# China builds largest and most sensitive radio telescope

**URL:** <https://boards.straightdope.com/t/china-builds-largest-and-most-sensitive-radio-telescope/726452>\
**Category:** Miscellaneous and Personal Stuff I Must Share\
**Created:** [July 29, 2015, 6:05am UTC](https://boards.straightdope.com/t/china-builds-largest-and-most-sensitive-radio-telescope/726452 "2015-07-29T06:05:54Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Measure\_for\_Measure](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/measure_for_measure/32/557_2.png) [@Measure\_for\_Measure](https://boards.straightdope.com/u/Measure_for_Measure)\
**Post date:** [July 29, 2015, 6:05am UTC](https://boards.straightdope.com/t/china-builds-largest-and-most-sensitive-radio-telescope/726452/1 "2015-07-29T06:05:54Z")

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For years, the radio telescope at [Arecibo Observatory](https://en.wikipedia.org/wiki/Arecibo_Observatory) has been the most sensitive in the world. 300 meters wide, it is the world’s largest single-aperture telescope, whatever that means. Built in 1963, it continues on the cutting edge to this day.

China will soon top it. Construction of the [_Five hundred_ meter Aperture Spherical Telescope](Five hundred meter Aperture Spherical Telescope) commenced in [2011](http://www.iflscience.com/technology/assembly-worlds-largest-radio-telescope-has-begun). It will be three times as sensitive. Both Arecibo and AST are built in a valley; the difference is that the newer model will have an active surface. Unlike Arecibo it will not be restricted to just pointing upwards. Its cost is about $110 million US. It is scheduled for completion in September 2016.

Pic of the telescope under construction:  
[![](https://pbs.twimg.com/media/CLDvOyNUYAASvRJ.jpg) ](https://pbs.twimg.com/media/CLDvOyNUYAASvRJ.jpg)  
Kudos to the Chinese for sponsoring this scientific endeavor.

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**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\
**Post date:** [July 29, 2015, 10:11am UTC](https://boards.straightdope.com/t/china-builds-largest-and-most-sensitive-radio-telescope/726452/2 "2015-07-29T10:11:22Z")

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$110 mil is chump change for a radio telescope. Try [ALMA](https://en.wikipedia.org/wiki/Atacama_Large_Millimeter_Array) which costs $1.4 bil.

As for the single-aperture bit, it means the scope has a single bowl-shaped collector of radio waves. Most big radio telescopes, such as ALMA have multiple antennae. The signals from these antennae can be combined in a process called interferometry. It makes an image with the resolution of the two widest set telescopes in the array. There’s drawbacks to using interferometry as opposed to a single bowl of the same size (they’re technical in nature, so I’m not going to go into them now), but the advantages are such that virtually all new large radio scopes are such arrays.

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**Author:** ![The\_Stainless\_Steel\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/the_stainless_steel_rat/32/5727_2.png) [@The\_Stainless\_Steel\_Rat](https://boards.straightdope.com/u/The_Stainless_Steel_Rat)\
**Post date:** [July 29, 2015, 12:18pm UTC](https://boards.straightdope.com/t/china-builds-largest-and-most-sensitive-radio-telescope/726452/3 "2015-07-29T12:18:31Z")

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> [@dtilque](#):
>
> $110 mil is chump change for a radio telescope. Try [ALMA](https://en.wikipedia.org/wiki/Atacama_Large_Millimeter_Array) which costs $1.4 bil.

Building in the Atacama at over 16,000’ above sea level does drive the cost a wee bit.

> [@](#):
>
> As for the single-aperture bit, it means the scope has a single bowl-shaped collector of radio waves. Most big radio telescopes, such as ALMA have multiple antennae. The signals from these antennae can be combined in a process called interferometry. It makes an image with the resolution of the two widest set telescopes in the array. There’s drawbacks to using interferometry as opposed to a single bowl of the same size (they’re technical in nature, so I’m not going to go into them now), but the advantages are such that virtually all new large radio scopes are such arrays.

If you live in the USA, you can visit one of the earlier multi-antenna displays at the Very Large Array in New Mexico. Paved road all the way, with a walking tour and small museum. Been there, have the T-shirt. 🙂 [Very Large Array - Wikipedia](https://en.wikipedia.org/wiki/Very_Large_Array_Radio_Telescope)