The likelihood of debris from the defunct space station hitting Italy is 0.2 percent, the agency (ASI) said on Monday after a meeting with the Civil Protection Department, which helps prepare for and manage disasters.
The ASI is one of 13 international space agencies monitoring the satellite as it approaches earth for an uncontrolled crash landing. ASI experts calculate that Tiangong-1 will re-enter earth's atmosphere on April 1st at 12:25 pm Italian time, though that estimate could be as much as 48 hours off.
Debris could potentially hit the centre-south of Italy, from roughly Florence downwards.
The satellite's trajectory will only become clear once it gets much closer, within 36 hours of impact – which means that the zone affected could get as little as 40 minutes' warning.
"We have very limited time windows and so, if the final analyses confirm the possibility that fragments of the satellite could hit our country, we need to give the public the clearest information possible," said head of the Civil Protection, Angelo Borrelli.
Once the satellite falls below 200 kilometres above earth, tracking radar in western Europe would pick it up before it reached Italy and allow authorities to sound the alarm, according to this graphic from ASI.
Nuovo incontro del Tavolo Tecnico presso la sede Protezione Civile con ASI, istituito per discutere ed analizzare le strategie da attuare per il rientro in atmosfera della stazione spaziale cinese Tiangong-1https://t.co/HI6VkMw7b0 pic.twitter.com/fQqAL9ZLr4— Agenzia Spaziale ITA (@ASI_spazio) March 26, 2018
Wherever Tiangong-1 ends up, the chance of being hit by debris is extremely small – around one in 100,000 billion, according to Ansa.
The space station is expected to break up on re-entry and scatter fragments over an area as large as 2,000 by 70 kilometres. Much if not all of the debris is likely to fall into the sea.
In the meantime, the upside of being within the zone that Tiangong-1 orbits is that the space station is visible from Italy.
The satellite flies over Italy between three and four times a day for around three minutes at a time, Paolo Volpini of the Italian Amateur Astronomers Union (UAI) told Ansa. Having fallen to around 220 kilometres above earth, it should be visible to the naked eye at night, he said.
The UAI has compiled a table that lists when Tiangong-1 will be passing over or near parts of Italy: find the data here. Let us know if you see it!