YOKHOH

YOHKOH was a Japanese satellite designed to analyse X-rays coming from the Sun. It had instruments to take images of the Sun and a spectrometer to provide spectra of the Sun's X-rays. The name 'YOHKOH' is the Japanese for sunbeam and was chosen after a competition run by a Japanese newspaper.

YOHKOH was launched from southern Japan in August 1991 on a Japanese-built rocket. A picture of the launch is shown above.

Since X-rays in the Sun's corona are emitted by very hot plasma, YOHKOH's images show us where the very hot plasma is and how it moves.

Unfortunately, after over 10 years of operation, control of YOHKOH's pointing was lost and it had to be shut down by the Japanese operators. However, over its lifetime YOHKOH gave scientists much new information about the solar corona and they will be analysing the data for many years to come.

Although YOHKOH isn't working anymore, we’re now working with our friends from Japan, the UK and USA on a follow-up mission called Solar-B, which should be launched in 2006.

If you'd like to know a bit more about what we've learnt from YOHKOH, then have a look at the section on 'solar explosions' in the 'Hot Solar Atmosphere'.