Where are the color images from Cassini?

[rindain]

Hey everyone,<br /><br />I was wondering why NASA has released so few color images from Cassini. For a $3 billion mission, it can't be a cost issue. Also, I would think that the scientists in charge of the mission would also want to get an idea of what the human eye would see.<br /><br />Does anyone know where I can find color images from Cassini of Saturn and its satellites? <br /><br />Thanks for your help---here's to some great (hopefully color) pictures of Titan on October 26.<br /><br />~Mike

 

[CalliArcale]

Cassini is the first outer solar system mission where the raw data is being made available to the public via the World Wide Web. To get the raw data, go to the mission website at saturn.jpl.nasa.gov and follow the links. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[CalliArcale]

Oh, I just remembered something significant. The raw data is actually in black-and-white. To get a color picture, you need to download three images shot at about the same time through three different filters, process them digitally with some kind of image editing software, and combine them. This is actually how all color pictures from spacecraft are obtained. Since the filters aren't exactly the same frequencies as those to which the cones in the human eye are most sensitive, some massaging is neccesary to get a picture approximating what you'd see with the naked eye. (Indeed, many of the Cassini pictures incorporate colors which we cannot see with our eyes.) As a consequence, you might come out with pictures slightly different than those which NASA releases. It's partly a question of what you're trying to get out of the picture (speed, an approximation of what a human eye would see, or emphasis of certain frequencies for scientific purposes) and partly a question of asthetics. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[Swampcat]

<font color="yellow">"Does anyone know where I can find color images from Cassini of Saturn and its satellites?"</font><br /><br />There are a few color images available on the JPL website here and at the Ciclops Cassini Imaging team website here.<br /><br />Making your own color images is possible, but it does require some effort. Simply combining the raw images into a composite will not produce natural color. In addition, both the spacecraft and the body being imaged are in constant motion so in many cases some adjustments are necessary to align the images.<br /><br />The image below is my effort at producing a natural color image of Saturn's moon Titan. The raw images used in this color composite were taken on October 6 at an approximate distance from Titan of 5.4 million kilometers. <div class="Discussion_UserSignature"> <font size="3" color="#ff9900"><p><font size="1" color="#993300"><strong><em>------------------------------------------------------------------- </em></strong></font></p><p><font size="1" color="#993300"><strong><em>"I hold it that a little rebellion now and then is a good thing, and as necessary in the political world as storms in the physical. Unsuccessful rebellions, indeed, generally establish the encroachments on the rights of the people which have produced them. An observation of this truth should render honest republican governors so mild in their punishment of rebellions as not to discourage them too much. It is a medicine necessary for the sound health of government."</em></strong></font></p><p><font size="1" color="#993300"><strong>Thomas Jefferson</strong></font></p></font> </div>

 

[rybanis]

That sir, is awesome. <div class="Discussion_UserSignature"> </div>

 

[rindain]

That's a great image swampcat.<br /><br />Does anyone know why spacecraft imaging systems need to take three consecutive separate, filtered images to produce a color image? From what I know, personal digital cameras record light through all three filters (R,G,B) simultaneously.<br /><br />Also, has NASA released any color photos of Phoebe?

 

[Swampcat]

Thanks, for the kind comments, but I must admit to a little embarrassment...I posted the wrong image. I had another one with a little more processing that I intended to post. Here it is...<br /><br />BTW, I fixed the links if anybody noticed. Uplink has a habit of borking my html code. <img src="/images/icons/crazy.gif" /> <div class="Discussion_UserSignature"> <font size="3" color="#ff9900"><p><font size="1" color="#993300"><strong><em>------------------------------------------------------------------- </em></strong></font></p><p><font size="1" color="#993300"><strong><em>"I hold it that a little rebellion now and then is a good thing, and as necessary in the political world as storms in the physical. Unsuccessful rebellions, indeed, generally establish the encroachments on the rights of the people which have produced them. An observation of this truth should render honest republican governors so mild in their punishment of rebellions as not to discourage them too much. It is a medicine necessary for the sound health of government."</em></strong></font></p><p><font size="1" color="#993300"><strong>Thomas Jefferson</strong></font></p></font> </div>

 

[najab]

<blockquote><font class="small">In reply to:</font><hr /><p>Does anyone know why spacecraft imaging systems need to take three consecutive separate, filtered images to produce a color image? From what I know, personal digital cameras record light through all three filters (R,G,B) simultaneously.<p><hr /></p></p></blockquote>It's a matter of maths. You have a finite number of cells in your CCD array, each of which records the <i>intensity</i> of the light hitting it, not the colour. In order to get colour information you have to filter the light before it impinges the array. So you have the choice of using the full resolution of the array - making three separate images to get colour by putting a single filter in front of the detector at a time - or cutting the resolution of the image by 2/3 and making a single colour image in one go - by binding the filters directly to the CCD array.<p>In other words, it's the choice between three 3000x1000 monochromatic images or a single 1000x1000 colour image.</p>

 

[rindain]

Swampcat, how did you make those?

 

[Swampcat]

<font color="yellow">"Swampcat, how did you make those?"</font><br /><br />The short answer...download the <font color="red">red</font>/a>, <a href="http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS04/N00020887.jpg" target="new"><font color="#00c000">green</font> and <font color="blue">blue</font>/a> filter raw images from the JPL <a href="http://saturn.jpl.nasa.gov/multimedia/images/raw/index.cfm" target="new">Cassini Raw Images website and, using Jasc Paint Shop Pro (I wouldn't recommend downloading this unless you have broadband), change the raw images to greyscale, and combine channels to create the composite. Then adjust the color balance to match a known reference, in this case a previously downloaded image of Titan from JPL. The Histogram Window is useful with color balancing.<br /><br />The long answer depends on what graphics software you have and on how good the alignment of the image target is in the three raw images. <br /><br />If you are using Photoshop, try the following links:<br /> The Caves of Mars<br /> ATSNN article on Mars Imaging.<br /><br />There are more websites out there that explain the process using Photoshop, but since I don't use it I haven't saved those links.<br /><br />If you will post which graphics software you have I'm sure you will get responses here on how to proceed.</a></a> <div class="Discussion_UserSignature"> <font size="3" color="#ff9900"><p><font size="1" color="#993300"><strong><em>------------------------------------------------------------------- </em></strong></font></p><p><font size="1" color="#993300"><strong><em>"I hold it that a little rebellion now and then is a good thing, and as necessary in the political world as storms in the physical. Unsuccessful rebellions, indeed, generally establish the encroachments on the rights of the people which have produced them. An observation of this truth should render honest republican governors so mild in their punishment of rebellions as not to discourage them too much. It is a medicine necessary for the sound health of government."</em></strong></font></p><p><font size="1" color="#993300"><strong>Thomas Jefferson</strong></font></p></font> </div>

 

[spacechump]

If you don't have a fancy photoshop program (or other costly alternative) use GIMP!<br /><br />http://www.gimp.org/windows/<br /><br />Its free and almost identical in features compared to PS.