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New Horizons Payload Gets High Marks on Early Tests
March 29, 2006

In-flight checks of the New Horizons science payload are going well, as
six of the seven instruments on board have completed tests proving they
survived launch and demonstrated their basic functionality.

Over the past month, spacecraft controllers at the Johns Hopkins
Physics Laboratory (APL) flipped the “on” switches for Ralph, Alice,
LORRI, SWAP, PEPSSI and the Student Dust Counter and confirmed that the
instruments’ thermal control systems work, their computer processors
boot up and run the correct code, and they can receive commands and
telemetry (or status data) back to Earth. In addition, both the Alice
and SWAP instruments have opened the aperture doors that protected them
from contamination on Earth and during launch. The PEPSSI and Ralph
aperture doors will be opened later this spring; LORRI’s door will be
opened in early fall. (The dust counter and radio science experiment,
named REX, do not have such doors.)

The team will complete the set of initial instrument checkouts in
mid-April when it conducts similar exercises with REX, which is
incorporated into the electronics of the spacecraft’s communications

“The instruments are sending back a lot of housekeeping data that says
they’re working the way they’re supposed to,” says Mark Tapley, New
Horizons science payload systems engineer from Southwest Research

New Horizons Principal Investigator Alan Stern, also of Southwest
Research Institute, adds, “The mission science team is just beaming to
know that the entire payload survived the stresses of launch in good

Performance Testing Ahead

Through spring and summer the team will focus on actual payload
performance tests, making sure each instrument is fully functional and
ready to gather science data. This will include “first light” and
calibration activities for the various instruments.

So far, only the Student Dust Counter has passed this battery of
checkouts, and is now collecting dust-impact data along the
path to Jupiter. The first student-built instrument to fly on a NASA
planetary mission, the SDC will detect microscopic dust grains produced
by collisions among asteroids, comets and Kuiper Belt Objects during
Horizons’ long journey - giving scientists an unprecedented look at
how collisional debris is distributed across the solar system.

Full payload commissioning is planned to be complete by early fall,
several months before New Horizons passes through the Jupiter system in
February 2007. “The Jupiter encounter will be a real confidence
when we see how the instruments perform in a real-world flyby,” Tapley