The New Horizons probe is closing in on the Pluto system, which it will fly by in July. the latest pictures from the spacecraft are processed to enhanced the details Pluto’s moons :

85 Years after Pluto’s Discovery,
New Horizons Spots Small Moons Orbiting Pluto

Exactly 85 years after Clyde Tombaugh’s historic discovery of Pluto, the NASA spacecraft set to encounter the icy planet this summer is providing its first views of the small moons orbiting Pluto.

The moons Nix and Hydra are visible in a series of images taken by the New Horizons spacecraft from Jan. 27-Feb. 8, at distances ranging from about 125 million to 115 million miles (201 million to 186 million kilometers). The long-exposure images offer New Horizons’ best view yet of these two small moons circling Pluto, which Tombaugh discovered at Lowell Observatory in Flagstaff, Arizona, on Feb. 18, 1930.

“Professor Tombaugh’s discovery of Pluto was far ahead its time, heralding the discovery of the Kuiper Belt and a new class of planet,” says Alan Stern, New Horizons principal investigator from Southwest Research Institute, Boulder, Colorado. “The New Horizons team salutes his historic accomplishment.”

Assembled into a seven-frame movie, the new images provide the spacecraft’s first extended look at Hydra (identified by a yellow diamond) and its first-ever view of Nix (orange diamond). The right-hand image set has been specially processed to make the small moons easier to see.

“It’s thrilling to watch the details of the Pluto system emerge as we close the distance to the spacecraft’s July 14 encounter,” says New Horizons science team member John Spencer, also from Southwest Research Institute. “This first good view of Nix and Hydra marks another major milestone, and a perfect way to celebrate the anniversary of Pluto’s discovery.”

These are the first of a series of long-exposure images that will continue through early March, with the purpose of refining the team’s knowledge of the moons’ orbits. Each frame is a combination of five 10-second images, taken with New Horizons’ Long-Range Reconnaissance Imager (LORRI) using a special mode that combines pixels to increase sensitivity at the expense of resolution. At left, Nix and Hydra are just visible against the glare of Pluto and its large moon Charon, and the dense field of background stars. The bright and dark streak extending to the right of Pluto is an artifact of the camera electronics, resulting from the overexposure of Pluto and Charon. As can be seen in the movie, the spacecraft and camera were rotated in some of the images to change the direction of this streak, in order to prevent it from obscuring the two moons.

The right-hand images have been processed to remove most of Pluto and Charon’s glare, and most of the background stars. The processing leaves blotchy and streaky artifacts in the images, as well as a few other residual bright spots that are not real features, but makes Nix and Hydra much easier to see. Celestial north is inclined 28 degrees clockwise from the “up” direction in these images.

Nix and Hydra were discovered by New Horizons team members in Hubble Space Telescope images taken in 2005. Hydra, Pluto’s outermost known moon, orbits Pluto every 38 days at a distance of approximately 40,200 miles (64,700 kilometers), while Nix orbits every 25 days at a distance of 30,260 miles (48,700 kilometers). Each moon is probably between 25-95 miles (approximately 40- 150 kilometers) in diameter, but scientists won’t know their sizes more precisely until New Horizons obtains close-up pictures of both of them in July. Pluto’s two other small moons, Styx and Kerberos, are still smaller and too faint to be seen by New Horizons at its current range to Pluto; they will become visible in the months to come.

The Johns Hopkins University Applied Physics Laboratory manages the New Horizons mission for NASA’s Science Mission Directorate in Washington. Alan Stern, of the Southwest Research Institute (SwRI), headquartered in San Antonio, is the principal investigator and leads the mission. SwRI leads the science team, payload operations, and encounter science planning. New Horizons is part of the New Frontiers Program managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama. APL designed, built and operates the spacecraft.

Image credits: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.

Alan Stern, principle investigator for the New Horizons fly-by of Pluto mission, gives this update as they wait for next July’s encounter with the distant planet:

It’s Pluto Eve!

December 31, 2014: As 2014 ends and 2015 begins, I’m reminded of something senior planetary scientist and New Horizons science team member Rick Binzel said a while back: “It’s Pluto Eve!”

New Horizons has been awake from hibernation since mid-day on Dec. 6, having completed its almost nine-year-long cruise phase from Earth to “Pluto space.” We’re currently in the very earliest stages of Pluto approach.

Since waking New Horizons, we’ve been checking out spacecraft systems and some of the instruments, calibrating gyroscopes, collecting trajectory tracking information, and undertaking many other spacecraft preparations before the Pluto encounter starts on Jan. 15. At the same time, our science, engineering and operations teams have been planning and testing spacecraft command loads (detailed flight plans) for the first parts of encounter operations in early 2015. Needless to say, it’s been a busy time.

When the encounter begins we’ll still be very far from Pluto, about 135 million miles (220 million kilometers). We won’t get close enough to be at our “BTH” — Better than Hubble —imaging point until mid-May, but there is still a lot to do before then.

Throughout January to early-May, we’ll be taking essentially continuous data on the interplanetary environment where the Pluto system orbits. We’ll do that daily using our charged particle sensors (called PEPSSI and SWAP) to measure both solar wind and high-energy particles, and we’ll use the Venetia Burney Student Dust Counter to measure dust-particle concentrations in the inner reaches of the Kuiper Belt.

We’ll also do a great deal of radio tracking of New Horizons using NASA’s Deep Space Network to refine our knowledge of the approach trajectory, and we’ll use our Long-Range Reconnaissance Imager (LORRI) to take hundreds of pictures of Pluto against star fields to better refine the spacecraft’s distance to Pluto. Our navigation teams will use that information to compute burn solutions for midcourse maneuvers we may want to make using New Horizons’ rocket engines in mid-March and mid-May. We should know whether the March burn will be needed by early February and we’ll keep you posted.

Some other data we’ll be planning to take before May include:

• January, February and April: A series of better and better approach movies of Pluto and its satellites orbiting around it.
• April: Distant color imaging of Pluto and its large moon Charon, and brightness-variation measurements of smaller moons Nix and Hydra as they rotate on their axes.

The gap in imaging observations in March has been timed to give our ground teams a bit of a break before the sprint to Pluto encounter from April to July.

In all the images we’ll take through April, Pluto will just be a few pixels across at most, so the imagery will look like the Hubble images you may be familiar with. Nonetheless, these datasets will provide important science information because they will be taken from angles that can’t be observed from Earth, and taken more frequently than observations we typically make from the ground. We plan to release results from these approach observations one to several times each month, at a pace that quickens with time.

Pluto as seen by the Hubble Space Telescope.

Back on Earth, from January to April, we’ll inspect all these datasets and determine what they can teach us about Pluto and its environment from afar. We’ll also be planning encounter command loads for both this period and for May and June, during which the pace of Pluto observations will increase dramatically (as will our resolution of Pluto). And our ground team will also further refine our trajectory information and range-to-Pluto measurements, conduct a final set of instrument checkouts, complete final training simulations for encounter, and build and test some of the software we’ll use to analyze the detailed Pluto-system data that begins flowing home in the later stage of approach in early summer.

New Horizons: NASA’s First mission to the Pluto system (based
on an artist’s conception of Pluto by planetary scientist Dan Durda).

In early 2015 we also plan to celebrate the 85th anniversary of the discovery of Pluto — made in 1930. More on that soon, too.

We’ve been waiting for 2015 for so long, so I hope you have a safe and joyous New Year’s celebration. And until I write again, I hope you’ll keep exploring—just as we do!

– Alan Stern