Hi
According to my list (yes, I'm so pathetic I actually make lists of these things), it is indeed transponder D6S on "the satellite formerly known as Eurobird". (I believe it's called Eutelsat28A now. Others will correct me if I'm wrong.) The frequency is 11565V. (BTW, isn't Challenge unencrypted these days?)
Anyway, it isn't an Astra satellite at all. It uses the transport streams 0961-0966 (2401-2412 in decimal numbers) and 08fd-0902, 0907-090a, 090c, 0a26, 0a29, 0a2a, 0a2c, 0a33-0a36 and 0a85 (and some others).
The Astra satellites at 28E are easier, as they're mostly sequential. They use o7d1-0818 (2001-2072 in decimal).
Regards,
Bengt