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Testing, Testing

Testing, testing, testing! Key to the success of any spacecraft mission is thorough checkout and testing along every step of assembly. This week the MESSENGER team installed two temporary "engineering models" of the Power Distribution Unit (PDU) and the Integrated Electronics Module (IEM). An engineering unit is not the actual component that will be launched with the spacecraft - rather, it is a test device that behaves as the "flight" unit behaves, thus allowing engineers to check out the spacecraft assembly. (Both units are obscured in this view by the Turnover Fixture.)

The PDU serves a function similar to that of a circuit breaker box in a house. It routes power from the solar panels and battery to the various subsystems and instruments on the spacecraft. The IEM contains the main processor, fault protection processor, the solid state recorder and interface circuits to the rest of the spacecraft - in essence, MESSENGER's brain.

Installation of these test components indicates that the spacecraft is getting ever closer to its March 2004 launch date. After the spacecraft checks out, these test components will be removed and the real flight units will be installed.

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Last updated: May 20, 2003

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