SOL 242 - Dust Devil Watch
21 Images -- 1 Stance -- 1:00 PM
-- no DDs detected ---

SOL 249 Dust Devil Watch
360 degree quick peek (3 frames each in 5 stances) -- 11:00 AM local

Only showing stance 1 -- others are quiet
Stance 1 has a minor DD on the far left - GIF is wiggled back and forth...
Click to view attachment

SOL 250 Dust Devil Watch
360 degree quick peek (3 frames each in 5 stances) -- 11:50 AM local

Well-formed DD in Stance 4
Click to view attachment

SOL 252 Dust Devil Watch
360 degree quick peek (3 frames each in 5 stances) -- 11:30 AM local

Another DD in Stance 4
Click to view attachment

SOL 255 Dust Devil Watch
360 degree quick peek (3 frames each in 5 stances) -- 12:15 PM local

Only Stance 1 is shown -- a distant DD (or two) in the center
(the other Stances were very quiet) - a little wiggle back and forth too...
Click to view attachment

SOL 256 - Dust Devil Watch
21 Images -- 1 Stance -- 1:50 PM

A DD marches across in all 21 images -- then another walks in from the left
Click to view attachment

SOL 257 Dust Devil Watch
360 degree quick peek (3 frames each in 5 stances) -- 12:30 PM local

-- NO DDs

SOL 258 - Dust Devil Watch
21 Images -- 1 Stance -- 11:45 AM

A wide and whispy DD in all images (low dust load? not enough contrast?)
-- then another appears to the right of Kodiak
Click to view attachment

May be a change in the nature of the vortex. Remember that the atmosphere is changing with the approach of Summer. The dynamics of the cyclonic thermal updrafts is bound to change. Dust devils are a visible manifestation of thermals with dust entrained.

SOL 262 Dust Devil Watch
360 degree quick peek (3 frames each in 5 stances) -- 1:15 PM local

Stance 4 -- far off DD, center, climbing the crater rim
Click to view attachment

SOL 263 - Dust Devil Watch
21 Images -- 1 Stance -- 1:30 PM

DD -- right of center - Distant and moving
Click to view attachment

... a little catch-up...
Three posts coming... SOL 264, 265, 267

SOL 264 Dust Devil Watch
360 degree quick peek (3 frames each in 5 stances) -- 4:50 PM local ( very late in the day! )

Large DD in Stance 4 on the crater hill
Click to view attachment

SOL 265 - Dust Devil Watch
21 Images -- 1 Stance -- 12:55 PM

Dual DDs -- right of center - Distant and moving -- one fizzles
Click to view attachment

edit -- I meant my other "right" (LEFT! of center)

SOL 267- Dust Devil Watch
21 Images -- 1 Stance -- 11:25 AM

A nice DD on the march ( a comrade DD falters )
Click to view attachment

SOL 269 Dust Devil Watch
360 degree quick peek (3 frames each in 5 stances) -- 4:06 PM local
NO DDs -- all quiet -- late in the day --

SOL 271 Dust Devil Watch
360 degree quick peek (3 frames each in 5 stances) -- 1:10 PM local

Well-formed DD in Stance 4
Click to view attachment

SOL 274 Dust Devil Watch
21 Images -- 1 Stance -- 12:45 PM

DD Conveyor Belt -- one marches off to the right -- another in the center -- and one pops up on the left
Click to view attachment


SOL 275 -- 3 images in 5 stances (15 images) -- 3:55PM -- No DDs

SOL 278 Dust Devil Watch
21 Images -- 1 Stance -- 3:55 PM

Two DDs -- One is so easy to see -- can you see the other?
Click to view attachment

... a little catch up ...

SOL 279 Dust Devil Watch
21 Images -- 1 Stance -- 4:20 PM -- NO DDs


SOL 280 Nav Cam (part of a LR pair) 1:32 PM
GIF
Click to view attachment

SOL 280 Dust Devil Watch
360 degree quick peek (3 frames each in 5 stances) -- 2:38 PM local
DD in Stance 4 (center) and Stance 5 (right of Kodiac - faint)
Click to view attachment


Sol 281
21 images -- 1 stance - 3:05 PM -- NO DDs

SOL 283 - 15 images (3x5 quick peek) -- 3:15 PM -- NO DDs, but there were clouds over Kodiak.

SOL 284 - 45 images ! -- 1 Stance - JPL Broke my simple-minded Detector
12:06 PM to 12:27 PM (21 minute session)
** 15 images = 496 x 1296 pixels
** 30 images = 256 x 656 pixels
** Interleaved...
** (I'll see what I can do later...)

But there was another DD watch at 12:30 -- 15 images -- 3x5 quick peek
There is a DD in Stance 3
Click to view attachment

SOL 285 -- 21 images -- 1 Stance -- 11:42 AM
A DD seems to have come over the top of the Rover -- then we pick up the action.

4 DDs -- one on the crater wall --- the one that passed over the Rover -- a 'fire hose' DD off to the right
Near the end, a DD moves in from the left.
Click to view attachment

Great capture

We sure could do with one like that passing over InSight

Storyboard (corrected version) for the dust devils on sol 285.
Click to view attachment

Edit: The frames at second 17 and 21 were accidentally mixed up, which I didn't notice until I made an animation.
The storyboard is now corrected.

SOL 286 -- 21 images -- 1 Stance -- 12:05 PM -- No DDs

Tau - I love that storyboard!

Animated dust devils from sol 285.
The interaction of the dust devil with the dunes and ripples in the first frame is interesting (see also "storyboard").

Click to view attachment

WOW! stunning

SOL 287 -- DD Watch -- 15 Images -- 3 images in 5 Stances -- quick peek --- Noon
DDs in Stances 4 and 5:
Stance 4: minor DD in the center -- larger DD on right
Stance 5: pick up the progress of the larger DD from Stance 4
Click to view attachment

SOL 291 -- 21 images -- 1 Stance -- 1:10 PM
We have 3 things going on ... a DD coming in from the left -- a gust passing the Rover -- and Clouds!
Click to view attachment

NO DDs detected: SOL 292, 293, 294, 295, 296

SOL 297 -- 21 images -- 1 stance -- 1:00PM
A well-formed and slow-moving DD in all frames

NOTE: Slow-moving DDs play havoc with the standard technique of averaging or median-ing all the frames to arrive at a 'normal background image' to analyze each individual frame against -- it causes the dark 'shadow' near the DD. -- I am starting to investigate another technique.
Click to view attachment

SOL 298 -- 21 images -- 1 Stance -- 1:25 PM
A DD on the deltas
Click to view attachment

HAPPY SOL 300 -- 21 images -- 1 Stance -- 11:10 AM
only Frame #1 has a DD before it 'evaporates' (if that's the word)
It is centered and on the deltas (far)
Here is the single frame:
Click to view attachment

The median is the special case of a given percentile rank per pixel, where that percentile happens to be 50. You might have better results with a different percentile, say, 25.

SOL 300 DD Bonus
NAV Cam 11:45 AM
Click to view attachment

JRehling: That is a brilliant idea... I will give that a try

SOL 301 -- 15 images -- 5 stances -- 1:40 PM
DD in stance 5
Here is just that sequence
Click to view attachment

SOL 302 -- 21 images -- 1 Stance -- Noon
Distant DD, center, wait for it...
Click to view attachment

A "storyboard" an an animation of a dust devil on sol 308 during a Mastcam-Z multispectral photo series.
The Mastcam-Z filter number and the time in seconds after start of the series are annotated in the storyboard.
The difference-to-average method does not work here because of the spectral filters, therefore contrast enhancement was used.

Click to view attachment Click to view attachment

The dust devil on sol 308 continues into the infrared region of the spectrum with Mastcam-Z right eye filters 1 to 5.
The Mastcam-Z filter number and the time in seconds after start of the series in the previous post are annotated.
Contrast enhancement did not work here. Instead the difference-to-average method with manual adjustments to each image was used.
Overexposed and/or clipped highlights (link to the first raw image) in the bright landscape around the dust devil resulted in featureless patches of medium gray, which are masked here with red color.
A second dust devil appears in this series.
Starting with filter ZR5, the dust devils merge with the bright infrared background.

Click to view attachment

Mastcam-Z images, an orthorectified HiRISE image, and a HiRISE digital terrain model were used to determine the route of the sol 308 dust devil on the ground.
Twenty control points of corresponding features were set in the Mastcam Z image and the HiRISE image.
With some measurements and calculations, pixel coordinates in the Mastcam-Z image could be transformed into map coordinates of the HiRISE image.
The length of the visible part of the dust devil's route is about 820 m.
The average horizontal ground speed was about 30 km/h, and even 36 km/h on average between second 0 and 57.
To verify the calculations, it would be interesting to see if the dust devil left a visible track.

Click to view attachment Click to view attachment Click to view attachment

Edit: corrected typo km/s to km/h (thanks to Floyd)

Was the horizontal ground speed actually m/s not km/s?

8.2 m/s, 30 km/hr.

It was a typo. Of course, supersonic dust devils are not possible.

820 m / 100 s = 8.2 m/s = 29.52 km/h (rounded value 30 km/h)

I can't wait for the day when I don't make typos.

What is the diameter of the devil. Some years ago I identified an empirical law for the longevity of dust devils on Earth and Mars : Duration (s) = 40 * d^0.66 with d in m.

Apropos of this topic
Anyone interested in dust devils on Earth and Mars might enjoy my
Physics Today webinar to be held 2pm EST January 12, 2022 (I guess you
can view it online thereafter)
https://event.on24.com/wcc/r/3543264/A422D6...BBA18667191242C

I wondered about the possibility of transferring the DDs we see to a groundtrack on a map and seeing if a track was left.

--Bill

Here is a very rough estimate of the diameter of the dust devil using a scaled image.
The last three subimages where the dust devil begins to dissipate were not taken into account.
1 pixel corresponds to 0.76 m in nature.
Diameter of the brightes part where it touches the ground: 25 to 40 m
Diameter of the shadow: 60 to 70 m (local mean solar time was 11:09)
It was a nice coincidence that the dust devil entered the field of view exactly at the moment when the image series started.

Click to view attachment

Groundtracks on a map can be reconstructed only if we see in the photos the point where the dust devil touches the ground. In most cases this point is hidden behind local elevations.
For example, in this image a second dust devil emerges to the left from the existing one. However, its distance from the rover can be anywhere between 50 m behind the nearest ridge and 7000 m on the inner slope of the crater wall.

Control points are necessary to tie a photo taken by the rover to an orthorectified orbital photo.
Here are my 20 control points. Some small features are hidden by the crosses.
In this case, it was of great advantage that the dust devil passed a smooth slope with an incline towards the rover.

Click to view attachment

Sol 372 DD watch
21 images - 11:40 AM

Click to view attachment

(I have a backlog of DDs -- broke my wrist -- sold my house - moved to a new one -- crashed PC -- but all set now....)

Be well!!
Looking forward to the Backlog.

--Bill