Allen Thomson wrote:

OK, now that your real question has been answered, I have another:

How do the ISSonauts keep the inside surfaces of big windows optically
clean?

Absolute ethyl alcohol (which we used to use for optical surfaces at
LPL and helped with Solstice Celebrations) and cotton cloths? Probably
not, given alcohol's unfortunate propensity to combine energetically
with oxygen.

Windex and paper towels?

Saliva and shirtsleeves?

Or what?

Good question. I know it's not alcohol. There was a presentation a few
years ago on "ISS alcohol ban" and I read it thinking it was the
drinking kind, but it was the cleaning kind. But for the life of me, I
don't know what the "approved" glass cleaners on ISS are.