disk and a 10 km/pixel image would put about 45,000 pixels on its disk. Also keep in mind that as Pluto and its satellites rotate as we approach, we’ll not only be getting higher and higher resolution, but we’ll also be seeing new terrains coming into view. (In the last column, P = Pluto, C = Charon, N = Nix, and H = Hydra.)

And here's a second table that shows some of the other data types that the spacecraft will be sending home each day.

As you can see, there’s a wide variety of data coming down in July to reveal many kinds of details about Pluto, Charon, and Pluto’s small satellites. We'll also be searching for rings, mapping surface compositions, studying Pluto’s atmosphere, and measuring its surface temperature and radar reflectivity.

By the time July is over, we’ll have a pretty good sampling of the many kinds of data New Horizons obtained when close to the Pluto system. But the real deluge that fills in the details — and which comprises the other 99% of the data taken — will have to wait for the long downlink that begins after the flyby.

Planetary scientist S. Alan Stern of the Southwest Research Institute is the Principal Investigator of NASA's New Horizons mission to Pluto. He is writing a series of blogs for Sky & Telescope before and during the spacecraft's historic encounter.