Author Topic: LIVE: Chang'e-3 lunar probe and rover Lunar Landing December 14, 2013  (Read 456411 times)

Offline Steven Pietrobon

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Here are some snapshots taken during the descent about 30 or 15 seconds apart.
Nice work.

Thanks.

Quote
Are you able to put into just one image a scale showing size of a crater or distance between two craters?

That's a bit difficult, but Laplace F is 6 km in diameter. You can download a nice map of the region from

http://www.lpi.usra.edu/resources/mapcatalog/LAC/lac24/
« Last Edit: 12/17/2013 08:04 AM by Steven Pietrobon »
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline Garrett

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Here are some snapshots taken during the descent about 30 or 15 seconds apart.
Nice work.
Are you able to put into just one image a scale showing size of a crater or distance between two craters?
Looking at Google Moon and using the Charts feature to identify the craters, the distance between the respective centers of Laplace A and Laplace FA in the first picture is about 24 miles (38 km).
- "Nothing shocks me. I'm a scientist." - Indiana Jones

Offline saturnapollo

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Yeah... that's all fine.. but what I'm asking is: on what basis do we claim that the image carries more scientific information if it's colour corrected to "look like it would on Earth"

Don't think we are talking about colour correcting the images to look like on Earth. If anything the colour correction might be needed if the cameras were calibrated for Earth but might need correcting once on the Moon. As I said previously all the Apollo Hasselblad imagery shows a predominately grey landscape and these were not colour corrected to look as if it were under an Earth sky.


However to answer your other question about why, NASA colour corrects the curiousity photos just that way so that scientists can make out geological information easier (see quote below).

"The image has been white-balanced to show what the rocks would look like if ther were on Earth."

Personally I wish they would release the proper Mars environment coloured images as I much prefer seeing what Mars actually looks like. They used to publish both, but I see they have stopped that and only releasing the colour corrected version (you can still access the original RAW but a lot of work to stitch them all together).

Keith

Offline ugordan

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Personally I wish they would release the proper Mars environment coloured images as I much prefer seeing what Mars actually looks like.

Have you ever, for example, taken a digital image of an outdoor scene under overcast skies while your camera white balance setting was left on normal daylight and noticed it looks nothing like what your eyes see?

There is no single "actually looks like", your eye does way more white balancing than you might realize. In a sense, both NASA versions are right in some way and both are also wrong. I suspect the actual appearance to a human eye would be somewhere in between the two versions. Closer to which one? I don't know.
« Last Edit: 12/17/2013 10:45 AM by ugordan »

Offline saturnapollo

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Have you ever, for example, taken a digital image of an outdoor scene under overcast skies while your camera white balance setting was left on normal daylight and noticed it looks nothing like what your eyes see?

Err, yes, I'm a photographer!  :)

Not talking about such extremes of white balance - which are caused by incorrect white balance settings.

Early morning tends to have blue light on earth and late evening light tends towards the red, which you are correct the camera will pick up and which the eyes /brain might not. However there is only so much correcting the eyes/brain do. The colour you see comes purely from reflected light from objects. If in the case of Mars everything is of a red hue then that is what the light coming into your eyes sees. Similar to some indoor yellow lighting as in sports halls. You can never get a properly white balanced photo as there is no blue in the output from the bulbs. All the light being output is at the sodium end of the spectrum. Try working in a photo studio under a red light (in the old days when film was used) and your eyes/brain certainly can't handle this. Mars lighting conditions, whilst no where near so dramatic is similar.

However NASA learned during the Viking missions that they were tending to process too much to the blue and as the Martian dust tends to give a red atmosphere rather than the Earth's blue, they had to re-correct the images so the sky was more salmon tinted. As NASA states they have deliberately changed the colouring of the latest images for scientific reasons. They admit this is not how Mars looks under its conditions. Look at the RAW images before alteration and you will see a very different colouring - albeit perhaps a bit too rich.

However we are getting way off topic here, so apologies for going off on a tangent.

Keith
« Last Edit: 12/17/2013 11:26 AM by saturnapollo »

Offline ugordan

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However there is only so much correcting the eyes/brain do.

Agree, that's why I said the most accurate representation would probably be somewhere between the two versions NASA produces. The eye would certainly pick up that the general tone of the scene was reddish, but if there are any gray rocks, they should look fairly gray to the eye. I don't think Mars color is as bad as an incandescent light, the vast majority of the light coming down is still unfiltered sunlight, I'm not sure if the diffuse skylight is as bright as on Earth.

Look at the RAW images before alteration and you will see a very different colouring - albeit perhaps a bit too rich.

AIUI, raw images from MSL Mastcam that are posted on the web are uncalibrated, they weren't corrected for things like optics transmission function and quantum efficiency so should not be considered a good reference. That's probably a reason why they tend to be more on the greenish side.

To get back to Chang'e, I'm not that surprised the moon turned out brown. Every time I worked with spacecraft color imagery of the Moon, if I white-balanced it to the solar spectrum in vacuum, I got a similar brown color, whereas things like ice would turn out white. Same for Mercury.
« Last Edit: 12/17/2013 11:45 AM by ugordan »

Offline JT355

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ok I been waiting for 3 days now, I have seen about 2 or 3 photos and a 6 minute landing movie put together from stills. Where is the direct video feed and they money shots of the Earth, etc. Things are too quiet now, let's spice it up a little. Otherwise people just going to get bored and forget the whole thing. Why isn't there a website with direct webcam from the rover  :P

Offline Blackstar

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Actually, the common descent stage was obvious from what the first concepts of the Chang'e 3 lander and Chang'e 5 sample-return mission were published.   What is missing from the above is the Earth return stage which remains in selenocentric orbit.

There is a very crude illustration of the entire stack that was presented in a paper. The stack is pretty big. plutonogo may be able to post it.

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Offline jumpjack

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Thanks to Steven Pietrobon and to this site http://target.lroc.asu.edu/q3/?mv=eqc&mcx=111055.01204&mcy=792434.77158&mz=16&ml=FTFB00TT# I was able to setup a Google Sketchup 3d model of Chang'e 3 landing site.

http://win98.altervista.org/change3-google-earth.zip


(Please don't embed huge images. Attach them please - Chris).
« Last Edit: 12/17/2013 02:46 PM by Chris Bergin »
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Offline saturnapollo

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To get back to Chang'e, I'm not that surprised the moon turned out brown. Every time I worked with spacecraft color imagery of the Moon, if I white-balanced it to the solar spectrum in vacuum, I got a similar brown color, whereas things like ice would turn out white. Same for Mercury.

To be honest not quite sure how you arrived at that as it doesn't gel with Apollo Hasselblad images.

I've tried to colour correct what I think is closer - and I must stress - purely my interpretation of the photos. You will see from the lander photo, that space is a lot blacker instead of a murky brown.

Keith




Offline ugordan

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To get back to Chang'e, I'm not that surprised the moon turned out brown. Every time I worked with spacecraft color imagery of the Moon, if I white-balanced it to the solar spectrum in vacuum, I got a similar brown color, whereas things like ice would turn out white. Same for Mercury.

To be honest not quite sure how you arrived at that as it doesn't gel with Apollo Hasselblad images.

It's just the way it is when using calibrated reflectance (I/F) data. The Moon invariably appears more reflective in the red end of the spectrum than in the blue end. If it was equally reflective, a RGB composite of such I/F data would end up perfectly grey (and it does do so for some Saturnian icy moons). I know this is at odds with how the moon appears to our eyes on the ground, but that's the end result when you put in a "hard" limit on the white balance, in this case completely dividing out the Sun's visible spectrum and don't do any other tweaks like a human eye probably would. I suspect Chang'e 3 cameras are operating in this mode. Hence why I said I wasn't very surprised at the outcome.

Here's one example of what the Moon looked like to the Deep Impact spacecraft while transiting Earth's disc: http://farm7.staticflickr.com/6143/5927214387_6f0e61e39f_o.gif

Images of the Moon taken from ISS also often show such a pale brown color, although I don't know the specific camera white balance settings used. I can't speak for Apollo Hasselblad photography other than it looks spectacular.

Offline plutogno

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There is a very crude illustration of the entire stack that was presented in a paper. The stack is pretty big. plutonogo may be able to post it.

I think you are referring to the one posted here
http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=33431.0;attach=562163;image
« Last Edit: 12/17/2013 04:22 PM by plutogno »

Offline jumpjack

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Calibrating true colors should be much easier on the Moon rather than on Mars: on Mars the red sky prevents from proper calibration, but on the Moon there is just a perfect-dark sky, and during Earth-night there's a minimal light contribution from Earth itself.
So it's just a matter of taking a snapshot of a white surface during Earth night, and you're done.
« Last Edit: 12/17/2013 04:58 PM by jumpjack »
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Offline jumpjack

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U
Thanks to Steven Pietrobon and to this site http://target.lroc.asu.edu/q3/?mv=eqc&mcx=111055.01204&mcy=792434.77158&mz=16&ml=FTFB00TT# I was able to setup a Google Sketchup 3d model of Chang'e 3 landing site.

http://win98.altervista.org/change3-google-earth.zip


(Please don't embed huge images. Attach them please - Chris).
Updated verison of just KMZ file (some images were slightly misaligned):
http://win98.altervista.org/Chang_e_3_landing_site-2.kmz
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Offline jumpjack

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Damn, the landing footage watched while listening Strauss's Danubio Blu is just amazing! :-)
Is anybody able to upload a short version of the video which includes this song? You've just to make moment 04:30 of the song match with the touch down and you're done! :-)
« Last Edit: 12/17/2013 05:24 PM by jumpjack »
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Offline Nick

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To get back to Chang'e, I'm not that surprised the moon turned out brown. Every time I worked with spacecraft color imagery of the Moon, if I white-balanced it to the solar spectrum in vacuum, I got a similar brown color, whereas things like ice would turn out white. Same for Mercury.

I don't understand what's going on there. I have always read that, in bulk, the Moon is a very dark grey - similar to a tarmac road surface. More technically, I am sure that I have read that the Moon's spectral curve is extremely similar to the Sun's - which is, of course, saying the same thing, and which wouldn't be possible if it had a bulk brown colour. (So much so, that I think Hubble has imaged the Moon as a calibration target for other planetary bodies, because it can't image the Sun. Somebody here probably knows that, one way or the other...)

That's not to say that individual areas of the Moon don't differ slightly from grey - I have seen highly Photoshopped amateur images that bring out colour differences ranging from blue to brown. but those were highly processed with the specific intention of bringing out slight colour differences.

On a personal, anecdotal, level, a few years ago I photographed the Taj Mahal by the light of a full Moon. When I got back home and loaded the images up into Lightroom, I found that simply "overexposing" the images produced an excellent rendering of the scene as it appeared the following day in daylight... (Camera on daylight balance in both cases.) I wished I hadn't done it, because it rather shattered the magic of the scene...  :(

Nick

Online Phil Stooke

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Look up at the full moon tonight - is it brown? 

Color is too complicated to trust any rendition of it.  I just set image mode to Grayscale when I want it to look right.

Offline woods170

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http://v.youku.com/v_show/id_XNjQ4OTUzMjY0.html

From 9ifly
http://bbs.9ifly.cn/thread-12967-1-1.html

Sorry, newbie here, don't know how to post a vid.  :-[

No problem. The links are fine. And welcome to the forum. :)

Offline AJA

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Here's one example of what the Moon looked like to the Deep Impact spacecraft while transiting Earth's disc: http://farm7.staticflickr.com/6143/5927214387_6f0e61e39f_o.gif

Wow.. you can really make out the highlands on the far side of the moon. There's a bright part in the centre of the lunar disc (when it's near/past the terminator on the Earth) interrupting what should've been a smooth continuation of the lunar terminator..

Split the gif into individual frames (I used ezgif.com/split) to illustrate that..
« Last Edit: 12/17/2013 07:27 PM by AJA »

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