Dawn's latest orbit reveals dramatic new views of Occator crater

[Judi Lynn]

(2 July 2018 - JPL) NASA's Dawn spacecraft reached its lowest-ever and final orbit around dwarf planet Ceres on June 6 and has been returning thousands of stunning images and other data.

The flight team maneuvered the spacecraft into an orbit that dives 22 miles (35 kilometers) above the surface of Ceres and viewed Occator Crater, site of the famous bright deposits, and other intriguing regions. In more than three years of orbiting Ceres, Dawn's lowest altitude before this month was 240 miles (385 kilometers), so the data from this current orbit bring the dwarf planet into much sharper focus.

These low orbits have revealed unprecedented details of the relationships between bright and dark materials in the region of Vinalia Faculae. Dawn's visible and infrared mapping spectrometer had previously found the bright deposits to be made of sodium carbonate, a material commonly found in evaporite deposits on Earth. Last week Dawn fired its ion engine, possibly for the final time, to fly nearer Cerealia Facula, the large deposit of sodium carbonate in the center of Occator Crater.



This mosaic of a prominent mound located on the western side of Cerealia Facula was obtained by NASA's Dawn spacecraft on June 22, 2018 from an altitude of about 21 miles (34 kilometers). (courtesy: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA)

"Acquiring these spectacular pictures has been one of the greatest challenges in Dawn's extraordinary extraterrestrial expedition, and the results are better than we had ever hoped," said Dawn's chief engineer and project manager, Marc Rayman, of NASA's Jet Propulsion Laboratory, Pasadena, California. "Dawn is like a master artist, adding rich details to the otherworldly beauty in its intimate portrait of Ceres."

More:
http://www.spacenewsfeed.com/index.php/news/1563-dawn-s-latest-orbit-reveals-dramatic-new-views-of-occator-crater

[muriel_volestrangler]

1. Rayman's blog: "assuming the absence of tall trees (or giant Cerean spiders)..."

I love his blog. Here he describes the manoeuvres to get that low:

In contrast to the distant, serene probe, the operations team has been working quite intensively to prepare for a bold new phase of the mission. They have been assiduously working through all the tasks necessary to prepare for piloting this unique spaceship, late in its life and low on supplies, through maneuvers it was never designed for and to conduct observations never conceived of prior to late last year. Since the previous Dawn Journal, the team has generated more than 45,000 trajectories to study how to fly Dawn to two new orbits. Often there are more than 100 computers operating simultaneously to perform the necessary calculations. Many thousands more trajectories are yet to be computed and analyzed. If all goes well, by June, the probe will have followed an intricate flight plan that will allow it to glide a mere 22 miles (35 kilometers) above the alien landscapes almost every day in an orbit dramatically and poetically designated XMO7 (but occasionally summarized as "Whoa, that's low!&quot .
...
In XMO7 (shown in the two figures below), Dawn will range from as high as 2,500 miles (4,000 kilometers) to as low as about 22 miles (35 kilometers). (The minimum altitude will vary by a few miles, or kilometers, from revolution to revolution, for reasons we will explain in a future Dawn Journal.) It will take a little more than a day to complete one loop.



The two solid ellipses illustrate the relative sizes of Dawn's next two science orbits around Ceres. The outer one is XMO6, which is the inner orbit in the figure above. (As in that figure, the spacecraft orbits counterclockwise here, and sunlight comes from the right.) After completing its work in XMO6 in May, Dawn will set sail for its final orbit, XMO7. The dashed circle represents Dawn's lowest orbit so far, LAMO/XMO1. It demonstrates that XMO7 is low! But assuming the absence of tall trees (or giant Cerean spiders), the operations team will be prepared to pilot the spacecraft safely. Dawn complies with planetary protection protocols, which prohibit coming in contact with Ceres, even for decades after the mission concludes. XMO7 is also shown in the figure below. Image credit: NASA/JPL-Caltech
...
At the high point of XMO7, Dawn will move at only about 120 mph (190 kph). Then as gravity pulls it back down, the spacecraft will accelerate until it streaks northward at 1,050 mph (1,690 kph) above a relatively narrow strip of ground before starting to soar up again. Dawn was designed for mapping uncharted worlds, not making specialized observations under such conditions, and traveling so fast and so low means it cannot take pictures as sharp as you might expect. Nevertheless, even with a little bit of motion-induced blur at low altitude, any sights we photograph certainly will reveal finer details than we have seen before. This is going to be exciting!

https://www.jpl.nasa.gov/blog/2018/3/dear-vernal-dawnquinoxes