Dawn | Nears Close Orbit of Ceres

My five previous updates to the Dawn Mission to Dwarf Planet Ceres are located at this link.


As of 4 August 2015

On 17 July 2015, the NASA Dawn spacecraft started the spiral descent from survey mapping orbit #2 to the much closer high altitude mapping orbit (HAMO) #3. The descent will move Dawn from 2,700 miles (4,400 km) above dwarf planet Ceres to 915 miles (less than 1,470 km) by mid-August 2015. Dawn’s view of Ceres will be equivalent to looking at a soccer ball from a distance of 13 inches (33 cm).

This graphic describes the descent of Dawn to HAMO. In this point of view, Dawn orbits counter-clockwise. Blue shows ion-thrusting to leave survey orbit #2. Red shows ion-thrusting upon arrival at HAMO. It will take over 20 orbits to complete the transition. The red dashed sections show where Dawn is coasting for telecommunications. Once a week, Dawn pauses ion-thrusting and points toward Earth. Updated flight plans and status checks occur during these communications sessions. Click images to embiggen.

NASA | JPL

The latest images of surface details can be browsed at this link, updated almost daily. Below is an example of the fine detail in an image posted 3 August 2015. The HAMO will increase detail by 3x.

NASA | JPL-Caltech/UCLA/MPS/DLR/IDA

Mission scientists have converted elevation detail into this color animation of the rotating dwarf planet Ceres. The color scale extends 3.7 miles (6 km) below the surface in purple, to 3.7 miles (6 km) above the surface in red. The bright white spots are as yet un-explained highly reflective material. Some scientists think they are freshly exposed ice due to recent impacts.

Unlike the New Horizons mission which gathered data during a short time of high-speed flyby, Dawn will remain at Ceres permanently in close low-altitude orbit. From the Dawn Press Kit:

The resource that will ultimately limit Dawn’s lifetime is its hydrazine fuel. Once the fuel is exhausted, the spacecraft will no longer be able to point its instruments at the surface. It also will be unable to point any of its ion engines for maneuvering purposes, nor point its antenna at Earth or its solar arrays at the sun. The battery will be depleted in a matter of hours. The spacecraft will remain in orbit around Ceres, but it will cease operating.

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6 thoughts on “Dawn | Nears Close Orbit of Ceres

  1. Well! It look slike their propulsion system definitely works. Have they released any conclusions about teh formation of rocky planets, yet? I recently learned that granite is super rare outside of the earth and that our explanations for that rarity aren’t terribly satisfying. Maybe this exploration will shed some light.

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    • I haven’t seen any conclusions about that. You are right about granite. On Earth, it is common due to the heated origins and plate tectonics that have moved rock layers into heated zones. Such tectonic and volcanic origins are less common elsewhere.

      You are correct about shedding new light. The earlier visited object, Vesta, was very rocky and dry. Ceres appears less rocky with a density suggesting a lot of ice that makes it up. More to come for sure about their different origins.

      Thanks for your comments.

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  2. The data-gathering is impressive enough. But the real trick is the interpretation. I suspect “tentative,” “provisional,” and “apparent” will find their way into papers and reports.

    That business about “a soccer ball from thirteen inches” is nearly unbelievable. It’s going to be fascinating to see what emerges from the closer view.

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