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Comment by wlievens | Hacker News Reader

> Let's reformulate the question: Why not keep the same enclosure, the same lens assembly, the same mechanical parts and simply swap the 2MP sensor for a 20MP sensor?

You do know that a 20MP sensor is significantly (~10 times) larger than a 2MP sensor, right? So the mechanics would probably simply not fit.

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Not necessarily, and this is important

If they are of the same size, the pixel size - area - will be 10 times smaller for 10x more pixels (or a dimension - length x width - reduction of ~3.1x)

Now, noise is bigger if the pixels are smaller. This is one of the ways to radiation harden components: make their features larger.

I'm sure a small sensor like those in a compact camera would be subject to a lot of noise. Bigger sensors like 3/4 or full-frame are usually better (but they're probably using something else)

So yeah, maybe a 20Mp sensor with the apropriate feature size would be huge

Obviously I was assuming same pixel size. Sorry if that wasn't clear. You're correct about the noise, of course. Pixel size is at least as important as the number of pixels. That's why a 4 megapixel cell phone sensor ($15) is vastly inferior in image quality to a 2 megapixel industrial sensor that's ten times larger in area ($200).

I have a 24 megapixel sensor lying on my desk. Its pixels are 6 micron wide, which is large (but not huge), and the thing is about 4 cm by 3 cm in size. I don't know much about cameras but I think that's about the biggest you can fit in a typical consumer camera body.

Huh, no, not at all. The last 10 years have been spent increasing photosite density. Today's sensors can have 10-20 times the resolution, and be the same physical size or smaller. Today's sensors are also more reliable, less sensitive to dust and noise than sensors made 10 years ago.

Sure it is, when we're talking about the same sensor and pixel design, which is implied when you say "simply swap the sensor". Otherwise it's a completely different camera setup.

Also, while obviously technology has improved, the industry doesn't necessarily move towards smaller pixels as a rule. To illustrate that: I work for a company that designs and produces image sensors, and I can tell you that we have one sensor product that has a resolution of just over one megapixel, but it's larger in area than our seventy megapixel product.

It all depends on the specifics of the project, and I can imagine that operating in space has certain constraints that prohibit just swapping in another sensor. These camera's are scientific instruments, and that means different rules apply.

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