As of April 30, NASA has been running its High Definition Earth Viewing Experiment (HDEV) which, as well as testing certain aspects such as a camera's ability to survive the radiation levels present in low-Earth orbit, is giving viewers the breathtaking experience of observing their planet in exquisite detail from space.
The video feed is streamed from one of four high-definition cameras mounted on fixed positions of the Columbus External Payload Facility of the ISS. The cameras being used in the experiment are commercially available "off the shelf" models, with the experiment in part aiming to test the usefulness and longevity of existing imaging devices for use in future long term missions.
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The cameras are contained in a protective pressurized box, pumped full of nitrogen at the pressure of one Earth atmosphere. The cameras are positioned with one facing towards the station's velocity vector, two to the rear, and one pointed directly at the Earth's surface.
The stream is Ethernet compatible, allowing it to be viewed with any computer with an active internet connection. The feed is almost always available, however when the ISS is outside of communication range, viewers will be presented with a grey-screen.
If users witness a prolonged black screen don’t panic, the feed isn't down, this is just what happens when the Sun is on the opposite side of the Earth. The up side is that, if the user perseveres, they will be treated to what is arguably one of the most spectacular sights available on the internet – a sunrise as seen from space.
There is a growing trend in Earth observation, with commercial companies such as UrtheCast attempting to cash in on the ever expanding public interest by offering both commercial and public packages, granting everyone the opportunity to observe the Earth in unprecedented levels of detail. These commercial enterprises, augmented by programs from NASA such as the current HDEV experiment, are allowing mankind to view the planet as never before.
The near-live stream of Earth from space is available via Ustream.
Source: NASAView gallery - 3 images