The international space station. Photo: NASA

An experiment that could make the Space Station an even better place to conduct microgravity experiments is undergoing tests this week in the orbiting laboratory.

The Active Rack Isolation System (ARIS) located in EXPRESS Rack 2 in the Destiny lab module is designed to act like a powered shock absorber to dampen vibrations from powered equipment and crew activities.

During the past week, the Station crew and controllers and the science team on the ground began readying the system and a related experiment called the ARIS ISS Characterization Experiment (ARIS-ICE) that will precisely test and then measure the performance of the ARIS vibration dampening system.

The crew began setting up the ARIS system on May 29. On Friday, June 22, they completed setup work for the ARIS-ICE hardware, allowing ground controllers to send commands to check out the equipment on Monday, June 25.  Those checkouts continued this week. Thursday, Flight Engineer Jim Voss tightened a pair of pushrods to make sure the dampener functions correctly. Using sensors and pushrods, ARIS acts like a sophisticated shock absorber to provide a reactive force between the payload rack and the lab module, providing a better low gravity environment for delicate experiments.

"We're very happy with initial installation and checkout activities," said James Allen, ARIS-ICE project lead and payload developer. "We've verified the ARIS control system is stable and doesn't put the rack into an oscillation. "We'll continue checkout tests to get ready for the Space Shuttle docking, which adds greater mass to the Station and will allow us to do low frequency testing."

Flight Engineer Susan Helms conducted additional tests with the Middeck Active Control Experiment II during the past week. The joint U.S. Air Force Research Laboratory/Massachusetts Institute of Technology experiment will provide data on decreasing the effects of vibration in moving structures in space. This will allow future spacecraft to be designed with low-cost structures lighter in weight than those currently used, and still achieve performance requirements by actively decreasing the effects of vibration. The MACE hardware consists of a platform roughly 60 inches (152 centimeters) long, made of four struts less than 1 inch (2.5 centimeters) in diameter connected to five nodes. It is equipped with sensors and reaction wheels that control the motion and 20 sensors to measure motion and vibration. When gimbals on one end create a vibration, gimbals on the other end should remain steady.

Photography targets uplinked to the Station for the Crew Earth Observations experiment in the past week included European smog, Saharan dust and volcanic ash and gasses from the smoldering Mt. Etna volcano; water levels and smog in the Yellow River area around Beijing, urban smog over the coastal plain of the Eastern United States; urban development and agriculture along the Suez Canal: runoff sediment in the Gulf of St. Lawrence; commercial development in the Yangtze River Delta; Turkish water diversion projects on the Tigris River; smog and haze in the Appalachians; and urban development in the Ganges River Basin. The crew may also have a chance to photograph aurorae during the current period of high solar activity and gas clouds from the Mayon volcano in the Philippines. Lighting and the Station's orbital path have prevented the crew from photographing flooding in Texas.

Planning is under way to return Protein Crystal Growth Single Thermal Enclosure System Units 9 and 10 on the STS-104 Shuttle mission, now scheduled for July 12. The last of six growth cylinders in Unit 10 was deactivated June 18 as planned. The six growth cylinders in Unit 9 are expected to be deactivated right after the STS-104 launch. Scheduled for early return on STS-104 is the Commercial Generic Bioprocessing Apparatus, which experienced a failure earlier in the mission and is being returned for analysis.

Also returning is the Advanced Astroculture plant growth experiment, which has completed full plant growth and seed production. It was originally scheduled to return on the STS-105 Shuttle mission, which has been delayed. Ground controllers sent commands Monday, June 25, that will preserve the seeds. The station crew Thursday began reducing the humidity and increasing the heat in the growth chamber to further dry out the plants and preserve the seeds. The ADVASC science team is running an identical experiment on the ground to determine how long the experiment will require power before deactivation.

The Microgravity Acceleration Measurement System was reactivated as planned on Tuesday, June 26 and will be on for the next four weeks to help characterize the microgravity environment of the Station. The other microgravity measurement device, the Space Acceleration Measurement System, continues to actively record data.

Other payloads continuing to operate nominally, include: Commercial Protein Crystal Growth; Experiment on the Physics of Colloids in Space; and three radiation monitoring experiments - Bonner Ball Neutron Detector, Phantom Torso, and Dosimetric Mapping. The crew is also completing weekly questionnaires as part of the Interactions experiment.

The crew continued to conduct normal maintenance of active science experiments - re-charging radiation sensors, downloading sensor data to computers, checking experiment status panels and photographing hardware setups. Controllers on the ground continued to downlink data from the Station and distribute it to scientists around the country.

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.