A Deeper Understanding: Dawn Reaches Third Science Orbit, Shows Closest View of Ceres Yet

From NASA/JPL: "The Lonely Mountain The Lonely Mountain NASA's Dawn spacecraft spotted this tall, conical mountain on Ceres from a distance of 915 miles (1,470 kilometers). The mountain, located in the southern hemisphere, stands 4 miles (6 kilometers) high. Its perimeter is sharply defined, with almost no accumulated debris at the base of the brightly streaked slope." This image was taken August 19. Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

From NASA/JPL: “The Lonely Mountain: NASA’s Dawn spacecraft spotted this tall, conical mountain on Ceres from a distance of 915 miles (1,470 kilometers). The mountain, located in the southern hemisphere, stands 4 miles (6 kilometers) high. Its perimeter is sharply defined, with almost no accumulated debris at the base of the brightly streaked slope.” This image was taken Aug. 19. Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

2015 may be shaping up to be one of the biggest years in deep space exploration’s history, with historic milestones achieved by several spacecraft including Rosetta, Curiosity, and New Horizons. While the world was enthralled by New Horizons’ Pluto flyby during the summer months, another spacecraft with otherworldly targets quietly maneuvered to its third orbit, reaching it in mid-August.

NASA’s Dawn spacecraft is currently delivering its closest views of Ceres yet as the spacecraft is settling into its High Altitude Mapping Orbit (HAMO). In addition, the Dawn team recently released a video revealing what it looks like to “cruise” over the dwarf planet, which is the largest object in the main asteroid belt between Mars and Jupiter.

Dawn Successfully Reaches HAMO, Sends New Images

On Aug. 17, Dawn reached its third orbit, the High Altitude Mapping Orbit (or HAMO). The spacecraft is currently orbiting Ceres at an altitude of approximately 915 miles (1,470 kilometers). NASA’s Dawn website revealed: “Dawn takes 11 days to capture and return images of Ceres’ whole surface. Each 11-day cycle consists of 14 orbits. Over the next two months, the spacecraft will map the entirety of Ceres six times.” NASA added that the spacecraft’s framing camera maps Ceres’ surface, allowing for three-dimensional models to be made, while its visible and infrared mapping spectrometer will give scientists a better look at Ceres’ mineral composition.

From NASA/JPL: "NASA's Dawn spacecraft took this image that shows a mountain ridge, near lower left, that lies in the center of Urvara crater on Ceres. Urvara is an Indian and Iranian deity of plants and fields. The crater's diameter is 101 miles (163 kilometers)." Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

From NASA/JPL: “NASA’s Dawn spacecraft took this image that shows a mountain ridge, near lower left, that lies in the center of Urvara crater on Ceres. Urvara is an Indian and Iranian deity of plants and fields. The crater’s diameter is 101 miles (163 kilometers).” Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

The space agency also stated that scientists are studying Ceres’ gravity field in preparations for its fourth and final orbit. In late-October, Dawn will begin its transition to its Low Altitude Mapping Orbit (LAMO), which will serve as the spacecraft’s final “resting place.” Using a series of maneuvers, the spacecraft will descend to an orbital altitude of 230 miles (375 kilometers). This distance will undoubtedly reveal more about Ceres, at an even higher resolution.

Marc Rayman, Dawn’s chief engineer and mission director at NASA’s Jet Propulsion Laboratory, was enthusiastic about the spacecraft’s latest mission milestone: “Dawn is performing flawlessly in this new orbit as it conducts its ambitious exploration. The spacecraft’s view is now three times as sharp as in its previous mapping orbit, revealing exciting new details of this intriguing dwarf planet.”

The new orbit has already yielded spectacular images, including one referred to as “The Lonely Mountain,” featuring a tall mountain (four miles high) that partially “shines” on the dwarf planet’s surface. As Dawn has gotten closer to Ceres, the dwarf planet has revealed many surprises, including mysterious “bright spots.” Amateur space watchers and planetary scientists alike are curious as to what gives these features their “gleaming” appearance.

Dawn was en route to HAMO after briefly experiencing some hiccups in its operations this summer. A previous AmericaSpace article detailed issues with the spacecraft’s ion propulsion system: “Early in its five-week trek to HAMO, ion thruster #3 developed an issue with its gimbals, which affects the direction the spacecraft is ‘pointed.’ Dawn entered into a ‘safe mode,’ designed to protect the ship in case it encounters a potentially harmful situation. Controllers switched to ion engine #2, and after some observation Dawn was observed to be in fine fitness, with spacecraft systems and hardware otherwise in good health.” The spacecraft was designed and built by Orbital ATK, based in Dulles, Va.

Video Released Showing “3D Cruise” Over Ceres’ Surface

NASA’s Ceres team released a video employing 3-D modeling that shows Ceres’ enigmatic topographical features, including “The Lonely Mountain.” NASA stated: “The peak’s shape has been likened to a cone or a pyramid. It appears to be about 4 miles (6 kilometers) high, with respect to the surface around it, according to the latest estimates. This means the mountain has about the same elevation as Mount McKinley in Denali National Park, Alaska, the highest point in North America.”

Video Credit: NASA Jet Propulsion Laboratory on YouTube

Dawn science team member Paul Schenk, a geologist at the Lunar and Planetary Institute in Houston, Texas, underscored why the mountain is so surprising to those observing the spacecraft’s findings: “This mountain is among the tallest features we’ve seen on Ceres to date. It’s unusual that it’s not associated with a crater. Why is it sitting in the middle of nowhere? We don’t know yet, but we may find out with closer observations.”

In addition, the video shows the “bright spots” that have captured the public’s imagination, located inside what is called the Occator crater. Dawn’s principal investigator at the University of California in LA, Chris Russell, discussed the still-puzzling bright spots at Occator. “We are now comparing the spots with the reflective properties of salt, but we are still puzzled by their source. We look forward to new, higher-resolution data from the mission’s next orbital phase,” he said. NASA revealed that it is not believed the “shiny” nature of these features are due to ice. It is hoped the team will learn more as the spacecraft continues to map Ceres through HAMO and eventually LAMO later this fall.

The team also revealed that it has been able to better determine Ceres’ diameter; the estimate has been revised to 584 miles, versus the previous estimate of 590 miles, due to data returned during Dawn’s orbits.

A Continuing Deeper Understanding of a Dwarf Planet

While the Dawn mission has been overshadowed this summer by the New Horizons Pluto flyby, the spacecraft remains the first to reach a dwarf planet, and is the first to “the first to orbit two distinct extraterrestrial targets,” as NASA puts it. Having toured the asteroid Vesta from 2011 to 2012, Dawn arrived at Ceres in March this year, making its first survey orbits shortly thereafter. It is also the first spacecraft to employ a futuristic, innovative ion propulsion system, which “gently, but persistently” pushes it through space. As Dawn continues its third orbit, scientists, space watchers, and researchers on Earth will continue to make more discoveries about a mysterious, as-yet-undiscovered world.

Please check back with AmericaSpace for more updates about the Dawn mission.

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