While I have been waxing poetic about the James Webb Space Telescope, set to launch in 2018, there is another massive telescope that has been in the works. This time it is a ground based telescope that will dwarf its rivals with a 30-meter (m) diameter primary mirror. Its closest competitors are about ten meters in size and include Keck 1 and Keck 2. The Thirty Meter Telescope (TMT) Observatory blows them out of the water with its 30-m primary mirror, giving it the ability to see objects that are nine times fainter then what is seen by the Keck telescopes.
As opposed to the James Webb Telescope, TMT is ground based. Ground-based telescopes have less risk and lower long-term costs than do space telescopes. A good example of this price savings is the Hubble telescope. Discovering a problem with the mirror on Hubble after hauling it into space, supplies and astronauts had to be dispatched to fix the telescope at a great cost. With James Webb, it will not be possible to fix the telescope if there are problems since it will be orbiting the Earth at a distance much further than the Moon. Ground based telescopes can be fixed and upgraded with much less cost. Also, new instruments can be added with ease. While TMT is primarily capturing visible, infrared and near-ultraviolet wavelengths, additional instruments will be added to support key scientific initiatives.
Ground-based telescopes will always be hampered by distortion from Earth’s atmosphere, which is the major benefit of space-based telescopes like Hubble and James Webb. To counteract the effects of Earth’s atmosphere on the telescope, an adaptive optics system will measure and correct for atmospheric turbulence and distortion.
If you were ever nerdy enough to go to astronomy camp, like moi, you would have seen how the mirrors for telescopes are created: using a honeycomb mold, they melt glass into it and spin the mold in a rotating furnace to give it a convex shape. With a telescope of this size, it would be very difficult to create one large piece for the mirror. Borrowing from the Keck telescope, they will use a segmented approach, combining smaller sections of glass to create a large, 30-m sheet. This is much more feasible and cost effective, as if there is a problem with one of the segments, it can be individually replaced without having to replace the entire structure.
The Thirty Meter Telescope in tandem with the James Webb Telescope will open doors into the birth of our Universe and its cosmic makeup. There is no telling what these telescopes will uncover and what questions they will answer.
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