No, it's not a joke - NASA TV comes to Sky Digital on the 1st of October.

NASA TV will be shown on Channel 268 at these times:-

Weekdays:
*16:00-17:00 (LIVE ISS coverage)
*20:00-21:00 (Recorded ISS coverage)

Weekends
*17:00-18:30 (Live broadcast)

More time will be allocated to NASA TV should it prove popular, so please
spread the word, and also e-mail any comments/suggestions/praise to
David(at)friendlytv.com

If they receive enough encouraging emails, hopefully they'll add more NASA
TV to the channel.