SETSUKO Satellite System

The SETSUKO Satellite System (: "せつこ", fully 世界付航法衛星系;  Se kai- tsu ki kō hō eisei-kei, Worldwide Navigation Satellite System) is a Yamataian space-based satellite navigation system. It consists of two separate satellite constellations.

Development of SETSUKO began with the SEIKO Satellite Navigation Experimental System ("せいこ", fully 世界付航法衛星系) in 1976, which provided limited coverage over Yamatai with four satellites and was decommissioned in 1993. Beginning on 13 July 1982, UKAJI began development of SETSUKO, with the 24-satellite constellation completed in 1996. SETSUKO is the most expensive program of UKAJI, consuming a third of its budget in 2010. By 2010, SETSUKO had achieved full global coverage.

Yamataian ballistic missiles and other military systems are known to use the SETSUKO system for guidance.