China's Tiangong-1 space station will crash to Earth this weekendFri 30 Mar 2018 15.40 BST
(...) On Friday, the Chinese space station was still hurtling around the planet more than 180km above the surface. The atmosphere is tenuous at that altitude, but thick enough to drag on the solar panels and body of Tiangong-1. Gradually this slows the spacecraft down until gravity can pull it from orbit. When the spaceship falls below 100km, it will begin its re-entry in earnest.
“Within minutes it will be fully decelerated and the energy it carries will be translated into heat and aerodynamic forces that rip it apart,” said Krag. Between 1.5 to 3.5 tonnes of the spaceship may survive the ordeal and reach the Earth’s surface in dozens of pieces cast over hundreds of miles. The most dangerous could be fuel tanks that typically hold toxic hydrazine propellant. (...)
https://www.theguardian.com/science/2018/mar/30/chinas-tiangong-1-space-station-will-crash-to-earth-this-weekendUpdate 30 March 2018The current estimated reentry window runs from the night of 31 March to the late evening of 1 April (in UTC time); this is highly variable.
Today’s new forecast is a noticeable change from that of yesterday, and is due to solar activity.
One of the main reasons why it is so difficult to make an accurate reentry predictions, even if just a few days in advance of an expected reentry, materialised during the last 24 hours.
A high-speed stream of particles from the Sun, which was expected to reach Earth and influence our planet’s geomagnetic field, did, in fact, not have any effect, and calmer space weather around Earth and its atmosphere is now expected in the coming days.
This means that the density of the upper atmosphere, through which Tiangong-1 is moving, did not increase as predicted (which would have dragged the spacecraft down sooner) and hence the ESA Space Debris Office has adjusted the predicted decay rate.
This implies that the new (and still uncertain) reentry window has shifted to later in the day on 1 April.
Tiangong-1 reentry window forecast as of 30 March Credit: ESA
Tiangong-1 altitude decay forecast as of 30 March Credit: ESAhttp://blogs.esa.int/rocketscience/2018/03/26/tiangong-1-reentry-updates/http://m.esa.int/Our_Activities/Operations/Space_Debris/ESA_reentry_expertise
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