NASA's Juno spacecraft sends back its first images of Jupiter moon Ganymede

Shawn Knight

Posts: 13,181   +132
Staff member
In brief: NASA has shared the first two images captured by its Juno Spacecraft earlier this week as it zipped by Jupiter’s largest moon, Ganymede. The flyby happened on June 7 and is the closest a spacecraft has come to Jupiter’s icy moon in more than two decades.

Juno Principal Investigator Scott Bolton of the Southwest Research Institute in San Antonio said they are going to take their time before drawing any scientific conclusions from the images, but for now, “we can simply marvel at this celestial wonder.”

The images – one from the orbiter’s JunoCam imager and the other from its Stellar Reference Unit star camera – highlight craters, dark and light spots on the terrain and what NASA believes could be structural features linked to tectonic faults.

The JunoCam managed to capture almost an entire side of the moon using its green filter. Later, once versions of the same photo are beamed back using the red and blue filters, NASA will be able to provide a color portrait of the moon.

NASA's Juno space probe left Cape Canaveral on August 5, 2011, and entered a polar orbit of Jupiter on July 5, 2016. Earlier this year, NASA extended the probe's mission span to September 2025. Once its work is done, it will be sent into Jupiter's atmosphere for disintegration.

More images are expected in the coming days and will be available on NASA’s website.

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captaincranky

Posts: 16,803   +5,577
It's colour in English, color in American.
Yeah,he Brits pepper those "or" endings with a "U", across the board.

I've often pondered whether.the British are being pretentious, while the Americans are either lazy, practical, or simply rebelling the way we're so prone to do..
 

bviktor

Posts: 407   +724
Yeah,he Brits pepper those "or" endings with a "U", across the board.

I've often pondered whether.the British are being pretentious, while the Americans are either lazy, practical, or simply rebelling the way we're so prone to do..
Well the Brits had the English language first (you know, it's called England for a reason), that pretty much rules out the first option lol.
 

captaincranky

Posts: 16,803   +5,577
Gosh, they spent a tremendous amount of money, and expended a massive amount effort, in trying to find our moon's missing twin sister.
 

captaincranky

Posts: 16,803   +5,577
There is no colour in space, it's all black and white. You've been spoiled by false colour images from NASA
Do you have any idea what you're saying?

Here's a clue,
Mars is the fourth planet from the sun. Befitting the Red Planet's bloody color, the Romans named it after their god of war. In truth, the Romans copied the ancient Greeks, who also named the planet after their god of war, Ares.

Now, to the best of my knowledge NASA wasn't sending back "false color images", to either the Greeks or the Romans.

Light has no color until it is either reflected, transmitted through, or emitted by, something.

"False color" has been used for decades in infrared color films. The colors shown depend upon the color of the filter placed in front the of the lens.

Here's one of many samples:

AislinnChuahiock_2_web_large.jpg
 
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wiyosaya

Posts: 5,943   +4,205
There is no colour in space, it's all black and white. You've been spoiled by false colour images from NASA
If you count the fact that human eyes are not sensitive enough to see colour (I hope those not from the US are happy with my spelling) even with relatively large amateur telescopes, you are correct.
However, there are "true color" images that exist. For an amateur, to take an astrophoto that ends up being true colour is not an easy task. I would imagine that for NASA and other similar institutions, it is easier, but it is still complicated.
Here is an interesting article, assuming you are interested, of course, about colour in space https://www.bellaonline.com/articles/art300516.asp There's a link in the article to two versions of the Butterfly Nebula. One, an amateur astrophotographer went through the painstaking gyrations of making a "true color" image, I.e., matching wavelengths in the data to what our eyes would see and the other was apparently a Hubble image using what is known to astrophotographers as the "Hubble Palette" which makes certain wavelengths stand out. Here's the link - https://www.pinterest.com/pin/250090585533702218/ The amateur's image is not as striking as the Hubble image, but it is probably as close to True Colour as is possible given the resources used in producing the image.
 

captaincranky

Posts: 16,803   +5,577
If you count the fact that human eyes are not sensitive enough to see colour (I hope those not from the US are happy with my spelling) even with relatively large amateur telescopes, you are correct.
Well first, I sometimes throw in that "U" in "behaviour", where it seems to be appropriate. I also throw in a "U" now and again when I'm posting with residents in the ANZAC nations, and those in Great Britain, out of respect for their customs. (Not quite sure if they take it that way, but that's my intent)

Second, if you have to shift the wave length of light to enable humans to see it, that, by any definition is, "false color".

That said, the idea that "there's no color in space", is completely insane.

Light doesn't become "light", (as we perceive it), until it is reflected by, transmitted through, or emitted by an object..

Our moon appears, "black and white", because it is composed of gray rock, with an albedo of 3 to 12%. An photographic exposure calculation "gray card", is by comparison, approximately. 18% reflectance.

BTW, I don't believe I couldn't coax a "like" out of you for this post:
https://www.techspot.com/community/...ly-change-their-ad-policy.269575/post-1893382

Oh well, I suppose we don't want to encourage me, now do we?
 
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wiyosaya

Posts: 5,943   +4,205
Well first, I sometimes throw in that "U" in "behaviour", where it seems to be appropriate. I also throw in a "U" now and again when I'm posting with residents in the ANZAC nations, and those in Great Britain, out of respect for their customs. (Not quite sure if they take it that way, but that's my intent)

Second, if you have to shift the wave length of light to enable humans to see it, that, by any definition is, "false color".
Yup. That's the purpose of the "Hubble Palette". For instance, in the link to the pictures I posted, the Hubble image has UV wavelengths shifted to the visible AFAIK.
While the image taken by the amateur sounds like the astrophotographer intended to represent the true visible wavelengths that were in the recorded data.

That said, the idea that "there's no color in space", is completely insane.
Well, you do have to go to great lengths to see the color that is there for certain things like nebulae and galaxies, or similar objects - mainly because the flux density is not high enough for the human eye to be able to detect the colours.

So, my point was, if you are visually looking through a telescope that is not a big scope the intensity of the existing colour is, in many cases, not sufficient for the human eye to detect it - so you see no colour and not, of course, that colour is not there. :rolleyes:

Light doesn't become "light", (as we perceive it), until it is reflected by, transmitted through, or emitted by an object..

Our moon appears, "black and white", because it is composed of gray rock, with an albedo of 3 to 12%. An photographic exposure calculation "gray card", is by comparison, approximately. 18% reflectance.
In the article that I linked is this:
The colors of diffuse nebulae
Diffuse nebulae are extended clouds without evident boundaries or structure. There are two types: reflection and emission. You can tell them apart in visible light by their color, and the color is the key to how they're illuminated.
And BTW - emission nebulae are probably red in colour because of the "Hydrogen Alpha" emission line - you know, in the range of colours that are difficult to photograph with a standard DSLR because of the built-in IR filters that most DSLRs contain. Reflection nebulae are probably blue since they reflect light from nearby stars, assuming the star is blue.

As the informed know, though, many stars themselves are bright enough so that we can see what colour they are. Take, for example, Betelgeuse https://en.wikipedia.org/wiki/Betelgeuse (Don't say that three times ;)) And, of course, your Mars example - for planets, that is.
BTW, I don't believe I couldn't coax a "like" out of you for this post:
https://www.techspot.com/community/...ly-change-their-ad-policy.269575/post-1893382

Oh well, I suppose we don't want to encourage me, now do we?
I don't think you really need encouragement, captain, :laughing: however, I did like your post.
 
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captaincranky

Posts: 16,803   +5,577
"Color is the spelling used in the United States. Colour is used in other English-speaking countries." - I.e. the rest of the world.
This has been covered thoroughly by myself and others, both humorously and with more gravity.

Do you have anything pertinent to the topic to add?
 

captaincranky

Posts: 16,803   +5,577
Why do these pictures have to be taken in black and white? Why are we still using this tech?
Nobody has answered this question directly. I'm going to undertake trying to do that.

The process they're using is called, "color separation". This splits the data stream into three separate files, or "channels", using colored filters, one for each primary colour. (red green, and blue.)

Obviously the transmitted data is more manageable in three small files, as opposed to one huge file.

By reversing the process and recombining these files, (exposing the image through the same set of filters), you will get the actual colour rendition of the original scene at the image sensor..

Here is an explanation of the "Harris shutter". Color separation has been used to artistic effect for decades: It also is mandatory for color printing, but there the inks used are secondary colors, "CMYK". (Cyan, Magenta, Yellow,, and "base" or black)


There is a wealth of information on color separation on the web if you're interested. I wasn't about to blow up a dozen or so links pertaining to the process.
 
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