Both of Japan's space agencies, ISAS (Institute of Space and Astronautical Science) and NASDA (National Space Development Agency) – now part of JAXA – tend to give two names to their satellites, one English and one Japanese. However, to make matters confusing these two names are completely unrelated. For example, NASDA's ETS (Engineering Test Satellite) series is also referred to by the Japanese name Kiku which means "chrysanthemum." Many of NASDA's satellites are similarly named after flowers – Momo ("peach blossom") for MOS (Marine Observation Satellite), Sakura ("cherry blossom") for the CS series of communications satellites, and Ajisai ("hydrangea") for EGS (Experimental Geodetic Satellite). ISAS, on the other, uses national names that are more diverse and sometimes loosely linked to the spacecraft's mission, such as Haruka ("far away"), Tenma ("galaxy"), and Hinotori ("phoenix").

A more important distinction between the two agencies' naming schemes is that whereas NASDA uses English and Japanese names as alternatives for its operational satellites, ISAS uses the English name before launch and then switches to a Japanese name after launch but only if the launch is successful. The ISAS pre-launch name indicates to which series the craft belongs; for example, Astro-D is the fourth spacecraft in the Astro- series devoted to astronomical observations, mainly in the X-ray region of the spectrum. After its successful launch Astro-D became known as Asuka ("flying bird"). On the other hand, Astro-E never received a Japanese name because it failed to reach orbit. To add to the confusion, some ISAS spacecraft have an alternative post-launch name, especially if they have involved collaboration with other nations or institutions. For example, Asuka (Astro-D) is also known as ASCA (Advanced Satellite for Cosmology and Astrophysics). Furthermore, NASDA has recently tended to move away from the pattern of always providing a Japanese name. TRMM (Tropical Rainfall Measuring Mission) and SELENE (Selenological and Engineering Explorer), for example, have no other designations. In this encyclopedia, all NASDA missions are identified by their English names and all successfully-launched ISAS missions by their Japanese names.