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6.7 Meter Telescope To Capture 30 Terabytes Per Night
Lumenary7204 writes "The Register has a story about the Large Synoptic Survey Telescope, a project to build a 6.7 meter effective-diameter ground-based telescope that will be used to map some of the faintest objects in the night sky. Jeff Kantor, the LSST Project Data Manager, indicates that the telescope should be in operation by 2016, will generate around 30 terabytes of data per night, and will 'open a movie-like window on objects that change or move on rapid timescales: exploding supernovae, potentially hazardous near-Earth asteroids, and distant Kuiper Belt Objects.' The end result will be a 150 petabyte database containing one of the most detailed surveys of the universe ever undertaken by a ground-based telescope. The telescope's 8.4 meter mirror blank was recently unveiled at the University of Arizona's Mirror Lab in Tucson."
The basic problem is that a 6.4 meter aperture can't fit in a launch vehicle, Ares V is only to be 5.5 meters.
Hubble was built at the diameter it was (2.4 meter) because thats about the maximum you could build of a stiff mirror that held its shape well enough through launch to remain optically sound on orbit. When you require 10-nm level precision, it takes a hefty structure to keep things that stiff.
In order to go bigger, the methods they're using for James Webb manage to double the aperture while halving the weight. The way they do this is using active controls and sensors to correct errors rather than rely on avoiding all errors. But looking at James Webb, you'll notice it focuses on IR which is very hard to observe from Earth, while no optical band concept is out there. This is because the new, big Earth-bound scopes use adaptive optics to eliminate seeing errors (the variations in the atmosphere that Hubble avoids), and get potentially better images than Hubble since larger mirrors can be used.
Of course, if the money shows up, there are other advantages to having a space-based observatory, particularly access time and not having to worry about the effectiveness of the adaptive elements, so I'm sure we'll see a proper Hubble replacement eventually, but it's certainly not as critical for scientific progress as some might think.