Rhea's Tirawa Basin

As Voyager 1 receded from its close flyby of Rhea, it snapped this view of Rhea's Tirawa basin, a large impact structure seen on the terminator in this crescent view. It is on of the worst-imaged parts of this world, and this Voyager view is still the best. Rhea is a moon that shows some similar features to more active Dione and Tethys, but seems to have been inactive for longer, as evidenced by the fact that all of its surface is extremely worn from impacts and the evidences of internal activity are much more subtle.

Voyager's Hyperion

Today Cassini is returning images from its flyby of Saturn's moon Hyperion. I have reprocessed some Voyager 1 images. This is a sequence from they flyby:



Here is a super-resolution color view. It is amazing to see the intricate patterns of bright
and dark areas. Cassini is now revealing this peculiar world.

Cassini Approaching Tethys (And Hyperion Too!)

This orbit by the Cassini orbiter will include flybys of both Hyperion and Tethys. The Tethys flyby was added a few months ago due to increasing interest in this moon as a contributor of ring material. Here are the best Voyager views of this moon.



This view, from Voyager 1, clearly shows a dark band across the center of the disk. The existance of this has been seen in Cassini's images too, but the orgin is not yet known.


This is a color view of Tethys from Voyager 2's approach to the moon. It shows on the terminator the degraded Ithaca Chasma, a huge canyon bisecting this moon.



This is the last Voyager 2 view, showing Ithaca Chasma in the center and to the left. Within the next view days, Cassini should supercede this view. This was the best view (5 km/pixel) that either Voyager obtained before pointing errors and scan platform problems ruined imaging sequences.



With the scan platform sticking and the spacecraft off target, this is the only frame from the highest resolution mosaic of Tethys, taken at 2.2 km/pixel, to catch a corner of the moon. For years, this stood as the mysterious best view of this world. Cassini has already doubled this resolution, and at last the weekend has arrived where Tethys receives true closeup treatment! Stay tooned!

A Craggy Rock On Venus

I have watched with great excitement how the Mars Exploration Rovers have explored the red planet. However, Venus, while it has had more successful landers on its surface, was the subject of much less capable spacecraft. There are four color image sets of the surface, all with blank or nearly blank blue channels. Venera 13 sent back one full pan in color, which is the best set we have, and another partial one (complete in black and white) that hs much poorer color data. Venera 14, which landed in a much rockier area, took a pretty good partial color pan (again, complete in black and white), but while the other pan was complete in both black and white and through color filters (althoug again the blue was almost useless), the color data in this set was horribly underexposed. Below is the Venera 14 partial pan, my favorite of the set because of the cool rock right near the lander. It seems to be sitting on the rocky plain...it makes one wonder how it got there. I don't see anything else like it in the Venera pans, although given their limited coverage, it doesnt mean there aren't perhaps a few more rocks like it around. But still , it is lucky it was so close to the lander and in a color zone.



Here is the other Venera 14 pan. The color data is OK on the sides, but in the center, all color data is nearly blank, making any color variations dubious in that part of the image.



Here is a composite of Venera 13 images, looking towards a ridge on the horizon.

New Color Views of Europa

Below is a mosaic of color versions I have processed of all the Galileo global color views of Europa. The large mosaic on the bottom is partially from color from the dataset used to make the greyscale data and partially from the G1 orbit. Despite Galileo's limitations, these are some real gems. (Please note that the large mosaic on the bottom is at greatly reduced resolution, and the image in the upper left hand corner is reduced somewhat from the super-resolution product size, although it is larger than the original image size.

Remnants of a Lost Approach

When Galileo approached Jupiter in the 1990s, the antenna problem, as well as a tape recorder problem in fall of 1995 that cost the images from the arrival orbit pretty much wiped out the return of images from this part of the mission, other than the Ida encounter, from which the images were piddled back over many months. In 1990, before even the Gaspra encounter, Galileo took some images for calibration that could be returned more easily while it was still in the inner solar system. Here is a color view of Jupiter and some of its moons generated from this data. It has the appearance of being taken through a small telescope.



Galileo would next image Jupiter during the SL9 imacts, a year and a half before arrival. It used a technique known as an "on chip mosaic," taking multiple images on the same frame so it could be returned as one picture. There were several techniques used that involved smearing the image to look for flareups from the impact. For the last impact, Galileo took multiple unsmeared images, providing a neat perspective, as its images are the only ones to see the impacts directly, and not coming over the limb. Perhaps another entry will be dedicated to these images. But here is one showing the impact and Jupiter, produced from several images on the on-chip mosaic.



The tape recorder problem caused the end of imaging until the G1 orbit in the summer of 1996. However, as Galileo approached in 1995, it took optical navigation frames showing Ganymede slowly looming larger to help plan for the G1 orbit. It is a little taste of the sights Galileo saw that fall but could not show us.