The robots stand 34 centimetres (17 inches) tall and weigh around one kilogram (2.2 pounds) each.
Kirobo, whose name is derived from the Japanese word for hope, has the capacity to function in space.
The robot astronaut is scheduled to travel onboard the Kounotori 4 cargo spacecraft due to launch from the Tanegashima Space Centre on August 4, on a mission to the International Space Station.
Meanwhile, back-up crew member Mirata will be based on land.
The robots are able to engage in converation and developers hope that they will one day be able to assist astronauts working in space.