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How it works: UrtheCast

Next year, UrtheCast (pronounced "EarthCast") will begin to broadcast the first ever live, HD video of the Earth from space - think Google Earth meets YouTube. Here's how it will work...

From early 2013 onwards, you’ll be able to watch images and video footage of the Earth taken from space, for free. Unlike YouTube videos or Google Earth, the footage being streamed will be almost live.

Images and video will be captured by two cameras flown into orbit by the Canadian company UrtheCast in late 2012. They’ll be attached to the Russian module of the International Space Station (ISS). From this vantage point 350km above Earth, the cameras will survey the ground below as they make 16 orbits per day. The ISS’s orbit takes it between 52 degrees north and 52 degrees south, thereby covering almost all inhabited areas.

 

How the Earth will be filmed from space (click for full-size image):

 

The cameras were designed and built by the UK’s Rutherford Appleton Laboratory. The medium-resolution camera takes still images while the high-resolution camera captures video that shows detail as small as 1m across, which is similar to that of Google Earth. To ensure they’re pointing in the right direction, and to cope with vibrations on the Space Station, the cameras will be linked to star trackers. These are small cameras that take images of space and locate patterns of stars in order to calculate which way the main cameras are pointing.

The cameras will capture raw data and compress it using the JPEG2000 algorithm. Data from each camera will then be stored on a computer and transmitted when the Station is in sight of a receiver on the ground. This will happen at least once per orbit, or every 90 minutes.

From the receivers, the data will be uncompressed and uploaded to servers. On the UrtheCast website, you’ll be able to fast-forward, pause, rewind and skip the near-live footage. You’ll also be able to tag segments of video on Facebook and Twitter, and track the Space Station’s position to see when it will next pass over an area of interest.

 

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