Cameras For Msl, MSSS gets all the contracts Options

[Bob Shaw]

On the identifying dust devils front, perhaps optical identification is a bit of a red herring. Rather than having the cameras staring constantly in the hope of picking up the subtle hints of one starting, why not link the imaging system (however smart it may be) to the meteorological instruments and simply start the intensive optical analyses when the pressure changes start. After all, Pathfinder recorded a fair number of such events purely through the instrumentation...

[deglr6328]

On the identifying dust devils front, perhaps optical identification is a bit of a red herring. Rather than having the cameras staring constantly in the hope of picking up the subtle hints of one starting, why not link the imaging system (however smart it may be) to the meteorological instruments and simply start the intensive optical analyses when the pressure changes start.  After all, Pathfinder recorded a fair number of such events purely through the instrumentation...

It might even be simpler than using meteorological instruments like anemometers etc and then waiting untill a devil is right on top of you. The swirling fine dust in a dust devil is thought to produce (through triboelectric processes) high electrostatic field gradients exceeding thousands of V/m. An electric field measurement device would be ideal. Very simple construction, no moving parts, temperature insensitive, small, very low power consumption, very fast response times and it would be potentially capable of detecting the dust devil from at least a few 10s of meters away giving ample time for imaging.

[tedstryk]

So did Viking, though unlike Pathfinder it never photographed one (not because they weren't there, but because with the Vikings' slow line scanning camera, a dust devil would be impossible to indentify.

[djellison]

Once you measure a pressure drop - the devil is 'on' you literally - and then you start taking picture in ...well..which direction I guess you could have pseudo code like...

if delta-pressure > X over Y seconds then....
point cameras in direction of wind from 1 minute ago ( i.e prevailing downwind )
take movies for 5 minutes

but - far better would simply be to point the camera in a direction - and then when it notices something different in the field of view, start taking pictures - then once the 'difference' in frames is in the middle of the f.o.v., start moving the camera in the direction of travel.

Doug

[Phil Stooke]

In the case of a rock or a 'ripple' etc., you can make a case that the closer you view it the more you can see. From Navcam to Pancam to MI we see more and more on these targets. But is this true for a dust devil? Up to a point, certainly - it's better to see it from 500 m than 5 km. Recently we have had these 'movies' in which a fair bit of structure is visible.

But I would suggest there's no advantage to getting much closer than that. A big diffuse object is seen better from a distance than close up. So I think a strategy of viewing across a wide area from a good vantage point - e.g. looking west from Larry's Lookout - is the best way to view dust devils. You may see a bit of structure in the nearer ones - though that doesn't teach you much... but you get good stats on occurrence, direction, height, optical depth and so on. Waiting until a rover experiences a wind/pressure signature and then taking images is the worst way to study them. (IMHO)

Phil

[dvandorn]

If I'm not mistaken, didn't Pathfinder actually detect a dust devil pass nearly over it? I remember reading a report of the event -- the wind direction changed through 360 degrees over less than a minute and the pressure shifted at all three spots along the mast where the meteorological pressure sensors were located, consistent with a dust devil passing.

IIRC, there were no visible changes in Pathfinder's area after its devil passed -- perhaps it passed overhead (i.e., a funnel that lifted off the ground and passed over Pathfinder itself)? So it's possible that instruments to detect a dust devil passing directly overhead might still not manage to let a probe capture images of it.

I think the only really effective way of capturing images of the little devils is a synoptic survey. But, hey -- any rover worth its salt can do that while performing other tasks, right? Like while doing a long Mossbauer or APXS integration?

-the other Doug

[Mark Rejhon]

Spirit just captured a spetacular series of dust devils:



That's 20 seconds between most frames. Wait till MSL with full color high-def at 0.1 seconds between frames!

[dilo]

OK, I'm a little bit disappointed why NASA didn't consider also some kind of "panospherc" camera, in order to take fast 360-deg panoramas and eventually detect transient events like dust devils... This kind of "super fish-eye" is easy to make putting a vertically mounted camera below a spherical or conical reflector:
http://www.frc.ri.cmu.edu/projects/vista/i...panomirror1.jpg
System is widely employed and was successfully used on "pseudo mars rover" traversing the Acatama desert: http://www.ri.cmu.edu/projects/project_153.html
One more sophisticated version could be done with a "column scanning" device made by a rotating wide angle lens joined to a linear sensor; if we put in the focal plan more than one sensor row, each with different coated filter, we could realize fast panoramic multi-spectral images of all around objects, easily identifyng geologically interesting targets!
For example, a system with 70 deg vertical field of view and a dozen of 4kpixel linear sensors could easly accomplish all MER Panoramic Camera functions in terms of spatial/spectral resolution!
Yes, there some small side effects (small compared to advantages):
1) Rover shouldn't move during aquisition of image.
2) In case of rotating system, this introduce a moving part, more prone to fail...
3) All people that partecipate to this Forum dooing MER images stitching (like me) should find something else to do!