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TOPIC: Dawn spacecraft


L

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RE: Dawn spacecraft
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Having fulfilled all of its assignments for 2008, the Dawn spacecraft has been unusually quiescent recently. While its operators on faraway Earth have no shortage of work, the probe patiently coasts in its orbit around the Sun, awaiting a brief encounter with Mars on February 17, which will steer it into a new orbit.

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NASA's Dawn spacecraft shut down its ion propulsion system this week as scheduled. The spacecraft is now gliding toward a Mars flyby in February of next year.

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The Dawn spacecraft continues on course and on schedule for its bold campaign to unexplored worlds. The probe is thrusting gently with its ion propulsion system, as it has been for most of its time in space, gradually modifying its path around the Sun.

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On the first anniversary of its departure from Earth, Dawn continues with what it has been doing for most of its time in space: with the greatest patience it is gently reshaping its orbit around the Sun with its ion propulsion system.

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Dawn continues its flight through the solar system with all systems functioning well. It is vitally important that the spacecraft is reliably staying on course and on schedule, gently and steadily thrusting with the bluish glow of its ion propulsion system; yet that doesn't lend itself to the sorts of spine-tingling, heart-pounding, hair-raising, planet-shattering logs for which Dawn is famous (at least among immigrants from brown dwarf systems reading these reports in the vicinities of active galactic nuclei). So let's turn out attention to consider a particular aspect of flying a mission with ion propulsion.
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The Dawn mission continues smoothly, as the spacecraft reliably thrusts with its ion propulsion system, demonstrating all the patience of a well, of an ion-propelled spacecraft! In the 243 days since launch, the probe has thrust a total of about 140 days. While only around 7% of the total thrusting it will do in its mission, this figure represents vastly more powered flight than any spacecraft that uses conventional chemical propulsion would be capable of. In all this time, the ion thruster has consumed only 37 kilograms  of xenon propellant but yielded a change in the spacecraft's speed of 0.87 kilometres per second.
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NASA's Dawn Spacecraft Begins Interplanetary Cruise Phase Jet Propulsion Laboratory December 18, 2007

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A UT geology professor is working with NASA and other scientists worldwide on an eight-year project that could link two asteroids in space with conditions on Earth in its early years of formation.
Hap McSween, University distinguished professor of Science and department head of the Geological Sciences Department, is a co-investigator for the spacecraft mission, Dawn , which launched in September 2007.

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NASA's Dawn spacecraft successfully completed the first test of its ion propulsion system over the weekend. The system is vital to the success of Dawn's 8-year, 1.6 billion-kilometre journey to asteroid Vesta and dwarf planet Ceres.

"Dawn is our baby and over the weekend it took some of its first steps. We have two months more checkout and characterization remaining before Dawn is considered mission operational, but this is a great start" - Dawn project manager Keyur Patel of NASA's Jet Propulsion Laboratory in Pasadena, California, US.

Members of the Dawn mission control team have been sending up commands and checking out spacecraft systems ever since its successful launch on Sept. 27. The first test firing of one of Dawn's three ion engines was the culmination of several days of careful preparation.
On Sunday, Oct. 7 at 02:07 GMT (Oct. 6 , 9:07 p.m. Eastern Daylight Time), the ion propulsion system began thrusting. Over the next 27 hours, spacecraft controllers and navigators at JPL monitored the engine's performance as it was put through its paces.

"We evaluated the engine's capabilities at five different throttle levels. From flight idle through full throttle, the engine performed flawlessly" - Jon Brophy, the Dawn project's ion propulsion manager at JPL.

Dawn's ion engines are extremely frugal powerhouses. The 27 hours of thrusting from the ion engine resulted in the consumption of less than .28 kilograms of the spacecraft's xenon fuel supply -- less than the contents of a can of soda. Dawn's fuel tank carries 425 kilograms of xenon propellant. Over their lifetime, Dawn's three ion propulsion engines will fire cumulatively for about 50,000 hours (over five years) -- a record for spacecraft.
Dawn will begin its exploration of asteroid Vesta in 2011 and the dwarf planet Ceres in 2015. These two icons of the asteroid belt have been witness to so much of our solar system's history. By utilizing the same set of instruments at two separate destinations, scientists can more accurately formulate comparisons and contrasts. Dawn's science instrument suite will measure shape, surface topography, tectonic history, elemental and mineral composition, and will seek out water-bearing minerals. In addition, the Dawn spacecraft itself and how it orbits both Vesta and Ceres will be used to measure the celestial bodies' masses and gravity fields.

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