China Building World's Biggest Radio Telescope 121
Zothecula writes "Since its completion in 1963, the Arecibo Observatory in Puerto Rico, with a diameter of 305 m (1,000 ft) and a collecting area of 73,000 square meters (790,000 sq ft), has been the largest single-aperture radio telescope ever constructed. But Arecibo is set to lose its title with construction now underway in Guizhou Province in southern China of the Five-hundred-meter Aperture Spherical radio Telescope (FAST). Upon its expected completion in 2016, FAST will be able to see more than three times further into space and survey the skies ten times faster than Arecibo."
It's been awhile since astro classes, but... (Score:5, Informative)
Given the 5 to 3 ratio in apertures between the two telescopes, I think that it will be able to "peer" (25/9)^0.5 = 5/3 = 1.67 times "further into space," where "peer" means resolve an object at a given signal to noise ratio. Collected light scales with the square of aperture, but signal to noise ratio only improves with the square root of the number of collected photons. In more useful terms, it should be able to resolve the same thing to the same statistical certainty in 3/5 of the time.
Re:'Build it Bigger' indeed (Score:5, Informative)
I dunno. The politics over SKA, where it would be located, etc, show that people do indeed care. Nobody can put a telescope even the size of the Lovell dish into space, never mind the size of this monster. Single dishes have benefits (such as reduced edge effects) that arrays do not, which is extremely important for some of the science needed. Radio telescopes are still the only systems you can build large interferometers from (you can do small optical interferometers, but that's it). RFI is an increasing problem for radio observatories, due to flagrant abuse of the spectrum by many nations, and it's much easier to shield one site than a hundred. Precision-engineering a single dish of this size will require advances in material science that will have spin-off benefits in other fields.
In short, there's lots of reasons for them to do this and no obvious reason for them to copy SKA or SHA.
Re:It's been awhile since astro classes, but... (Score:3, Informative)
The SNR you quote, which improves as square root of the collected radiation (radio waves), is voltage SNR. In terms of power, you still get a 9dB SNR improvement for 3 times the collected radio waves, and in these electronics, it is electric power which is the ultimately used. However, the improvement factor should again be raised to power 1/3 to get distance, since the amount of signal power collected by an aperture, after spherical dispersion from a star, drops as the third power of the star's distance. So.. (25/9)^(1/3) = 1.4 times.