Pre-flight image of the "shaker" device used to induce known disturbances into EXPRESS Rack 2 to test the Active Rack Isolation System. Photo: NASA

An experimental "powered shock absorber" to reduce vibrations aboard the Space Station continued another week of intensive testing to get ready for its operational debut next year.

The Active Rack Isolation System (ARIS) uses actuators that act like powered shock absorbers to counter vibrations caused by crew activities, operating equipment and other disturbances. Installed in EXPRESS Rack 2 in the Destiny lab module, it is designed to protect delicate microgravity experiments from vibrations that could negatively affect them. The first experiment to benefit from the ARIS system will be Zeolite Crystal Growth, scheduled to begin operations in March 2002.

The ARIS ISS Characterization Experiment (ARIS-ICE) was developed to test the ARIS system. Recent tests have focused on understanding how a pair of cables going into the EXPRESS Rack affects the vibration dampening qualities. Cable materials, thickness, length, and position can all affect vibration. Of particular interest is a set of newly developed experimental "vibration-free" cables that appear to be 200-300 percent less stiff than the original cables.

"The cables connect the Station Z panel, a power and utility interface panel, and the ARIS rack to provide power," said Naveed Quraishi, ARIS-ICE project manager at NASA's Johnson Space Center. "The majority of vibration to the rack comes from the Z panel through the umbilicals into the rack. We have so far successfully characterized the performance of ARIS from .01 to 1 hertz and from 30 hz to 300 hz. Now we're working on the 1-30 hz regime. We are in a very aggressive testing mode until the end of the expedition. The new cables have improved performance quite a bit."

ARIS-ICE is scheduled for return to Earth next year, but it could offer advantages in making the checkout of future ARIS-equipped racks simpler and more efficient, Quraishi said.

The Experiment on Physics of Colloids in Space (EXPPCS) completed a 48-hour test run on Monday, October 22. Like most of the runs in the past two weeks, it continued to examine the colloid polymer gel and colloid glass samples. Colloids are found in many everyday products on Earth, like paint and milk, and are used in many other manufacturing processes ranging from foods to computer chips. This basic research, managed by NASA's Glenn Research Center, could contribute to engineering of new materials and processes.

The Station's main vibration measuring experiments, the Space Acceleration Measurement System and the Microgravity Acceleration Measurement System (MAMS), recorded Tuesday's docking of a Soyuz taxi craft and the arrival of three new cosmonauts aboard the Station. The science team now has recorded several events such as Shuttle, Soyuz and Progress spacecraft dockings, a Soyuz re-location, and spacewalks for building a better picture of the microgravity environment on the Station.

The NASA payload team this week was preparing to downlink some experiment results recorded during earlier experiments with the Dynamically Controlled Protein Crystal Growth, MAMS, Bonner Ball Neutron Detector, and Hoffman Reflex.

Targets uplinked for the Crew Earth Observations photography program this week included: land use patterns along the Parana River in Argentina, stream patterns and sand dunes along the Somalia coast, flood waters from the Aswan Dam on the Nile River, reef damage in the Tuamotu Archapelago, smog in the Ohio River basin and the northeast U.S., vegetation color signatures in California's Central Valley, fault lines in Ethiopia, and new dams along the Euphrates River in Turkey.

On Wednesday, October 24, the Station crew and controllers in the Payload Operations Center teamed up to successfully install a computer software upgrade in EXPRESS Rack 4. The upgrade is designed to prevent software problems observed with EXPRESS Racks 1 and 2, which received a similar upgrade.

Editor's Note: The Payload Operations Center at NASA's Marshall Space Flight Center in Huntsville, Ala., manages all science research experiment operations aboard the International Space Station. The center is also home for coordination of the mission-planning work of a variety of international sources, all science payload deliveries and retrieval, and payload training and payload safety programs for the Station crew and all ground personnel.