ESA Sentinel 1A: Collision Avoidance maneuvre to avoid dead satellite

At the end of the first day after the launch (4 April): all deployments have been executed during the night and completed early in the morning at the beginning of the first ‘day shift’.

As the first day shift nears its end, a serious alert is received: there is a danger of a collision with a NASA satellite called ACRIMSAT, which has run out of fuel and can no longer be manoeuvred.

A collision avoidance manoeuvre during LEOP has never been done before, and has not been simulated.

The satellite had not yet reached its ‘normal pointing mode’, the ESA team could not manoeuvre it before this milestone was reached.

But there was no alternative. After a brief team consultation Juan, the ‘day shift’ Deputy Flight Operation Director, decided to start preparing the satellite in case a manoeuvre was needed, and it was to be executed by his colleagues on the night shift.

It is decided to manoeuvre Sentinel-1A. Its orbit altitude needs to be changed to escape the chaser satellite (debris).

The manoeuvre takes 39 seconds. The sequence of commands was uplinked during pass 37 over Alaska/Svalbard/Kiruna/ at 04:33 UTC for execution at 05:14 UTC, outside visibility.

The atmosphere was tense and the Main Control Room was filled with suspense.

All eyes were watching the big screens on the wall, waiting for a sign, good or bad.

As the satellite approached Troll ground station on the next pass and the telemetry started to scroll down in the twilight of the control room, the team held their breath.

But there was no need for concern. The satellite was in Orbit Control Mode and the GPS on-board showed a change in its orbit status.

The manoeuvre had been a complete success. The collision and premature end of the mission had been avoided. Just another day in the office for the ESA Flight Operations team.

But it does highlight the need for continued vigilance in the debris littered orbits around the Earth. A more permanent solution is vital to allow the continued use of Earth orbits for scientific research.

Avoid meteorite fragments: Russian Government tells citicens

Sutter's Mill Meteorite fragments

Russia's authorities on Friday cautioned residents of the Urals to stay away from any unidentified objects after a meteor dramatically burned up above the region, with a precious meteorite apparently plunging into a local lake.

"Russia's emergency ministry warns all residents of the Urals... not to approach unknown objects," the ministry said on its website, listing several numbers for people to use if they found something unusual.

The meteor spectacularly fell early Friday, causing blasts which blew out windows in the city of Chelyabinsk and left almost a thousand people injured.

Televised reports showed footage from the Chebarkul lake, about 60 kilometres from Chelyabinsk, where a circular hole was discovered in the ice, which regional police said was cut by a meteorite.

Local fishermen saw the falling meteor, which disintegrated into seven pieces. "One of them fell on the shore opposite of the (Chebarkul) town, whipping up a pillar of ice, water and steam," the police said in a statement.

"As a result, a giant circular ice hole eight meters (26 feet) in diameter was formed," the report said. Police secured the area and specialists measured radiation, which was normal, it said.

Pictures on the police website showed people standing around looking at the ice hole. One also showed a tiny rock about one centimetre in diameter, laying on ice next to a ruler.

Several such fragments, "hard, black pieces, which look like rock segments," have been recovered, police said.

Classified ad websites quickly had notices put up by enterprising or jestering Russians, offering pieces of the new meteorite for sale. "Two vans of the Chelyabinsk meteorite," said one notice, posted in the "jewelry" section of a Russian website Avito. "Price can be negotiated."

The regional emergency ministry said it had sent people to the Chebarkul area but could not confirm the hole in the ice was caused by an object from space. It also asked people not to panic and keep warm by closing shattered windows with plywood and plastic.

"It's a hole in ice, we have sent a team to inspect (look into) it, but I cannot confirm it's from a meteorite," spokesman of the Chelyabinsk branch of the emergency ministry Vyacheslav Ladonkin told AFP.