I think it is a humidity sensor. From astro-pi.org: "Young people write a simple program to take a humidity reading onboard the International Space Station and

I think it is a humidity sensor. From astro-pi.org: "Young people write a simple program to take a humidity reading onboard the International Space Station and communicate it to the astronauts with a personalised message, which will be displayed for 30 seconds!" https://astro-pi.org/mission-zero/ https://astro-pi.org/mission-zero/