Steve, you forgot InSight

And InSight...

During the press conference it was noted that velocity at entry interface was ~12,000 mph. IIRC Curiosity's entry interface speed was about 13,000 mph. Did they extend the coast phase a bit to have a lower entry interface speed because this is a heavier payload than Curiosity, or was this just rounding error in the presser?

US Mars landings technics so far :

Powered descent : 4
Air Bags : 3
SkyCrane : 2
Lithobraking : 1

Powered descent: Viking 1 & 2, Phoenix and INSIGHT
Air bags: Pathfinder, Spirit and Opportunity
Skycrane: Curiosity and Perseverance

Which one did the lithobraking?

Mars Polar Lander

And the New Millennium penetrators as well.

The arrival speed would differ some because the interplanetary trajectory is not always the same. For any given arrival, Mars is at a different distance from the sun, due to its elliptical orbit. When Mars is farther from the sun, the interplanetary trajectory (the spacecraft orbit around the sun) is slower at Mars arrival (but Mars is moving faster, "catching up" to the spacecraft, therefore such a slower spacecraft speed around the sun is actually faster relative to Mars). Assuming this explanation is correct, it tells us that Mars was farther away from the sun when Curiosity arrived. Being closer to the sun yesterday is at least partly what made it possible for Perseverance to be a heavier payload as you pointed out (because less speed was need at Earth departure). OK, so I left out the detail that Mars would have been moving slightly slower also for the arrival of Curiosity, but I think the relative speed difference as described here still applies.

Does anyone know when we get to see the video from the sky crane camera looking at Perseverance and vice versa, also the camera looking at the ground during EDL? Please post links when appropriate.

Near term, the press conference in about an hour is my best bet for EDL: https://www.youtube.com/watch?v=Xz-Id5ZNopM

BTW, the documentary "Built for Mars: The Perseverance Rover" on NatGeo last night was excellent. Usually I find these things pretty cringeworthy for a variety of reasons, but this one was great. As someone who has on occasion gotten to be a technician (I torqued several screws on MCZ) it's a nice perspective of what it's like to build flight hardware, not often seen on TV.

This is regarding remaining fuel in the sky crane, as discussed in post numbers 126, 131, 142, 146, 150, 151, 155, 157, 158, and 167 in the topic "Perseverance Lands In Jezero Crater, Sol 0-." I will put a note in that other topic to point here (the EDL topic).

The second link in Post 167 explains that the sky crane engines are run at full throttle until the fuel depletes (page 12, upper left corner).
https://trs.jpl.nasa.gov/bitstream/handle/2...708/08-0255.pdf
That was for MSL, and a similar publication from the 2019 IEEE Aerospace Conference says the same for Mars 2020.
(Nelessen et al, Mars 2020 Entry, Descent, and Landing System Overview)

The third and fourth links in Post 167 show that the fuel is hydrazine, pressurized by helium gas.
https://trs.jpl.nasa.gov/bitstream/handle/2...13-0606_A1b.pdf
https://trs.jpl.nasa.gov/bitstream/handle/2...13-0737_A1b.pdf
In the fuel tanks, the helium is separated from the liquid by flexible bladders, so there is no mixing, and the liquid can be used up without the helium getting to the engines. Upon ground impact, the pressurized helium is still in the tanks and certainly there is some residual liquid (in tanks and in tubing), so one would expect that the tanks burst open and the remaining liquid decomposes quickly. The main reason for the bladders is to keep the helium away from the tank outlet tubes to the engines, so that the engines receive only liquid during intense maneuvering (liquid slosh).

A few of the posts used the word "hypergolic," which usually refers to fuel and oxidizer burning on contact. While hydrazine is hypergolic with some oxidizers, there is no oxidizer in the sky crane. The engines have catalyst to cause a decomposition reaction (N2H4 goes to H2, N2, and NH3 gases at high temperature).

From 1988 to 1994, I was a customer at the company that had built the Viking engines in the seventies (then Rocket Research, now part of Aerojet). I got to know engineers who subsequently dusted off the Viking design and made modifications for MSL, used again for Mars 2020 (way to go folks!). I agree that propulsion engineers would like for the rover to visit the sky crane crash site.

Adam said in his slightly drunken (whiskey ) Instagram live video that the descent stage was sent by the scientists somewhat surprisingly North ( they had a choice north or south), and he did indeed say they'd love to visit the descent stage.

Glad you mentioned the show, watching it now, 3 mins in and it's awesome.

Sorry to belabor this point - but they are not. I asked the EDL Phase lead. I refer you again to this paper : https://ieeexplore.ieee.org/stamp/stamp.jsp...rnumber=8742167

Some googling gives me speed at EI of 19,000 km/h for Percy and 21,250 km/h for MSL.

MSL and Percy had quite different trajectories getting to Mars. I think what makes the main difference in the relative speed between Mars and the spacecraft is that Percy carried "excess" speed that would have taken it 10m km further away from the Sun than Mars was at landing (if Mars hadnt "run over" Percy on the way); that additional speed means the difference to Mars' speed was a tad less than for MSL. MSL's aphelion was pretty much exactly the distance to Mars at landing, so it was at its slowest in its orbit. MSL was closer to the Sun at landing, but also had a lower perihelion.

I dont know if that was part of the design to be able to land a heavier payload. I also most vaguely seem to remember that the 7 minutes of terror for MSL was more like 6 minutes. Memory a bit vague, it was nearly 10 years ago. How time flies ...

Percy
Distance to Sun at landing: 235m km
Aphelion: 243m km
Perihelion: 151m km
Eccentricity: 0.2322

MSL
Distance to Sun at landing: 230m km
Aphelion: 230m km
Perihelion: 147m km
Eccentricity: 0.2188

Source: SSD Horizons. Orbital elements before Mars' gravity started to affect them.

I guess this belongs in the EDL thread... Perseverance hasn't quite landed.

This is a highly tinkered image to bring out the engine swirls (equalized, curves, etc)

Click to view attachment

I haven't lined up any rocks with the Hazcam shots yet... (is the vehicle drifting?) ... and there is an interesting 'rock' at the far-left middle

I don't know about the rest of you, but I am really, really impressed by the performance of the Terrain Relative Navigation (TRN) during EDL. If you look at the landing site, you can see all sorts of hazards such as dune fields and boulders that TRN successfully avoided. Congrats to the team; I cannot imagine how challenging the engineering was for this.

I had a different sort of EDL question: does the thickness of Mars' atmosphere vary enough to necessitate course and trajectory corrections just before EDL?

They had a target box they were in 2 days before entry, the thickness does affect how far up range or downrange of the target you go, they do guidance when on the heat shield to hit the target landing spot, ofc we do not know how much deflection TRN did to get to a safe spot, might have been 20 meters, who knows ?, but that ofc is after the time on parachute.

OK by me to "belabor," it is worth some effort to find right answers. Thanks for the link to the Nelessen paper, which I did mention in my Post 61 above. Near the bottom right corner of Page 3, the paragraph starting with "Flyaway" says the following.
Ouch, do we have to mistrust the published technical literature?

Besides the "whether or not," it is more interesting to know the pros and cons, why (or why not) the sky crane should use up the hydrazine before crashing.
For example, it seems to make sense to fly the skycrane as far away as possible, so maybe the EDL Phase Lead could shed further light on why not to do that.

Full video - a few seconds before touchdown.

Amazing.

https://youtu.be/4czjS9h4Fpg

Skycrane crash: Don't forget that a plan published in the past (over a year ago in the case of that paper) might not match the current thinking, so the mission might not follow exactly what was discussed earlier. Also, it seems they had plenty of fuel to spare, so if it did use all the fuel it might end up way out in the delta somewhere, where the rover might want to be later on.

It turned out to be good to "mistrust" the published technical literature since Alan Chen confirms that it indeed no longer reflects the procedure used.

Science, generally, is based on "mistrusting" as long as you do it in an evidence-based manner...

Spent all day working at the job that pays me, just saw the video. RIDICULOUSLY cool, utterly mind-blowing!

Just a quick and dirty run on the Perseverance Rover Down-Look camera. Just quick corrections applied.
https://youtu.be/vkhzyxqQeus

Credit for the data and the whole accomplishment of landing another rover on Mars:
NASA/JPL-Caltech

Sources:
https://mars.nasa.gov/mars2020/multimedia/raw-images/
https://www.youtube.com/watch?v=4czjS9h4Fpg

I have trouble downloading all the data in bulk. Can anyone point me to a trick? Is there another place to download the data with wget possibly?

I am having that same issue. I usually just use a JSON list, like the one that Curiosity has and the DownThemAll firefox plugin. But I'm having trouble locating a simular JSON file for Perseverance. I am aware of the raw image site API quick "hack" to pull up a partial JSON list, but it seems to be very limited. Any other ways to bulk download, I'm also all ears.

Does anyone know if the springs on the heat shield are supposed to be captured or not ?

Assume you've already tried this, and I'm learning as I go here. The default one limits to 50-images per page. But by messing with that query you can get a huge file with all images and their data (at least for a given sol), including direct filename links, pointing data, subframe, etc...You're looking for something else?

For Perseverence, "https://mars.nasa.gov/rss/api/?feed=raw_images&category=mars2020&feedtype=json&sol=0&order=sol+desc&&&extended=" gets at present a 6.5MB file with details for the 3559 sol 0 images there right now.

For example on sol 2 one "full res" link is "https://mars.nasa.gov/mars2020-raw-images/pub/ods/surface/sol/00002/ids/edr/browse/rcam/RRB_0002_0667129492_604ECM_N0010052AUT_04096_00_2I3J01.png")

There are other fields too. If you know an image filename you can go straight to the metadata for that image, e.g. "https://mars.nasa.gov/rss/api/?feed=raw_images&category=mars2020&feedtype=json&id=RRB_0002_0667129492_604ECM_N0010052AUT_04096_00_2I3J01"

If I knew anything about web development I'd try to reformat and post it for general use somehow.

Press conference said that the free spring was surprising, but not alarming. It sure is neat to watch, though.

That query is perfect for redisplaying from their site. I'm sure there are better ways, but your question piqued my interest. I got this far using PHP to decode a result from the API for display, say in a sidebar widget in WordPress (and maybe add a link to the large version, etc.).

I have a python script that write all links to a file, then you can use wget on that

Regarding the parachute movies/images. They're from two different upward-pointing cameras so in principle it should be possible for our imaging wizards to do a 3D-version. Can't think of a better subject matter for a 3D movie.

MarsInMyLifetime & erentar, so cool - I knew there were folks here with interest.

Note they do have a suggested way to embed images (in the sidebar of the individual image pages):

In order to keep this thread focused on EDL rather than data wrangling, may I suggest we reconvene on this thread in the Image Processing Techniques subforum... looks like phase4's Marslife 3D browser is already playing with Percy images and y'all speak the same language I suspect

(unless the MODS think we can/should start a dedicated Perseverence image processing thread, as happened for MSL, Juno, etc.)?

I have already had a look at it. But the second cam has only a few images. Anyway, it will be possible, but it will make your eyes hurt. The tangles from the parachute are right in between the both cams, if I interpreted the image correctly.

Also thanks everyone for the help with the code!

I really wish those of us outside the U.S. could also get to see these kinds of documentaries without this geo-lock stuff.

The MARDI camera on Curiosity captured the heatshield impacting the surface while still on the parachute.

https://www.youtube.com/watch?v=vVLPXfF3l_U

It looks like the impact site for Perseverance's heatshield moved out of view while on the parachute???

EDIT: Have rewatched the decent video and im pretty sure the impact site goes out of view now.

I was wondering at what moment exactly the upward-looking cameras on the backshell started recording images. Was it just before parachute deployment? Were they turned on during atmospheric entry and the peak heating phase? That might have been interesting.

Turned on just before chute deploy - but behind the cover that comes off at deployment, hence some black frames at the start of the sequence

This raw image shows what I think we can much more confidently assert is the Skycrane crash plume. Marshall Eubanks on the Asteroid Explorer's Facebook posted a contrast-enhanced image showing the plume in more detail, which I've attached here.

Edit: there's two images showing the plume, posted here. Also attached.

Certainly seems so much larger than the Curiosity plume (though that is a much lower quality image). Great catch!

I think there ever was only one frame of Curiosity's skycrane plume.
I'm not sure how many frames will come down for this one though, but hopefully a lot more, as it will be interesting to get a visceral sense of how the plume develops and decays within Mars' gravity and atmosphere.

Also quite surprising to me was the lack of any visible exhaust gas plume or heat refraction wavelet distortion emanating from the nozzles in the skycrane images as you would expect terrestrially, i guess it owes to the negligible atmospheric pressure being not enough to generate a refraction difference against the surrounding gasses perhaps. Video like this can really illustrate the otherworldliness of Mars so much better than anything else.

Yes, the Martian atmosphere is a pretty high vacuum from a rocketry perspective and so any gas exiting the nozzle will also tend to expand outward due to virtually no atmospheric backpressure - not like a tightly collimated exhaust plume you can get at 1bar on the surface of Earth.

Additionally, the hydrazine monopropellant thrusters use catalytic decomposition and the temperature goes up to around 1000 deg C in the chamber (quite a bit lower than a bipropellant fuel), but once it passes the chamber throat and starts expanding in the nozzle that exhaust will drop in temperature fast. The exhaust hitting the surface is moving fast, but it might not actually be all that hot*. Even if there was some refraction happening (IMHO I'm skeptical that it would be noticeable), it would happen some ways downstream where the chaotic mixing is strongest and neither camera view really showed that. Maybe if there was a camera on the rover looking sideways toward the horizon through the plumes, while hanging under the bridles something could have been seen, but at that point there was a lot of dust kicked up anyway.

* Well, "(not) hot" is probably the wrong term to use here, the gas molecules will have pretty much the same kinetic energy, it's just more directional than random. There probably is still quite a bit of localized shock heating once the plume hits the surface.

Comparing pre- and post-landing high resolution imagery shows that small (< 5m long) ripples or dunes just NW of the landing site appear to have been blasted away by the descent stage/sky crane.

pre-landing (25cm HiRISE mosaic)

Click to view attachment

post-landing (Mars2020 MRO image)

Click to view attachment

These ripples may represent the source of the majority of the dust seen in the descent video. One could probably estimate the volume (and the mass) of the apparently removed material. Perhaps the next generation hazard avoidance system could take such second order features into account since these small features could be identified in advance.

Here is a slide flip for checking map cross-registration:

http://bit.ly/PercyRIPPLEs

Sources:
https://planetarymaps.usgs.gov/mosaic/mars2...n0_first_dd.tif (> 9GB !)
https://mars.nasa.gov/system/downloadable_i...No-Contrast.jpg

Monoprop hydrazine exhaust has been called "warm" (not "hot") by some rocket people, and the plume is not bright. When run in Earth's atmosphere the hydrogen in the exhaust is likely to burn upon mixing with oxygen, but an infrared camera is still the best way to see those flames.

I was surprized when they showed the EDL videos so quickly considering those were supposed to be tens of thousands of frames. But I assume now that the frames were compressed into video onboard (they mentioned using ffmpeg) and sent back quickly. Now the raw frames will presumably take some time to return, but once we get them we will be able to make beautifully clean videos...

For future missions the EDL video was high priority, just incase anything bad happened to Percy before the info was transmitted.

I realized that you can actually see the ripple just to NW of the landing site mentioned above getting disrupted and eventually completely removed on the descent video. Here is a series of frames where I circled the ripple in red, and the landing site in blue, linked to the video at these times:

I learned that on youtube you can move back and forward by single frames with the ',' and '.' keys.









The white arrow points out what I think may be a sharper, retreating edge from blast erosion. Most of the erosion appears to occur during hovering in preparation for the "abseiling" of the rover.

I don't think that ripple is removed. In the hirise imagery the lighting is different before and after and it's the shadows that determine the visibility of the ripples. And in the landing images the dust kicked up blocks the direct sun and so reduces the visibility of the shadows.

If fact taking one of your frames with the ripple in question circled in red we can identify the same ripple in the rear hazcam imagery, as well as other ripples and rocks. Here I've identified features with the same colour outlining:
Click to view attachment
Click to view attachment

Has anyone found out why the secondary timestamp on the EDL image files are off from camera to camera?

For example, the A and B cameras looking upward at the parachute have different timestamps for images taken at the same time (eg parachute deploy).

Camera A - Chute deploy MET 0667110215

Camera B - Chute deploy MET 0667022753

These are both stamped Sol 2 when they are clearly sol 0. Is there a way to reconcile all these to a standard sequence so we know definitively what order they were take in?

The ground-pointing camera images from the descent also have differing timestamps.

M.

There are timestamp issues on the raw images website which are being worked on.

Thanks!

The video that came down of the landing seems to have been a separate file or series of files as pieces were missing in the raw images downloaded. Was a video stream generated by the EDL cameras and then uploaded straight to the DSN or were they programmed just to shoot stills at regular intervals which were then combined into a video?