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ExoMars - Schiaparelli landing
neo56
post Oct 21 2016, 07:25 PM
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I looked at Oppy's new images on Midnight Planets and spotted this pic I've not seen yesterday: http://www.midnightplanets.com/web/MERB/im...RP2857L6M1.html

Do you think the two bright spots above the horizon could be Schiaparelli and its parachute? I circled them:
Attached Image


Time of acquisition seems too early (2:44:13 PM UTC) but Mike specifies that acquisition times are approximate.


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Explorer1
post Oct 21 2016, 07:30 PM
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We know from the CTX images that it landed near the middle of the landing ellipses, way below the local horizon, so it can't be. I also withdraw my own speculation from earlier in the thread, given the ground truth.
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fredk
post Oct 21 2016, 07:43 PM
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On top of that, with the landing site over 50 km from Oppy, the pancam pixel scale would mean that those two specks were about 2.4 km apart! (So I guess theoretically possible if taken just after the parachute/backshell separated.)
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fredk
post Oct 21 2016, 08:39 PM
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I see a couple of possibly interesting features on the after CTX image. Marked with the black ellipse is some faint dark streaking that roughly aligns with the main lander splat. And circled is a small dark spot. Both weren't in the before image:

Attached Image

It's easiest to see them by flipping between the before and after images. Even though the image is very noisy, both features appear to rise above the noise fluctuations but still could be extreme fluctuations or other artifacts.

Perhaps the streaks, being dark and so perhaps due to removed dust, are associated with the engine firing, and the dark spot the heat shield?
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tolis
post Oct 21 2016, 09:49 PM
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QUOTE (fredk @ Oct 21 2016, 09:39 PM) *
I see a couple of possibly interesting features on the after CTX image. Marked with the black ellipse is some faint dark streaking that roughly aligns with the main lander splat. And circled is a small dark spot. Both weren't in the before image:

Attached Image

It's easiest to see them by flipping between the before and after images. Even though the image is very noisy, both features appear to rise above the noise fluctuations but still could be extreme fluctuations or other artifacts.

Perhaps the streaks, being dark and so perhaps due to removed dust, are associated with the engine firing, and the dark spot the heat shield?


Indeed, I pointed those two out here

They appear to be downrange of the crash site. That's what you would expect for something that continues on ahead of the decelerating EDM.
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marsophile
post Oct 23 2016, 05:49 AM
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QUOTE (fredk @ Oct 19 2016, 04:32 PM) *
...the exposures are very short. I wouldn't expect the lander to be streaked,


If the retro-rockets were firing, wouldn't they show up as a streak even in a short exposure?
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James Sorenson
post Oct 23 2016, 06:35 PM
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When pancam auto-exposes images through each filter, it does so until it reaches a specified DN value. If I recall, that is about a DN of 3000. So Images taken with L2 or R2 would have a lower exposure time then say images taken with L6, L7 or R1. You can even see this in the raws as you approach the blue and UV end, the images start to get more noiser from CR hits and hot pixels since it takes more time to reach the specified DN. So I'd expect L6 images would be in the few second range and If schiaparelli went through the FOV (which is now extremely unlikely if not ruled out since we know where it landed), I would think it would leave a small streak. Images taken with R2 would be a fast exposure and would likely not show a streak at all.
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mcaplinger
post Oct 23 2016, 08:23 PM
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These images were likely not autoexposed, but you're ignoring the fact that these are frame transfer cameras and would show artifacts with anything moving in the scene, which would probably lead to some kind of streaking for fast-moving objects regardless of exposure time. That said, the team looked at these images and said they saw nothing but cosmic-ray hits, so I'd say leave it at that.


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Disclaimer: This post is based on public information only. Any opinions are my own.
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nogal
post Oct 23 2016, 08:26 PM
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A minuscule tribute to the ExoMars team. I have updated the kml file with the latest CTX images and also reviewed and extended the text of the several item's descriptions. Zoom in to see the "after" image. Enable (check) the "Hardware" to get small icons of Schiaparelli and its parachute.
Fernando
Attached File  Schiaparelli.kmz ( 408.86K ) Number of downloads: 63
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marsophile
post Oct 24 2016, 01:20 AM
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One way to rule out the streak in

http://qt.exploratorium.edu/mars/opportuni...ARP2857L6M1.JPG

as being from Schiaparelli is to examine the times involved. From the filename, the above image was taken at 530160694 seconds in the epoch beginning on January 1, 2000 at 11:58:55.816 UTC. Using a J2000 calculator and subtracting the 64.2 seconds until 12:00:00 would put the image acquisition at 2016-10-19 14:50:29.799 UTC. However, the loss of signal from the Schiaparelli lander reportedly occurred about a minute before the scheduled landing time of 14:48 GMT (= UTC). Thus, the lander would have already crashed before the image was taken, unless I have made some error in my calculation.
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mcaplinger
post Oct 24 2016, 03:32 AM
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The time in the file name is an SCLK value and drifts around in a way tabulated by the NAIF group http://naif.jpl.nasa.gov/pub/naif/MER/kernels/sclk/mer1.tsc . According to the quick Python program I just wrote (below) this time corresponds to 2016 OCT 19 14:51:27. But your conclusion is right. I'm not sure how the imaging times for the MER imaging were commanded but this seems late.

CODE
import math
import sys
from spice import *
furnsh("naif0001.tls")
furnsh("mer1.tsc")
t0 = scs2e(-253, sys.argv[1])
print "t0", t0, et2utc(t0, "c", 0), et2utc(t0, "isod", 0)


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Disclaimer: This post is based on public information only. Any opinions are my own.
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Deimos
post Oct 24 2016, 05:19 PM
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The images were taken with fixed exposure times to minimize a streak. The contrast was expected to be low, even in the unlikely event the lander came to a part of the sky where Opportunity had a line of sight. So, spreading the sub-pixel feature over lots of pixels would just further reduce it.

The few red images were to mitigate against model error or tau change--the contrast was predicted to go through 0 within the Pancam bandpass. But they were few due to bits and to image timing. Pancam is slow; slower still in the rover's current operational mode. Tests ahead of time struggled to demonstrate a way to go fast--generally, when the images have gone fast, subframes were used. So, after the first 5 images (4 L, 1 R), there was no chance. I was expecting ~6 L images, and was betting the descent would be a little later and farther downrange (not having a better option--imaging from inside the crater was like looking for your keys under the streetlight, even if you thought you might have dropped them off in the dark spot off to the left).
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tolis
post Oct 25 2016, 06:51 AM
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Reported in Anatoly Zak's website:

"By October 24, engineers narrowed down a possible culprit to an error in the software of the Schiaparelli's Doppler radar altimeter, which misled the main computer into thinking that the spacecraft had already reached the landing altitude."

That sounds like something you should catch during testing on the ground (Earth ground, that is)
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Decepticon
post Oct 25 2016, 08:40 AM
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ohmy.gif
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vikingmars
post Oct 25 2016, 09:57 AM
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QUOTE (tolis @ Oct 25 2016, 08:51 AM) *
Reported in Anatoly Zak's website:

"By October 24, engineers narrowed down a possible culprit to an error in the software of the Schiaparelli's Doppler radar altimeter, which misled the main computer into thinking that the spacecraft had already reached the landing altitude."

That sounds like something you should catch during testing on the ground (Earth ground, that is)

Maybe the radar caught the heatshield flying down in its line of sight...
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