NASA MESSENGER Mission News October 7, 2003 – An Instrumental Milestone

On October 3, the Gamma-Ray Spectrometer Pre-Amp Box was re-
installed on the MESSENGER spacecraft. By itself, this was one of
seemingly countless small steps toward launch. However, this small
step marked a major milestone for the MESSENGER mission: all seven
science instruments were completely installed on the spacecraft!

In this image, the MESSENGER team can be seen installing the Pre-Amp
Box, which includes electronics that amplify low-level signals from
the sensor that collects gamma-ray data. Engineers had removed,
tested and repaired the box last month after learning, through a
NASA-wide alert system, of potential problems with two vendor-
supplied diodes inside. The actual location of the device is hidden
from view behind the Launch Vehicle Adapter.

The Gamma-Ray Spectrometer (GRS) will provide information that
allows scientists to estimate the abundance of geologically
important elements in Mercury’s crust (oxygen, silicon, sulfur,
iron, hydrogen, potassium, thorium, and uranium). The spatial
resolution of the GRS measurements, while relatively coarse (200- to
1,000-kilometer scale), will allow scientists to investigate major
questions such as: how did Mercury’s crust form?

The GRS measurements will also provide key information that allows
more confidence in mineralogical and compositional interpretations
from instruments – such as the Mercury Atmospheric and Surface
Composition Spectrometer or the Mercury Dual Imaging System – with
much higher spatial resolutions (100 meters to 1 kilometer). Linkage
of science data from all the spacecraft’s instruments, at scales
ranging from tens of meters up to a whole hemisphere, is key to
MESSENGER’s science strategy.