npj Microgravity Article: Observational study: microgravity testing of a phase-change reference on the International Space Station
This article by T Shane Topham, Gail E Bingham and Harri Latvakoski (Utah State University Research Foundation, North Logan, UT, USA), Igor Podolski and Vladimir S Sychev (Institute of Biomedical Problems of the Russian Academy of Sciences (SSCRF-IBMP RAS), Moscow, Russia) and Andre Burdakin (Russian Scientific Research Institute for Optical and Physical Measurements (VNIIOFI), Moscow, Russia) was published online by npj Microgravity on August 20, 2015.
Orbital sensors to monitor global climate change during the next decade require low-drift rates for onboard thermometry, which is currently unattainable without on-orbit recalibration. Phase-change materials (PCMs), such as those that make up the ITS-90 standard, are seen as the most reliable references on the ground and could be good candidates for orbital recalibration. Space Dynamics Lab (SDL) has been developing miniaturized phase-change references capable of deployment on an orbital blackbody for nearly a decade.
Improvement of orbital temperature measurements for long duration earth observing and remote sensing.
To determine whether and how microgravity will affect the phase transitions, SDL conducted experiments with ITS-90 standard material (gallium, Ga) on the International Space Station (ISS) and compared the phase-change temperature with earth-based measurements. The miniature on-orbit thermal reference (MOTR) experiment launched to the ISS in November 2013 on Soyuz TMA-11M with the Expedition 38 crew and returned to Kazakhstan in March 2014 on the Soyuz TMA-10 spacecraft.
MOTR tested melts and freezes of Ga using repeated 6-h cycles. Melt cycles obtained on the ground before and after launch were compared with those obtained on the ISS.
To within a few mK uncertainty, no significant difference between the melt temperature of Ga at 1 g and in microgravity was observed.