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Perseverance EDL, 18 Feb 2021
MarkL
post Mar 3 2021, 08:35 PM
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QUOTE (JRehling @ Mar 3 2021, 08:01 PM) *
There are video compression algorithms that typically achieve much better performance than you would get from a sequence of n compressed images, and these take advantage of the fact that typically there is high correlation from one frame to another. For example, with video of a newscaster in a studio, the pixels representing the background, the desk, etc., don't often change from one frame to the next, so a compression algorithm can achieve big wins by storing only those portions of each frame which changed significantly from the last frame. However, with something like Perseverance's rapid descent, the fluttering of its parachute, etc., you have a lot more rapid change than you would normally expect.

Occasionally, you see compressed video break down suddenly and momentarily in quality when the frame-to-frame change exceeds expectations. One example I'll always remember is the way the image of the crowd "pixelated" when I was watching a basketball game on TV when there was a fast break in the game and the camera suddenly panned, causing the entire image to fluctuate from one frame to the next.

All that said, I'm not sure if either of these things was ever at a premium with the descent videos: (1) Returning to Earth, eventually, a video with the absolute highest degree of detail. (2) Achieving optimal bandwidth in the transmission of an initial compressed video.

It seems that with these videos "pretty good" is all that was needed in both respects. Descent video isn't the high-value science data for which the mission was launched.


Thanks for replying and agreed.

But it is very cool and will be an artifact of historic significance being the first video ever captured of a spacecraft during descent as well as the image data having been captured by very good cameras. It is also capable of providing a good quantity of valuable engineering data from chute deploy to TD and the more frames and higher quality the better.

My initial point was, where is the actual video file they uplinked? It was pretty high resolution. Maybe they can release it in raw form (unedited I mean).
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mcaplinger
post Mar 3 2021, 08:59 PM
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QUOTE (MarkL @ Mar 3 2021, 12:42 PM) *
Who knows if or when they will publish all the individual frames of which there must be several thousand.

They have said they were going to do that, and there are several thousand RDC raw frames on the website already, so why don't you give them a chance? It is only sol 13.


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Disclaimer: This post is based on public information only. Any opinions are my own.
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MarkL
post Mar 3 2021, 09:06 PM
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Point taken. cool.gif
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MahFL
post Mar 9 2021, 11:18 PM
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Nice new image came down.


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djellison
post Mar 10 2021, 12:30 AM
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All of them came down - including a view of the Heatshield impact.

Here's a page of just the LCAM pics, from Ryan's awesome raw browsing interface
https://rkinnett.github.io/roverpics/?mars2...&filter=ELM


(Congrats Mike C - great work from the La Jolla team)
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JRehling
post Mar 10 2021, 01:19 AM
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That heat shield impact sequence is on the very short list of the greatest "action" videos in the history of planetary exploration!
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Andreas Plesch
post Mar 10 2021, 05:00 AM
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Here is a quick animation of all the LVS frames: https://bit.ly/PercyLCAM

It will take a while before the higher resolution versions become available (looks like they did).


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xflare
post Mar 10 2021, 07:37 AM
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WOW, iso it did catch the impact!!!!! I thought it had gone out of frame.
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Marvin
post Mar 10 2021, 01:09 PM
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The heat shield took a quite the bounce when it impacted (cropped and zoomed):

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djellison
post Mar 10 2021, 02:09 PM
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If it bounced it would be visible separately from the impact ‘splat’ in the crime scene HiRISE image.....which it isn’t..

I think you’re seeing the dust cloud of impact and its shadow move with the wind. These are 1hz images, so it’s actually pretty slow.
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MarT
post Mar 20 2021, 09:42 AM
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Hi!

I tried to combine 23 of the LCAM images into a panorama. I combined that with the compressed RDCAM images, which I already had stitched. I filled the rest, which did not overlay, with cloned color. The colors for the atmosphere was taken from one of the PUCAM1 images. There is definetly no scientific value in this, as there was a lot of postprocessing involved. Stretching, contrast, brightness, sharpening, colorization, resolution upscaling etc. I tried to do it to my best understanding of what it would approximately look like from 11km above the Jezero crater. I will post a 360 version on youtube later. If someone is interested in the version without inpainted color, just say so smile.gif

On Windows, I use FSPviewer to look at 360 images.

Youtube version:
https://www.youtube.com/watch?v=m1hwTNgZK7E
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Brian Swift
post May 14 2021, 11:19 PM
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My take on processing the Descent Down-Look Camera raw images.

Left image colors are based on camera response and and illumination optimized from calibration target on top of rover, and includes chromatic adaption from modeled illuminant to D65 standard. In right image, only camera response is modeled and illumination is fixed at D65, so no chromatic adaption is applied.

Image processing done with custom software in Mathematica.
Mathematica notebook is open source and available at https://github.com/BrianSwift/image-processing
Notebook also contains links to various Mars 2020 and color processing papers and resources.

Video on YouTube

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MichaelJWP
post May 20 2021, 10:30 AM
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Just wondered if anyone knows if there's been a report shared yet which compares how the EDL went in relation to what was expected?
Or is it too soon for that maybe?
Particularly interested in the improved guidance/hazard avoidance in Perseverance vs Curiosity and how that panned out.
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stevesliva
post May 20 2021, 05:46 PM
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QUOTE (MichaelJWP @ May 20 2021, 05:30 AM) *
Particularly interested in the improved guidance/hazard avoidance in Perseverance vs Curiosity and how that panned out.


FWIW, you can read somewhat open discussion starting at 21:16 here:
https://www.rev.com/blog/transcripts/nasa-p...or-life-on-mars
... but I am not sure if not mentioning hazard avoidance is evidence of omission or omission of evidence, as they say.
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Phil Stooke
post Oct 29 2021, 08:35 PM
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Waking up an old thread to mention the impacts of the two cruise balance masses. They were ejected just prior to arrival to allow control over the flight and struck the surface about 100 km west of the landing site. For Curiosity the same applied and the impact sites were imaged by HiRISE. Now with little fanfare we have the same for Perseverance, it seems. See the InSight thread for a reference to this in connection with an attempt by InSight to pick up a seismic signal.

This map locates the impacts:

Attached Image


The background is MOLA elevation and THEMIS daytime IR imaging. The overlay is a CTX image. The grid spacing is 0.1 degree or 6 km.

Phil


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... because the Solar System ain't gonna map itself.

Also to be found posting similar content on https://mastodon.social/@PhilStooke
NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain)
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