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Mars rover camera project manager explains 2MP camera choice

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

#21

Post by DanBC »

mtgx wrote: 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…

If your camera phone sensor fails you walk to a shop and get a new camera.

If the sensor on a Mars rover fails there are thousands and thousands of dollars of wasted opportunity.

Thus, they pick something reliable that they know, and test the hell out of it, and fix the spec.

This has pros and cons.

Pros include a well known set of kit with extensive testing and documentation.

Cons include being locked into a manufacturers product line. If that product goes obsolete you're stuck searching for stock of product in various resellers inventory. I guess NASA can just buy extra stock. But I've seen the result of odd devices being used on aerospace kit, and it becomes impossible to create a sensible quote. Subcontractor A puts a request in for obsolete part, and that goes to a bunch of vendors. Subcontractor B puts the same request in, and so you end up in a bidding war for parts that you might not buy. Given that yo're quoting on something that you'll be building in maybe three months there's no chance of providing an accurate quote.

tl:dr when designing a Mars rover use components that you know and buy lots of them. When designing an aircraft avoid anything that is listed near end of life, and try to pick something that's not going to go obsolete in 3 years, and try to find something that can have alternatives.

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

#22

Post by DanBC »

krschultz wrote: post #7
mtgx wrote: 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.

People tend not to understand the tracability requirements either.

Every single part - each nut, bolt, and washer, has a batch number and can be traced from the rover back through assembly, through stores, through goods in, through the suppliers, through to the manufacturers.

This paperwork alone adds significant;y to the cost.

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

#23

Post by nollidge »

danso wrote: post #12

I think the explanation is satisfactory, but how often, if at all, do other components of such projects change, up until lift off? I imagine engines and other propulsion parts won't be upgraded much after the original spec, even if such components even remotely followed the same curve of improvement as digital chips do. But what about other types of sensors used by the rover? What is the most recent piece of tech use…

Personally I'd be very wary of that. As I said on another comment, this is a planned two-year mission. So if they drop-in a compatible component and later found out there was a manufacturing problem that shortens its life, that's not acceptable. I think NASA's very failure-avoidant, and I really can't blame them, because their mistakes are extremely expensive and occasionally deadly.

The alternative they chose, it sounds like, was extreme caution, using well-tested components at the possible expense of image quality. It's Good Enough.

And like others have said, macroscopic images aren't the sole or even primary purpose of this mission. At this point, it's just whiz-bang PR, since Spirit and Opportunity got enough pictures to last a lifetime. The secret sauce here is the spectrum analyzers, close-up camera, rock-vaporizing laser, etc. THAT'S the important stuff, scientifically.

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

#24

Post by cstross »

mtgx wrote: 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 camera would be sensible if and only if they could have doubled their wireless bandwidth across a 300 million kilometre gap. Bandwidth is the killer bottleneck on interplanetary missions, not pixels.

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

#26

Post by jonhendry »

arrrg wrote: post #18
danso wrote: post #12

I think the explanation is satisfactory, but how often, if at all, do other components of such projects change, up until lift off? I imagine engines and other propulsion parts won't be upgraded much after the original spec, even if such components even remotely followed the same curve of improvement as digital chips do. But what about other types of sensors used by the rover? What is the most recent piece of tech use…

Last minute changes are made. Or at the very least I know of one such change in the case of Curiosity. The dust covers over the haz cams (the navigation cameras on the belly of Curiosity) were added in the last minute. Here is the engineer who implemented them writing about the covers: http://forum.nasaspaceflight.com/index.php?topic=29612.msg93... Basically, the Phoenix lander (landed on May 25th 2008) kicked up mor…

Yeesh, I don't even remember the Phoenix lander. Kinda crazy that there have been enough to start losing track of them.

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

#28

Post by Sharlin »

It should be noted, as well, that the Hazcams and Navcams are "build-to-print" exact copies of the ones that flew on the MERs in 2003. So most of the images we've been seeing thus far are actually taken with tech much older than the Mastcams, probably designed around the turn of the millennium. And there's nothing wrong with that -- they are very reliable and do exactly what is needed.

Source: http://www-robotics.jpl.nasa.gov/publications/Mark_Maimone/f...

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

#29

Post by roc »

treelovinhippie wrote: post #9

Why not change the system so that new technology is able to be fitted?

The limiting factor is the testing and integration, not the new technology.

if it takes X years to do sufficient radiation and integration testing on new technology, you can't possibly include any technology "newer" than X years old. And trying to keep yourself open to include the latest-technology-you-possibly-can means you need to have manpower ready to do that testing at the last possible moment, which has scheduling implications on everything else.

So you need to prioritize which technologies you most want to be able to integrate in their latest/greatest form. And slightly fancier pictures are just not going to be that high on the list.

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

#30

Post by freehunter »

senthilnayagam wrote: post #27

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

They have sent back at least one color photo, which has been released [1] as a test that the cameras are working. They're still getting everything operational (and I believe they have a software upgrade to do yet) before the major operations get underway. The black and white cameras don't need to be deployed and calibrated like the color/high-res cameras do.

[1] http://www.reuters.com/article/2012/08/08/us-usa-mars-idUSBR...

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