May 15, 2018 — Dawn Ready for New Ceres Observations
Yesterday Dawn completed one month of maneuvering with its ion engine to a new orbit around dwarf planet Ceres. Now in extended mission orbit 6 (XMO6), Dawn will take pictures as well as infrared and visible spectra starting today. The March Dawn Journal described the plans for this new phase of the mission.
Dawn was aiming for an elliptical orbit that ranged in altitude from 270 miles (440 kilometers) to 2,900 miles (4,700 kilometers), and measurements of the orbit parameters by Dawn's navigation team after thrusting completed confirmed that the spaceship is right on target.
May 10, 2018 — Dawn Flying Closer to Ceres
Dawn is continuing to fire its ion engine to reduce its altitude above Ceres. The spacecraft has now decreased the size of its elliptical orbit so much that on May 8, it dipped down to less than 560 miles (900 kilometers) above the dwarf planet. The last time it was that close to the ground was in September 2016.
Dawn started today at an altitude of nearly 3,500 miles (5,600 kilometers). Tonight it will reach down to 450 miles (720 kilometers) before it begins sailing up again. It now takes the ship less than two days to complete one revolution around the dwarf planet. The April Dawn Journal shows Dawn's spiral descent.
May 4, 2018 — Dawn Pauses Thrusting for an Update
Dawn's spiral descent to a new orbit is going smoothly. (The April Dawn Journal includes an illustration of Dawn's descent profile.) Today the spacecraft is scheduled to pause ion thrusting and point its main antenna to Earth. Controllers will radio the spacecraft a routine update to its flight plan, which will cover the next week of ion thrusting.
Today Dawn's shrinking elliptical orbit carries it from 2,000 miles (3,200 kilometers) up to 4,300 miles (6,900 kilometers). Whereas the peak altitude presented in the April 26 mission status update was 7,300 miles (11,800 kilometers), the next orbital crest, which occurs early tomorrow morning, will be 4,300 miles (7,000 kilometers). It now takes the probe only three days to complete one revolution around Ceres, or one-tenth of what it was before ion thrusting began on April 16.
April 26, 2018 — Ion Thrusting Contracts Dawn's Orbit
Dawn is continuing to thrust with its ion propulsion system to lower its orbit around Ceres in preparation for taking new pictures and conducting other scientific observations next month. (The March Dawn Journal has an overview of the plan.) As explained in the April 17 mission status, this maneuvering makes each peak in the spacecraft's elliptical orbit lower than the one before. And in the April 5 mission status, we saw that the elliptical orbit reached 24,300 miles (31,900 kilometers) before ion thrusting began. Today Dawn will sail up to a peak again, but now it will be only 7,300 miles (11,800 kilometers).
As Dawn's orbit shrinks, it takes less time to complete each revolution. Prior to thrusting, Dawn looped around the dwarf planet once every 30 days. Now it takes less than a week, and as thrusting continues, the orbit period will get even shorter.
April 17, 2018 — Dawn Maneuvering to Lower Orbit
Dawn is flying to a lower altitude over Ceres. Under the gentle thrust of ion engine #2, the spacecraft is gradually reshaping its orbit around the dwarf planet. It will take a month to maneuver to the new orbit, designated extended mission orbit 6 (XMO6). Last month's Dawn Journal gives an overview of the plans.
Today Dawn will descend from 16,900 miles (27,300 kilometers) to 15,200 miles (24,400 kilometers).
Although the new orbit will be lower than the previous orbit, Dawn continues to follow an elliptical path around Ceres. The ion thrusting will gradually shrink that ellipse. As a result, most of the time Dawn will get closer to Ceres but sometimes it will ascend, although to a lower peak altitude each time. This will become more apparent as we track the altitude in upcoming mission status reports.
April 12, 2018 — Dawn About to Fly Lower
Mission controllers are putting the finishing touches on the instructions Dawn will follow to fly to a new orbit. Ion thrusting will begin next week. It will require about a month to descend so the probe can undertake new observations, as described in the most recent Dawn Journal.
As it turns out, Dawn is already descending today, but that is for a different reason. The spacecraft is continuing in its elliptical orbit. It reached the high point on April 7. Over the course of the day today, Dawn's altitude will decrease from 22,700 miles (36,500 kilometers) to 21,900 miles (35,300 kilometers).
Tomorrow, Dawn will celebrate its 3,000th Cerean day in orbit around the dwarf planet. The adventurer arrived in orbit in 2015 (an unprecedented and exciting accomplishment that was described here). Ceres turns on its axis in 9 hours, 4 minutes (one Cerean day), considerably faster than Earth, although not all that different from the giant planet Jupiter, which takes 9 hours, 56 minutes.
April 5, 2018 — Dawn Approaching Orbital Summit
Dawn's 30-day elliptical orbit is carrying it to its highest point above Ceres. Just as a ball thrown upward gradually slows before falling downward, the spacecraft is decelerating under the constant pull of the dwarf planet's gravity. Orbiting at an average altitude today of 24,000 miles (38,700 kilometers), the spacecraft is ascending at only 11 mph (18 kph). On April 7, it will reach the crest of its orbit, 24,300 miles (39,100 kilometers) high.
Meanwhile, the mission control team at JPL is continuing to prepare for piloting Dawn to a new orbit for new observations, as described in the most recent Dawn Journal.
March 29, 2018 — Dawn Sailing Upward on Noteworthy Anniversary
As Dawn follows its elliptical orbit around Ceres, it is sailing higher. Over the course of the day today, it will climb from 11,300 miles (18,200 kilometers) to 12,100 miles (19,600 kilometers). As the latest Dawn Journal explains, the spacecraft will not remain in this orbit for much longer.
Today is the 211th anniversary of the discovery of Vesta, the first stop on Dawn's deep-space mission of exploration. For two centuries, that enigmatic world, the second largest in the main asteroid belt, appeared as little more than one of the myriad glowing jewels in the nighttime sky. In 2011-2012, Dawn transformed it into a complex, fascinating world, finding it to be more closely related to the terrestrial planets than to typical asteroids. Some of the discoveries are summarized here.
March 20, 2018 — Dawn Operating Smoothly as Team Prepares for Ambitious New Observations
Dawn has been in excellent health and continues to operate smoothly in orbit around Ceres. The operations team has made excellent progress in preparing to guide Dawn to lower altitudes and perform important new observations. Maneuvering with the ion propulsion system will begin next month. The latest Dawn Journal presents an overview of the plans for the two new orbits Dawn will occupy.
As the spacecraft continues its current elliptical orbit, it will descend today from 11,800 miles (19,000 kilometers) to 9,100 miles (14,600 kilometers) above the dwarf planet. On March 23, it will dip down to a little under 2,800 miles (4,400 kilometers) before going up again.
January 3, 2018 — Dawn Flight Team Planning for New Activities
The Dawn flight team is hard at work developing methods to fly Dawn much closer to Ceres than it has ever been. The December Dawn Journal describes some of the plans.
Meanwhile, the spacecraft is healthy as it continues in its high-altitude elliptical orbit. Over the course of the day today, the spacecraft will climb from 23,400 miles (37,600 kilometers) to 23,700 miles (38,200 kilometers). It will reach the crest of its orbit at 24,030 miles (38,670 kilometers) on Jan. 6.