After more than 12 years of successful operations and
contributions to two diverse defense
missions, the APL-built and -operated Midcourse Space
Experiment satellite, known as MSX, is
retiring, having operated well beyond its designed
four-year life span. Ground crews from APL and the
Air Force shut the spacecraft down on July 10, turning off
transmitters and draining its batteries,
and last week were verifying the spacecraft's inoperable
status.
In January, several of the spacecraft's remaining
operational systems began to fail, rendering it
too "sick" to continue, said MSX program manager Glen Baer,
of APL's Space Department. Its
remaining horizon sensor failed; the attitude processor,
used since launch to safely "drive" the
spacecraft, locked up and didn't recover. While switching
to the other attitude processor — no trivial
task, Baer said — the battery nearly froze, and then
a gyro failed, as expected.
Shutting a spacecraft down isn't an overnight process.
"Through July 10, we verified various Air
Force regulatory processes and procedures used to disable
the spacecraft," Baer said. "Using MSX's
Space-Based Visible sensor, we also collected data to test
some theories and concepts for the Space-
Based Surveillance System Pathfinder, the follow-on to the
SBV sensor for detecting and tracking
deep-space objects."
At 18 feet long, about the size of a small school bus,
MSX is APL's largest spacecraft. It has
served two government sponsors, making critical
contributions to both national security and space
science missions.
Built for the Ballistic Missile Defense Organization,
MSX — the first space-based platform to
track missiles in their midcourse flight — was
launched from Vandenberg Air Force Base, Calif., in 1996
and collected vital data for designing missile defense
systems.
Additionally, MSX's sensors gathered readings of the
Earth's atmospheric composition,
captured images of comets and galaxies, and flew untouched
through a Leonid meteor shower. And the
spacecraft made history during space shuttle observations
when APL's Alice Bowman commanded MSX
while Lt. Col. Eileen Collins piloted NASA's craft —
the first time two women were at the helm of the
two spacecraft at the same time.
After completing BMDO's mission, the spacecraft was
transferred to Air Force Space Command
in October 2000, becoming the Air Force's first operational
space-based sensor to track and monitor
objects in orbit around Earth. Operations were conducted
via a successful partnership with Schriever
Air Force Base with its 1st and 7th Space Operational
squadrons providing all Air Force Satellite
Control Network connectivity and some vehicle commanding,
and APL providing primary mission
operations. The Lab's mission ops team modified its
operations to support a fivefold increase in data
collection.
"I've come to understand the MSX program's value from
a perspective few can appreciate," said
Duane Deal, APL's National Security Space Business Area
executive, a former Space Control Center
operator and former commander of the Cheyenne Mountain
Operations Center. "As our only space-
based asset, MSX played a unique and invaluable role
tracking thousands of objects in Earth orbit
while filling a vital niche in our space situational
awareness portfolio. Now, at APL, I see firsthand the
people and effort involved in building and operating this
remarkable spacecraft," he said. "MSX is
truly a testament to APL's innovation and effectiveness in
meeting the nation's challenges. I'd say the
government got an 'APL bargain' operating the satellite for
12 years on a four-year program. That's
impressive by anyone's standards."
Although operations have ceased, MSX could spark the
curiosity of future generations. "With
no fuel on board, by design, its trajectory can't be
changed to force its re-entry into the atmosphere,"
Baer said. "It'll take approximately 200 years for it to
re-enter and burn up in our atmosphere. I can
imagine our grandchildren's great-grandchildren seeing a
fiery ball streak across the sky and
wondering what MSX was all about."
After seeing the mission from concept to completion,
Baer — serving as MSX's first mission ops
lead and then as its second program manager — said he
has mixed emotions about the mission's end. "I'm
proud to have been part of such a successful mission," he
said. "It's a bittersweet ending, and feels
like I'm losing a close friend, but I'm looking forward to
new challenges."