NASA Beams Hi-Def Video From Space Via Laser

An anonymous reader writes "NASA successfully beamed a high-definition video 260 miles from the International Space Station to Earth Thursday using a new laser communications instrument. Transmission of 'Hello, World!' as a video message was the first 175-megabit communication for the Optical Payload for Lasercomm Science (OPALS), a technology demonstration that allows NASA to test methods for communication with future spacecraft using higher bandwidth than radio waves." Last September, NASA's LADEE (Lunar Atmosphere and Dust Environment Explorer) showed that they could supply a lunar colony with broadband via lasers.

For those wondering why a laser?

[Solandri]

Why is a laser better than other forms of EM radiation like radio? Channel capacity depends not just on the frequency-limited bandwidth, but also on the ratio of signal to noise [wikipedia.org]. Increasing signal strength or reducing noise will improve bits per second. (The Nyquist limit of twice the frequency bandwidth only governs frequency modulation, not amplitude modulation.)

Assuming background noise is constant, a laser's (much) better focus means more of the energy pumped into the signal reaches the destination, rather than spreading out and being lost to space. More signal => better signal to noise ratio => higher channel capacity for a given frequency bandwidth.