Electric Comets

[viscount aero]

LOL! At roughly 17:00 "We have to keep reminding ourselves that isn't snow. We've cranked the gain on the images and that stuff is not white, it's black as coal."

And if it's "black as coal" then why is the first "true color" image looking like a piece of rusty brownish red Mars?

[bdw000]

LOL! At roughly 17:00 "We have to keep reminding ourselves that isn't snow. We've cranked the gain on the images and that stuff is not white, it's black as coal."

And if it's "black as coal" then why is the first "true color" image looking like a piece of rusty brownish red Mars?

Yeah, how believable is it that the ESA can't even tell what color their comet is? If they were using a black and white, or greyscale, or whatever, camera, then why on Earth would they say that "it's black as coal" when clearly it could be any color, just very dark?? I am no expert.

Article talking about the color image: I don't think the reddish comet in this article is the actual pick from the ESA, which is due to be released Dec 15.

http://www.dailymail.co.uk/sciencetech/article-2855874/Is-true-colour-image-Rosetta-s-comet-Stunning-shot-67P-suggests-RED-charcoal-black.html

[viscount aero]

LOL! At roughly 17:00 "We have to keep reminding ourselves that isn't snow. We've cranked the gain on the images and that stuff is not white, it's black as coal."

And if it's "black as coal" then why is the first "true color" image looking like a piece of rusty brownish red Mars?

Yeah, how believable is it that the ESA can't even tell what color their comet is? If they were using a black and white, or greyscale, or whatever, camera, then why on Earth would they say that "it's black as coal" when clearly it could be any color, just very dark?? I am no expert.

Article talking about the color image: I don't think the reddish comet in this article is the actual pick from the ESA, which is due to be released Dec 15.

http://www.dailymail.co.uk/sciencetech/article-2855874/Is-true-colour-image-Rosetta-s-comet-Stunning-shot-67P-suggests-RED-charcoal-black.html

They even said "blacker than charcoal" which implies the removal of all color. Now it's suddenly dusky red, even if very dark and near black. Of course initial impressions can be wrong. If all they were seeing, themselves, were black and white images then I can see how ESA confused themselves. From what I gather the albedo is very very low regardless of color.

[StefanR]

Hi Viscount aero,

By accident I posted something on the other forum about those "colour" images.
This reddish one seems to come from here:
https://agu.confex.com/agu/fm14/meetingapp.cgi#Paper/22395

The reddishness could possibly be due to tholins.

[viscount aero]

Hi Viscount aero,

By accident I posted something on the other forum about those "colour" images.
This reddish one seems to come from here:
https://agu.confex.com/agu/fm14/meetingapp.cgi#Paper/22395

The reddishness could possibly be due to tholins.

I'm gonna wait to see what other colors they begin to render into the comet's "true color"

[seasmith]

ESA finds FOURTH comet touchdown for Philae lander

http://www.theregister.co.uk/2014/12/01 ... ae_lander/

[Rossim]

ESA finds FOURTH comet touchdown for Philae lander

http://www.theregister.co.uk/2014/12/01 ... ae_lander/

From that article... wow!

"We think that Philae probably touched a surface with one leg only – perhaps grazing a crater rim – and after that the lander was tumbling. We did not see a simple rotation about the lander’s z-axis anymore, it was a much more complex motion with a strong signal in the magnetic field measurement.”

[madkevo]

no mention of the mystery cloud said to be the source of the video sensor saturation - giving the effect of an explosion ? The cloud that failed to obscure a single background star ?

Dusty comet, my my.

[Metryq]

Yeah, how believable is it that the ESA can't even tell what color their comet is?

I'm no expert on spacecraft cameras, but I know a little about the imagers used on Earth. Anyone who's done a little film photography knows about the different films for different lighting conditions. Some of the variations in color temperature have to do with artificial lighting, while others are due to atmospheric effects. Video cameras have electronic compensation known as "white balancing," in which (like film) a white or gray reference is presented.

I remember the first published photos from the Viking landers showed Mars with a pink sky. A later photo including some of the lander's white cowling (with an American flag decal) gave the imaging team the information they needed to color correct the photos. Mars is red, but not that red.

I know that older probes used black-and-white cameras, yet provided color images by taking a sequence shot through different color filters. This "color separation" is how color photos were once prepared for printing. It is also how older video cameras worked. Today's cameras might use three imagers (CCD, CMOS) built into a prism, or full color may be delivered by a single imager with the colored filters patterned over the face. However the data are gathered, reproducing the correct color is still a debated issue.

On top of all that, electronic imagers have a natural sensitivity to infrared, which must be filtered. Some photographers will have the IR filter removed from an older camera so that they can use it to experiment with infrared photography. (Do not confuse IR photography with thermography.)

At a guess, I would say B&W imagers are still preferred for higher resolution, although a three-sensor camera (as opposed to a single sensor) might cover that need. One might also think that there should be enough sensors of other sorts on board a space probe to establish what kinds of light are in the environment, but that still leads us back to the debates over color reproduction.

(Still, processing images to show what a scene would look like to human eyes may throw away vast amounts of data.)

[+EyeOn-W-ANeed2Know]

Yeah, how believable is it that the ESA can't even tell what color their comet is?

I'm no expert on spacecraft cameras, but I know a little about the imagers used on Earth. Anyone who's done a little film photography knows about the different films for different lighting conditions. Some of the variations in color temperature have to do with artificial lighting, while others are due to atmospheric effects. Video cameras have electronic compensation known as "white balancing," in which (like film) a white or gray reference is presented.

I remember the first published photos from the Viking landers showed Mars with a pink sky. A later photo including some of the lander's white cowling (with an American flag decal) gave the imaging team the information they needed to color correct the photos. Mars is red, but not that red.

I know that older probes used black-and-white cameras, yet provided color images by taking a sequence shot through different color filters. This "color separation" is how color photos were once prepared for printing. It is also how older video cameras worked. Today's cameras might use three imagers (CCD, CMOS) built into a prism, or full color may be delivered by a single imager with the colored filters patterned over the face. However the data are gathered, reproducing the correct color is still a debated issue.

On top of all that, electronic imagers have a natural sensitivity to infrared, which must be filtered. Some photographers will have the IR filter removed from an older camera so that they can use it to experiment with infrared photography. (Do not confuse IR photography with thermography.)

At a guess, I would say B&W imagers are still preferred for higher resolution, although a three-sensor camera (as opposed to a single sensor) might cover that need. One might also think that there should be enough sensors of other sorts on board a space probe to establish what kinds of light are in the environment, but that still leads us back to the debates over color reproduction.

(Still, processing images to show what a scene would look like to human eyes may throw away vast amounts of data.)

I don't claim to be an expert in imaging either, but I've been into photo/video for a long time too. LOL! I used a Baby Brownie camera until I couldn't get film for it anymore and the first video camera I used was a Sony B&W with a separate reel to reel recorder unit.
From what I read, ROLIS is a miniature CCD imager & incorporates four independent arrays of light emitting diodes (LEDs) irradiating through the visible and near IR.
Boosting the gain either on the camera itself or adjusting the brightness/contrast levels on the images just so they can get a viewable image is going to immensely distort any idea of "color accuracy".
I'm pretty sure these rocket scientists were smart enough that during testing they did a white sampling on some point on the lander.
Of course, with Philae's touchdown acrobatics there is a pretty good chance that the exterior of the unit picked up some of that superfine dust from 67P's surface, so that test patch might not be quite the same color brightness as it was in the prelaunch facility.

There is another point to consider.
If there is even a very weak plasma field occurring on the 67P surface, it's luminance will further "tint" the color balance.

[viscount aero]

Of course, with Philae's touchdown acrobatics there is a pretty good chance that the exterior of the unit picked up some of that superfine dust from 67P's surface, so that test patch might not be quite the same color brightness as it was in the prelaunch facility.

There is another point to consider.
If there is even a very weak plasma field occurring on the 67P surface, it's luminance will further "tint" the color balance.

I wasn't aware of that, a good point.

[seasmith]

Says Jordan, “Sparking is a process in which electrons, released from the soil grains by strong electric fields, race through the material so quickly that they vaporize little channels.” Repeated sparking with each large solar storm could gradually grow these channels large enough to fragment the grains, disintegrating the soil into smaller particles of distinct minerals, Jordan and colleagues hypothesize.

The study, published recently in the Journal of Geophysical
Research-Planets, proposes that high-energy particles from
uncommon, large solar storms penetrate the [moon]’s frigid,
polar regions and electrically charge the soil. The charging
may create sparking, or electrostatic breakdown, and this
“breakdown weathering” process has possibly changed the...

The above research was supported in part by NASA’s Solar System Exploration Research Virtual Institute (SSERVI).

For more information about the LRO and CRaTER, visit http://www.nasa.gov/lro and http://crater.sr.unh.edu.

http://www.ieap.uni-kiel.de/plasma/ag-piel/dlr/index_dlr_dateien/wellen.mpg

electro-physics

viewtopic.php?f=3&t=159

[Maustin]

ESA finds FOURTH comet touchdown for Philae lander

http://www.theregister.co.uk/2014/12/01 ... ae_lander/

[excerpt:]

"We think that Philae probably touched a surface with one leg only – perhaps grazing a crater rim – and after that the lander was tumbling. We did not see a simple rotation about the lander’s z-axis anymore, it was a much more complex motion with a strong signal in the magnetic field measurement.”

Ya, I don't understand this at all. The initial information told of a brief, hard bounce from which the lander stayed 'airborne' for almost two hours.
Based on the time delay (110 minutes) and calculations of local gravity strength, they estimated a bounce height of about 1000 meters.
There is no physical structure to hit at near apogee on this proposed trajectory (near apogee because the newly discovered 'contact' occurred at 45 minutes, which is near half of the elapsed time of the 'bounce'). They offer that the lander may have 'grazed a crater rim' without mentioning there are no 800 meter crater rims, spires, boulders, etc on the target area of the comet. This target area was chosen (at least in part) because it is relatively smooth! There is no crazy topography nearby.
So either: the bounce trajectory is correct and the lander was high above the comet surface when this second event occurred; or the calculations of local gravity strength are horrifically wrong and the interpretation of the lander's initial bounce impact are also misinterpreted.
How can they claim the lander 'hovered' near enough to the comet surface (presumably drifting laterally) to make an incidental contact with a crater rim, when all their math indicates a bounce height of 1000 meters?
There's a disconnect somewhere.

[StefanR]

Embers from a Rock Comet

Dec. 12, 2014: December has arrived, and for backyard sky watchers that means one thing: It is time for the annual Geminid meteor shower. Every year in early December, Earth passes through a stream of gravelly, dusty debris from "rock comet" 3200 Phaethon. This causes a meteor shower that sometimes lasts more than two weeks.
[..]
Everyone has heard of "comets"--icy visitors from the outer solar system that sprout long tails of gas and dust when they come close to the sun. But what is a rock comet?

A "rock comet" is a new kind of object being discussed by astronomers. It is, essentially, an asteroid that comes very close to the sun--so close that solar heating scorches dusty debris right off its rocky surface. Rock comets could thus grow comet-like tails that produce meteor showers on Earth.

The source of the Geminid meteor shower, 3200 Phaethon, looks a lot like an asteroid. Indeed, it comes from the asteroid belt and its colors resemble the colors of other asteroids in the rocky zone between Mars and Jupiter. Yet 3200 Phaethon has an unusual orbit that brings it deep inside the orbit of Mercury. When this happens, it brightens and sprouts a little tail in mimicry of a comet. A team of astronomers led by Dave Jewitt of UCLA have been monitoring 3200 Phaethon using NASA's twin STEREO probes. They think that intense solar heating blasts the asteroid's rocky surface, causing 3200 Phaethon to shed meteoroids like embers spitting off a log in a roaring campfire.

http://science.nasa.gov/science-news/science-at-nasa/2014/12dec_embers/

Well, I don't know about you, but that is just ... amazing. A rocky asteroid decides it had enough, takes the plunge, gets its rocky dust 'blown' off its rocky surface by scorching heat (!), and like the little rocky caterpillar that it was transforms in a tailed mimicry of an cometary butterfly, sprinkling fairy fireballs and magical meteors over Earth.
My hats of to the astronomers. ***stands up and gives a one-man-ovation***

ps. Its probably just the way this article is popularised, the paper about such things must be far more intricate...it must be.

[seasmith]

~
StefanR wrote:

...the paper about such things must be far more intricate...it must be.

Well, there you go again, poking fun at those nice men over at NASA.

Obviously you just don't understand all the careful research, the horrendous number-crunching and rigorous scientific reasoning it took to come up with the meticulously worded explanation that it: "sprouts a little tail in mimicry of a comet", because "solar heating scorches dusty debris right off" ...

Haven't you ever burnt your toast, and thrown it across the room ?