MESSENGER Mission News: A Powerful Move Forward

MESSENGER’s propulsion system is now in place and has passed
critical tests as work moves forward on spacecraft assembly. See
this week’s annotated Webcam image at

http://messenger.jhuapl.edu/annotated-20030730.html .

The MESSENGER spacecraft is starting to come alive. Much of the
propulsion system has now been integrated and tested. Since the
spacecraft is not complete, some components are simulated using
special electronics test equipment that allows full up testing of
newly installed hardware. Here an engineer can be seen working on
the Power Distribution Unit (PDU) — see May 15 image — during
the propulsion system checkout.

Time-lapse sequences (link to movies) show how engineers can turn
the spacecraft through 360 degrees of rotation with the Turnover
Fixture and spin the spacecraft on its z-axis by turning the
Rotisserie Hand Crank. In this orientation many key components of
the spacecraft are visible. The digital Sun Sensor (one of six)
plays a critical role ensuring that the spacecraft does not turn
the Sunshade away from the Sun. The Solar Array Drive Electronics
work to keep the solar panels in the correct orientation to balance
the need for power and the temperature of the surface of the panel.
The Integrated Electronics Module is one of two main computer
processors that control all functions of the spacecraft.