Wednesday, July 30, 2014

Another crescent view of Triton

Two years ago, I posted these views of Triton.  They represent two of the best global color views.  The bottom one is one of the first image sets taken (but with the wide angle camera), and shows an extremely slender crescent.  The upper image shows the first (and best) global color set taken with the narrow angle camera.  The image I am posting here was taken about three hours later.  This was the last view of Triton taken on encounter day and shows it from a slightly different angle...essentially Triton's last closeup from Voyager. 

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

Tuesday, July 22, 2014

A Voyager 2 View of Europa

As Voyager 2 approached Europa, this was the highest resolution global view it obtained before Europa filled more than the entire frame.  Europa was still quite small in the field of view at this point (the time in between this and the global mosaics it would later take was spent studying other targets), and, given the intricate, low contrast nature of its surface, this made this dataset very hard to work with.  It was taken on July 8, 1979, from a range of about 1.2 million kilometers. 

Raw data courtesy NASA/JPL, Processed images Copyright Ted Stryk

Sunday, July 20, 2014

Standing on Venus in 1975

Getting the thrill of seeing what it would be like to stand on another planet is one of the big thrills of planetary exploration.  This year, we have gotten to stand on the Moon thanks to Chang'e 3 and the short trek of the Yutu rover.  We have also gotten to ride along and tour Mars with Curiosity and Opportunity.  Later this year, the Philae lander will allow us to stand on a comet. 

This August, it will be 44 years since the first probe to send data from the surface of another planet (ignoring atmospheric probes and failed landers - key word is "surface") plunked down on the surface of Venus. Venera 7 did not function well after landing, sending back only temperature and pressure data. It was followed in 1972 by Mars 3, which briefly sent a signal from the surface of Mars before failing, and Venera 8, a highly successful Venus lander but one that did not carry a camera. Veneras 7 and 8 informed us, but they didn't allow us the feeling of being there.

In 1975, Veneras 9 and 10 became the first landers to image the surface of another planet, scanning 180-degree panoramas during the ~ hour that each lander functioned on the surface.  Stacking available data, this is what Venera 9 saw when, on October 22 1975, it landed (I've posted this previously, but am posting it again for context).

On October 25, Venera 10 followed.

The cameras scanned the scene one pixel at a time.  Given the rate at which the image could be taken and transmitted and the available amount of time, the images had to be of low resolution, even for the time. Given these limits, there were several options.  One would have been to image a very narrow area at high resolution from the lander base to the horizon, but that would have been hard to interpret.  Scanning from surface to horizon over a large area would have been so coarse that again, it would have had limited value.  The compromise worked out was that the camera would scan in a U-shape, meaning that the tips of the panorama would look at the horizon, while the middle would look down ant the base of the lander.

For science, this worked well. Visually, however, they are unnatural.  Of course these panoramas can be rectified to show the surface at a more natural angle.  Still, this leaves the center, the focal area of the images, as a gaping hole, and is thus visually unsatisfying. In the past, I tried to make views out out of corrected corners of the images, but these proved too small to do much with and were still very awkward.  After seeing Don Mitchell's excellent work on Venera 13 and 14 data, I got the idea of creating an image for both landers created by sampling each image at different distances from the lander to create a "proper" picture.  The objects in the image would be real, though the arrangement would not.  However, given that the original images are only 128x512 pixels (and not all of that shows the surface), making this convincing was very difficult (Venera 13 and 14 took panoramas on both sides of the lander and at much higher resolution, allowing much more image data to sample).  The first attempt was a failure.

I recently tried again.  This time, I accepted the fact that, in the case of Venera 9, I would have to use somewhat distorted versions of the same rocks at times to make a sufficiently big image.  I still don't love the result, but given the limited data and the complexity of the landscape, it is the best I've been able to do. The fact that the illumination is clearly different on the left-hand side and the right hand side of the panorama exacerbates the problems.  Still, it makes for a neat view. 

And here is the same view with Venera 13-based color.  

 Venera 10 is much more pleasing.  The flatter surface made illumination less of an issue.  It was also easier to resample areas without being obvious.  

And here, again, is the same view with Venera 13-based color. 

 Clearly, these are in no way scientific products.  But they do, I think, allow us to get a bit of the true feel of what it is like to stand on these two very different locations on the surface of Venus.  And as our nearly 39-year old first views from the surface of another planet, they deserve that.  

Lastly, since I found the ideal size for these to be 400x275, I made some composites(black and white and color) that are larger (in these cases, I enlarged the new images to match the panoramas. 

Data Courtesy the Russian Academy of Sciences, Processed Images Copyright Ted Stryk

Thirty-eight years ago today: Viking 1 lands on Mars.

In recognition of the first successful Mars lander, I am posting two views from Viking 1 that I have processed.

Raw data courtesy NASA/JPL, Processed images Copyright Ted Stryk