OrbitalHub

ESA dixit:

“The high performance of ESA’s new generation ‘Planetary and Asteroid Natural scene Generation Utility’ or Pangu software enables real-time testing of both landing algorithms and hardware. Entry, descent and landing on a planetary body is an extremely risky move: decelerating from orbital velocities of multiple km per second down to zero, at just the right moment to put down softly on an unknown surface, while avoiding craters, boulders and other unpredictable hazards.

But Pangu can generate realistic images of planets and asteroids on a real-time basis, as if approaching a landing site during an actual mission. This allows the testing of landing algorithms, or dedicated microprocessors or entire landing cameras or other hardware ‘in the loop’ – plugged directly into the simulation – or run thousands of simulations one after the other on a ‘Monte Carlo’ basis, to test all eventualities.

Seen here is a Pangu recreation of the Mars Curiosity’s rover’s approach to Mars, using original telemetry, and then a view of Mars moon Phobos. This is followed by another recreation the Japanese Hayabusa probe’s encounter with the rubble-strewn Itokawa near-Earth asteroid, and finally a telemetry-based recreation of the field of view of the New Horizons mission as it performed its rapid flyby of Pluto.

This new generation of Pangu was developed for ESA by the University of Dundee in Scotland.”

Video credit: ESA

NASA dixit:

“February 21, 2017. NASA’s Cassini spacecraft captured these remarkable views of a propeller feature in Saturn’s A ring. These are the sharpest images taken of a propeller so far, and show an unprecedented level of detail. The propeller is nicknamed “Santos-Dumont,” after the pioneering Brazilian-French aviator. This observation was Cassini’s first targeted flyby of a propeller. The views show the object from vantage points on opposite sides of the rings. The top image looks toward the rings’ sunlit side, while the bottom image shows the unilluminated side, where sunlight filters through the backlit ring.

The two images are reprojected at the same scale (0.13 mile or 207 meters per pixel) in order to facilitate comparison. Cassini scientists have been tracking the orbit of this object for the past decade, tracing the effect that the ring has upon it. Now, as Cassini has moved in close to the ring as part of its ring-grazing orbits, it was able to obtain this extreme close-up view of the propeller, enabling researchers to examine its effects on the ring. These views, and others like them, will inform models and studies in new ways going forward.

Like a frosted window, Saturn’s rings look different depending on whether they are seen fully sunlit or backlit. On the lit side, the rings look darker where there is less material to reflect sunlight. On the unlit side, some regions look darker because there is less material, but other regions look dark because there is so much material that the ring becomes opaque. Observing the same propeller on both the lit and unlit sides allows scientists to gather richer information about how the moonlet affects the ring. For example, in the unlit-side view, the broad, dark band through the middle of the propeller seems to be a combination of both empty and opaque regions. The propeller’s central moonlet would only be a couple of pixels across in these images, and may not actually be resolved here. The lit-side image shows that a bright, narrow band of material connects the moonlet directly to the larger ring, in agreement with dynamical models. That same thin band of material may also be obscuring the moonlet from view. Lengthwise along the propeller is a gap in the ring that the moonlet has pried open. The gap appears dark on both the lit and unlit sides. Flanking the gap near the moonlet are regions of enhanced density, which appear bright on the lit side and more mottled on the unlit side.

One benefit of the high resolution of these images is that, for the first time, wavy edges are clearly visible in the gap. These waves are also expected from dynamical models, and they emphasize that the gap must be sharp-edged. Furthermore, the distance between the wave crests tells scientists the width of the gap (1.2 miles or 2 kilometers), which in turn reveals the mass of the central moonlet. From these measurements, Cassini imaging scientists deduce that the moonlet’s mass is comparable to that of a snowball about 0.6 mile (1 kilometer) wide.”

Image credit: NASA/JPL-Caltech/Space Science Institute

NASA dixit:

“February 14, 2017. Daphnis, one of Saturn’s ring-embedded moons, is featured in this view, kicking up waves as it orbits within the Keeler gap. The mosaic combines several images to show more waves in the gap edges. Daphnis is a small moon at 5 miles (8 kilometers) across, but its gravity is powerful enough to disrupt the tiny particles of the A ring that form the Keeler gap’s edge. As the moon moves through the Keeler gap, wave-like features are created in both the horizontal and vertical plane.

Images like this provide scientists with a close-up view of the complicated interactions between a moon and the rings, as well as the interactions between the ring particles themselves, in the wake of the moon’s passage. Three wave crests of diminishing sizes trail Daphnis here. In each subsequent crest, the shape of the wave evolves, as the ring particles within the crests collide with one another.

Close examination of Daphnis’ immediate vicinity also reveals a faint, thin strand of ring material that almost appears to have been directly ripped out of the A ring by Daphnis. The images in this mosaic were taken in visible light, using the Cassini spacecraft narrow-angle camera at a distance of approximately 17,000 miles (28,000 kilometers) from Daphnis and at a Sun-Daphnis-spacecraft, or phase, angle of 71 degrees. Image scale is 551 feet (168 meters) per pixel.”

Image credit: NASA/JPL-Caltech/Space Science Institute

NASA dixit:

“January 30, 2017. In its season of “lasts,” NASA’s Cassini spacecraft made its final close approach to Saturn’s moon Mimas. At closest approach, Cassini passed 25,620 miles (41,230 kilometers) from Mimas. This mosaic is one of the highest resolution views ever captured of the icy moon. Close approaches to Mimas have been somewhat rare during Cassini’s mission, with only seven flybys at distances of less than 31,000 miles (50,000 kilometers).

Mimas’ surface is pockmarked with countless craters, the largest of which gives the icy moon its distinctive appearance. The left side, which is lit by reflected light from Saturn, has been enhanced in brightness in order to show the full surface. Imaging scientists combined ten narrow-angle camera images to create this mosaic view. The scene is an orthographic projection centered on terrain at 17.5 degrees south latitude, 325.4 degrees west longitude on Mimas. An orthographic view is most like the view seen by a distant observer looking through a telescope.

This mosaic was acquired at a distance of approximately 28,000 miles (45,000 kilometers) from Mimas. Image scale is approximately 820 feet (250 meters) per pixel. The images were taken in visible light with the Cassini spacecraft narrow-angle camera.”

Image credit: NASA/JPL-Caltech/Space Science Institute

NASA dixit:

“January 16, 2017. The wavemaker moon, Daphnis, is featured in this view, taken as NASA’s Cassini spacecraft made one of its ring-grazing passes over the outer edges of Saturn’s rings. This is the closest view of the small moon obtained yet. Daphnis (5 miles or 8 kilometers across) orbits within the 42-kilometer (26-mile) wide Keeler Gap. Cassini’s viewing angle causes the gap to appear narrower than it actually is, due to foreshorteneing.

The little moon’s gravity raises waves in the edges of the gap in both the horizontal and vertical directions. Cassini was able to observe the vertical structures in 2009, around the time of Saturn’s equinox. Like a couple of Saturn’s other small ring moons, Atlas and Pan, Daphnis appears to have a narrow ridge around its equator and a fairly smooth mantle of material on its surface — likely an accumulation of fine particles from the rings. A few craters are obvious at this resolution. An additional ridge can be seen further north that runs parallel to the equatorial band.

Fine details in the rings are also on display in this image. In particular, a grainy texture is seen in several wide lanes which hints at structures where particles are clumping together. In comparison to the otherwise sharp edges of the Keeler Gap, the wave peak in the gap edge at left has a softened appearance. This is possibly due to the movement of fine ring particles being spread out into the gap following Daphnis’ last close approach to that edge on a previous orbit. A faint, narrow tendril of ring material follows just behind Daphnis (to its left). This may have resulted from a moment when Daphnis drew a packet of material out of the ring, and now that packet is spreading itself out.

The image was taken in visible (green) light with the Cassini spacecraft narrow-angle camera. The view was acquired at a distance of approximately 17,000 miles (28,000 kilometers) from Daphnis and at a Sun-Daphnis-spacecraft, or phase, angle of 71 degrees. Image scale is 551 feet (168 meters) per pixel.”

Image credit: NASA/JPL-Caltech/Space Science Institute

NASA dixit:

“December 18, 2016. This image from NASA’s Cassini spacecraft is one of the highest-resolution views ever taken of Saturn’s moon Pandora. Pandora (52 miles, 84 kilometers) across orbits Saturn just outside the narrow F ring. The spacecraft captured the image during its closest-ever flyby of Pandora, during the third of its grazing passes by the outer edges of Saturn’s main rings.

The image was taken in green light with the Cassini spacecraft narrow-angle camera at a distance of approximately 25,200 miles (40,500 kilometers) from Pandora. Image scale is 787 feet (240 meters) per pixel.”

Image credit: NASA/JPL-Caltech/Space Science Institute