SODI COLLOID: Yet another achievement on board the ISS

On October 2010, another fluid physics challenge of great interest for the scientific community has been successfully faced up on board the International Space Station (ISS). It is about the COLLOID experiment completion which performance, lasting for three weeks around, was supported by the E-USOC.

The COLLOID project stems from the proposal “Advanced Photonic Devices in Microgravity” that focuses on three-dimensional photonic structures which possess appealing properties that make them candidates for new types of optical components. The study of such structures has been to try and construct them from self-assembly of dielectric nano-spheres. However, the increased difficulty in fabrication due to the presence of gravity (sedimentation) makes the study to proceed more slowly than for their two-dimensional counterpart (e.g. photonic crystal fibres). Following this line of research, the COLLOID experiment proposal was aimed to study the aggregation phenomenon within colloidal systems in a microgravity environment, in order to try to tackle the puzzling and still not fully understood mechanisms that lie behind.

For that purpose, COLLOID hardware, developed by QinetiQ Space Industry, was envisaged to probe five different samples grouped in an array by Near Field Scattering technique, for what the array could be positioned depending on the sample that was to be probed. 96 dedicated runs were originally planned over the five samples, being six temperatures cyclically covered for a total of four cycles. Afterwards, as the analysis of the so far obtained results made scientists believe that the goals set up at the start of the experiment were not yet achieved, further 24 runs were performed.

The experiment performance was completed in 18 days on board the ISS, inside Columbus. Its execution was carried out within an international cooperation environment together with our NASA partners on a week coverage support of 24 hours 7 days (reduced to 24/5 when getting closer to the end), and the participation of the Italian delegate of ESA in Naples, Telespazio, as they contributed in the monitoring of SODI instrument.

Summarizing, the experiment completion was reached through the following steps-runs:

• Aggregation Temperature Detection run & Reference run: ~3 days.
• Science team evaluation and assessment on the measurements resulted: 2 days.
• 96 Experiment runs : ~9.5 days.
• 24 Additional experiment runs : ~3 days.

It is not to be forgotten the ISS crew contribution of the astronauts Shannon Walker and Tracy Caldwell for the installation and removal of the hardware inside the MSG, as well as for the activity to exchange the two flash disks where all data from experiment was stored.

Next step for E-USOC follows with the upcoming flight back to Earth of the two flash disks storing the experiment data for the scientist to proceed with their research. Let’s wait then for the Space Shuttle ULF5 return which undocking from the ISS is currently planned for November the 10th!