Snape flying away

[Carol]

No: HPFGUIDX 187302

Karen wrote: 
> So I think Dumbledore may well have given Snape some intensive Occlumency training in the quiet years after V's disappearance. Even so the 'Are you ready, are you prepared?' at the end of TGoF betrayed anxiety over Snape's possible fate.
> 
Marianne responded:
snip>
> Also at the end of "Are you ready?  Are you prepared" there is also:
> 
> "I am." said Snape.
> 
> He looked slightly paler than usual, and his cold, black eyes glittered strangly.
> 
> "Then good luck," said Dumbledore, and he watched, with a trace of apprehension on his face, as Snape swept wordlessly after Sirius.
> 
> 
> I was always under the impression  at the good luck paragraph that the apprehenison on Dumbledore's face was because he didn't totally trust Snape and perhaps had a bit of worry that Snape would not be his spy and go to and stay with LV and DE.  Not necessarily Snape's fate in the end.
>
Carol responds:

Possibly that was Harry's impression and the reader is supposed to share it, but if Dumbledore didn't completely trust him, he wouldn't have sent him on a mission that could backfire so completely. I'm sure that his apprehension and his silence reflected concern for Snape, both as a person and an excellent staff member and, probably more important to Dumbledore, an irreplaceable spy who had already shown his loyalty and determination to undermine Voldemort by spying "at great personal risk" during the year or so between the time he came to Dumbledore to ask him to protect "her--them" and the vaporization of Voldemort at Godric's Hollow. If he didn't trust Snape completely, he certainly wouldn't have allowed him to teach at Hogwarts, not to mention allowing him to be alone with Harry for various detentions. Snape had, after all, attempted to thwart Quirrell and had saved Harry's life. And Voldemort had killed Lily. Dumbledore knew quite well that Snape would never be a loyal DE again.

I doubt that he would have asked him if he were ready and prepared (meaning, I think, have you prepared your cover story) and wished him good luck if he weren't sure that he was on his own side. He's afraid that Snape may not come back (if his Occlumency fails or his story has holes in it, he'll be killed). And where will Dumbledore find another former DE willing to take the risks that Snape takes, to lie and spy and protect Harry? Snape is one of a kind and irreplaceable.

Carol, noting that the description of Snape's pale face and glittering eyes echoes, perhaps deliberately, the description of Harry as he prepares to enter the third-floor corridor in SS/PS