Evaluation of On-orbit Data inside the Inflatable Space Terrarium on the International Space Station

The Inflatable Space Terrarium (IST) was launched as one of the experimental equipment of the Space Inflatable Membrane Structures Pioneering Long-term Experiments (SIMPLE) module attached to the Exposed Facility of the Japanese Experimental Module (JEM, Kibo). It aimed to verify the retainment of the pressurized membrane structure in which the atmospheric environment is simulated. It was deployed in orbit successfully on August 18, 2012 (JST), however, a slight gas leak then occurred and the pressure inside the IST has gradually decreased owing to this leak. The SIMPLE mission ended its regular operation in orbit at November 2014. Although the criteria for containment remained unattained owing to the leakage, we had monitored the conditions inside the IST by using cameras, and pressure and temperature sensors for about two years after deployment. In this paper, based on the pressure reduction profile we estimate size of a defect on the assumption that the air leakage occurred through one small orifice. And we analyze the relation between pressure and temperature using on-orbit data and numerical results.