Astronauts onboard the International Space Station have released into orbit 5 micro satellites, including ones made by Japanese companies and universities.

The satellites, small enough to be held in the palm of the hand, were transported to the space station by Japan's unmanned cargo carrier Kounotori 3 in July.

Japan's Akihiko Hoshide and other astronauts conducted the first-ever operation to launch the satellites using a robotic arm. They finished the task at 15:44 UTC on Thursday.

3 of the 5 satellites were developed by Japanese companies and universities. The Fukuoka Institute of Technology made a satellite which uses light-emitting diodes to send messages in Morse code to earth.

The satellites will orbit earth for about 100 days and eventually disintegrate when entering the atmosphere.

Micro satellites can be developed substantially cheaper than conventional satellites, prompting corporations and universities to make their own for experimental and business purposes.