QUESTION:
What instruments are used on the MPF and what do they do?

ANSWER from Nick Miller on January 27, 1997:
Taken from http://quest.arc.nasa.gov/mars/background/pint.html
"There are three main instruments on the Mars Global Surveyor. The
Imager for MESUR Pathfinder will primarily provide stereoscopic images
via CCD camera. The surface elemental chemistry is the focus of the
Alpha Proton X-ray Spectrometer. Finally the Atmospheric Structure
Instrument/Meteorology Package has been given the task of taking data
such as temperature and pressure for scientific analysis. 

Imager for MESUR Pathfinder (IMP)
This stereo imaging system with color capability consists of
three main sections: camera head, extendable mast with electronic
cabling, and two plug-in electronics cards.  The camera is located at
the top of a deployable mast, which when deployed, can provide an
elevation of one meter. This instrument will also investigate
magnetic properties. Magnets of varying field strengths are mounted to
a plate that is attached to the lander. Magnetic particles from the
Martian "air" will be attracted to the plates, which will be imaged
for mineral composition. Also included in this investigation is the
study of wind direction on Mars. A small wind sock will be mounted
above a reference grid with a target for reference and calibration on
the lander. 

Alpha Proton X-ray Spectrometer (APXS)
This instrument will determine the elemental chemistry of materials
found on the surface for all major elements except hydrogen. The APXS
is mounted inside the rover where the temperature can be controlled.
Its sensor head is mounted on a deployment mechanism. The spectrometer
consists of an alpha particle source and detector for back-scattered
alpha particles, protons and x-rays. Material will be exposed to a
radioactive source that produces alpha particles of a certain energy,
and by looking at the energy spectrum of the alpha particles, protons
and x-rays emitted, the elemental composition can be determined. 

Atmospheric Structure Instrument / Meterology Package (ASI/MET)
This instrument will collect data during descent and landing in order
to provide information on atmospheric density, temperature and
pressure at about 100 km down to the surface. Temperature and pressure
sensors are mounted on the lander at various locations. Depending on
the vertical descending rate of the lander, the sampling rate from the
sensors can be increased or decreased. After landing, the ASI/MET will
continue to sample the temperature and pressure to record the daily
changes during the mission."

For more information on the instruments please refer to one of these
Intenet sites:
http://quest.arc.nasa.gov/mars/background/pathfinder.html
http://mpfwww.jpl.nasa.gov/default.html
http://mpfwww.jpl.nasa.gov/mpf/science.html
http://marsmirror.lerc.nasa.gov/mpf/sci_desc.html#APXS