HST is not cost effective any more.
http://medusa.as.arizona.edu/lbto/whybuild/grbsspc.html
$this->bbcode_second_pass_quote('', 'T')oday the pace of technological advances in space has slowed; future instruments in space, more powerful than the Hubble Space Telescope (HST) or similar observatories operating at other wavelengths, will be very expensive and slow in coming. It has been realized worldwide that, for optical and infrared observations,
new advanced mountaintop telescopes offer huge potential for future discovery, at a much smaller cost. Light grasp more than an order of magnitude larger than HST can be obtained from the ground, allowing detailed analysis of fainter, more distant sources. Moreover, taking advantage of the latest sensors and fast computers adaptive optics allows the potential of correcting atmospheric blurring and enormously improving image sharpness to a level far exceeding that of the HST. Mountaintop telescopes are entering a new golden era.