MESSENGER Mission News October 24, 2003: Simulating Space

Before MESSENGER is launched, the spacecraft team will test each
component using various engineering methods to simulate aspects of
the space environment — testing under normal Earth conditions may
not reveal potential technical issues.

For example, the wire coils resting on the portable scaffold in this
week’s Webcam image are used to simulate the weaker magnetic fields
MESSENGER will encounter at Mercury. Earth’s magnetic field is 100
times stronger than Mercury’s, so the MESSENGER Magnetometer (MAG)
has two settings: one for testing at Earth and the other for science
observations at Mercury. To make sure the instrument works properly
at "Mercury" settings, engineers artificially lower the magnetic
field at the MAG sensor during testing, by positioning these coils
around the sensor and sending electric current through them to
cancel (locally) Earth’s magnetic field.

The Magnetometer blends with its surroundings in this view. Note the
small silver dish at the end of the thin vertical black boom; the
actual MAG sensor is inside the small yellowish cylinder just above
the arrow labeled (G). In this orientation many other critical
MESSENGER components are visible:

(A) phased-array antenna [one of 2]; (B) solar monitor for the X-Ray
Spectrometer instrument; (C) hydrazine auxiliary fuel tank [under
its protective cover]; (D) low-gain antenna; (E) helium pressurant
tank; (F) star simulator [for testing Star Tracker cameras]; (G)
Magnetometer boom [with Magnetometer in stowed position]; (H) low-
gain antenna; (I) Digital Sun Sensor; (J) Fast Imaging Plasma
Spectrometer [part of the Energetic Particle and Plasma Spectrometer
instrument]; (K) umbilical harness [wiring]; (L) power system
electronics; (M) solar panel simulator; (N) Inertial Measurement
Unit; (O) thruster module.