Comment by toss1

When I was in college before Hubble was launched, my astronomy professor told me that the original design for the Hubble space telescope was for a smaller mirror, but got upgraded because the larger one would be cheaper to make the larger mirror, because larger mirror size was already being made. Also the Space Shuttle was sized for the larger mirror diameter. The strong inference is that the US DOD was already making that size, so existing tooling could be used. Consider Hubble pointed at a target only 200-3mmkm away...