NASA recently changed its channels to HD.
NASA TV’s PUBLIC, MEDIA CHANNELS NOW IN HD
NASA Television’s Public (101) and Media (103) channels are now transmitting in high definition.
NASA Television’s Public Channel (channel 101), the "NASA TV" most often carried by cable and satellite service providers, provides coverage of NASA missions and events, plus documentaries, archival and other special programming.
NASA TV’s Media Channel (channel 103) provides mission coverage, news conferences and relevant video and audio materials to local, national and international news-gathering organizations.
(HD Channel 105 is no longer in service.)