In article ,
Derek Lyons wrote:
These men had NO IDEA why they were being summoned. NONE.

Something I've never debated.

Actually, many of the guys in the second bunch knew what was going on,
because the first bunch passed the word.

And they weren't "summoned"; they were invited. Deke Slayton:

...Invitations were sent out to each group in turn, asking
them to come to Washington for a briefing... when most of
the guys agreed to at least hear the proposal, NASA didn't
bother going beyond the first two groups...

Note that they had the option of not bothering to go, and some didn't.

But they were not summoned to the
astronaut corps, they were summoned to a briefing on the space program
and given the oppurtunity to apply to join the corps...

Slayton again:

The briefing was pretty straightforward... Volunteers were
needed. NASA hoped to select twelve test pilots... I think
the enthusiastic reception surprised NASA. ...

I was invited to go to the Lovelace Clinic in Albuquerque in
a couple of weeks for the first round of medical tests... A
total of thirty-six guys were invited, but four of them turned
it down at that point...

[more tests... selection board...]
Then came the call from Charlie Donlan. It was pretty terse:
"You've been selected to join us, if you're still interested."

"Yes, sir, I am."

Voluntary all the way, in other words.

There might perhaps be some slight lingering doubt because Slayton had a
co-author (although Michael Cassutt is reliable). However, Michael
Collins -- who applied for the second astronaut selection and made it in
on the third -- writes his own books, and he confirms that he had to
apply both times.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |