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In this issue:
Environmental testing of Dawn spacecraft begins
Dawn Instrument Integration Completed
Ceres a 'Dwarf Planet'
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Environmental testing of Dawn spacecraft begins
Carol A. Raymond
Dawn Deputy Principal Investigator, JPL
The Dawn project is deep into the testing phase of ATLO (Assembly, Test, and Launch Operations) with completion of all the Comprehensive Performance Tests demonstrating subsystem functionality, the successful completion of the Environmental Test Readiness Review held September 6-7, and the first major environmental test (Electromagnetic Interference/Compatibility) due to begin next week. After EMI/EMC, the spacecraft undergoes acoustics and dynamics testing, then is shipped to the Naval Research Lab in Washington, DC for one month of testing (late Dec-Jan) in a large thermal-vacuum chamber. This chamber is large enough to allow a test-firing of the ion thrusters. After thermo-vac testing, the spacecraft ships directly to Cape Canaveral for launch, in a 20-day window that opens June 20, 2007.
The spacecraft is fully assembled except for the two outboard thrusters of the ion propulsion system (IPS), to be installed after dynamics testing and before thermo-vac (TVAC), to avoid damage to these critical appendages. The center thruster has been installed in the spacecraft core, as well as the large high-gain antenna. The solar panels are currently being installed.
The Power Processing Units (PPUs) of the IPS system, that had been an item of concern a year ago, each underwent 500 hours of run-in testing before delivery to the spacecraft to certify their robustness against workmanship defects and early parts failures. After integration, the PPUs were exercised during IPS comprehensive performance testing and have operated trouble-free. There are no outstanding issues with the flight hardware, and the flight software needed for environmental testing has been delivered.
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