Thursday, March 18, 2010

On September 29, 2009, the Messenger spacecraft flew by the planet Mercury.  The approach data was successfully obtained, but thanks to a safe mode incident, the departure data was lost.  On October 3, the spacecraft finally recovered.  It took this image through its wide angle camera that day

Only albedo features can be seen.  Had the Narrow Angle Camera taken data that day, good imagery could have been obtained, but since it would have been of little value had closer data been taken, none were scheduled until October 10th.  In that view, shown below, a few large craters can still be seen on the terminator despite a distance of 2 million kilometers - it is still better than the image above. 

While the loss of departure imagery is disappointing, all in all the Messenger flybys proved very successful.  One can only look forward to the beginning of the orbital mission next year!

Raw Data Courtesy APL/JHU/NASA   Processed Images Copyright Ted Stryk

Tuesday, March 16, 2010

Luna 20

On February 21, 1972, Luna 20 landed in the Apollonius Highlands, a highlands region  located between Mare Crisium and Mare Fecunditatis.  It was the only Soviet sample return mission to land in the highlands, and also the only one to return imagery of its surroundings.  Due to difficulties with the sampling apparatus, the drill only penetrated 25 centimeters and returned 55 grams of lunar material. Despite the small size, given the unique regional setting, these samples proved extremely valuable.    Reports of how much image data it returned are conflicting, but only fragments have been published.  These images were assembled by piecing together the available fragments.   Because quality varied greatly, some areas are notably sharper.

The first pair shows the drilling arm as it moves while preparing to drill into the surface. Hills can be seen in the distance in the upper left-hand corner.  One of Luna 20's antennae can also be seen (the long, skinny pole to the left of the sampling arm).  It is much closer to the camera and higher above the surface than the sampling arm, which is why it casts no shadow within the field of the camera.

The next image shows more hills and some craters near the landing site. It is possible that this segment is a continuation of the panorama above, but I am not at all sure of this.  The left hand half of the image is made of much poorer data than the right hand side.  The lower right hand area is obstructed by part of the spacecraft.

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

Friday, March 12, 2010

Tyre Macula

Building on yesterday's post, here is another view of Europa.  It shows Tyre Macula, one of the few large impact structures identified on Europa.  This view shows it nestled among the Europan lineaments. 

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

Thursday, March 11, 2010

Europa from Voyager 2

When the Voyager Jupiter flybys were planned, very little was known about the Galilean moons.  Because it was impossible for both Voyagers to make a close flyby of each moon and still get to Saturn, planners were forced to be selective.  They gave the two largest moons, Ganymede and Callisto, a close flyby from each spacecraft.  Io, known to be an oddball, got an extremely close (by Voyager standards) flyby by Voyager 1.  Europa, the smallest of the Galileans, was given the lowest priority.  Voyager 2 made the only relatively close flyby, and it was relatively distant.  Still, it obtained some beautiful imagery.  There is a crescent image, which is the closest mosaic and has the best filter coverage, that has been reprocessed several times.  There is also a slightly more distant mosaic, taken from about 250,000 km.  It is limited in filter coverage, but shows Europa at a half phase, therefore showing significantly area.  The base color was created using orange filter data as red, blue as green, and a mix of violet and ultraviolet as blue. I have mixed the color data with OGV wide angle data taken later and reconstructed in the areas not covered by the later data.  The grayscale data is stacked and shown at 1.7x original size.  The result is one of the better global views of Europa presently available.

Here is a second version, leaning more heavily on the OGV data described above for color balance.

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