Abstract
In this paper, we report on an on-orbit optical frequency tunable control mission using a CubeSat for realizing
inter-satellite coherent optical communication using a 1550 nm narrow linewidth laser. The satellite
that carried out this mission was a 3U-sized CubeSat called OPTIMAL-1. This satellite was released
from the ISS (International Space Station) in January 2023 to low earth orbit. It was confirmed that optical
frequency tunability exceeding ± 5 GHz, which is necessary for inter-satellite optical coherent communications,
can be achieved by laser temperature control. Furthermore, the characteristics of the coherent
laser source did not deteriorate even after half a year of operation in the space environment. We
achieved all the success criteria for the on-orbit optical module including extra success.
