Operations with two long-running experiments have resumed onboard the International Space Station following a holiday break, and the station crew has completed a labor-intensive cell science experiment.

Research with the Active Rack Isolation System ISS Characterization Experiment (ARIS-ICE) and the Experiment on Physics of Colloids in Space (EXPPCS) experiments resumed Jan. 2 following a Dec. 21 break for the holidays. The Payload Operations Center at NASA's Marshall Space Flight Center in Huntsville, Ala., issued a series of commands that powered up EXPRESS Rack 2, which provides both experiments with power, data, cooling, and other utilities. Both experiments, which began on Expedition Two in early 2001, are controlled remotely from the ground, supported by periodic crew maintenance.

On Dec. 27, the crew completed all Expedition Four cell research using the Cellular Biotechnology Operations Support System. Human blood, renal and tonsillar cells grown during the 12-day experiment have been placed in cold storage for later return to Earth for analysis.

One of the most crew-intensive experiments, the cell research required the crew to inject cells into 32 containers of nutrient solution, place them in an incubator and then periodically sample and replenish the nutrient solution. Throughout operations, the crew stopped the growth of different samples at various stages in development.

Cell research aboard the Station could contribute to the studies of cancer and other diseases. In microgravity, cells can be cultivated into healthy, three-dimensional tissues that retain the form and function of natural, living tissue. On Earth, studying normal growth and replication of human cell tissue outside living organisms is difficult, because most cells cultivated outside the body form flat, thin specimens that limit insight into the way cells work together.

The principal investigators for the Expedition Four experiments were Dr. Timothy Hammond, Tulane University Medical Center, New Orleans; Dr. Arthur J. Sytkowski, Beth Israel Deaconess Medical Center, Boston, Mass.; and Dr. Joshua Zimmerberg, National Institutes of Health, Bethesda, Md.. The experiment was managed by the Cellular Biotechnology Program at NASA's Johnson Space Center in Houston.

On Dec. 26, Flight Engineers Dan Bursch and Carl Walz filled out their Crew Interactions surveys, and Commander Yury Onufrienko completed his survey on Dec. 27. The computer-based experiment, which includes ground controllers as well as Station crews, will identify and characterize important interpersonal and cultural factors that may affect the performance of the crew and ground support personnel during Space Station missions.

Also on Dec. 27, Bursch and Walz conducted computer based familiarization training with the Pulmonary Function in Flight (PuFF) experiment, followed on Dec. 28 by PuFF tests by both astronauts. PuFF focuses on lung function inside the Space Station, as well as during spacewalks. Each PuFF session includes five lung function tests to measure changes in the evenness of gas exchange in the lungs, and on detecting changes in respiratory muscle strength.

On Dec. 31, Walz and Bursch completed the third session of the Hoffman Reflex experiment. This session was added to the Expedition Four program at the principal investigator's request, as a similar session was added to Expedition Three. Dr. Doug Watt, from McGill University in Montreal, Canada, realized from the results received during Expedition Two that this additional session would better define the time course of changes of this neurovestibular reflex. The experiment is designed to study spinal cord excitability and whether exercise could be made more effective on long spaceflights.

Untended operations continue with a pair of protein crystal growth experiments, a suitcase sized collection of materials samples attached to the outside of the space station, and vibration measuring experiments in the Destiny lab module.

The crew continues normal status checks and maintenance on science payloads onboard. Their task list of optional items during the past week included Earth science photography and documentary photography of experiments onboard.

On Thursday, Jan. 3, the crew was scheduled to perform background radiation readings on their Astronauts in EVA Radiation Study radiation badges. The Zeolite Crystal Growth furnace unit was installed into its location in EXPRESS Rack 2 on Dec. 29, with a checkout planned for Jan. 7. The Advanced Astroculture experiment is tentatively planned for activation later this month or early February. The Earth Knowledge Acquired by Middle school students (EarthKAM) photography program is expected to resume in early February.

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.