Also note that the ISS has an orbital period of just 93 minutes - for a considerable part of that time the station is in the Earth's shadow and can't see much. If the feed is permanently gray then HDEV is switched off - or communications have been lost. If you watch the stream you will notice that it hops between the four cameras in sequence, with gray and black color slates in between each switch. The box was connected up to the underside of the ISS via EVA/spacewalk, with one camera pointing forward (Hitachi), two cameras facing aft (Sony/Panasonic), and one pointing nadir (Toshiba, down towards Earth).

HDEV, which consists of just a single enclosure, was delivered to the ISS a couple of weeks ago by SpaceX CRS-3.

The purpose of HDEV, beyond providing us with a live stream of our own frickin' planet, is to see if commercial cameras are viable for future space missions, potentially saving a lot of money (space cameras have historically been expensive, custom-designed things). HDEV is notable because it consists of four, commercial off-the-shelf (COTS) high-definition video cameras that are each enclosed in a pressurized box, but otherwise they exposed to the rigors of space (most notably cosmic radiation). This rather awesome real-time video stream (which also includes the ISS-to-mission control audio feed) comes by way of the High Definition Earth Viewing experiment. There are some recorded clips on Ustream from last week (Opens in a new window) if you want to see what the footage looks like. Updated 12:15 May 5: Unfortunately it seems the HDEV experiment has been 'temporarily offline' for the last couple of days. You can open up the Ustream page at any time, and as long as it isn't night time aboard the ISS, you'll be treated to a beautiful view of the Earth from around 250 miles (400 km) up. This video feed (embedded below) comes from from four high-definition cameras, delivered by last month's SpaceX CRS-3 resupply mission, that are attached to the outside of the International Space Station. After being continuously inhabited for more than 13 years, it is finally possible to log into Ustream and watch the Earth spinning on its axis in glorious HD.

Space station live view of earth