Robots need a place to stay in space, too. NASA is attaching a “robot hotel” to the outside of the International Space Station with the upcoming launch of the Robotic Tool Stowage (RiTS), a protective storage unit for critical robotic tools.

On Dec. 4, RiTS is slated to launch  aboard the 19th SpaceX commercial resupply mission. Its first residents will be two Robotic External Leak Locators (RELL). Outfitted with mass spectrometers capable of sniffing out the presence of gases such as ammonia, these robotic tools are used to detect leaks from the station. Two RELL units are on board the station right now: the first RELL launched in 2015, and it proved to be such a success that a second RELL was launched as a backup earlier this year.

In this image, RiTS spacewalk installation procedures were being tested in the Neutral Buoyancy Lab at Johnson Space Center in Houston.

Image Credit: NASA