The eruption in Iceland has paralysed air travel
A field full of antennae in a sleepy Ceredigion village is helping scientists track ash in the atmosphere from the Icelandic volcano.
A radar system, called a lidar, in Capel Dewi, near Aberystwyth, has been picking out thin layers of fine ash.
The work is being carried out by the University of Manchester.
The eruption of Eyjafjallajokull paralysed large parts of European airspace for days, and left thousands of people stranded around the world.
Six days after the volcanic ash cloud triggered the first airspace closures, the International Air Transport Association (IATA) said airlines had lost $1.7bn (£1.1bn).
The information used by the Met Office and airlines to make crucial decisions about air travel in the UK has been collected by atmospheric scientist Professor Geraint Vaughan.
His lidar system, near Aberystwyth, a cousin of radar, is able to pick out thin layers of fine ash at different heights in the atmosphere.
He formerly worked at Aberystwyth University, but he still manages the lidar site in Ceredigion from the University of Manchester.
He said: "There are a number of lidar sites, but we've been using the facility in Capel Dewi to say where the ash is.
"We're not able to say how much ash there is.
"We can measure where the ash is, at what heights, and the thickness of the layer. We have learned it's at all kinds of heights, from about 1km to the aircraft-cruising altitude of 10km-12km."
Prof Vaughan said he had received some positive feedback about his work.
"I've had e-mails saying the research and information we've provided has been vital," he said.
"We've had several encouraging e-mails and it's nice to think that this facility (in Capel Dewi) has been at centre stage for a few days."
He said there was not as much ash in atmosphere on Thursday.