Fill a position as a successful astronaut? (2,4,5)

'fill a' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.

'position as a successful astronaut?' is the wordplay.
I cannot quite see how this works, but
'position' could be 'space' (spacing is a kind of positioning) and 'space' is present in the answer.
'as' could be 'in' (I've seen this in other clues) and 'in' is found within the answer.
The remaining letters 'goto' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?