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The Integrated Electronics Module - or IEM
- is MESSENGER's "brain." The spacecraft carries a pair
of identical IEM boxes for backup purposes; this week the MESSENGER
team installed the second box. Both boxes house a main processor
(running at 10 million instructions per second) and a fault protection
processor (that can handle 5 million instructions per second).
Provided by BAE Systems, the four RAD6000 processors are built
to withstand high doses of radiation in space.
Both fault protection processors are always
active and protect the spacecraft from faults by turning off components
and/or switching to backup components when necessary. The main
processor runs the Command and Data Handling software for data
transfer and file storage, and the Guidance and Control software
used to point and navigate the spacecraft.
Last updated: July 3, 2003
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