The robotic Japanese cargo vessel now en route to the International Space Station is loaded with food, clothes, equipment — and a set of tiny amateur radio satellites, including one that will write Morse code messages in the sky.

Japan's unmanned H-2 Transfer Vehicle-3 launched July 20 and is slated to arrive at the station Friday (July 27). The ultrasmall satellites it's carrying, which are known as cubesats, will likely remain on the orbiting lab until September, when they'll be deployed by Japanese astronaut Akihiko Hoshide using the Kibo module's robotic arm.

One of the cubesats, FITSAT-1, will write messages in the night sky with Morse code, helping researchers test out optical communication techniques for satellites, researchers said.