Question Grail:Launch Phase - Have I understood it correctly?

[SuprunP]

This Phase begins prior to liftoff when the Spacecraft are switched to internal power during the final minute of the last built-in countdown hold at T-4 Minutes.
(The Source)

Would you be so kind to tell me if I have understood this bit correctly?

"The countdown stops 4 minutes before the launch. We don't know how long this countdown hold continues. When the countdown is resumed and the last minute is counting down we are expecting the Spacecraft to be switched to internal power."

Thanks.

 

[Urwumpe]

This Phase begins prior to liftoff when the Spacecraft are switched to internal power during the final minute of the last built-in countdown hold at T-4 Minutes.
(The Source)

Would you be so kind to tell me if I have understood this bit correctly?

"The countdown stops 4 minutes before the launch. We don't know how long this countdown hold continues. When the countdown is resumed and the last minute is counting down we are expecting the Spacecraft to be switched to internal power."

1. They do know exactly how long the countdown hold will last, holds are phases in the countdown, during which the procedures are relaxed and not everything needs to be done in a coordinated and accurately timed fashion.

2. The spacecraft is switched to internal power in the final minute of this hold. It is no critical action that requires all launch controllers working together (usually only for things that apply to the launcher itself), so it can be done during the final hold.

3. The spacecraft is expected to be on internal power during the last four minutes of the countdown, because there is no time left to power it on in the four minutes.

The payload is not critical for the launch, and every payload has different procedures that refer to it - it could be a brick of concrete and still be a valid payload. The payload managers decide when it is best to power it on internal electricity, usually it is done during the last instant possible - but not when it is too late to stop the countdown should it fail.

 

[SuprunP]

Thank you, Urwumpe!

I got it now.