MESSENGER Mission News December 5, 2003

In the Swing

This image captures the MESSENGER team carrying out a critical test to measure
the magnetic field from the spacecraft. Over the past two years, the MESSENGER
Magnetometer team measured all of the magnetic components used in the
spacecraft and added up these contributions to estimate MESSENGER’s total
magnetic field. The team then figured out what magnets were needed and
where to put them on the spacecraft to cancel out its overall magnetic field.

To make sure this "magnetic balancing" was done right, on Nov. 28, engineers
lifted the spacecraft off its rollover fixture with four heavy-duty straps,
suspended it from the crane in the high-bay area and pulled on it slightly
using a nylon rope "leash." After releasing the rope the spacecraft swung in a
gentle pendulum motion that took about 5 seconds for each back-and-forth swing.
Tripod-mounted magnetometers placed around the spacecraft accurately measured
MESSENGER’s magnetic field as it moved from side to side.

The test showed that the balance magnets were chosen properly and mounted
correctly – so that the spacecraft is magnetically clean. This ensures that
once MESSENGER is in orbit around Mercury, the Magnetometer will detect only
the natural magnetic field of the planet.

MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and
Ranging) is a scientific investigation of the planet Mercury, and
the first NASA mission designed to orbit the planet closest to the
Sun. Dr. Sean C. Solomon, of the Carnegie Institution of Washington,
leads the mission as principal investigator. The Johns Hopkins
University Applied Physics Laboratory in Laurel, Md., is building
and will operate the MESSENGER spacecraft and ma£;õës the Discovery-
class mission for NASA.