MESSENGER Mission News October 16, 2003

MESSENGER Phones Home

Testing of critical MESSENGER subsystems continued last week. In this
week’s Webcam 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.

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
(some 62 million miles) of outer space with a 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.