APOD: Perseverance from Ingenuity (2021 May 01)

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APOD: Perseverance from Ingenuity (2021 May 01)

Post by APOD Robot » Sat May 01, 2021 4:05 am

Image Perseverance from Ingenuity

Explanation: Flying at an altitude of 5 meters (just over 16 feet), on April 25 the Ingenuity helicopter snapped this sharp image. On its second flight above the surface of Mars, its color camera was looking back toward Ingenuity's current base at Wright Brothers Field and Octavia E. Butler Landing marked by the tracks of the Perseverance rover at the top of the frame. Perseverance itself looks on from the upper left corner about 85 meters away. Tips of Ingenuity's landing legs just peek over the left and right edges of the camera's field of view. Its record setting fourth flight completed on April 30, Ingenuity collected images of a potential new landing zone before returning to Wright Brothers Field. Ingenuity's fifth flight would be one-way though as the Mars aircraft moves on to the new airfield, anticipating a new phase of operational demonstration flights.

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Re: APOD: Perseverance from Ingenuity (2021 May 01)

Post by alter-ego » Sat May 01, 2021 4:36 am

Great news!
Program ahead of schedule, and additional flight demos being added.
NASA’s Ingenuity Mars Helicopter to Begin New Demonstration Phase wrote: ...
This new phase will begin after the helicopter completes its next two flights. The decision to add an operations demonstration is a result of the Perseverance rover being ahead of schedule with the thorough checkout of all vehicle systems since its Feb 18 landing, and its science team choosing a nearby patch of crater bed for its first detailed explorations. With the Mars Helicopter’s energy, telecommunications, and in-flight navigation systems performing beyond expectation, an opportunity arose to allow the helicopter to continue exploring its capabilities with an operations demonstration, without significantly impacting rover scheduling.
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Re: APOD: Perseverance from Ingenuity (2021 May 01)

Post by Astronymus » Sat May 01, 2021 8:02 am

This will spark new possibilities in planetary exploration. Fascinating. One can imagine a whole swarm of probes scoutings and analyzing large areas. Or highly mobile probes not dependent on wheels.
I wonder if blimp-like probes for denser atmospheres are still in development.
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Re: APOD: Perseverance from Ingenuity (2021 May 01)

Post by neufer » Sat May 01, 2021 10:59 am

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Re: APOD: Perseverance from Ingenuity (2021 May 01)

Post by orin stepanek » Sat May 01, 2021 12:36 pm

PIA24625fromIngenuity1024.jpg
I love all the news I can get on Perseverance and Ingenuity! Hopefully
soon there will be some actual exploration photos they send back of
mars! :D
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Re: APOD: Perseverance from Ingenuity (2021 May 01)

Post by johnnydeep » Sat May 01, 2021 4:23 pm

Glad to see Ingenuity being given more stuff to do, especially now that it's graduating to "operational" goals instead of just "technology demnstration" goals.

And this gives me an excuse to ask again about photos of shadows of the rotors taken from Ingenuity. Here's a video that shows several still shots taken in quick succession, starting at 0:45 with the rotors apparently unblurred but rotating a few degrees during all the shots.

Click to play embedded YouTube video.

Is the reason the images show no blur solely because the shutter speed is great enough to "stop the motion", or is it because of some weird 2D attributes of shadows that almost makes some sense, but is not totally convincing to me? I'm talking specifically about the explanation I got from a reply to my question on the video about why the rotors look stationary. The guy seems like he knows what he's talking about, but if so, I'm having a hard time understanding the explanation. [ Another reply said the frame rate of the video - does Ingenuity even have video capability in it's downward facing camera? - matches that of the rotors, which I replied could make reasonable sense. ]

Me - original question:
Hmm, how is it that the rotors appear almost stationary in that last segment showing Ingenuity in motion from the on-board camera? [ EDIT: ok, it looks like the rotors did rotate a few degrees during the period of motion. Still, why aren't they just a blur? ]
"Gage":
Videos are a bunch of pictures.
Like, 60 FPS, 60 pictures per second.
The rate it took the pictures matched the rotors RPM
Me:
@Gage Hmm, I guess that makes sense. Per NASA, the rotors spin at 2400 rpm, which is 40 FPS. That seems like a reasonable - if a little fast - video speed. EDIT: and 20, 10, or 5 FPS would also result in apparently stationary rotors, and even 24 FPS might work if we allow for a little rotor image rotation, which there is.
"One by Land, Two if by Sea Run if by Air":
The key here is understanding the "Shadow". Its 2 dimensional surface. But they are also negative light space, without light bouncing off a moving object. So the light doesn't get scattered or shifted by reflections.

So if you're thinking about a shadow as an object there: We need to look at this a different way.

If a rotating object casts a shadow: the area underneath will simply get lighter and darker (in any fixed spot), but won't move. No motion: no blur.

Or to put it a different way: the "shadow" is not an inherent property of the object (rotor blades). It's not like mass and volume.

Your photographing the ground, which isn't moving.

You can see shadows of hummingbird and insect wings easily, but they blur too much to see them directly in flight.

Shutter speed here is close to an interval of blade rotation. That's not too surprising, since there are 4 blades and each can occupy 2 positions and still be symmetrical in rotation axis.
Me:
@One by Land, Two if by Sea Run if by Air - You’ve said this before in a reply to a similar question I had in another Ingenuity video about the rotors, but I still don’t believe it. Your explanation would seem to imply that it is impossible to take a blurry [photo] of the shadow of a moving object. Is that the right conclusion?
"One by Land, Two if by Sea Run if by Air":
@Johnny Deep The shadow isn't moving. It's a picture of the ground. If the ground isn't blurry, it is impossible for the shadow to be blurry. They're quite literally the same thing. ...So yes, such a thing would defy all known physics.

The shadow is not an object.
The photos are consistent with this also. The ground simply can't blur under in some spots, and not blur in others, because it's all moving as one object at one speed, regardless of any light that shines on it.
Me:
@One by Land, Two if by Sea Run if by Air - Would the situation be any different if we were photographing a rotor "shadow" cut out of a piece of black paper and spinning at 3200 RPM on the ground? Surely that's a "real" object, so it should be possible for it to be blurred in a photo, no?
So, what's really going on with those rotor shadows?
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Re: APOD: Perseverance from Ingenuity (2021 May 01)

Post by Astronymus » Sat May 01, 2021 5:32 pm

johnnydeep wrote:
Sat May 01, 2021 4:23 pm
So, what's really going on with those rotor shadows?
The "slow" movement of the rotor is due to a nearly synchronous shutter speed. As explained a video is not a continuous stream but a rapid series of pictures. You can find lots of other examples of shutter speed combined with helicopters and planes on YouTube.

The shadow isn't blurred because the ground is lit up well. This means the camera can work with short exposures to take a proper picture or video. The faster the cam the lesser the blurr.
It's actually the purpose of high speed cameras. To capture sharp pictures of fast processes you speed up the shutter to insane velocities. This is achived by different systems like rotating mirrors for example. Later you can watch these blurr-free videos in slow motion or study them fame by frame.
In photography you can create blurr on purpose if you adjust aperture and shutter speed.

Here they explain it very well:
Click to play embedded YouTube video.
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Re: APOD: Perseverance from Ingenuity (2021 May 01)

Post by johnnydeep » Sun May 02, 2021 6:42 pm

Astronymus wrote:
Sat May 01, 2021 5:32 pm
johnnydeep wrote:
Sat May 01, 2021 4:23 pm
So, what's really going on with those rotor shadows?
The "slow" movement of the rotor is due to a nearly synchronous shutter speed. As explained a video is not a continuous stream but a rapid series of pictures. You can find lots of other examples of shutter speed combined with helicopters and planes on YouTube.

The shadow isn't blurred because the ground is lit up well. This means the camera can work with short exposures to take a proper picture or video. The faster the cam the lesser the blurr.
It's actually the purpose of high speed cameras. To capture sharp pictures of fast processes you speed up the shutter to insane velocities. This is achived by different systems like rotating mirrors for example. Later you can watch these blurr-free videos in slow motion or study them fame by frame.
In photography you can create blurr on purpose if you adjust aperture and shutter speed.

Here they explain it very well:
Click to play embedded YouTube video.
Thanks, that was a perfect video explanation of this exact thing! So it's all just shutter speed and a synchronized frame rate.

Finally, was the guy talking about some fundamental difference between photographing moving shadows versus "real" objects, and that it's possible to "easily" see the shadows of hummingbird and insect wings (presumably in flight, just wrong?
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Re: APOD: Perseverance from Ingenuity (2021 May 01)

Post by alter-ego » Tue May 04, 2021 3:52 am

The conversation about shadows was pretty oblique to me, and I don't find any interest in pursuing it's understanding (at least in the context of that discussion). However, I have a few comments:
1. The maximum frame-rate of the Nav Camera = 10 fps.
2. The minimum exposure possible is around 10us.
3. One attribute of that video that threw me at first, and afik wasn't clearly acknowledged, was the moving shadow.

:arrow: From Ingenuity's view, it's own shadow is stationary - the ground is moving :roll:. In the video the ground is almost stationary. At the start of the video, visible distortion is evident at the bottom of the frame (copter at top), and moves to the top of the frame at the end (copter at bottom). The Nav camera is fixed pointing towards nadir. So what's going on? The only possibility for this short flight is the frames were cropped to reference the same ground features. Aligning all the frames to the ground features would result in a video showing the ground is stationary and Ingenuity is moving. The distortion occurs when Ingenuity is furthest from ground features, and pushing the clarity limits of the 100° FoV in the forward direction

Funny, the stationary rotors were not a conceptual problem for me, but I had to replay the video several times to make sense :idea: out of the moving copter shadow. Maybe I missed something and I'm the last to realized this; maybe your earlier conversation was about this? Anyway, what creative way to give a different perspective on the flying Ingenuity from itself.
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Re: APOD: Perseverance from Ingenuity (2021 May 01)

Post by johnnydeep » Thu May 06, 2021 9:44 pm

alter-ego wrote:
Tue May 04, 2021 3:52 am
The conversation about shadows was pretty oblique to me, and I don't find any interest in pursuing it's understanding (at least in the context of that discussion). However, I have a few comments:
1. The maximum frame-rate of the Nav Camera = 10 fps.
2. The minimum exposure possible is around 10us.
3. One attribute of that video that threw me at first, and afik wasn't clearly acknowledged, was the moving shadow.

:arrow: From Ingenuity's view, it's own shadow is stationary - the ground is moving :roll:. In the video the ground is almost stationary. At the start of the video, visible distortion is evident at the bottom of the frame (copter at top), and moves to the top of the frame at the end (copter at bottom). The Nav camera is fixed pointing towards nadir. So what's going on? The only possibility for this short flight is the frames were cropped to reference the same ground features. Aligning all the frames to the ground features would result in a video showing the ground is stationary and Ingenuity is moving. The distortion occurs when Ingenuity is furthest from ground features, and pushing the clarity limits of the 100° FoV in the forward direction

Funny, the stationary rotors were not a conceptual problem for me, but I had to replay the video several times to make sense :idea: out of the moving copter shadow. Maybe I missed something and I'm the last to realized this; maybe your earlier conversation was about this? Anyway, what creative way to give a different perspective on the flying Ingenuity from itself.
No, was only taking about the shadows of the stilled rotors, and didn't even take note of the incongruity of the stationary ground! I agree some post-processing chicanery seems to have been done. Here's the video of the same flight from the proper perspective of Ingenuity, along with a caption mentioning that the stationary rotors is due to a synchronous or fast enough frame rate:

Click to play embedded YouTube video.

So, now my question is why does only one rotor appear stationary? I would have thought that the two counter-rotating rotors would have the same RPM. Apparently not? Hmm, or is this how they accomplish horizontal movement? [I guess I have to look that up...and how do any of these small copter drones manage horizontal movement anyway?]
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Re: APOD: Perseverance from Ingenuity (2021 May 01)

Post by alter-ego » Fri May 07, 2021 4:42 am

johnnydeep wrote:
Thu May 06, 2021 9:44 pm
...

No, was only taking about the shadows of the stilled rotors, and didn't even take note of the incongruity of the stationary ground! I agree some post-processing chicanery seems to have been done. Here's the video of the same flight from the proper perspective of Ingenuity, along with a caption mentioning that the stationary rotors is due to a synchronous or fast enough frame rate:

Click to play embedded YouTube video.

So, now my question is why does only one rotor appear stationary? I would have thought that the two counter-rotating rotors would have the same RPM. Apparently not? Hmm, or is this how they accomplish horizontal movement? [I guess I have to look that up...and how do any of these small copter drones manage horizontal movement anyway?]
Apparently differential rotor speed is not used to control Ingenuity. Instead its independent rotor pitch control.
Regarding the different rotor speeds, I suspect the independent DC rotor motors are naturally not exactly the same speed, or maybe different speeds mitigate destabilization induced from "rotor blade flapping" (not explicitly stated, "see Technology Demonstrator" link).
Mars Science Helicopter Conceptual Design wrote:
Ingenuity Flight Control.jpg
 
Mars Helicopter Technology Demonstrator
Ingenuity Rotor Assembly.jpg
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Re: APOD: Perseverance from Ingenuity (2021 May 01)

Post by johnnydeep » Fri May 07, 2021 2:24 pm

alter-ego wrote:
Fri May 07, 2021 4:42 am
johnnydeep wrote:
Thu May 06, 2021 9:44 pm
...

No, was only taking about the shadows of the stilled rotors, and didn't even take note of the incongruity of the stationary ground! I agree some post-processing chicanery seems to have been done. Here's the video of the same flight from the proper perspective of Ingenuity, along with a caption mentioning that the stationary rotors is due to a synchronous or fast enough frame rate:

Click to play embedded YouTube video.

So, now my question is why does only one rotor appear stationary? I would have thought that the two counter-rotating rotors would have the same RPM. Apparently not? Hmm, or is this how they accomplish horizontal movement? [I guess I have to look that up...and how do any of these small copter drones manage horizontal movement anyway?]
Apparently differential rotor speed is not used to control Ingenuity. Instead its independent rotor pitch control.
Regarding the different rotor speeds, I suspect the independent DC rotor motors are naturally not exactly the same speed, or maybe different speeds mitigate destabilization induced from "rotor blade flapping" (not explicitly stated, "see Technology Demonstrator" link).
Mars Science Helicopter Conceptual Design wrote: Ingenuity Flight Control.jpg
 
Mars Helicopter Technology Demonstrator
Ingenuity Rotor Assembly.jpg
Thanks - those are great links to very detailed PDFs! For some reason I thought rotor swash plates were too complex to be used here, but with coaxial rotors and only one axle I believe it is essential. Quadcopters on the other hand, can employ altering the speed of separate rotors to change flight direction.
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Re: APOD: Perseverance from Ingenuity (2021 May 01)

Post by alter-ego » Fri May 07, 2021 7:21 pm

johnnydeep wrote:
Fri May 07, 2021 2:24 pm
alter-ego wrote:
Fri May 07, 2021 4:42 am
johnnydeep wrote:
Thu May 06, 2021 9:44 pm
...

No, was only taking about the shadows of the stilled rotors, and didn't even take note of the incongruity of the stationary ground! I agree some post-processing chicanery seems to have been done. Here's the video of the same flight from the proper perspective of Ingenuity, along with a caption mentioning that the stationary rotors is due to a synchronous or fast enough frame rate:

Click to play embedded YouTube video.

So, now my question is why does only one rotor appear stationary? I would have thought that the two counter-rotating rotors would have the same RPM. Apparently not? Hmm, or is this how they accomplish horizontal movement? [I guess I have to look that up...and how do any of these small copter drones manage horizontal movement anyway?]
Apparently differential rotor speed is not used to control Ingenuity. Instead its independent rotor pitch control.
Regarding the different rotor speeds, I suspect the independent DC rotor motors are naturally not exactly the same speed, or maybe different speeds mitigate destabilization induced from "rotor blade flapping" (not explicitly stated, "see Technology Demonstrator" link).
Mars Science Helicopter Conceptual Design wrote: Ingenuity Flight Control.jpg
 
Mars Helicopter Technology Demonstrator
Ingenuity Rotor Assembly.jpg
Thanks - those are great links to very detailed PDFs! For some reason I thought rotor swash plates were too complex to be used here, but with coaxial rotors and only one axle I believe it is essential. Quadcopters on the other hand, can employ altering the speed of separate rotors to change flight direction.
Yup, pretty detailed. I'm pretty much convinced nothing's too complex for those guys. It's in the details where Ingenuity's $80M development cost becomes apparent. Just glancing at the copter, it just looks like a spindly toy.
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Re: APOD: Perseverance from Ingenuity (2021 May 01)

Post by Chris Peterson » Fri May 07, 2021 8:58 pm

alter-ego wrote:
Fri May 07, 2021 7:21 pm
johnnydeep wrote:
Fri May 07, 2021 2:24 pm
alter-ego wrote:
Fri May 07, 2021 4:42 am


Apparently differential rotor speed is not used to control Ingenuity. Instead its independent rotor pitch control.
Regarding the different rotor speeds, I suspect the independent DC rotor motors are naturally not exactly the same speed, or maybe different speeds mitigate destabilization induced from "rotor blade flapping" (not explicitly stated, "see Technology Demonstrator" link).

 
Mars Helicopter Technology Demonstrator
Ingenuity Rotor Assembly.jpg
Thanks - those are great links to very detailed PDFs! For some reason I thought rotor swash plates were too complex to be used here, but with coaxial rotors and only one axle I believe it is essential. Quadcopters on the other hand, can employ altering the speed of separate rotors to change flight direction.
Yup, pretty detailed. I'm pretty much convinced nothing's too complex for those guys. It's in the details where Ingenuity's $80M development cost becomes apparent. Just glancing at the copter, it just looks like a spindly toy.
It's also in overhead. That budget includes all kinds of little bits of NASA, right down to the people who clean the bathrooms. And a lot of big ticket stuff, too. I imagine the burdened cost of operating the Mars simulation chamber is many thousands of dollars an hour. And it includes part of the salaries of dozens, if not hundreds of researchers who will still be working on this project for years to come. (Even if they only fly it a few more times, the data that is collected will be studied for a long time... and that's part of the project budget.)
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Re: APOD: Perseverance from Ingenuity (2021 May 01)

Post by alter-ego » Sat May 08, 2021 4:13 am

Chris Peterson wrote:
Fri May 07, 2021 8:58 pm
alter-ego wrote:
Fri May 07, 2021 7:21 pm
johnnydeep wrote:
Fri May 07, 2021 2:24 pm


Thanks - those are great links to very detailed PDFs! For some reason I thought rotor swash plates were too complex to be used here, but with coaxial rotors and only one axle I believe it is essential. Quadcopters on the other hand, can employ altering the speed of separate rotors to change flight direction.
Yup, pretty detailed. I'm pretty much convinced nothing's too complex for those guys. It's in the details where Ingenuity's $80M development cost becomes apparent. Just glancing at the copter, it just looks like a spindly toy.
It's also in overhead. That budget includes all kinds of little bits of NASA, right down to the people who clean the bathrooms. And a lot of big ticket stuff, too. I imagine the burdened cost of operating the Mars simulation chamber is many thousands of dollars an hour. And it includes part of the salaries of dozens, if not hundreds of researchers who will still be working on this project for years to come. (Even if they only fly it a few more times, the data that is collected will be studied for a long time... and that's part of the project budget.)
That's true. I don't know the OH for Ingenuity but I expect at least 40% the total design and development cost. Those numbers I've experienced for multi-million dollar prototype programs. However, everything considered, Ingenuity's high cost for its size and weight indicates a high level of technical challenge. Last year the new space toilet was installed in the ISS. I remember being astounded by the $23M cost, but comparatively, Ingenuity seems to be a good deal :D
 
NASA Hardware Cost Comparison.jpg
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