Expose has been built to allow exposure of biological specimen and material samples whilst recording data on temperature and radiation spectra.
The Expose assembly includes the facility and its supporting structure. The facility provides common functionalities, services and a controlled environment to the experiment samples (e.g. shutters, scientific and housekeeping data acquisition and transmission, thermal control).
The facility includes the following subsystems:
- Structure and mechanisms;
- Shutters (incl. lids, hinges, shutter drives);
- Trays (incl. windows, seals, valves, connectors);
- Sample carriers (incl. windows, filters, controls);
- ECU (Expose Control Unit: motor and valves control, data acquisition);
- Sensors (temperature, pressure, UV, proximity); 4 sensors packages (UVB + radiometer) are positioned on the 4 facility corners;
- TCS (Thermal Control System), based on heaters, MLI, coatings;
- Electrical I/F to EuTEF Data Handling and Power Unit (DHPU) for Expose-E.
The experiment trays are supporting and sealing structures for the scientific payload. The trays are equipped with four squared recesses, 77 x 77 x 26 mm each, where the sample carriers are inserted. These are lightweight elements provided with a number of sample cells, whose quantity, geometry and characteristics depend on the experiment typology.
Each tray hosts four carriers, sealed with optical windows or left open to the space environment. The trays have a mechanical interface to the structure and comply with the design of the shutters. Their configuration allows a free field of view for the sample carriers (no shade from rim or other protruding elements).
The trays are electrically connected to the structure by matable/dematable connectors.
Expose-E and Expose-R
Expose-E has a set of trays filled with terrestrial organisms and was installed on the outside of the European Columbus laboratory as one of the nine payloads of the European Technology Exposure Facility (EuTEF) in July 2008.
The nine experiments, part of the Expose-R payload, were installed on the outside of the Russian segment of the International Space Station (ISS) during a spacewalk in March 2009.
Expose-R is equipped with three trays, which are loaded with a variety of biological samples including plant seeds and spores of bacteria, fungi and ferns, which will be exposed to the harsh space environment for about one and a half years.
Away from the protective environment of Earth, the organisms will be exposed to solar UV, vacuum, cosmic rays and perpetual temperature variations as the Station continuously passes between areas of direct sunlight and the cold darkness of Earth's shadow.
The Expose-R and -E experiments are part of ESA’s research in astrobiology - the study of the origin, evolution and distribution of life in the Universe. Some Expose experiments investigate to what extent particular terrestrial organisms are able to cope with extra-terrestrial environmental conditions. Other Expose experiments test how organic molecules react when subjected for a prolonged period of time to unfiltered solar light (chemical evolution).
At the end of the exposure period, the Expose trays will be retrieved from their location outside the Station and returned to Earth with either a Space Shuttle or Russian Soyuz spacecraft. From the landing site in the United States or Kazakhstan the trays will be returned to the Microgravity User Support Centre (MUSC) in Cologne, Germany. From there the samples will be distributed to the scientists for further analysis in the laboratory.
Last update: 2 December 2009