In a world where we can throw gigabytes of information around in seconds, we get a bit blasé about the technical achievement it takes to get that done. Case in point: The Mars Curiosity Rover fields 17, count em, 17 cameras. For the most part these cameras store their data in "raw" or unprocessed format (I am not going to get into raw and jpeg and what is best, let's just take it on faith for the moment that raw is big, jpeg....not so much)what NASA/JPL has to deal with however is the size of Curiosity's data stream which is huge by comparison is an amazingly small 30meg per Sol. No, you are reading that right. Curiosity can stream 30 megabytes of data a DAY. (Hell, one frame off my ancient dslr in raw is bigger than that!) So you can imagine that the rover's controllers are not snapping away like a bunch of Japanese tourists on the GW bridge. Nor are they downloading everything that the rover takes either. Why? Because that 30meg a Martian day also has to carry all the other scientific data that Curiosity generates as well.
Well you must be saying, how do they know what to download or upload....depending on you point of reference (confused yet? lol) Well Curiosity does the same trick your camera does. When you look at the pictures in your camera, you are actually looking at the "thumbnail" (a low resolution representation)of each photo. The rover just sends thumbnails from which decisions are made as to what gets sent from the rover. Another trick they use is one I have harped on for years (people that have taken my photography courses have heard this one before) Megapixels are a myth, you don't need them. Yes, I have heard the arguments, more megapixels clearer better pictures. True in part, but unless you are printing wall sized pictures, you many never see the difference between 6 and 16 megs. Most people never print a picture so anything over 1 megapixel is a waste and to prove that point Curiosity's cameras for the most part are on 2 megapixels! Oh I know...sensor size and all that, but still it is vastly smaller picture which takes up little space on the rover's memory cards. But most importantly is the kind of hoops NASA/JPL controllers have to jump through each day just to get data back and forth!
You really should read this article here about the cameras and what they do. It is fascinating material. Go here for more on the Economist
Well you must be saying, how do they know what to download or upload....depending on you point of reference (confused yet? lol) Well Curiosity does the same trick your camera does. When you look at the pictures in your camera, you are actually looking at the "thumbnail" (a low resolution representation)of each photo. The rover just sends thumbnails from which decisions are made as to what gets sent from the rover. Another trick they use is one I have harped on for years (people that have taken my photography courses have heard this one before) Megapixels are a myth, you don't need them. Yes, I have heard the arguments, more megapixels clearer better pictures. True in part, but unless you are printing wall sized pictures, you many never see the difference between 6 and 16 megs. Most people never print a picture so anything over 1 megapixel is a waste and to prove that point Curiosity's cameras for the most part are on 2 megapixels! Oh I know...sensor size and all that, but still it is vastly smaller picture which takes up little space on the rover's memory cards. But most importantly is the kind of hoops NASA/JPL controllers have to jump through each day just to get data back and forth!
You really should read this article here about the cameras and what they do. It is fascinating material. Go here for more on the Economist