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Say you were developing a website, and once you get the first real life visitor, you can't SSH in any more; it's set in stone forever. Would you swap out a JSON parser on your backend just before you ship? They're functionally equivalent, and should be interchangeable, right? Your unit tests say it's fine, so what's the problem?

Any kind of change is adding risk to a project that costs billions of dollars.

The rover a one of a kind project, and any issues are set in stone before any kind of real world testing can be done.

If anything, the team should be praised for being conservative enough that they managed to pull it off with success.

You're right that dropping an extra 20 megapixel camera in there would be less risky than changing the main lens; but it's still an unspecced addition to the plan. I don't blame them for choosing not to.

In the future when launch costs are cheaper, people with a hacker approach are going to make rovers on their own. Lots of experimental designs, safety in numbers, and they'll do amazing things.

But when you've got one shot, your risk profile makes you conservative in the extreme.

> We can go on and on about familiarity considerations, and planning considerations, and instrumentation considerations, and scientific concerns, etc. It all sounds like excuses after a bit.

It sounds like excuses? By what standard? That NASA operations don't move at the same speed as consumer technology? By what qualifications do you even have the balls to make a flippant comment like this?

> Further, let's say you are really not sure about that spanking new 20MP sensor, because it is new, you are not familiar with it, and it was not part of the plan drafted 10 years ago, why not add 1 extra camera with a 20MP sensor?

You don't even sound remotely technical when you blurt out some nonsense like this. Ever heard of the phrase: "Fast, good, cheap: pick two"? Well when you're sending shit to other planets it ain't gonna be fast and it ain't gonna be cheap, so it better damn well be good. And not good the way an iphone is good where it dazzles you and your hipster friends to wait in line so they can sell a hundred million of them. Good as in, you build one of them, you get one shot at it, and if you fuck up some small detail hundreds of millions of dollars and years of people lives are utterly wasted.

> 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 can't "simply" swap the sensor. What about the processor behind it, that interpolates the sensor data and produces a viewable image? Then you need more power for both of those units, and if you're moving to a 20MP sensor, probably size too.

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?

sigh

I expected more from the people of HN than be stuck in some stupid megapixels race like they're comparing cameras at Best Buy

There, I said it

The first Canon Digital EOS Cameras had a 3Mp sensor. I can bet they wipe the floor with most of today's compact cameras

In a camera, the sensor is much less important than optics. In a 20Mb sensor, the noise in a high radiation environment would probably be much worse as well

  > Why not keep the same enclosure, the same lens assembly,
  > the same mechanical parts and simply swap the 2MP sensor for a 20MP sensor?

Because:

  > The other advantage of the Truesense Imaging chips was the team's familiarity
  > with their behavior. 'We've built-up decades of cumulative experience of working
  > with Kodak and now Truesense interline sensors. We know how to clock them and
  > drive them - they're a very easy CCD to drive,' says Ravine. A similar level of
  > confidence was needed for the cameras’ memory, he says: 'the flash we ended up
  > using was because we had a lot of radiation test data for it.'

http://www.dpreview.com/news/2012/08/08/Curiosity-interview-...

> 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.

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.

I think there's also the factor that there's no real advantage to the mission in a 20MP camera.