MOSCOW, January 10 (Itar-Tass) — Tuesday marks the opening of the "time window" for falling to Earth of the fragments of the Fobos-Grunt interplanetary probe which have not burnt in dense atmospheric layers.
"Specialists are constantly monitoring the descending Fobos-Grunt /literary Fobos-Ground/ unit launched on November 9, 2011, and presently flying at a low Earth orbit. As of January 6, the probe was at an orbit with the following parameters: maximum altitude 229.4 kilometers, minimal altitude 189.2 kilometers, and inclination 51.49 degrees," the press service of the Federal Space Agency /Roskosmos/ said.
"The dynamics of deceleration of the interplanetary probe in the Earth atmosphere depend on a variety of technical and space factors, including those which are beyond human control," Roskosmos said, "the main factor is a volatile atmosphere, heavily influenced by the sun."
According to the available information and preliminary calculations of the group which is monitoring Fobos-Grunt's breaking orbit, the predicted "window of its fall is between January 10 and January 21, 2012, with tentative midpoint on January 15. The area where the probe will fall may lie within a strip of Earth from 51.4 degrees of southern latitude to 51.4 degrees of northern latitude. The exact place, or the date or time cannot be predicted sooner than one day before the fall.
"Probe fragments consisting of heat-resistant metals - in all 20 to 30 pieces - and weighing not more than 200 kilograms may reach the ground," a Roskosmos official said, "the fuel the probe is carrying will burn in dense layers of the atmosphere at an altitude of approximately 100 kilometers."
"The Cobalt-57 radio-isotope source installed in one of the Fobos-Grunt instruments /Mossbauer spectrometer/ has a mass not exceeding 10 micrograms, and a small half-life period, so it will not cause radioactive contamination. Years of international statistics prove that descending spacecraft almost always fully burn in dense atmosphere, while their remaining fragments cause no harm, as a rule.
According to the U.S. outer space monitoring system, Fobos-Grunt is expected to fall to Earth on January 15.
The Fobos-Grunt unit, massing 13,505 kilograms, was to have reached an orbit around Mars to send a landing module to one of its satellites, Fobos. Simultaneously, the unit was to have conducted a remote study of the planet. After taking samples of Fobos ground, the unit had to return to Earth. The project cost some five billion roubles.
However, the spacecraft, launched from the Baikonur cosmodrome, failed to reach the trajectory of flight towards Mars, as its cruise engine failed for unknown reason.