Contents |
Next - Ground Telescope: Design Optimization Challenge
Ground vs. Space Telescopes
Almost all astronomical research and discovery prior to 1950 was made by optical telescopes on the ground.
The leading observational advances in the period of 1900-1950 came from telescopes located in the southwestern
United States using photographic methods.
After World War II, the technologies developed for radar and rocketry were applied to astronomy, opening the
whole electromagnetic spectrum to observation, as well as allowing direct exploration of the solar system. These
advances, along with the development of electronic imaging, revolutionized astronomy at all wavelengths. However,
no significant advances were made in ground-based telescope design; no telescopes more powerful than the Palomar
200-inch, completed in 1947, were built.
Today 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.
The image above shows the spiral galaxy NGC 4535 moved to a redshift of 1.0 and synthetically imaged with various
telescopes at a wavelength of 2 microns. The upper left frame shows the ground-based seeing limit under excellent
conditions (0.4 arcsec). The upper right frame is the galaxy imaged by HST (a 2.4 meter telescope) with 0.2 arcsec
resolution. The lower two frames show how the galaxy will appear with LBT. The lower left frame gives the appearance
of the galaxy with full adaptive correction of a single 8.4 meter mirror (0.06 arcsec diffraction limit), while the
lower right frame shows the detail attainable with a near infrared beam combiner which provides the diffraction limit
of the full 22.8 meter baseline (0.02 arcsec). These images were provided by Drs. Hans-Walter Rix and Tom Herbst of
MPIA Heidelberg who are part of a team studying the near infrared beam combiner design.