In June 1978, U.S. Naval Observatory
astronomer James Christy examined a set of grainy telescope pictures with designs
on learning more about Pluto’s orbit. In doing so, he fortuitously spotted a
moon circling the solar system’s outermost planet.

The New Horizons team recently marked that discovery by dedicating its Christy
Science Operations Center at the Johns Hopkins University Applied Physics
Laboratory (APL) in Laurel, Md. During a New Horizons science team meeting
on Sept. 27, Principal Investigator Alan Stern presented Christy with a copy
of the plaque that will adorn the “CSOC” when it’s established at APL within
the next 18 months.

New Horizons is set to become the first mission to Pluto, its moon, Charon,
and the Kuiper Belt of rocky, icy objects beyond. The spacecraft is scheduled
to launch in January 2006, swing around Jupiter for scientific studies and
a gravity boost in 2007, reach Pluto-Charon as early as 2015, and then visit
up to three Kuiper Belt objects.

While the Tombaugh Science Operations Center at Southwest Research Institute
– dedicated last February to Pluto’s discoverer, the late Clyde Tombaugh –
serves as the science team’s home base, the team will use the CSOC during
the mission’s busiest times. From the same room where mission operators guided
the NEAR Shoemaker through its monumental mission at asteroid Eros, New Horizons
scientists can monitor their spacecraft during integration and prelaunch testing,
and examine data during encounters with Jupiter, Pluto, Charon, and Kuiper
Belt objects.

“It’s an honor to be associated
with such an historic effort,” Christy said. “It’s been about 20 years since
I last worked on Pluto, but now I feel like I’ve been reconnected.”

Christy named Charon after the
mythological ferryman who carried passengers to Pluto’s realm of the underworld
across the River Styx. Among planetary scientists it’s usually pronounced
“Shar-on” in honor of Charlene “Char” Christy, discoverer Christy’s wife.

< The largest moon relative to the size of the planet it orbits, Charon's diameter spans 740 miles (1,200 kilometers), about half that of Pluto. Scientists have shown that Charon is so big in comparison to Pluto that the system's center of mass actually falls between the two bodies, making Pluto-Charon the only binary planet in the solar system.

“Jim Christy’s discovery of Charon
was a real feat for its time,” Stern says. “Furthermore, the discovery of
Charon was one of the first signposts that indicated to the scientific community
just how unique and fascinating the Pluto system is.”

“Studying Charon is a very important
part of the New Horizons mission,” says New Horizons Project Scientist Andrew
Cheng, of APL. “It could hold a record of collisions in the Kuiper Belt, quite
different from what we’d see on Pluto because of the atmosphere and changing
surface conditions on Pluto. We also intend to address questions of how Charon
formed and why its surface is compositionally different than Pluto’s.”

The New Horizons team is preparing
for the mission’s next major milestone, the Preliminary Design Review, set
for later this month.

Read about James Christy’s discovery
of Charon at www.usno.navy.mil/charon.html