<blockquote>
  <p>Shouldn't it be the other way around, that shorter wavelength telescopes like those in IR and the visible and UV generate more data because they have higher resolution per unit of aperture?</p>
</blockquote>

<p>This is a very interesting question! </p>

<p>My answer is no, not currently, but someday it may be the case.</p>

<p>Because we have big fast computer and fiber optic technology, we can generate images from arrays of antennas <em>computationally</em>. We can form images and even implement <a href="https://astronomy.stackexchange.com/q/13930/7982">adaptive optics for wavefront correction at radio frequencies</a> in software (rather than mechanical actuators correcting wavefronts by brute-force bending mirrors).</p>

<p>An order-of-magnitude description of ALMA is 100 dishes each one delivering 1 GHz of bandwidth, and SKA arrays will be far larger. While the Event Horizon Telescope <a href="https://astronomy.stackexchange.com/q/20082/7982">literally records all raw data on boxes of hard drives</a> that's not currently possible for ALMA and larger arrays, so only much smaller, heavily processed intermediate results files can be saved for later analysis and fine-tuning of calibrations and parameters.</p>

<p>For "shorter wavelength telescopes" in this context it's better to think of them as "higher frequency telescopes". Even a 100 nm wide band at say 800 nm (near IR where <a href="https://astronomy.stackexchange.com/q/14795/7982">wavefront correction is working well</a> represents 47,000 GHz! Even with conversion to a baseband frequency we don't have the ability to digitize signals at that rate, much less perform correlations of multiple signals.</p>

<p>So instead <em>we let the light do the interferometry for us!</em> </p>

<p><strong>An optical telescope is just a big, simple, one-trick-pony optical computer.</strong> We design the surfaces to perform an integral of the electric field at the aperture. The center pixel receives the integral of all electric fields incident on the telescopes clear aperture without any phase bias. A pixel at one edge of the sensor receives the integral of the same electric fields <em>times a phase function that increases linearly from one side to the other.</em> </p>

<p>One day if and/or when detection and computing speeds and parallelisms are big enough, I am sure an electronic optical computer will probably be built. </p>

<hr>

<p>For more on optical telescopes versus computational interferometry see answers to </p>

<ul>
<li><a href="https://astronomy.stackexchange.com/q/34566/7982">Would “layered” radio interferometry work?</a></li>
<li><a href="https://astronomy.stackexchange.com/q/14351/7982">Could mirrors be replaced with CCDs?</a></li>
<li><a href="https://astronomy.stackexchange.com/q/32014/7982">How would a Fast Fourier Transform Telescope work without a mirror, dish or lenses?</a></li>
</ul>

CC BY-SA 4.0
2020-02-22T17:12:45.597Z
Would quantum computing be helpful for the calculations required for interferometry?
LocalFluff
CC BY-SA 4.0
2020-02-22T23:26:06.437Z
@antispinwards that's a great point and if you could add a few numbers would make a great additional answer! To an astronomer [ten million alerts per night](https://astronomy.stackexchange.com/a/32784/7982) will certainly sound big!
uhoh
CC BY-SA 4.0
2020-02-22T23:27:16.323Z
@LocalFluff it doesn't look like quantum computing has ever been discussed in this site anywhere, which makes that an *excellent new question!*
uhoh
CC BY-SA 4.0
2023-03-03T15:47:23.337Z
Hello there – thanks for the links elsewhere. I asked [a related question](https://physics.stackexchange.com/questions/168432/what-prevents-digital-interferometry-in-an-optical-telescope-array) on Physics stack exchange, which might be a nice one to include in your links.
Benjohn
CC BY-SA 4.0
2023-03-03T16:54:19.180Z
@Benjohn very nice! See also [Has optical interferometry been done at radio frequency using heterodyning with a laser in a nonlinear material?](https://astronomy.stackexchange.com/q/36633/7982)
uhoh
CC BY-SA 4.0
2020-02-22T00:24:08.963Z
2020-02-22T00:24:08.963Z
uhoh
<p>Only with new radio telescope arrays like ALMA and SKA, have I heard of this "problem" with too much data come up. Too big to store. That one cannot archive it all for future studies, but that one has to select beforehand what fraction of the data to analyse and erase the rest, and the most, of it.</p>

<p>Shouldn't it be the other way around, that shorter wavelength telescopes like those in IR and the visible and UV generate more data because they have higher resolution per unit of aperture?</p>

<observational-astronomy><radio-telescope><raw-data>
Why do radio telescopes, but not shorter wavelengths, have this Big Data problem?
LocalFluff
# Why do radio telescopes, but not shorter wavelengths, have this Big Data problem?

(Asked by: username_0 on 2020-02-21)

Only with new radio telescope arrays like ALMA and SKA, have I heard of this "problem" with too much data come up. Too big to store. That one cannot archive it all for future studies, but that one has to select beforehand what fraction of the data to analyse and erase the rest, and the most, of it.

Shouldn't it be the other way around, that shorter wavelength telescopes like those in IR and the visible and UV generate more data because they have higher resolution per unit of aperture?

**Tags:** observational-astronomy, radio-telescope, raw-data

---

## 1 answers

### Answer by username_1 on 2020-02-22. Score: 3 | Accepted answer

> Shouldn't it be the other way around, that shorter wavelength telescopes like those in IR and the visible and UV generate more data because they have higher resolution per unit of aperture?

This is a very interesting question!

My answer is no, not currently, but someday it may be the case.

Because we have big fast computer and fiber optic technology, we can generate images from arrays of antennas *computationally*. We can form images and even implement [adaptive optics for wavefront correction at radio frequencies](https://astronomy.stackexchange.com/q/13930/7982) in software (rather than mechanical actuators correcting wavefronts by brute-force bending mirrors).

An order-of-magnitude description of ALMA is 100 dishes each one delivering 1 GHz of bandwidth, and SKA arrays will be far larger. While the Event Horizon Telescope [literally records all raw data on boxes of hard drives](https://astronomy.stackexchange.com/q/20082/7982) that's not currently possible for ALMA and larger arrays, so only much smaller, heavily processed intermediate results files can be saved for later analysis and fine-tuning of calibrations and parameters.

For "shorter wavelength telescopes" in this context it's better to think of them as "higher frequency telescopes". Even a 100 nm wide band at say 800 nm (near IR where [wavefront correction is working well](https://astronomy.stackexchange.com/q/14795/7982) represents 47,000 GHz! Even with conversion to a baseband frequency we don't have the ability to digitize signals at that rate, much less perform correlations of multiple signals.

So instead *we let the light do the interferometry for us!*

**An optical telescope is just a big, simple, one-trick-pony optical computer.** We design the surfaces to perform an integral of the electric field at the aperture. The center pixel receives the integral of all electric fields incident on the telescopes clear aperture without any phase bias. A pixel at one edge of the sensor receives the integral of the same electric fields *times a phase function that increases linearly from one side to the other.*

One day if and/or when detection and computing speeds and parallelisms are big enough, I am sure an electronic optical computer will probably be built.

---

For more on optical telescopes versus computational interferometry see answers to

* [Would “layered” radio interferometry work?](https://astronomy.stackexchange.com/q/34566/7982)
* [Could mirrors be replaced with CCDs?](https://astronomy.stackexchange.com/q/14351/7982)
* [How would a Fast Fourier Transform Telescope work without a mirror, dish or lenses?](https://astronomy.stackexchange.com/q/32014/7982)

> **Comments:**
> **username_0**: Would quantum computing be helpful for the calculations required for interferometry?  
> **username_1**: @antispinwards that's a great point and if you could add a few numbers would make a great additional answer! To an astronomer [ten million alerts per night](https://astronomy.stackexchange.com/a/32784/7982) will certainly sound big!  
> **username_1**: @LocalFluff it doesn't look like quantum computing has ever been discussed in this site anywhere, which makes that an *excellent new question!*  
> **username_2**: Hello there – thanks for the links elsewhere. I asked [a related question](https://physics.stackexchange.com/questions/168432/what-prevents-digital-interferometry-in-an-optical-telescope-array) on Physics stack exchange, which might be a nice one to include in your links.  
> **username_1**: @Benjohn very nice! See also [Has optical interferometry been done at radio frequency using heterodyning with a laser in a nonlinear material?](https://astronomy.stackexchange.com/q/36633/7982)  

---

