MER-B Dimes images

"mlm" wrote in message
...
In 1 of the 3 DIMES images taken by Opportunity on its approach to the
surface (at 1404m), there is a brightly ringed crater and a distinct,
slightly diffuse dark circular shadow about half a crater width to its
left. Is this the shadow of the spacecraft? I had thought the sunlight
incidence angle was lower since it is supposed to be around 2PM local time
at Meridiani. This seems to be directly below the spacecraft as it
descends. So maybe it is something else.


What do you make of the 2 bright parallel lines inside the crater? A 30
meter tall martian's sun-bed?

Keith

R Neutron wrote:

mlm wrote in message ...
In 1 of the 3 DIMES images taken by Opportunity on its approach to the
surface (at 1404m), there is a brightly ringed crater and a distinct,
slightly diffuse dark circular shadow about half a crater width to its
left. Is this the shadow of the spacecraft? I had thought the sunlight
incidence angle was lower since it is supposed to be around 2PM local time
at Meridiani. This seems to be directly below the spacecraft as it
descends. So maybe it is something else.

The 3 DIMES images are at:

http://marsrovers.jpl.nasa.gov/galle...20040125b/MER-
B_DIMES_1404m-B22R3.jpg

http://marsrovers.jpl.nasa.gov/galle...20040125b/MER-
B_DIMES_1690m-B22R3.jpg

http://marsrovers.jpl.nasa.gov/galle...20040125b/MER-
B_DIMES_1986m-B22R3.jpg

Mark
I think it is. Interestingly on the first of 3 DIMES in the lower
right quadrant you can see a black dot/line. This looks suspiciously
like the heatshield as seen on DIMES image from Spirit. Oh hell why
not speculate even more. My bet is that it the lander is in one of
the two craters down to the lower left of the larger crater that are
side by next vertically in the image. There's not a lot more that I
would call candidates. By the way I also think you can see a dimmer
version of the shadow in the second DIMES image. RN

If you make the simplifying assumption that the craft is falling on
some straight path, shouldn't the movement of the shadow be along a
line that intersects with the landing position? If so, you can draw a
line between the faint shadow on the 1690m frame through the 1404
frame and see what small craters that line passes through. I see only
one candidate within a reasonable distance. Of course, this geometry
does not take bounce and roll into account.
--
John Popelish

"Keith Edkins" wrote in message
...

"mlm" wrote in message
...
In 1 of the 3 DIMES images taken by Opportunity on its approach to the
surface (at 1404m), there is a brightly ringed crater and a distinct,
slightly diffuse dark circular shadow about half a crater width to its
left. Is this the shadow of the spacecraft? I had thought the sunlight
incidence angle was lower since it is supposed to be around 2PM local
time
at Meridiani. This seems to be directly below the spacecraft as it
descends. So maybe it is something else.


What do you make of the 2 bright parallel lines inside the crater? A 30
meter tall martian's sun-bed?

Keith

Most likely sand dunes.

When these three Dimes images were first shown on the JPL press
conference, Sunday or Monday, it was clearly stated from the rostrum
that the dark dot surrounded by a bright halo, direct opposite to the
sun on the ground, WAS indeed the parachute!
So, definitely no doubt about that.

Regards,
Bjørn Sørheim

(Gordon D. Pusch) wrote:

Highly unlikely, since this photo is almost certainly being taken from a
quite high altitude, and your alleged "shadow" is a substantial fraction
of the large crater's diameter --- whereas even the lander's parachute
is quite small compared to the diameter of a typical aregraphical feature !!!

Downloading the image and tweaking the image's intensity curve using the
image editing tool 'xv' clearly brings out an ejecta blanket surrounding
your dark spot, and gradations in intensity within said spot, that strongly
suggest to me that your "shadow" is merely a deep, relatively "fresh" crater,
and that the limited contrast range of a typical color monitor simply can't
easily display the full dynamic contrast range in this image.

Once this image has been processed a bit to "dodge out" the "over-exposed"
crater rim and "burn in" the darker regions away from the main crater
and within the dark, deep crater you've noticed, this picture will become
MUCH more photogenic, and the nature of its various features quite obvious.


-- Gordon D. Pusch

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When these three Dimes images were first shown on the JPL press
conference, Monday was it?, it was clearly stated from the rostrum
that the dark dot surrounded by a bright halo, direct opposite to the
Sun on the ground - WAS indeed the parachute!
So, definitely no doubt about that...

Regards,
Bjørn Sørheim

(Gordon D. Pusch) wrote:

Highly unlikely, since this photo is almost certainly being taken from a
quite high altitude, and your alleged "shadow" is a substantial fraction
of the large crater's diameter --- whereas even the lander's parachute
is quite small compared to the diameter of a typical aregraphical feature !!!

Downloading the image and tweaking the image's intensity curve using the
image editing tool 'xv' clearly brings out an ejecta blanket surrounding
your dark spot, and gradations in intensity within said spot, that strongly
suggest to me that your "shadow" is merely a deep, relatively "fresh" crater,
and that the limited contrast range of a typical color monitor simply can't
easily display the full dynamic contrast range in this image.

Once this image has been processed a bit to "dodge out" the "over-exposed"
crater rim and "burn in" the darker regions away from the main crater
and within the dark, deep crater you've noticed, this picture will become
MUCH more photogenic, and the nature of its various features quite obvious.


-- Gordon D. Pusch

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wrote in :

mlm wrote:

In 1 of the 3 DIMES images taken by Opportunity on its approach to the
surface (at 1404m), there is a brightly ringed crater and a distinct,
snip
Can you, or anyone, explain the bright ring? It does not seem to cross
from the inside to the outside at the 2 points where the solar rays
would be tangent to the ridgeline. It looks as if it is lit from the
outside all the way around.

Mitchell Timin

Mitchell, that is a very good question. You rarely see such a bright
ring around a crater becuase the sun is either left or right of the nadir
at the time the photo is taken. The incidence angle must be quite high
(hence the shadow of the parachute) but I thought MGS was in a 2PM polar
orbit so the sun should be slightly to the left of nadir. It seems there
is something reflective in the ring around the crater. Perhaps it could
be explained if MGS had to roll to take the image while it was close to
local noon over the crater.

The "sunbed" in the middle of the large crater looks mighty comfy.
Probably a long way down so the rover (I hate calling it Opportunity,
sorry it's just a silly name IMO) will have to behave like a Grand Canyon
burro to get down to see it up close. I'd bet there is a Martian or two
down there catching some uv and living off the fat o' the land.

Mark

wrote in message ...
mlm wrote:

In 1 of the 3 DIMES images taken by Opportunity on its approach to the
surface (at 1404m), there is a brightly ringed crater and a distinct,
snip
Can you, or anyone, explain the bright ring? It does not seem to cross
from the inside to the outside at the 2 points where the solar rays
would be tangent to the ridgeline. It looks as if it is lit from the
outside all the way around.

Mitchell Timin

Again one might look Spirits data as to compare to Oppurtunity images.
The heat sheild (in the Malin JPL image release) is shown as a disc
falling... the DIMES from the seconded lander shows a image that looks
to be "edge on" and certianly to big for an artifact. An estimate
would be be +- 5 pixels.