The Planetary Society Blog
By Emily Lakdawalla
Mars orbiting cameras are getting better and better
Aug. 12, 2005 | 11:42 PDT | 18:42 UTC
The Applied Physics Laboratory team responsible for the CRISM instrument aboard Mars Reconnaissance Orbiter has issued a press release extolling the virtues of their instrument. It really is pretty incredible, actually. I have been trying to visualize and compare the capabilities of CRISM to all the other Mars orbiting cameras. The image below is my attempt at making sense of the different instrument qualities. Each square on the image represents the size of one pixel, or picture element, in each image. (It has nothing to do with the size of the entire image -- each camera captures images that measure different numbers of pixels across.) If a camera has more than one "channel," or filter, or wavelength in which it takes pictures, you see a stack of squares, one for each channel. Smaller squares, and taller stacks, are considered better than bigger squares and shorter stacks.
Comparison of the pixel scales of Mars orbitersEach square on the image represents the size of one pixel, or picture element, in each image. (This is not the same as the size of the entire image; each camera captures images that measure different numbers of pixels across.) The depth of the stack of squares represents the number of filters or channels in which the camera is capable of cpaturing images, a measure of its color-sensing ability. (By comparison, the human eye has three such channels.) Smaller squares, and taller stacks, are considered better than bigger squares and shorter stacks. Click for a PDF version » Credit: Emily Lakdawalla |
The biggest purple square, at bottom left, represents Viking, which achieved global coverage at relatively lower resolution. MGS MOC and Odyssey are represented above that; they haven't gotten global coverage, but their resolution is much higher, so their squares are smaller. MRO and Mars Express are represented to the right. CRISM is the incredibly enormously tall stack. Its spatial resolution is better than Viking overall, with selected areas better than Odyssey, but its spectral resolution -- the number of channels -- is totally, completely, without precedent for an imaging instrument sent to Mars. And as for MRO's other instrument, the HiRISE camera: the size of the HiRISE pixels were almost too small to draw on this sheet. MRO's going to be one heck of a data set!
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