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Mars rover camera project manager explains 2MP camera choice

dpreview.com

31–40 of 89 posts

Re: Mars rover camera project manager explains 2MP camera choice

#31

just curious, why they are releasing only black and white pictures

The sensor is black and white. This lets them collect the most accurate information about how much light hits each part of the sensor. To take a color image they put a color filter in front of the lens, then they can recolor the black and white image according to the color of the filter. If they take multiple pictures with different filters, they can reconstruct a color image. http://areo.info/mer/

Re: Mars rover camera project manager explains 2MP camera choice

#33
post #2

Now that I find out that the main reason for using a 2 MP camera is because that's what the specifications were in 2004, I'm a lot more disappointed than if it was just about the speed of transfer between Mars and Earth. 2 MP cameras were in high-end phones in 2004, but you'd expect NASA to use something a little more advanced than what was available in phones in 2004. How much more would it have cost them to use a 5…

Question: You've just won a trip to some interesting far off place (Australia, Italy, Peru, Alaska… whatever). Do you go out the day before you leave, and buy the latest $2,000 DSLR so you can get the best possible photos?

Practically anyone who is more than a point and shoot photographer, even a very amateur one will tell you that is complete insanity. There are too many things that could fail. You might not be comfortable with the camera in all lighting situations. It could have some defect in the lens that you won't have time to get replaced. You could find out the LCD preview is darker than what you're really shooting, and everything is over-exposed. The number of things that can go wrong just because it's an unknown quantity are huge.

On a trip like that, you take your trusty camera that you've shot thousands of photos with and know inside and out, even if that means that some of your photos won't be the absolute highest resolution money can buy.

Re: Mars rover camera project manager explains 2MP camera choice

#34
post #2

Now that I find out that the main reason for using a 2 MP camera is because that's what the specifications were in 2004, I'm a lot more disappointed than if it was just about the speed of transfer between Mars and Earth. 2 MP cameras were in high-end phones in 2004, but you'd expect NASA to use something a little more advanced than what was available in phones in 2004. How much more would it have cost them to use a 5…

For perspective, a single nut or bolt often costs hundreds to thousands of dollars by the time you are done with the Mil Spec qualification. You are off by a factor of at least 3, likely 4 or 5.

Of course, once you stop seeing this is as crazy, you are doomed to mediocre results.

Re: Mars rover camera project manager explains 2MP camera choice

#35
post #32

I really liked the article - it was very coherent and easy to follow. BTW, is there a full-res movie of the descent? I've only seen the 'thumbnails' stitched together of the heat-shield and the parachute.

Not yet. Only 20 or so of the full frames of the descent have been downloaded so far. Will probably be a day or more before they are all down.

You can see the frames that are down here: http://mars.jpl.nasa.gov/msl/multimedia/raw/?s=0

Re: Mars rover camera project manager explains 2MP camera choice

#36
post #24
post #2

Now that I find out that the main reason for using a 2 MP camera is because that's what the specifications were in 2004, I'm a lot more disappointed than if it was just about the speed of transfer between Mars and Earth. 2 MP cameras were in high-end phones in 2004, but you'd expect NASA to use something a little more advanced than what was available in phones in 2004. How much more would it have cost them to use a 5…

You didn't read the article, did you? The entire mission can return around 250 mbits of data per day to Earth, because it's on Fricking Mars! Going to a 4MP camera CCD was considered and rejected because it'd result in slower image capture during time-sensitive processes (such as the descent cam) and gobble down far more of that valuable bandwidth which is shared among all Curiosity's instruments. Going to a 4MP came…

I can understand their choice of a tested technology, but I don't understand the bandwidth argument. Is the processor so underpowered that it couldn't crop the image when needed?

Re: Mars rover camera project manager explains 2MP camera choice

#37
post #10
post #5

Earlier quoted context omitted.

What do you think extra megapixels would give you? Judging about quality of the camera by pixels count is silly.

In a mission to gather data then clearly extra megapixels give you extra data. You cannot argue against that! We aren't talking amateur photography here where the quality of the shot is important and a decent lens beats higher megapixels, we are talking acquiring measurements of the amount of photons in a discrete spatial region. Clearly a higher resolution of sensor might allow scientists to see something not visibl…

Actually, the opposite is true. Photon absorption/detection is a quantum event, and limited by probability. For a given sensor chip size (and technology generation), fewer, larger sensels are going to provide samples that are statistically closer to the Absolute Truth. (Averaging repeated samples will reduce the error further.)

Using a well-corrected lens of an appropriately longer focal length, and thus a narrower field of view, with or without panoramic stitching, will provide at least[1] the same linear resolution of a given subject, but with less sampling error.

[1] At least, since apochromatic correction is easier in longer focal length lenses provided that no super-wide-aperture bokeh heroics have gone into the design. Rectiliearity (the absence of barrel or pincushion distortion) is also easier to achieve. Flare can be reduced without inducing undue mechanical vignetting, increasing contrast.

Re: Mars rover camera project manager explains 2MP camera choice

#38
It would be neat if one day they send rovers in modules - one nuclear power supply to last dozens if not a hundred years, then a mini-robot sent to replace the modular camera with a 15MP one after they upgrade the bandwidth from 2mpbs to 10mbps and then one day 100mbps.

That 15-30 minute pingtime is a problem that cannot be overcome unless they find a faster than light wave that can be used for transmission - or a way to manipulate quantum entanglement for communications.

Re: Mars rover camera project manager explains 2MP camera choice

#39

2004 technology aside, this is called the "Good Enough Factor". Obviously every super geek at NASA wants an 20 MP camera with full zoom,100 year lifetime, 3d, blah blah blah. But, they are working in very exact specifications and budget. So, you have to opt for the option that satisfies the Good Enough Factor. What will get us closest to what we actually want, without totally breaking spec and screwing with the time…

Everyone is missing the point here. The problem isn't that these cameras are old tech and using outdated CCD censors. If these were the best images we've seen to date of Mars, you're right, there'd be a "Good Enough Factor" — the best images we've seen from a NASA mission, but not as good as modern DSLRs. Understandable.

The problem, that I think a lot of people are missing, is that Viking 1, from 1976, took higher quality pictures of Mars. http://f.cl.ly/items/0k2w2d1C1O3w3e0t300f/NASAQualityDegreda...

Re: Mars rover camera project manager explains 2MP camera choice

#40
post #36
post #24

Earlier quoted context omitted.

You didn't read the article, did you? The entire mission can return around 250 mbits of data per day to Earth, because it's on Fricking Mars! Going to a 4MP camera CCD was considered and rejected because it'd result in slower image capture during time-sensitive processes (such as the descent cam) and gobble down far more of that valuable bandwidth which is shared among all Curiosity's instruments. Going to a 4MP came…

I can understand their choice of a tested technology, but I don't understand the bandwidth argument. Is the processor so underpowered that it couldn't crop the image when needed?

(Sometimes I despair)

If you crop 2MP out of a 4MP image, you might as well have started out with a 2MP camera in the first place. Except that if your 4MP CCD is the same size as your 2MP CCD, the light gathering area per pixel is significantly less -- you capture fewer photons, hence less information about what you're pointing the camera at! Raw pixel count is not a good measure of the imaging accuracy of a digital camera. In the case of Curiosity, they may only be 2MP CCDs, but they're the best 2MP CCDs that money can buy, and they're being fed by the best optics NASA could source. It's a far cry from your phone camera ...

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