From September 10, 22:00UT until October 03, 10:00UT, the telescope "EIT" onboard of SOHO was taken from air. During that period, we could rely on SPIRIT data from the CORONAS-F satellite.
Every once in a while, forecasters have to deal with the fact that the Extreme ultraviolet Imaging telescope (EIT) is not available because of a so-called "CCD BAKEOUT". The detector of EIT is kept during operations at a temperature of about -67°C. At this low temperature, the camera condenses. During a bake out, the detector is warmed up to evaporate the condensation.
You may think that we are completely lost. We admit, it is not pleasant, but we have other tools to help us: namely SPIRIT data, coming from the satellite CORONAS-F.
The Coronas-F spacecraft was launched on July 31, 2001, in particular to watch the Sun during the descending phase of the 11-year cycle. Coronas is an international project between Russian and Ukranian space agencies. The instrument SPIRIT onboard has our special interest as it images the full Sun in extreme ultraviolet, similar like EIT. The blue SPIRIT image on the right is taken in 17.5 nm, while the EIT image on the left pictures the Sun in 17.1 nm. Both wavelengths are close to each other.
