Japanse for sunbeam
This satellite was launched in 1991 as a joined effort of Japan, the USA and the UK. With the goal to observe soft X-Ray radiation coming from the sun's atmosphere.
The launch took place on August 30, 1991 from the Kagoshima Space Center (KSC), responsable for the project is the Japanese Institute of Space and Astronautical Science (ISAS).
The scientific mission is to observe x-ray and gamma emissions made by solar flares. To do this their are 4 instruments onboard:
The Yohkoh Spacecraft is in a low-earth elliptic orbit at an altitude ranging from 570 to 730 km orbiting the earth in about 90 minutes. Of which aproximatly 75% is spent in direct sunlight.
Data is send to the Kagoshima Space Center and the Kennedy Space Center when in range and otherwise to the NASA Deep Space Network. The craft itself has 10 Mbyte of storage capacity.
Factual data from Yohkoh Solar Observatory Official Homepage at http://www.lmsal.com/SXT