The Proba-3 Occulter and Coronagraph. Image: Redwire Space
SiliconRepubilc.com spoke to engineer Dr Steven Buckley about the Irish-made tech aboard the spacecrafts.
A space mission with Irish technology on board launches this week, sending two satellites into space to create the first man-made solar eclipse.
The historic Proba-3 mission, which is set to launch from Chennai, India at 4.08pm Indian Standard Time, will deliver ultra-detailed images of the sun’s corona – the outermost part of the sun’s atmosphere.
The mission aims to solve several secrets of the sun, including why the solar corona is so much hotter than the sun itself. It will also examine solar winds and solar flares.
The natural phenomenon of an eclipse makes looking at the corona possible, so in order to capture these images, the European Space Agency (ESA) mission will use the two spacecrafts – the Coronagraph and the Occulter – to create a man-made solar eclipse.
This endeavour is made possible by cutting-edge technology made in Cork by Onsemi engineers.
Onsemi’s shadow positioning sensors and silicon photomultipliers allow the two satellites to fly in millimetre-scale formation at a speed of 22,000mph.
Dr Steven Buckley, lead engineer on the project at Onsemi, spoke to SiliconRepublic.com about the technology and the Proba-3 mission.
Precision measurements
“You have the Occulter, which has the disk on it and then you have the Coronagraph, which then looks at the eclipse that the Occulter is creating and then you have to hold this at 150 meters,” he said.
“If you can rigidly make them align with each other, dance with the stars as they keep pitching it, so the two of them work together then you create a virtual 150-metre pole. So, the challenge for us was to basically find a way of doing that.”
Buckley and his team worked on the sensors that will monitor the light from the eclipse and, using a complicated algorithm, use the information from these sensors to adjust the position of the Coronagraph to align with the Occulter down to a millimetre.
“That’s so important, because over 150 meters, just five millimetres [difference] and you start bringing the sun into view and once you bring the sun into view, which is a million times stronger, it doesn’t work. So it’s important to get down to this one millimetre.”
Once the satellites are up there and the sensors enable the Coronagraph to line up perfectly, the satellites create the eclipse and take the measurements and data over a few hours and then start coming back to Earth in what’s called a free spin before returning for realignment.
Buckley said the reason they do that is because of the amount of energy and fuel that’s needed to keep these crafts constantly aligned is huge, so in order to conserve this energy over the two-year mission, it does it for four hours at a time.
Getting space-ready
One of the biggest challenges in creating this technology was sourcing the materials needed to give accuracy while also remaining stable in space. In relation to the Onsemi sensors, which includes the four main ones and four back-up sensors, there was also an intense radiation assessment required.
“They’re the eight items that actually are stuck out in space being put into the radiation, which is quite high up there. Anything else inside the satellite is somewhat shrouded by its own box. So, these devices had to be studied to see what their effects were.”
Onsemi is a US sensor developer, which acquired Cork-based start-up SensL in 2018. SensL signed a contract with the ESA back in 2011 to utilise the company’s silicon photomultipliers. The start-up was also involved in EIRSAT-1 Ireland’s first satellite.
Buckley said that despite having worked on technology for ESA missions in the past, which were ground-based testing missions, this is the first time he will actually see the tech he worked on go up into space.
“I still find it difficult to believe because I had it in my hands, but there you go.”
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Updated 2.35pm, 4 December 2024: This article was updated as the timing of the mission launch was delayed.
