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Testing of critical MESSENGER subsystems continued last week. In this image, engineers remove a special device from one of the Star Tracker cameras that simulates the sky.

Attached to the sunshade frame is one of MESSENGER's twin phased array antennas, which will transmit most of the science data from the spacecraft to Earth. The rectangular red cover seen here is a called a hat coupler; this device captures the radio waves emitted by the antenna and safely transmits them by cable to a Deep Space Network antenna simulator, currently parked behind the Kershner Space Building at the Applied Physics Laboratory, where MESSENGER is being assembled.

(Click here for inside and outside photos of the DSN testing trailer)

The hat coupler allows critical communications-compatibility testing to take place without endangering the people working near the spacecraft. The phased array antennas transmit about 11 watts of power. For comparison: a cell phone has maximum power of about 1 watt, while an average microwave oven puts out about 700-1000 watts. MESSENGER will transmit data across more than 100 million kilometers (62 million miles) of outer space with power only 10 times greater than a cell phone! Thus, it is critical that the antennas are tuned perfectly to allow the best reception through NASA's DSN antenna stations.

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Last updated: October 16, 2003

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