(Hope I am not breaking any laws by posting this)

The expenditure required to repair Hubble is only justified if Hubble possesses unique capabilities that are worth that expense. What are Hubble's unique abilities? Well, Hubble CAN observe in the shorter (visible, and UV) wavelengths- ground based adaptive optics (AO) cannot function at these shorter wavelengths, but the technology is being actively worked on... another unique ability is that Hubble can image essentially any point in the sky with diffraction limited resolution. Ground based AO (without a laser) could only image objects located close to a bright (brighter than ~9th magnitude) star - this limits you to ~1-2 percent of the sky... A laser guide star lets you look at more of the sky- with a laser the object only needs to be close to a star brighter than 19th magnitude- this opens up 80-90 percent of the sky, technology can improve this but it wont be 100 percent.

Those are the two big advantages that Hubble has, there are a few others, but those are the two most important ones in my opinion.

The first advantage, shorter wavelengths, is something that a few hundred million dollars spent on ground based technology could remedy- there are MANY people working on this problem and its just a matter of money and advancing technology- ground based scopes WILL look at shorter wavelength- its part of the long term plan for many observatories... this is one point for spending the money on ground based technology.

Ten meter scopes regularly get several times the resolution of the Hubble in the near Infra-red wavelenths - The two Kecks cost something like $250 million to build- you could build several ten meter scopes for the price of the repair mission, or build a larger scope... additionally, if you develop the AO technology to allow shorter wavelenths to be observed then ALL observatories can utilize it and all the big scopes could outperform the Hubble on a nightly basis... And, if a ground based scope breaks, you can have lots of engineers working on the problem in a few minutes (I once helped fix a problem on Keck II with a sledgehammer and a 4x4 piece of lumber)

The sky coverage issue is one that Hubble will probably still win on, but is it worth the cost? How likely is it that a totally unique phenomenon will happen in the 10% of the sky we can't image with Laser Guide Star AO? IMHO the money would be better spent on ground based technology- more return for the buck...

There is, of course, the politics of the issue- Hubble is a great PR instrument- but maybe its time to toast it for its accomplishments, shed a few sentimental tears, and move on to grander things.

P.S. Anyone catch my 4 seconds on this week's NOVA? 8^)

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