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WHO needs weather forecasters? If all goes to plan, the world鈥檚 most advanced weather satellite will this week give Europeans access to a new pastime: do-it-yourself weather forecasting.

The Meteosat Second Generation (MSG) satellite will go live, providing the most detailed views ever of the weather systems over Africa and Europe. Better still, the images it produces will be available free to non-commercial users, allowing anyone with suitable equipment to see the weather heading their way.

MSG will image the Earth鈥檚 surface in 12 different visible and infrared frequency bands with a maximum resolution of 1 kilometre. This makes it far more sensitive than current Meteosat craft, which use only three frequency bands with a maximum resolution of 2.5 kilometres. And it will be twice as productive, generating images every 15 minutes instead of every half hour. Professional meteorologists who buy this data will be able to use it to generate improved climate models and forecasts.

For amateurs who want to download weather images from space, the impact will be even greater. Until now, this has been an expensive hobby, accessible only to the most dedicated and tech-literate enthusiasts. But almost anybody can receive MSG鈥檚 weather images cheaply and easily.

It wasn鈥檛 meant to happen. Eumetsat, the organisation responsible for operating Europe鈥檚 weather satellites and distributing their data, originally planned to operate MSG in exactly the same way as its existing satellites. These send raw data directly to its headquarters in Darmstadt, Germany, where it is processed. The resulting images are then beamed back up to the weather satellite, which rebroadcasts them in encoded form to national weather centres.

Expensive specialist decoders costing in the region of 拢2000 must be used to do the encoding, says John Tellick of the Remote Imaging Group, which represents 2500 satellite imaging enthusiasts from 45 countries.

Soon after the launch of MSG in August 2002, however, Eumetsat discovered that the satellite鈥檚 rebroadcasting equipment was not working. 鈥淲e had to look for another way to disseminate the images,鈥� says operations director Mikael Rattenborg. The solution was to broadcast the data using two TV satellites, Hot Bird 6 and Atlantic Bird 3, to encode the images in the same way as TV broadcasts so anyone with an ordinary satellite TV dish, the right decoder and a PC can pick up and display the satellite images.

While commercial users have to pay for a licence to decrypt the data, educational and scientific users can get a free licence. The status of the do-it-yourself crowd was unclear until November 2003, when after much lobbying by Tellick and others, interested amateurs were given the same status as educational users.

The free licence is set to give amateur meteorology a huge boost. A number of suppliers are gearing up to sell equipment for home users to plug into their PCs. And cheap software that sequences 6 hours of animations and allows limited image processing 鈥� such as overlaying images on maps 鈥� is beginning to appear. 鈥淚 expect the competition to grow,鈥� says David Taylor, who has set up a company called SatSignal to develop such software.

One activity likely to become popular among domestic users is forecasting local weather an hour or so ahead, so-called 鈥渘owcasting鈥�. This is already big business for meteorological organisations, which sell nowcasts to everyone from the military to sports organisers. They are too costly for individuals, so being able to generate a do-it-yourself forecast could appeal to people eager to know whether it will rain in the next hour while they are shopping.

A simple animation of the previous 6 hours of satellite images can be a powerful tool for nowcasting. 鈥淚 regularly use satellite images to work out which beach to go to,鈥� says Tellick. And organisations such as amateur sailing, gliding and astronomy clubs could benefit hugely by making their own nowcasts 鈥� not to mention the weather-related educational uses schools and colleges could dream up.

But amateur meteorologists cannot combine data from satellites, radar and ground stations to generate models of the atmosphere 鈥� so they won鈥檛 be putting their professional colleagues out of work just yet.