In this sense, we may state that JWST is more than able to replace the Hubble, but only in one area of competency.
3. Given the fact that the last servicing mission has been cancelled, in my opinion, Hubble is approaching an end. This is not necessarily because it is not doing its job anymore, but simply because time and use is already taken a toll on its equipment. Even initially it was only designed to be used until more than 2006, which is quite a long period of time. The fact that the servicing mission was cancelled entitles me to believe that there will be no further investments in the Hubble.
It is to be expected that NASA will wait a year or two and then will end Hubble's period of activity. The $350 million a year I have mentioned do not seem reasonable in this case. The JWST, for example, has cost an overall $1.6 billion. This means that five years of not working on the Hubble are enough to build an ultra- performing, last generation telescope. It does not seem cost effective anymore to invest in the Hubble. However, its accomplishments until now and the fact that it is still gathering important information should be enough arguments in favor of prolonging Hubble's life as long as possible.
4. In my opinion, we should, first of all, state again that there are several conceptual differences between Hubble and JWST, related to the objectives each has. JWST is much more focused on gathering information on early galaxies and the Big Bang. As such, it would probably be beneficial if both could be held in place and be used.
If we had to choose between one and another, it is like choosing whether to sell the old car and buy a new one or keep spending money on spare parts for the old one. If we take the cost effective argument, I have given some convincing figures previously: the cost for keeping Hubble 5-6 years...
Further more, we should also be discussing briefly quality. JWST does not only have last hour technology. The fact that it will be placed some 1 million kilometers away, four times the distance to the Moon, will mean that it will be much less available for permanent repairs, like a Hubble. The yearly costs of providing for it are much lower.
I have mentioned some of the technologies that JWST is equipped with. This will allow us to gather information about the very beginning of our Solar System and the Universe. There is no question that the technology used for JWST is more performing and that it will serve its purpose better than the Hubble (I have discussed some facts previously).
So, in terms of technology, purpose and cost effectiveness, JWST seems much more able to take over from the Hubble. There is only one exception that needs to be mentioned: the Hubble seemed to have a much more diversified field of activity, with the JWST being more focused.
Bibliography
1. Hesseldahl, Arik. Peering back at the Universe's past. Forbes. June 2004. On the Internet at http://www.forbes.com/infoimaging/2004/05/06/cx_ah_0506spaceimaging_ii.html
http://hubble.nasa.gov/overview/history.html
3. Hubble Space Telescope costs Americans less than $1 year. Lubbock Avalanche-Journal. 1997
http://www.jwst.nasa.gov/ISIM/
All data from the Internet, at http://hubble.nasa.gov/overview/history.html
Hubble Space Telescope costs Americans less than $1 year. Lubbock Avalanche-Journal. 1997
On the Internet at http://www.jwst.nasa.gov/ISIM/
Hesseldahl, Arik. Peering back at the Universe's past. Forbes. June 2004. On the Internet at http://www.forbes.com/infoimaging/2004/05/06/cx_ah_0506spaceimaging_ii.html
