The international space station. Photo: NASA

The Expedition Two crew continued to prepare the first plants and seeds produced on the International Space Station for their return trip on the Space Shuttle Atlantis set to visit the orbiting laboratory next week.

"The plants are the first to successfully go through three stages, seed germination, plant growth and seed development aboard the Station," said Dr. Weijia Zhou, the principal investigator for the Advanced Astroculture (ADVASC) plant growth experiment. Zhou is the director of the Wisconsin Center for Space Automation and Robotics at the University of Wisconsin-Madison -- one of 17 NASA Commercial Space Centers that helps companies fly space experiments. Eleven of these centers are managed by the Space Product Development Program at NASA's Marshall Space Flight Center in Huntsville, Ala. - NASA's lead center for flying experiments that take advantage of low gravity.

"The Advanced Astroculture has provided optimal environmental conditions, and the plants have entered their last stage of development -- seed maturity," said Zhou. "This stage will last another few days, and then we will change the conditions inside the plant growth unit to preserve the seeds."

To help the seeds dry out, Flight Engineer Jim Voss removed fluid from the plant growth chamber this week. Periodically, during Expedition Two, the crew has removed nutrients, fluids and gases so that investigators on Earth could study the growing conditions experienced by the plants in space. When the experiment is returned to Earth, scientists will analyze these samples as well as the plants and seeds. Throughout the flight, investigators on the ground have viewed video of the growing plants.

Zhou and his team at a telescience center at the University of Wisconsin-Madison are working with the team at the Payload Operations Center in Huntsville, Ala., on a plan for ending the experiment next week so that the Space Shuttle Atlantis can return the plants and seeds to Earth. The Advanced Astroculture was originally scheduled to return on the STS-105 Shuttle mission, but since the plants have finished their growth cycle, they will be brought back on the STS-104 mission. The ADVASC science team is running an identical experiment on the ground to determine how long the experiment will require power before deactivation being planned for next week.

The team at the Payload Operations Center is also planning for the return of the Protein Crystal Growth Single Thermal Enclosure System Units 9 and 10 on the STS-104 Shuttle mission. This experiment contains perishable biological crystals that will be returned to scientists for analysis. By studying the structure of the crystals, investigators can learn about substances that play important roles in humans, animals and plants.

Most of the growth cylinders that contain crystals have been deactivated and are ready for return to Earth. Next week, the crew is scheduled to deactivate the last six growth cylinders in Unit 9, right after the STS-104 launch, now scheduled for July 12. Different biological substances require different growth periods. Scheduled for return on STS-104 is the Commercial Generic Bioprocessing Apparatus, which did not perform as expected and is being returned for analysis.

The three radiation monitoring experiments - Bonner Ball Neutron Detector, Phantom Torso, and Dosimetric Mapping - all continue to collect data. The crew routinely uses the Human Research Facility computers to send data to scientists on Earth for analysis. The Space Shuttle Atlantis will bring back additional data on hard disks.

While a few experiments are being returned to Earth, several investigations are just getting under way on board the laboratory and will continue into Expedition Three, starting in August with the STS-105 mission. One of the main goals of early science operations on the Station is to characterize the laboratory environment so that scientists can accurately analyze the influence it has on their experiments.

In addition to measuring the radiation inside the lab, scientists are measuring the effects of vibrations and evaluating ways to reduce them. Next week when the Shuttle docks with the Station is a critical time for these measurements because more vibrations may be experienced when the Shuttle docks and during the increased activities while it is docked.

The Microgravity Acceleration Measurement System was reactivated last week 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.

An experiment that could make the Space Station an even better place to conduct microgravity experiments continues to under go tests this week and prepare for more specific tests during docked operations next week. 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 Payload Rack Officer at the Marshall operations center and the science team on the ground prepared the rack system for special tests during docked operations. While the Shuttle is docked, the ARIS ISS Characterization Experiment (ARIS-ICE) will precisely test and measure the performance of the ARIS vibration dampening system.

"We're continuing 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," said James Allen, ARIS-ICE project lead and payload developer, with The Boeing Company in Houston, Texas.

Other payloads continuing to operate nominally include: Commercial Protein Crystal Growth and the Experiment on the Physics of Colloids in Space. The crew is also completing weekly questionnaires as part of the Interactions experiment.