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KEY SPACECRAFT CHARACTERISTICS: |
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* | Extensive redundancy using flight proven assemblies from other Orbital and JPL spacecraft. |
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* | Ion propulsion system, based on the design validated on Deep Space 1. |
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* | Two 100 W (RF) travelling wave tube amplifiers, fixed 1.5 m high-gain antenna, 3 low-gain antennas, two small deep space transponders. |
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* | Solar array capable of producing more than 10 kW at Earth's distance from the Sun and more than 1 kW at Ceres's maximum distance. |
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* | Flight proven attitude control system used on Orbview, TOPEX/Poseidon ocean topography mission, and Far Ultraviolet Spectroscopic Explorer. |
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* | Simple hydrazine reaction control subsystem with two sets of six 0.9 N engines used on the Indostar spacecraft. |
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* | Command and data handling uses off-the-shelf components as used on the Orbview program |
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* | Modular flight software based on design used on Orbview. |
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* | Core structure is graphite composite. Panels are aluminum core, some with aluminum facesheets and others with composite facesheets. |
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SPACECRAFT DIAGRAM: 
ION PROPULSION:
The Dawn spacecraft uses ion propulsion to get the additional velocity needed to reach Vesta once it leaves the Delta rocket. It also uses ion propulsion to spiral to lower altitudes on Vesta, to leave Vesta and cruise to Ceres and to spiral to a low altitude orbit at Ceres. Ion propulsion makes efficient use of the onboard fuel by accelerating it to a velocity ten times that of chemical rockets. This efficiency is measured in terms of the specific impulse of the fuel, Isp. Dawn's engines have a specific impulse of 3100 s and a thrust of 90mN. While a chemical rocket on a spacecraft might have a thrust of up to 500 Newtons, Dawn's much smaller engine achieves an equivalent trajectory change by firing over a much longer period of time. The figure below shows the specific impulse and thrust of different thruster types.
The ion thruster is powered by large solar panels. The power ionizes the fuel (Xenon) and then accelerates it with an electric field between two grids. Electrons are injected into the beam after acceleration to maintain a neutral plasma.
Further information on Ion Propulsion Information
For more information contact C. T. Russell, ctrussell@igpp.ucla.edu.
Last updated November 13, 2007.
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