Science

How Ireland’s first satellite was almost lost a short time after launch

Rotation of Eirsat-1, which is no bigger than a brick, righted by ground teams after being ejected from SpaceX rocket

The Eirsat-1 satellite.

Ronan McGreevy
Tue Mar 12 2024 - 15:54

Ireland’s first satellite, Eirsat-1 has survived its first 100 days in space which is in itself an achievement.

Half of all so-called cube satellites, named after their distinctive shape, fail after being launched into orbit.

Eirsat-1, which is no bigger than a brick, almost ended up as space junk after being ejected from the Falcon 9 SpaceX rocket on December 1st.

Shortly after launch it was rotating at 5 degrees per second taking 72 seconds to do a full rotation which was in line with expectations.

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It quickly sped up to 30 degrees per second taking 12 seconds to do a full rotation. By the time mission control in UCD had established contact with it, it was spinning at 50 degrees per second and getting faster. “If it keeps spinning faster and faster, you won’t be able to communicate with it and you’ll lose the mission,” said Eirstat-1 engineering manager Prof David McKeown.

“The faster it gets the harder it is to make it slow down again. Once it gets to a certain speed you can’t even send the commands to it to slow it down. This was very worrying. If it went on, that would have been curtains for us.”

Ireland's first satellite, Eirstat-1, before its launch. Photograph: Julien Behal

Eirsat-1 chief engineer Joseph Thompson said they had only tested the satellite on the ground at a rotation speed of 30 degrees per second. “We had to get a bit creative to slow it down,” he explained. The drama began three days after the launch on December 1st.

The team finally found a solution to the spinning by doing simulations on the ground. “There was a very real risk there. We had tested some of this stuff on the ground. We were thrown straight into the situation,” he said.

All is well that ends well and the satellite is back in its rapid orbit around the Earth passing over Dublin seven times a day at a height of 515km.

“It is so much work, so much time over so many years. You get a mixture of relief and happiness. It is absolutely a technical success. We took no shortcuts. It was years of testing and it’s years of work that has paid off,” said Mr McKeown.

“We couldn’t be happier with the way things are working. All the critical systems are healthy. We have got data back from one of our payloads.”

Eirsat-1 has three experimental payloads on board to carry out three experiments, one on gamma ray radiation, a second on temperature regulation in space and a third on how to orient satellites in the right direction.

Mr McKeown said the satellite is sending back data which will be useful to the scientists on the ground who are doing experiments.

Ronan McGreevy

Ronan McGreevy

Ronan McGreevy is a news reporter with The Irish Times

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