Neptune's giant moon Triton is often called Pluto's "twin" -- so what better practice target, then, for New Horizons' telescopic camera?

New Horizons' Long Range Reconnaissance Imager (LORRI) snapped several photos of Neptune during the latest annual systems checkout, which ended July 30. Neptune was 23.2 astronomical units from New Horizons when LORRI took aim at the gas giant planet -- and Triton made a cameo appearance in these images.

In early 2007 New Horizons flew through the Jupiter system, getting a speed-boost from the giant planet's gravity while snapping stunning, close-up images of Jupiter and its largest moons.

Fast forward to 2010 and New Horizons has given us another glimpse of old friend Jupiter, this time from a vantage point more than 16 times the distance between Earth and the Sun, and almost 1000 times as far away as when New Horizons reconnoitered Jupiter.

A short but important course-correction maneuver kept New Horizons on track to reach the 'aim point' for its 2015 encounter with Pluto.

The deep-space equivalent of a tap on the gas pedal, the June 30 thruster-firing lasted 35.6 seconds and sped New Horizons up by just about one mile per hour. But it was enough to make sure that New Horizons will make its planned closest approach 12,500 kilometers (7,767 miles) above Pluto at 11:49 UTC on July 14, 2015.

New Horizons' fourth annual checkout is nearing its mid-point, and continues with a workout for the spacecraft systems, cameras and other instruments that will deliver the first data from Pluto and its moons. Preparations for a small but necessary course-correction maneuver are also on track.

Since "ACO-4" began on May 25, mission operators have uploaded new software for New Horizons' on-board autonomy system, and checked out most of the spacecraft's backup systems, including guidance and control, communications, command and data handling, thermal control, power and propulsion. All of these backup systems have performed well.

NASA has released the most detailed and dramatic images ever taken of the distant dwarf planet Pluto. The images from the Hubble Space Telescope show an icy, mottled, dark molasses-colored world undergoing seasonal surface color and brightness changes.

Pluto has become significantly redder, while its illuminated northern hemisphere is getting brighter. These changes are most likely consequences of surface ice melting on the sunlit pole and then refreezing on the other pole, as the dwarf planet heads into the next phase of its 248-year-long seasonal cycle. Analysis shows the dramatic change in color took place from 2000 to 2002.

NASA's New Horizons mission team marked four years of flight yesterday -- and their Pluto-bound spacecraft slept right through the celebration.

Operators at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., commanded New Horizons into hibernation on Friday after 10 days of maintenance, during which they downloaded Student Dust Counter data from the solid-state recorder, uploaded software updates to the Solar Wind Around Pluto (SWAP) instrument, made minor adjustments to the spacecraft's fault-protection system and collected navigation-tracking data.

The new year approaches with New Horizons zooming past another milestone: the NASA spacecraft is now closer to target planet Pluto than its home planet, Earth.

"This is the first of several milestones over the next 10 months that mark the halfway points in our journey to the solar system's frontier, where Pluto lies. We on the mission team know we will have a long way to go, but are proud to have brought the spacecraft to this important mile marker in our journey across the entirety of our solar system," says New Horizons Principal Investigator Alan Stern, of the Southwest Research Institute.

Call it a burst of activity between naps: the New Horizons team woke its Pluto-bound spacecraft from hibernation this week for some onboard housekeeping.

On pre-programmed commands from controllers at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. -- transmitted to the spacecraft in August through NASA's Deep Space Network of antenna stations -- New Horizons came out of hibernation on Nov. 9. The spacecraft had been "sleeping" since Aug. 27, when it completed its third annual instrument and system checkout.

New Horizons sails silently today through another milestone on the way to its historic reconnaissance of the Pluto system, reaching the halfway point between the orbits of Saturn and Uranus.

The NASA spacecraft will reach 14.41 astronomical units from the Sun - 1.34 billion miles, or nearly 14,5 times the distance between the Earth and Sun - between 22:00-23:00 UTC.

The New Horizons mission team has closed out a successful summer workout, putting its Pluto-bound spacecraft back into hibernation on Aug. 27 after seven weeks of functional tests and system checks.

The mission's third annual checkout (ACO-3), which started July 7, "went very well," says Mission System Engineer Chris Hersman, of the Johns Hopkins University Applied Physics Laboratory. "New Horizons is in good shape."

New Horizons is up from the longest nap of its cruise to Pluto, as operators "woke" the spacecraft from hibernation yesterday for its annual series of checkouts and tests.

The actual wake-up call went in months ago; the commands for New Horizons to power up and reawaken its hibernating systems were radioed to its computer before it entered hibernation on Dec. 16, 2008. During hibernation, as the spacecraft traveled almost 200 million miles toward its goal -- the Pluto system -- New Horizons sent back weekly status reports as well as biweekly engineering telemetry reports.

Add another moon to the New Horizons photo gallery: the spacecraft's Long Range Reconnaissance Imager detected Triton, the largest of Neptune's 13 known moons, during the annual spacecraft checkout last fall.

New Horizons was 2.33 billion miles (3.75 billion kilometers) from Neptune on Oct. 16, when LORRI, following a programmed sequence of commands, locked onto the planet and snapped away.

After an intense annual checkout -- more like a deep-space workout -- New Horizons is getting some well-deserved rest.

New Horizons operators at the Johns Hopkins University Applied Physics Laboratory (APL) eased the spacecraft into electronic hibernation on Dec. 16, wrapping up nearly four months of tests, data collection and software upgrades. The spacecraft's Earth-bound crew has now turned its attention to detailed Pluto-encounter sequencing.

The New Horizons spacecraft has a new "audience" for the electronic signals it beams back to Earth.

In a successful September demonstration of its growing capabilities, the Allen Telescope Array (ATA) detected transmissions from New Horizons while the spacecraft was more than a billion miles from home. The ATA is a radio interferometer used for astronomical research and searches for signals of intelligent, extraterrestrial origin. A joint effort of the SETI Institute and the Radio Astronomy Laboratory at the University of California, Berkeley, it's being constructed at the Hat Creek Radio Observatory in Northern California.

It's hard to believe, but Oct. 15 will be the 1,000th day of flight for New Horizons. And in that time we've traveled so far that only four other spacecraft - Pioneers 10 and 11 and Voyagers 1 and 2 - have ventured farther. Can you believe it's been this long? Sometimes it seems so, but other times, it seems like we just blasted off from Florida on that cool afternoon of Jan. 19, 2006.

Of course, it's been a busy 1,000 days for everyone involved. After an exciting launch day none of us will ever forget, we spent the first four months of flight checking out our spacecraft systems and making the initial course corrections to put us right down the middle of the pike to our Jupiter flyby aim point.