There are indeed some reasons, why it would be nice to have two JWST. Certainly, at least some costs would have been lower for building a second one. Though all the labor would have duplicated, and it seems a lot of labor went into just building JWST to spec.
But what would buy us the money spent on a second telescope. One often named reason is protection against failure. That is not so straigth forward, as it sounds. If there is a random chance for failure, then a second telescope lowers the risk accordingly. However, if there is a systematic problem with the design, you would have two defective telescopes. That means, you would have even wasted more money.
Then, if both succeed, you would have increased the "bandwidth", as they could be operated in parallel. But you wouldn't have added the capability to do things differently. With Voyager 1 and 2 and Spirit and Opportunity, they at least were sent on different mission profiles and thus justified the expense.
The thing is, 10 Billion is a huge amount of money, if another JWST had cost like 5 Billions, thats a lot of scientific projects not done because of building a second space telescope. I would rather see the money spent onto different capabilities. Hubble for example is failing, we should have another telescope in the visual range ASAP. As soon as Starship reaches orbit, plans should immediately start to convert one starship into a humungeous Hubble successor.
An instrument like the Thirty Meter Telescope costs just 1 Billion. There is so much other science those 5 Billion would finance. Even if you look around only in the field of astronomy and cosmology.
I really like what they did with Curiosity/Perseverance. They used a proven platform for a second mission with updated sensor and mission profiles. So in my eyes, it would be good to invest the money not spent on a second JWST to begin construction of a true successor, which should be operational before the end of the life time of JWST. With upgraded sensors and based on anything we learn in the first years JWST is used.
But what would buy us the money spent on a second telescope. One often named reason is protection against failure. That is not so straigth forward, as it sounds. If there is a random chance for failure, then a second telescope lowers the risk accordingly. However, if there is a systematic problem with the design, you would have two defective telescopes. That means, you would have even wasted more money.
Then, if both succeed, you would have increased the "bandwidth", as they could be operated in parallel. But you wouldn't have added the capability to do things differently. With Voyager 1 and 2 and Spirit and Opportunity, they at least were sent on different mission profiles and thus justified the expense.
The thing is, 10 Billion is a huge amount of money, if another JWST had cost like 5 Billions, thats a lot of scientific projects not done because of building a second space telescope. I would rather see the money spent onto different capabilities. Hubble for example is failing, we should have another telescope in the visual range ASAP. As soon as Starship reaches orbit, plans should immediately start to convert one starship into a humungeous Hubble successor.
An instrument like the Thirty Meter Telescope costs just 1 Billion. There is so much other science those 5 Billion would finance. Even if you look around only in the field of astronomy and cosmology.
I really like what they did with Curiosity/Perseverance. They used a proven platform for a second mission with updated sensor and mission profiles. So in my eyes, it would be good to invest the money not spent on a second JWST to begin construction of a true successor, which should be operational before the end of the life time of JWST. With upgraded sensors and based on anything we learn in the first years JWST is used.