It might involve some sort of surface roughness / opposition surge effect?
My guess that the "Nazca Images" are related to the black rotors and the solar panel, causing differential cooling/heat loss, or a different radiation spectrum (more IR, less UV) in the shadows.

Example for cooling, have you ever noticed that on a chilly night if you park your car within about 6 feet of a building, the side facing the building does not frost over while the side facing away will have frost? Same way that on a clear night you can get frost on a roof even though the average air temperature never officially gets below freezing.
Example for differential spectrum, ‘Margarita photodermatitis’ when cyclin carbon compounds in lime juice are activated by UVA light.

Call it a dew, or some photochemical process ultimately induced by the Sun, all these phenomena need some surface exposed to its rays.

Meanwhile, the martian surface is covered with microparticles: sand, dust… I would not be surprised if these 'photoprints' were left after some crane gently lifted Ingenuity from her helidrome. However, we know how passionately she cleans her 'bedroom' twice, upon arrival and upon departure. Clouds of dust are blown away with her rotors, so what is the surface that preserved all the traces on the ground?

…a good reason for Perseverance to include this location into its sampling list. Especially if these marks shall not disappear in 2-3 weeks.

I apologise for my minor amendment, but the NASA catalog timestamps these RTE images as the first ones from the flight on sol 163:

1. 12:34:20 (catalog page)
   
2. 12:34:31 (catalog page)
   
3. …etc.

The point is that we have been accustomed to figure out the heading of helicopter from the position of its shade on the photo. And flight 11 was unique because for the first time Ingenuity almost all the route was flying in reverse. As a keen reader of all the news about Ingenuity (I support the Wikipedia article, compile and upload there the animations of flights from the sets of NAV images), I am surprised that nobody from JPL wrote a single line about another technical triumph - outside the program of the tech demo.

Technically, coaxial rotors plus the state-of-art concept of image navigation allow Ingenuity to fly at any angle between the fuselage and the heading. The limitations of the tech demo phase did not allow to show all the aerobatic mastery. But from flight 6…

• Flight 6 was the first when helicopter was programmed to perform the sideways translation - that was on the second, short leg when the photo of Seitah was taken.
• Flight 10 was the second successful demonstration of the helpfulness of the sideways navigation for photographing objects extending parallel to the direction of flight like Raised Ridges.
• Flight 11, as I said was the first tech demo of the reverse navigation

Thus, the 'tech demo' stage ended only formally. I wish the Ingenuity team new technical achievements - "Fly high", as they use to repeat!

With the helicopter cyclic pitch, translations forward, backward and anywhere inbetween are possible. And with solid state gyros it is possible to maintain a heading lock with some precision. It is astounding what can be done with essentially off-the-shelf gear.
My own Ginny working model is progressing. I have an RC coaxial copter with an 18" rotor diam that I'm putting thru it's paces. Soon I'll be putting a 5" Borg cube underneath and adding telemetry and video transmission to it.
Why? Because I can.

--Bill

Instead of "fork and coco powder" it could basically be a "Xerox effect" where sunlight changes the static charge of the surface, at liftoff the dust gains a static charge and acts like toner in a photocopier, and is differentially attracted / repelled based on static charge.

We've known that Martian dust can create charges for many decades: "Physicist Joseph Kolecki and colleagues at NASA Glenn first noticed this problem in the late 1990s before Mars Pathfinder was launched. "When we ran a prototype wheel of the Sojourner rover over simulated Martian dust in a simulated Martian atmosphere, we found it charged up to hundreds of volts," he recalls."
https://science.nasa.gov/science-news/scien...0aug_crackling/

Why this effect was not noticed in the previous flights?

On NAV frames for flight 10 (July 24), available just after takeoff on 12:04:01 LMST, no Xerox effect is seen:



Same for flight 9 (July 5), etc...

The new status report as of today, August 15 is available at the JPL blog. The chief pilot of Ingenuity Teddy Tzanetos announces the next 12th flight fot tomorrow, August 16 (sol 174) at 5:57 a.m. PDT, or 13:23 LMST (local Mars time). Map is attached.

Well, we'll never know unless it is investigated and sampled, a few guesses:
- local topographic low where cold air collects and experiences frost that alters reactivity
- sediment is size-sorted by transport (e.g. cobbles, gravel, grit, sand, silt, clay) and this patch has just the right grain size or mix of grain sizes.
- mix of minerals alters oxidation states at this site to better hold a charge (e.g. Chrome 3 vs Chrome 6
- happened to travel through a vein of material (e.g. stumbled across a former "black smoker" vent or fissure)
- differential sorting of dust by density enriched an area in material that changes static charge / magnetic properties in response to friction or photosensitivity
So, oversimplified example, imagine the copter lands near a mineral vein with a mixture of galena & chlorargyrite. The rotor downwash creates a static charge (per Nasa citation above, up to hundreds of volts) which triggers some electro chemistry and thanks to oxidation-reduction it converts some chlorargyrite dust to a silver chloride. The chopper lands and casts a shadow.
Well, you now have a 'Kodak moment'...

Thanks Cherubino for having pointing this out, I corrected my post

Thank you, Schirmer, for the vast explication of your hypothesis. I think that each planetary geologist must ask himself: if it happened here (and not there), and the material carrier of the phenomenon, in any case, is the soil, which has preserved traces (whatever affected them), then it is necessary to begin with a study of the current physicochemical state of the substance that captured the picture.

For the sake of completeness: in addition to trivial solar radiation, there could also be radiation of a different kind, in other parts of the spectrum. Looking into the distant future of other martian missions, today's scientists should not miss the opportunity to find out the causes of the recent phenomenon. What happened once can be repeated twice, and one cannot be sure that these rays will not turn out to be destructive.

Therefore, my hint that Perseverance is now nearby, and its list of interesting points for sampling is probably not closed, was not unfounded. Especially considering the fact that besides Sample Handling Assembly there is also the most powerful RIMFAX on board, allowing to look 10 meters deep into the soil before you start drilling it.

Bill, your profound theoretical and practical experience can only be envied. For my part, being not a technician, but a humanitarian, sometimes I am not ashamed to ask some stupid questions, and here's one of this kind.

How do you estimate the real carrying capacity of Ingenuity by its known indirect parameters? I mean its performance, like rate of climb and its actual ceiling, maybe horizontal velocity etc.?

++plus: what is its actual ceiling? Before it started to fly, many sources spoke about something like 60 m, while by now the maximal flight height was only 12 m.

It seems obvious that a machine of this design should has some reserve of additional load, with which it could take off and navigate. Something more than the sand on the solar panel and on the legs. But exactly how many grams can it be?

Well, I didn't go through P-Chem doing gibbs free energy integration for nothing. Odd that the graduate lab rotation sampling divalent cation ion chelation spectrofluorescence and correlating it to electronegativity might actually be useful when considering weird dust on another planet!
Sometimes, it's that 'thinking outside the box' approach that leads to finding symmetry and simplification.

Ingenuity doesn't go above 12 m because that is the limit of its altitude sensor (which is required for proper functioning of the flight software), not because it couldn't lift the "load" substantially higher. Look up-thread for for further information as there has been extensive discussion.

I am unfamiliar with details of Ginny's parameters except to say that it is rotary wing aircraft operating in an atmosphere of Martian presssure, temperature and composition. And it has been worked out on paper and in a Martian atmospheric and by observing the telemetry of her Martian operations. Ginny could climb to a respectable altitude or attain a respectable horizontal velocity until the batteries discharged and the aircraft became what is called a "lawn dart" and crashed.
The constraint in Ginny's flight time is not much battery capacity as it is that the thin Martian atmosphere cannot remove heat efficiently from the motors windings and the flight time is limited by the motors' temperatures. Ironically the flight times of my initial coaxial helicopter mockup is limited by the motors overheating. In my situation I can use a small electric muffin fan to force our dense atmosphere into the motors and cool the motor armatures.

--Bill

Sol 174 NavCam images appear to show the helicopter landed safely after it's 12th flight
EDIT: It may have landed on a small Dune (ripple) and could be tilted slightly...
Click to view attachment

Here is Ingenuity's location after Flight 12.

Looks like it may have landed on that ripple.

Dear Floyd, I am afraid you've forgotten the discussion on page 23. There were no figures in this range. The only post which may be treated as the support of your figure "12 m limit of the altitude sensor" seems to be the following private opinion

without any links to the relevant statements of those "engineers of the team". This was a serious deviation from the known figures, so Mr. djellison found it necessary to visit this discussion personally to proclaim true figures and to support them with the proof link:



To sum up: the true figure for Garmin Lidar-Lite-V3 "altimeter" (laser rangefinder, LRF, as chief pilot Grip prefers to name it in his papers) is 3.3 times more than you supposed - 40 (forty) meters.

These parameters correlate to a certain extent. The density of atmosphere usually decreases while helicopter climbs higher, and each 10 meters added to the hovering height are equivalent to additional mass of load picked from the ground.

Another useful figure I know from the papers of H.Grip: during the initial takeoff a constant thrust setting is applied, corresponding to a level approximately 20% above the vehicle weight.

Test flight with a single task to identify the flight ceiling and meteorological conditions at successive flight levels is not a whim and not an empty venture. This data is vitally necessary to continue aeronautics on Mars. Whatever the design of the next generation vehicles shall be, hexa- or other multicopters, one must know the state of the atmosphere in its different layers. For the sake of higher scientific purposes, at least once, a helicopter must play the role of an ordinary meteorological balloon.



The envelope for such a 'meteoballon' flight seems similar to flights 1-2: no headache with finding a new landing site and prefetching terrain samples enroute to it. But it does not mean an 'idle journey' for the navigation system and especially for the NAV images processing. At 12m the shadow of the solar panel (10-12 px on 640×480 frame) is already too small to make a judgment upon the actual flight height.



Thus the new set of the surface elements of larger size must be ready to serve as a new starting point for these calculations.

During 60 seconds of that climbing by steps of 5 m the wind of 3 m/s may drift helicopter at 180 m away from the take-off point. Thus each ascending iteration should end with an obligatory (2 sec?) short-time hover for the backward horizontal translation. Series of figures showing the progressively diminishing utility of the same thrust at each next climbing step shall be used to define the criterion for exiting the "ascension loop" and proceeding to the standard landing procedures.

Total flight time (60 sec ascending, 30 sec descending) for this envelope is enough to avoid discharging the batteries

The most-quoted everywhere 'Bible of Balaram' ("Mars Helicopter Technology Demonstrator", 2018, p. 15) assures that



Another point: if it is the sand, did the legs stuck in it, and how deep.

First, great nickname "Ginny".
Second, is there any modeling of how the Martian atmosphere 1/20th Earth pressure but 150% density, scales with height?
Curious because it just occurred to me that Earth's atmosphere is dominated by nonpolar diatomic N2 and O2 and some Argon, while Mars has CO2, N2 Ar, but CO2 heavier, and is over-all nonpolar BUT which does have a partially positive center and partially negative ends.

So, Mars has a denser fluid -CO2- which has asymmetric charge, but is under less gravity.

Hmm, what minerals are soluble in CO2 over billions of years?

We might expect to see carbonates under the shifting sands and effusive basalts of the former North Polar Ocean. As to the provenance of that carbonate, I ain't saying!!

--Bill

I shall not argue the figures (exact data is widely available), but the answer is generally 'yes'. I know that the conceptual rotor (four-bladed, ∅ 8 ft, ultra-lightweight) originally designed by Larry Young and built by Micro Craft was tested in the N-242 environmental test chamber at Ames a decade before Bob Balaram got acquainted with this idea at some conference.

I also know that JPL has a simplier 10 ft vacuum chamber, maybe the one we all saw on their YouTube channel. However I've no idea how far simplification / extrapolation in both environment models go.


Furthermore both gas mixes differ by their thermal conductivity and this issue is focused back to the problem of rotor overheating recently raised here by Bill Harris. I shall continue in a reply to his post.

Absolutely!
I clearly remember that before the end of the media briefing (April, 30) Balaram named the rotor overheating rate: 1 degree per second. However less than a month after, on May 23, flight #6 lasted 140 sec, and from July the Ingenuity team surpassed the "90 sec limit" by more than 1.8 times, keeping the new flight time standard up to the recent flight (169.5 s).

What was the real temperature of rotor after these flights? Nobody khows it exactly because the cheap high-temperature sensor mounted in the place of contact between the radiator and the mast was not provided by the design. The rate of 1 deg/sec is an estimate, extrapolated on the Earth. Materials upon tests in Ames and JPL contain no words upon observations of rotor temperature. Such chambers, as I imagine, may be easily filled with the rarefied martian gas mix, but whether they set it to -30 / -50 deg temperature is unknown.

Overheat is a common problem from the times of the first engines. If fan on a heatsink in my computer breaks, processor shall melt sooner than Ingenuity's rotor being not stopped at a proper time.

The first glance at the CAD illustration of Ingenuity's rotor, published in many JPL papers from 2018 (see attachment) could have raised in a head of tecnician a question concerning the 'ribs' of rotor's heatsink. Why are they perpendicular to the air flow when every heat spreader designer places them parrallel (see attachment). That imaginary technitian could have asked much more question until having seen the actual construction. Rotors of Ingenuity seem to have no heatsinks at all! Therefore, it's no wonder that Ingenuity's rotor heats up at a rate of 1 degree per second?

Not quite true. Indeed there are not features for heat rejection to the environment, in that the atmospheric density is so low as to provide little convective cooling. But Pipenberg's VFS paper on the rotor/motor design does note that the motor housing is made of AlBeMet (a Beryllium material with high heat capacity) to function as a heat sink, soaking up as much heat as possible.

The motors used in Ginny are Direct Current Brushless type of the outrunner variety. The stator (windings) are in the nonrotating part fixed to the frame. The outer magnet bell contains the N-S-N-S... magnet array and rotates on a shaft carrying the propeller (rotor). Whereas a DC motor has carbon brushes on a copper commutator, the brushless motor is electronically commutated. The fixed windings are heatsunk to the frame and conducts waste heat away. This motor type has been popular on RC hobbyist aircraft for a decade.

The cyan-colored assembly on the left drawing is a flexible dust boot. The brushless outrunner motor is the black assembly at the bottom.
And as rlorenz points out, atmospheric cooling is minimal.

--Bill

Sol 174 Ingenuity helicopter high-resolution color camera photo (processed)

Click to view attachment

Wow, those will make some amazing DEMs when composited.
Welcome to "The Matrix" 'bullet time' aerial imagery!

Another processed color photo from Ingenuity's 12th flight

Click to view attachment

Yet another aerial color photo (processed)

Click to view attachment

Rover top right near edge?

This Ginny image has to be Epic.
From the Heiligeschein to the Glint of Percy.

--Bill

Here are the 8 pictures taken by RTE camera, corrected from distorsion, vignetting and colorimetry.
I ordered them by stereo pairs but they were not taken in this order since Ingenuity made a round trip to obtain these pairs.













On the second picture taken during Flight 12, we can see one more time Perseverance rover

wow - really nice images - thanks to all!

Is there a flight path for flight 12 ?

From the planning, we know it is a return trip to the NNE, about 235m one way. We also know the landing location.

Here is a quick gif of the navigation frames which gives a sense of when the target was reached. I think the navigation images start about 20s after take-off since the log book puts the total flight time at 169s.

Click to view attachment

And here is a rough first path of flight 12 based on major geographic features like the Seitah bordering ridge, large dunes and dune orientations. The nav. series suggests a much less straight progress than sketched here, and I could not quite find the point of return.

Click to view attachment

Somehow I overlooked Phil's adopted flight path: http://www.unmannedspaceflight.com/index.p...st&p=254209

Well, at least it is similar, and I agree that the end point is likely not quite right (not sure if mine is much closer).

After looking at many rocks and such, this is probably Ingenuity ??
(...your mileage may vary...)
Click to view attachment

This view of all 12 Ingenuity landing sites uses navigation frames, mostly just before touchdown. The exception is for flight 4 where the most useful image was taken just after liftoff on the next flight. Scales vary but the sizes of the helicopter image and shadow are indicative. North approximately at the top for each image.

The shadow is from the image used as a base. The drawing locates my predicted landing site at the end of the flight.

Phil

Click to view attachment

They have just updated the interactive mission map to show the details of flight #12.

There is a difference between the flight path and the end of flight waypoint marker (see screen capture)
Click to view attachment

I think that shows the planned path rather than the actual path.

Phil

That makes sense, thanks Phil

Just saw an announcement on Facebook that flight 13 was completed but don't see a full press release yet.

5 landing Images are now on the server
Click to view attachment

The capabilities of Ingenuity's flight and navigation software are quite impressive. I missed this post in this thread last month:
http://www.unmannedspaceflight.com/index.p...st&p=254053

--Bill

Enhanced color photo from Ingenuity's 13th flight on sol 193 with nicely layered outcrops at the edge and in Séítah south

Click to view attachment

Sol 193, another helicopter color photo (enhanced) with layered outcrops

Click to view attachment

I tried my best doing an orthomosaic with the color images of the flight #13 and projecting it over the HiRISE imagery. The improvement of resolution over orbital images is quite impressive.

Click to view attachment

Quite impressive!

--Bill

Slightly more than quite impressive, I would say. I hope we'll see more of your images.

Phil