The international space station. Photo: NASA

The past week saw the Expedition Two crew and supporting controllers and scientists on the ground celebrate the team's 100th day of science operations onboard the orbiting research facility.

More than 5,000 pounds of payload hardware representing 17 investigations have been launched, installed and operated on Space Station during this Expedition, which began in March.

New targets for Crew Earth Observations photography were uplinked to the Station last week. Flight Engineer James Voss reported he has been doing some photography daily. Targets include Kilimanjaro Tropical Glacier, High Central Andean glaciers, Andean lakes, water diversion, agriculture and population expansion around the Nile river and dams and reservoirs on the Tigris and Euphrates rivers in Turkey. Human development and global climate investigations are continuing themes for these photographic studies. Flight Engineer Susan Helms conducted additional tests with the Middeck Active Control Experiment on June 14, 15 and 18. This experiment, first begun during the Expedition One mission and continued by Helms, is testing control mechanisms that can be used in large articulated spacecraft as well as well as other industrial applications.

Following initial setup on May 29, the Active Rack Isolation System has continued to undergo a variety of calibrations and other tests this week, commanded by controllers on the ground. The science team plans to use the powered dampening device to "float" the rack on Friday and begin testing its ability to reduce vibrations caused by crew activity and equipment operations. Using sensors and pushrods, ARIS acts like a powered shock absorber to react to disturbances to provide a better low gravity environment for delicate experiments.

A pair of sensors that are part of the Space Acceleration Measurement System were activated Monday, June 18, marking the full activation of that experiment. SAMS measures vibrations that affect experiments located near the cause of the vibration. It includes five small remote sensors placed directly next to experiments throughout the Destiny lab module.

On Monday, June 18, Voss deactivated the last growth cylinder in Protein Crystal Growth Single Thermal Enclosure System Unit 10. The four other active growth cylinders in the experiment were deactivated Friday, June 15. The experiment is scheduled to return to Earth on the STS-104 Shuttle mission in July. In the meantime, all growth cylinders in an identical unit -- PCG-STES Unit 9 -- will remain active until about the time of the STS-104 mission. Protein molecules are involved in numerous biological processes. Scientists hope the space experiment will reveal more about their structure and yield advances in medicine, agriculture, the environment and other biosciences.

On Wednesday, Voss collected gas, condensate and nutrient samples with the Advanced Astroculture plant growth experiment. Seedlings, related to the family of radishes and cabbages, are continuing to grow. Scientists hope to use the long duration Station mission to grow plants from seeds to the seed production stage and learn whether there are any genetic changes. A commercial company is using the experiment as the basis for Internet-based education programs for classrooms.

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 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 at the Payload Operations Center and science teams around the world are working this week to plan for additional science activities beginning the week of June 25 due to the decision to reschedule the next Space Shuttle launch.

The payload team is also involved in planning the transition of the Expedition Two to the Expedition Three payload cadre, expected to occur before the Aug. 5 launch of the STS-105 Shuttle mission. STS-105 will carry the Expedition Three crew to Space Station and return the Expedition Two crew to Earth. Updates to Station computers to accommodate new capabilities and hardware also require updates to the computers that control Station payloads - both on the ground and onboard.

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.