Steins: Closest Approach

Following up on my previous post with the best Narrow Angle Camera image of the asteroid Steins from ESA's Rosetta spacecraft, I have reprocessed the images taken by the Wide Angle Camera around closest approach.  While the apparent image size in the frames at closest approach isn't much bigger, the phase angle is higher, meaning that there are more shadows.   Higher contrast features are easier to positively identify even when they only take up a few pixels, since they are less likely to get lost in instrument noise.  What made this image harder to produce (despite only being able to decently align four frames) is that there is a serious change in viewing angle from image to image.  The images used are W20080905T183758428ID20F17, W20080905T183802520ID20F17, W20080905T183804306ID20F14 (used as a base to align the other frames), and W20080905T183805803ID20F15.   I am much more pleased with the result than the image in the previous post.   It seems to be reasonably sharp given the dataset available and large enough to be viewed comfortably.

The second version has been filtered to enhance the visibility of faint details.

Raw Data Courtesy ESA/OSIRIS Team/MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA
Processed images Copyright Ted Stryk

Steins from Rosetta's Narrow Angle Camera

As Rosetta approached the asteroid Steins in 2008, its Narrow Angle Camera (NAC) went into safe mode, costing it the highest resolution pictures.  As a result, the best images, taken near closest approach, were from the lower resolution Wide Angle Camera (WAC).  This image was produced from the last raw images taken before the NAC stopped taking pictures.  While not quite as good as the later WAC images, it shows Steins from a significantly different angle.  At some point, I plan to work with some of the best WAC frames.  However, since they were taken much closer to Steins, spacecraft motion has much more effect from frame to frame, meaning that stacking them will be much more difficult. 

 

Raw Data Courtesy ESA/OSIRIS Team/MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA
Processed image Copyright Ted Stryk

Mariner 7 far encounter imagery and the horrors of analog data...

As Mariners 6 and 7 approached Mars in 1969, they took a series of approach images for the purpose of creating a global map of the planet beyond the limited coverage they could obtain during the fleeting moments of the flyby.  During near encounter, limited portions of the digital data were returned, as well as analog data for the entire image.  The analog data was sent in its original form and also after being filtered to bring out fine details.  This allowed more images to be taken than could have been taken in an entirely digital format because, strange as it sounds today, there wasn't a tape recorder available that could hold more than three or four 7-bit digital images of about half a megapixel.  It did, unfortunately, also lead to serious degradation of the images.

For most of the far encounter (save a short bit at the end, which was all digital but with so much of the image missing as to render the frames extremely hard to use), the images were only sent in an unfiltered analogue format.  Thus, while similar in pixel size to many images taken by Hubble and by other approaching spacecraft, the images tend to be indistinct.   Worse, the crispness is very inconsistent.   Features of equal contrast within darker colored areas of mars are less distinct than in bright areas, and features near the terminator are less distinct than those in more brightly lit part of the disk.  Higher contrast features are sharper than lower contrast features.  Thus, while one can get a better result than this version from JPL's website (probably an original press-release image), it is next to impossible to get it to look like a modern image. 

In previous work with this set, I have focused on the digital color images (I need to rework this - I was focused on reconstructing the missing parts of the image and didn't make any attempt to do even relative calibration of the color) and on doing a cleanup of all the images from the approach.  Thomas Romer assembled my cleaned up images in to some neat movies that look like Nickelodeon movies from over a century ago (there is also some quality loss due to the use of the gif format) - you can view Mariner 6 and Mariner 7 by following the links.   I have made several attempts to make improvements on the images, but unlike my work with the near encounter images, I have had trouble developing techniques that meshed with the spongy oddities of the far-encounter analog-only images.   This version, done in 2007, was one of my most successful attempts, but it still looks off. 
Recently, after the images from ESA's Rosetta spacecraft's flyby of Mars in 2007 were released, I felt the need to take another crack at this dataset.  I also attempted to extrapolate from the color data Mariner 6 and 7 obtained for some areas of the planet to colorize the images.  I first worked on the famous image of Phobos (the dark blip near the top of the image) passing over Mars .   The result, while good considering the quality of the data, highlights a serious problem - high contrast features stand out - note how sharp Phobos itself is - while low contrast feature are lost, with the problem being inconsistent throughout the image.   There were also problems with the color overlay. 

In the final image, which in my view is the most aesthetically pleasing image to date, I stacked the images over various Mariner 7 images (from F76-F82).   Since there is significant rotation, the overlapping portions of the frame had to be reprojected to match.  Portions of images with near the limb or terminator were discarded except for portions of F78-F81, as foreshortening and differences in illumination would have been too damaging.  Color was reconstructed as faithfully as possible based on color images of similar regions (dark, light, polar, clouds, etc).   The result, while relatively good, still shows the limits of  the dataset, as some portions of the image are clearly sharper than others.  I may in time do a few more of these (they won't be as good, as this face was seen at the highest resolution by Mariner-7, and the image quality is somewhat better than Mariner 6). 

Processed Images Copyright Ted Stryk, Raw Data Courtesy NASA/JPL

Mars from Rosetta, 2007

Here is an image from ESA's Rosetta spacecraft, en route to a comet, as it flew by Mars in 2007.   The raw data finally hit the PDS this year, so I am posting this to celebrate.

 Processed Image Copyright Ted Stryk, Raw Data Courtesy OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA

Crescent Triton

I have posted some views from Voyager 2 of a crescent Triton before.  This is a version that is processed to appear as it might actually look if one were viewing it, instead of focusing on bringing out faint details.  

Additionally, here is an even higher phase crescent, taken with the wide angle camera (the above image is from the narrow angle camera).

Processed images Copyright Ted Stryk, Raw Data Courtesy NASA/JPL

A final post for 2011

The year 2011 has been a busy one for me, and I am resolving to make 2012 a more productive year in terms of image processing.   In the meantime, here is an improved version of the last Voyager 2 image of Ariel prior to near encounter in January 1986.

Processed image Copyright Ted Stryk, Raw Data Courtesy NASA/JPL