JWST is not a new HST
Is quite important to remember this. JWST will work mostly in mid-IR: is sensitive only as far as orange light. HST works mostly in visible with some near-IR. For much of its frequency range JWST will even not have as good resolution as HST – mirror is larger but wavelengths also are longer.
JWST is right thing to fly since mid-IR is where the cosmologically-interesting stuff is, but it's not a new HST.
(Also, just to head off inevitable 'vast overbudget' noise: JWST cost is about $9 billion in 2021 $. HST cumulative cost (including servicing) about $11.3 billion 2015 $. The thing to ask about JWST is not why it cost so much but why initial estimate ($500 million) was so absurdly low.)
Biting the hand that feeds IT
