About NASA TV,

NASA TV (originally NASA Select) is the television service of the United States government agency NASA.

NASA TV is broadcast by satellite with a simulcast over the Internet. Local cable television systems across the U.S. and amateur television repeaters may carry NASA TV at their discretion, as NASA-created content is considered a work of the U.S. government and is in the public domain. The network was formally created in the early 1980s to provide NASA managers and engineers with real-time video of missions. NASA has operated a television service since the beginning of the space program for archival purposes, and in order to provide media outlets with video footage.
The network airs a large amount of educational programming, and provides live coverage of an array of manned missions, including the Space Shuttle and International Space Station (ISS), robotic missions, and international launches. The network completed its conversion from analog to digital transmission in late 2005 following the launch of STS-114, ending a period of dual analog and digital broadcasting, although some cable television systems may still have transmitted in analog prior to the U.S. digital television transition. The satellite link uses the DVB-S system for transmission.

NASA TV operates four channels. The “Public Channel” provides 24-hour broadcasting of live and recorded events and documentaries aimed toward the general public. The “Education Channel” provides space and science programming for schools, museums, and other educational institutions. The “Media Channel” is dedicated to broadcast news organizations and other members of the press, featuring press release video, interviews, mission press conferences and other services. The final is the “Space Operations Channel”, an internal, encrypted feed for NASA spaceflight operations. A high definition simulcast of the “Public Channel” launched on July 19, 2010.
The NASA TV website also provides a channel featuring continuous live footage from inside and outside the ISS, established to celebrate the 10th anniversary of the station in orbit, as well as a continuous audio-only channel of ISS and Shuttle mission audio.

From Wikipedia®.