The X-ray Solar Eclipse

The Russian TESIS (FIAN) Solar Observatory has transmitted observations back to Earth of the solar eclipse made on July 22nd, 2009.

Thanks to the specific orbit of the space vehicle, the observatory's x-ray telescopes detected the eclipse twice. On the first occasion, the satellite passed through the eclipse area at 04:30 Moscow time, making it the first on our planet to see the shadow of the Moon, which was still in space and was only approaching the Earth (film 1.2 MB, wmv format). And 4 hours later, when almost all the inhabitants of the Earth had already said goodbye to the eclipse, TESIS telescopes captured images of the second deepest transit of the Moon across the Sun (film 1.2 MB, wmv format).

The eclipse became a challenge not only for the scientists themselves, who had been preparing for it for several days; calculating the reciprocal trajectories of the Moon, the Sun, and the satellite, and putting onboard special observational programmes; but also for the space vehicle navigation system - the basic element of which are the Sun sensors. The previous Japanese solar satellite, Yohkoh, which had been working in orbit for more than 10 years, was lost precisely during a full solar eclipse. The navigation system lost track of the Sun because it was temporarily covered by the Moon, and, in the process of searching for it, swung the space vehicle around so that its solar batteries no longer caught the light. As a result, after having fully exhausted its power cells, the satellite remained in orbit, but was completely lost.

However, the CORONAS-PHOTON found itself in a better position. This time the Moon never covered the Sun completely even during the maximal phase of the eclipse, and part of the solar disk remained visible - forming a thin crescent. And although handwheels "drove" the satellite round on its axis, while trying to adapt to the new and unusual distribution of brightness on the Sun sensor, generally speaking, the satellite remained in working position.