The Experiment on Physics of Colloids in Space (EXPPCS) team has expanded its research from studying colloid behavior to building "fractal structures" with them.

The ground-based science team this week continued its fractal test run aboard the Space Station that began on Jan 16 and will continue for five weeks. The fractal sample being studied is a gel made from colloids. It is made mostly of liquid but with enough binding material to prevent it from flowing. Gelatin is a common example. A fractal is something that appears to have the same structure under different degrees of magnification. One example is the coastline of a continent. Maps showing 25 miles or 250 miles of coastline will appear somewhat similar in the apparent amount of roughness.

Scientists are interested in studying the fractal structure of this colloid gel, which is 99.992 percent water and only 0.008 percent colloid. Among their questions is whether something with so little material will be able to form a gel. They are also studying aging of the gel.

Fractal gels are of interest to manufacturers and materials specialists on Earth. A primary mechanism for degradation of motor oil is the formation of fractal clusters of soot. Another example is the aging and spoilage of food. Fractal gels are also found in a specialized material known as aerogel, which is only 0.5 percent solid and possibly the best thermal insulator known. EXPPCS is managed by NASA's Glenn Research Center in Cleveland. The principal investigator is David Weitz of Harvard University.

The colloids experiment team last week concluded its 120-hour reexamination of the crystallization of the AB6 binary colloid, then conducted a successful follow-up 24-hour run and were successful in obtaining high quality data. The experiment has been extended from Expedition Four to Expedition Five.

The Active Rack Isolation System ISS Characterization Experiment (ARIS-ICE) ground team continued testing the experimental ARIS vibration dampening device during the past week. Located in EXPRESS Rack 2, ARIS is designed to protect delicate microgravity experiments from vibrations caused by crew motion, operating equipment, etc. The experiment was launched in April 2001 on the 6A Shuttle flight. Although not completed, ARIS-ICE has to date spent over 10 successful months on the Station, logged more than 2,300 hours on the ground station console, transmitted more than 15,000 commands from ground to the Station to conduct more than 1,446 ARIS-ICE on-orbit tests.

The experiment has helped enhance the vibration dampener's performance by improving the power umbilical design, validating its performance over a wide frequency range and resolving several other technical issues. On Tuesday, Jan. 22, the crew began tests in which they use a small hammer to tap on the Station's Z-panel containing power, data, fluid and other utility umbilical lines into the EXPRESS Rack 2, while the ground team measures the dampener's response. Those tests will continue through the end of the month. The science team would like more data synchronized with crew exercise periods and exercise equipment.

On Saturday, Jan. 19, the crew during their normal maintenance checks noticed and removed an ice buildup in the Biotechnology Refrigerator containing several cell science samples processed earlier in the mission and now awaiting transfer to Earth.Locations on a list of possible targets for the Crew Earth Observations program during the past week have included ice fields in the South Sandwich Islands, Reunion Island in the Indian Ocean where a major volcanic eruption was occurring on the island east of Madagascar, a severe tropical cyclone in the Indian Ocean , smog in southeastern Africa's industrialized heartland of the Vaal River, Patagonian ice fields in Chile, American Samoa's reefs and coral structures, and the Marquesas Islands.

Flight Engineers Dan Bursch and Carl Walz performed their Crew Interactions surveys on Wednesday, Jan. 23.

Also on Wednesday, the Expedition Three team was reunited during a teleconference for a post-mission debriefing with the Expedition Three crew in Houston. The science team uses these meetings to get feedback on procedures and improve instructions, planning and timelines for future missions.

Thursday, Jan. 24, is expected to be a light duty day for the crew in preparation for a Russian EVA scheduled for Friday. On Saturday, Jan. 26, Bursch will follow up his scheduled Friday spacewalk with a lung function test with the Pulmonary Function in Flight experiment. Walz also will perform PuFF for his regular monthly test.

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.