Obviously it’s actually *old* footage, but…
CNN has a copy of their Challenger launch broadcast footage. It’s available on CNN’s own YouTube channel, and it understandably has millions of views. CNN’s upload is a 360p video whose content is similar to what you see here — with three major differences: (1) this version is of substantially higher quality, (2) this version doesn’t have any CNN branding, and (3) this version continues NASA’s feed longer than CNN showed on air.
This is a direct copy of NASA’s broadcast feed. It was saved by NASA, and at some point a copy was transferred to the United States Geological Survey on a VHS tape. This video is a digitization of that tape; as far as I know, this is the first time it is being shown publicly.
It’s by no means high def, but it does looks substantially better – and goes on longer – than what I’ve seen before.
WARNING: if you’re of sufficient age, you might find that your room suddenly gets rather dusty when you watch this and think back to that day.