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Q & A With Steve Squyres, Coming in September
centsworth_II
post Aug 17 2005, 05:37 PM
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Steve Squyres mentions in his book an early plan for the mars rover to be used as a sample collector for a later sample return mission. Spirit has seen such a variety of rocks and soil in the Colunbia Hills, I wonder which 3 or 4 sites would be highest on the list for sample return if Spirit was collecting samples.
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mhoward
post Aug 17 2005, 06:01 PM
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Do you think the amateur community has a role to play in promoting the Mars missions?
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Phillip
post Aug 21 2005, 01:09 AM
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I just realized that the deadline is August 21, so I will submit these questions prior to reading his book. These are the questions I would ask Steve over a pint:

1. What has he learned or seen from the MER that most surprised/shocked him?

2. What issue/question caused the most heated debate among the MER team and how was that issue resolved? (possible follow up: did the MER team have a similar debate as seen on this forum about whether Spirit should stop for "boring science stuff" while going up Husband Hill versus "put the metal to the petal" to see if more promising science targets were found on the other side?)

3. Which is his favorite rover and why?

4. What date does he predict humans will set foot on mars? What will be the vintage of the first wine made from grapes grown on Mars? smile.gif

5. Any chance for a rover expedition to Titan?

6. Has there been any scientific (as opposed to PR) benefit from posting the raw data from MER so quickly on the internet -- have observations/analysis from the amateur community had any impact on the science conducted by the MER? Stated alternatively, is there any benefit he would tell to ESA of disseminating information rapidly to the public, aside from the PR aspects. Alternatively again, is there a down side to doing so? If so, what?

7. Does he still hope to find lacustrine materials in Gusev crater? If so, where does he think is the most likely place to find it?

8. How do the original space-based observations of Hematite at Meridiani compare with what was actually found on the ground and what does that tell us about Meridiani?

I will leave it at that!
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edstrick
post Aug 21 2005, 06:37 AM
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I hate to be a bit complainy or something, but I keep wondering just why the Pancam near-infrared images are clearly not in good focus... as you step through filters to longer and longer wavelengths, the pictures get noticeably less and less sharp.
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CosmicRocker
post Aug 21 2005, 07:37 AM
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It's a wavelength thing. The longer wavelengths of IR result in lower resolution. If you want the finest details visible to human eyes, go for L7 or R1. That said, there are some things the human eye cannot see. To "see" them, use the IR filters. The pancams are amazing instuments. pancam.gif


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edstrick
post Aug 21 2005, 09:57 AM
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I'd have to check pre-mission camera technical design stuff, probably published in Space Science Reviews or some such place.. That's where they often published that stuff before. I'd be surprised if the cameras were diffraction limited at longer wavelengths.. They aren't super telephotos and have much larger apertures than human eyes.. or am I missing some info?
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helvick
post Aug 21 2005, 07:24 PM
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QUOTE (edstrick @ Aug 21 2005, 07:37 AM)
but I keep wondering just why the Pancam near-infrared images are clearly not in good focus...
*

This comment from the Bell document probably gives a hint:
QUOTE
The approach for such a panorama will be to acquire red filter images at full resolution in both eyes,along with green and blue filter images at reduced resolution (using compression and/or downsampling) in the left eye. Such a panorama provides morphologic and textural information at the highest possible resolution, ‘‘true color’’ information at somewhat lower resolution, and good stereo ranging of the full scene around the rover.

That's for full panoramas obviously but I think the same type of strategy is used for most imaging. The highest quality imaging is done with one filter, additional images are for geological science data\context\colorizing and don't need to have the same resolution so they are downsampled. I don't think it's wavelength dependant it's a planning decision that maximises the science data returned.
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djellison
post Aug 21 2005, 09:24 PM
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QUOTE (helvick @ Aug 21 2005, 07:24 PM)
he highest quality imaging is done with one filter, additional images are for geological science data\context\colorizing and don't need to have the same resolution so they are downsampled. I don't think it's wavelength dependant it's a planning decision that maximises the science data returned.
*


That was done way back for the mission success pans for both rovers - the L2's were full size, the L5's and L6's were half res. But that's when they were unsure about UHF performance and only doing 32kbps. Now that they do 128 or 256kbps they can forgo that data-saving tactic.

I think it's just that things are not quite as sharp in the near IR perhaps?

Doug
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CosmicRocker
post Aug 22 2005, 05:53 AM
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QUOTE (helvick @ Aug 21 2005, 01:24 PM)
...
I don't think it's wavelength dependant it's a planning decision that maximises the science data returned.
*

I do not claim to be an expert in the area of optics and imagery, but am pretty sure I learned that image resolution was inversely proportional to wavelength in physics. Angular resolution = wavelenth divided by the diameter of the objective lens. Since blue light has a shorter wavelength than infrared, it should result in images with higher resolution...and that is what we see from the pancam filters.

I did some quick research on the web to see if I could find some examples to support my argument. Here is one example of longer wavelength IR images with lower resolution than similar images taken in visible (shorter) wavelengths.

http://www.afrlhorizons.com/Briefs/Feb04/DE0303.html

They say, "The two images shown in Figure 2 are from the AMOS 3.67 m telescope using infrared light. They have lower resolution than the visible-light images because infrared wavelengths are much longer than the wavelength of visible light. Telescope resolution is directly related to the wavelength of light, the mirror diameter, the mount stability, and atmospheric turbulence effects."

I think those images of the Space Shuttle show the affect on an object we are all familiar with. Is that not the same difference we see between the L7s and the longer wavelength filters on the pancams?

This could make an interesting thread in the imagery and tech area... Some of the people who are really knowledgeable in this area might miss this discussion here.


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edstrick
post Aug 22 2005, 06:54 AM
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Cosmic Rocker quotes: They say, "The two images shown in Figure 2 are from the AMOS 3.67 m telescope using infrared light. They have lower resolution than the visible-light images because infrared wavelengths are much longer than the wavelength of visible light. Telescope resolution is directly related to the wavelength of light, the mirror diameter, the mount stability, and atmospheric turbulence effects."

BUT.... the AFRL images are THERMAL infrared with a wavelength probably near 10 micrometers, not Near-Infrared, with a wavelength of around one micrometer.. which is twice the wavelength (0.55 micrometer) of yellow-green light (the wavelength of visual maximum sensativity)

Resolution is diffraction limited only if the image on the sensor is diffraction limited AND the sensor samples the image with a pixel spacing finer than the diffraction limit. Often, Imaging is not diffraction limited, but has other engineering constraints. Many camcorders have tiny (cheap) CCD detectors. They can take decent images, but have fewer square micrometers of area per pixel, are less sensative, and most importantly, can hold fewer electrons.. and "fill up" faster and saturate sooner, resulting in either lower-signal-to-noise-ratio or overexposed images.

One possibility, I'm not a silicon chip optics expert at all.. is the silicon of the CCD may be so transparent at 1 micrometer that there's "bleeding" of the image between pixels due to sheer transparancy of the chip at near-IR wavelengths.
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akuo
post Aug 22 2005, 09:08 AM
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Oh, there was a deadline. Well I'll add these questions anyhow:

1. Since solar panel performance has been so much better when the rovers are parked at an angle (eg. Opportunity in Endurance), was powered tilting of the rover body with the rocker-bogey system ever considered as an addition to the mobility system?

2. Do you have nicknames for the rovers, like Oppy for Opportunity as used by the web forum community?


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um3k
post Aug 22 2005, 06:50 PM
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Don't forget that the pancams use lenses (as opposed to mirrors), and therefore have chromatic abberation. I always assumed that that was the cause of the fuzzy IR images.
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djellison
post Aug 22 2005, 06:53 PM
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Well - I'll be nice and let the questions run over a little - but 4 pages of them is plenty smile.gif

Today - my copy and the best-question-prize copy arrived from the US - and actually -it's a very 'nice' book - nice paper, binding etc. A scrawl from SS will look good on there smile.gif

The best question I've seen asked is regarding using different filters in L and R simultaniously to get pseudo colour of the dust devils - but there's some nice ones in here.

Doug
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hendric
post Aug 22 2005, 06:57 PM
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With the rovers still alive, how do you ever find time to write scientific papers? Do you see your colleagues taking the data you're providing and publishing while you're stuck "behind the wheel" so to speak?


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elakdawalla
post Aug 22 2005, 07:29 PM
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The discussion about image resolution jogged my memory about the discussions I had with Jim Bell way back in October 2003 when the MER teams were doing their first real rehearsals. He was helping us figure out the best set of images we could get of the Red Rover Goes to Mars DVD within the smallest bandwidth footprint. Originally the planned sequence included L256R2, approximate color plus stereo. (The stereo was in there because the "Astrobot" at the center of the disk was once a lovely machined 3D LEGO astronaut, but due to requirements from NASA HQ the poor Astrobots were flattened into stickers.)

Anyway, when we got the test set of images back the Astrobot had disappeared from both the L2 and R2 images huh.gif -- turns out the flight-qualified label material we used was transparent at 750 nanometers! mad.gif Fortunately, Jim was able to get some different filter choices substituted into the final sequence. smile.gif One of his suggestions is appropriate to this discussion: "I would like to replace R2 with L1 (empty), which gives the highest resolution image detail in Pancam images. We will use a lower amount of compression for this filter to maximize image detail. The compression level will be set so that the total data volume for the new version of this sequence does not exceed the data volume of the existing version."

In other words, as helvick pointed out, it's likely that in each image sequence from the rovers, one or two -- most commonly L2 and R2, and occasionally the L456 if they are planning on making a particularly lovely press product -- are sent with lower compression. The rest, which are taken only for color information, are sent with higher compression rates -- not necessarily subsampled (though that would be another way to do it), just compressed more. When they were writing the sequences in ops during the mission they usually talked about compression rates of 8:1 vs 20:1, stuff like that, though I'm not sure if I'm remembering the exact choices of ratios correctly. This is particularly true for full 14-filter sequences that go all the way out into the infrared. A full multispectral stack of images contains in it a LOT of redundant information -- areas in light and shadow are lighter and shadowed in every image in the stack. They reduce the redundancy by compressing many of the images that are there just for spectral info at a higher rate. (Writing that down, I wonder why they don't consider ratioing the R3-7 bands with the R2 band before sending the data to Earth -- that would cut down on the redundancy. Hmm.)

--Emily


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