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The Russian TESIS Observatory will observe two solar eclipses from space

The Russian TESIS Observatory will observe two solar eclipses from space

Early in the morning on 22 July, 2009, at around 01.00 GMT (05.00 Moscow time) the trajectories of the Sun and Moon will converge at a particular point in the celestial sphere, and on Earth the Moon's shadow will fall on India. This will mark the beginning of one of the most beautiful phenomena in the natural world and astronomy - a full solar eclipse, which, this year, will move from Asia across India, China, Japan, the Marshall and Gilbert Islands, and will finish its journey on the Pacific Ocean at around nine in the morning Moscow time (05.00 GMT). This year's eclipse is unique in duration. At its climax, the Earth will be plunged into darkness for 6 minutes and 39 seconds. However, this long period of darkness will only be observed by sailors out at sea and a few lucky yacht owners - the point of maximum eclipse (northern latitude 2112.6', eastern longitude 14406.4') will be on the Pacific Ocean close to the edge of the Philippine Sea. India's inhabitants will be able to feast their eyes on the fiery-edged black disk of the Sun for around three and a half minutes, and China, across which the Moon's shadow passes, will be plunged into darkness for 4.5 to 6 minutes.

However, before the Moon's shadow hits the surface of the Earth it will pass across objects in space. Precisely these artificial Earth satellites will be the first to witness the approaching shadow of the Moon as it moves from deep space towards our planet, and will similarly be the last to "see off" the shadow after it has left the Earth's surface. Although most of the satellites situated in orbit will only be silent witnesses to the descending darkness, there are some types of devices which are capable of "seeing" the solar eclipse even from there. Namely, solar observatories - telescopes that allow us to photograph the transit of the Moon across the Sun's disk and capture details that are often impossible to observe from Earth.

Although, at the present time, there are 6 solar observatories belonging to leading space agencies in orbit around the Earth, the eclipse of 22 July, 2009, will only be seen by two of them: the Russian CORONAS-PHOTON satellite equipped with TESIS telescopes and Japan's HINODE satellite fitted with an XRT space telescope. Two of the other devices won't observe the Moon's shadow due to their orbit. These include the NASA STEREO satellite and the European Space Agency's SOHO observatory, which are so far from us that they no longer see the Earth or Moon. The remaining two space vehicles, NASA's small RHESSI and TRACE solar satellites, are in a low Earth orbit. However, the first of these is researching sources of hard solar X-rays and doesn't see the Sun (as such) within its range and the second satellite sees the Sun perfectly but has a very limited field of vision (less than half the Sun's radius).

TESIS and HINODE's XRT telescope will be able to enjoy the solar eclipse to the full. As part of a coordinated observation programme, together these two instruments will be able to simultaneously photograph 4 transits of the Moon across the solar disk. This is possible thanks to the specific nature of observing eclipses from space. An observer on Earth has to wait for the Moon's shadow to arrive and following its departure has to wait for the next eclipse to occur. In contrast, due to their rapid rotation around the Earth, space vehicles don't have to wait for the Moon, but instead fly into the Moon's shadow themselves. Moreover, due to the fact that the shadow takes several hours to moves across the surface of the planet and space vehicles take around 90 minutes to circle the Earth, they can enter the shadow several times during one eclipse. During this eclipse each satellite will pass through the Moon's shadow twice.

TESIS will be the first of the two devices (and the very first on Earth) to witness the solar eclipse. At 00:30 GMT (4:30 Moscow time), that is, half an hour before the Moon's shadow touches the Earth's surface, the telescopes will photograph the first transit of the Moon across the solar disk. Half an hour later at 01:00, at almost the same time as the start of the eclipse in India, HINODE will take its series of photographs. For HINODE this will be the maximal phase of the eclipse - the Sun and Moon will come together in its photographs at a distance of approach of only 0.15 degrees. In images captured by TESIS half an hour earlier, the distance of approach will be approximately 0.19 degrees. However, for TESIS, the maximal phase of the eclipse will still lie ahead.

After their first "meeting" with the Moon, both satellites will fly off on their orbits around our planet, while the eclipse will just be starting down below on Earth. Millions of people will start to follow the Moon's shadow as it moves from west to east, from India to the Pacific Ocean. At approximately 02:00 GMT (06:00 Moscow time), the Russian and Japanese satellites will return to the area in the shadow of the Moon, which will at that time be over the Pacific Ocean and reaching its maximum. However, the satellites will fly past the shadow with a poor view of the eclipse. The next sighting at around 03:00-03:30 GMT will also be "unlucky". Finally, at 04:30 GMT (08:30 Moscow time), TESIS will pass almost directly across the very centre of the shadow, which will already be leaving the Earth's surface. The distance between the centres of the Sun and Moon at the point of closest approach will be only 0.07 degrees. Half an hour later, HINODE will also have her moment. She will be the last to "see off" the largest solar eclipse of this century. At around 05:00 GMT, her telescopes will photograph the Moon at a distance of approach of 0.36 degrees from the Sun.

Eclipse-observation programmes are already in place aboard both satellites. Observational results - photographs and video footage - should be transmitted to Earth on the day of the eclipse, on 22 July at around 17:30 Moscow time.

The TESIS observatory


The Sun-Moon distance from the viewpoints of TESIS and HINODE/XRT (PNG; 86 KB)

First Moon transit from the TESIS viewpoint (PNG; 92 KB)    view data table

Second Moon transit from the TESIS viewpoint (PNG; 92 KB)    view data table