[meteorite-list] New Horizons Tracks an Asteroid (2002 JF56)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Jun 15 17:39:19 2006
Message-ID: <200606152137.OAA08722_at_zagami.jpl.nasa.gov>

http://pluto.jhuapl.edu/news_center/news/061506.htm

New Horizons Tracks an Asteroid
June 15, 2006

[Asteroid Image]
Asteroid 2002 JF56, through the eyes of New Horizons' Ralph imager.

It's a small object with big news for the New Horizons team: the first
spacecraft to Pluto tested its tracking and imaging capabilities this
week on asteroid 2002 JF56, a relatively tiny space rock orbiting in the
asteroid belt.

In photos snapped by the Multispectral Visible Imaging Camera (MVIC)
component of New Horizons' Ralph imager, from distances ranging from
1.34 to 3.36 million kilometers (about 833,000 to 2.1 million miles),
the asteroid (with an estimated diameter of about 2.5 kilometers)
appears as a bright, barely resolved pinpoint of light against the
background of space. That Ralph "saw" the asteroid demonstrates that it
can track and photograph objects moving relative to New Horizons - just
as Jupiter and its moons and then, later, Pluto and its moons will be.
This capability is critical as New Horizons closes in on Jupiter for a
gravity boost toward the Pluto system.

"The asteroid observation was a flight test, a chance for us to test the
spacecraft's ability to track a rapidly moving object and to refine our
sequencing process," says Gabe Rogers, New Horizons guidance and control
engineer from the Johns Hopkins University Applied Physics Laboratory,
Laurel, Md. "The objects we will observe this winter in the Jupiter
system will appear to be moving across the sky much more slowly than
this asteroid, so these observations were an unexpected opportunity to
prepare for the even faster tracking rates we'll experience in summer
2015, when the spacecraft zips through the Pluto system at more than
31,000 miles per hour."

Ralph's camera took separate images on June 11, June 12 and June 13. The
images had to be compressed (to save on the number of bits that must be
sent back), radioed back to Earth through NASA's Deep Space Network of
antenna stations, and checked out by mission team members before they
could be evaluated.

About an hour before closest approach to the asteroid - which occurred
at 4:05 UTC on June 13, at distance of 101,867 kilometers - Ralph began
scanning it to obtain color images and infrared spectra. Those data must
also be compressed before they're sent back to Earth next week.

"Ralph has performed flawlessly since the launch of New Horizons and
these asteroid observations are giving us more insight into the ultimate
sensitivity and capability of the instrument," says Ralph Instrument
Scientist Dennis Reuter, of NASA Goddard Space Flight Center, Greenbelt,
Md. "They are allowing us to use Ralph to view and track a single
fast-moving object as it changes from a dim speck of light in a bright
star field to a body whose brightness rivals that of Jupiter at the high
resolution that Ralph is capable of."

Launched last Jan. 19, New Horizons is currently 283 million kilometers
(176 million miles) from Earth, moving about the Sun at about 27
kilometers (17 miles) per second. The spacecraft is on course to fly
through the Jupiter system for science studies and a gravity assist,
with closest approach to the giant planet set for Feb. 28, 2007.
Received on Thu 15 Jun 2006 05:37:03 PM PDT