Mars Pathfinder Stereo Camera...

[P3D Shelley, Dan <dshelley@xxxxxxxx>]

I found information on the Web, including picture of the Imager For 
Mars Pathfinder (IMP). Enjoy:

 From: http://www.mars.ucar.edu/mpf/sci_desc.html#IMP

The Imager For Mars Pathfinder is a stereo imaging system with color 
capability provided by a set
of selectable filters for each of the two camera channels. It has been 
developed by a team lead by
the University Of Arizona with contributions from the Lockheed Martin 
Group, Max Planck
Institute For Aeronomy in Lindau, Germany, the Technical University Of 
Braunschweig in Germany
and the Orsted Laboratory, Niels Bohr Institute for Astronomy, Physics 
and Geophysics in
Copenhagen, Denmark. It consists of three physical subassemblies: (1) 
camera head (with stereo
optics, filter wheel, CCD and pre-amp, mechanisms and stepper motors); 
(2) extendable mast with
electronic cabling; and (3) two plug-in electronics cards (CCD data 
card and power supply/motor
drive card) which plug into slots in the Warm Electronics Box within 
the lander.




Figure 1. Close-Up of the IMP Camera Head

Azimuth and elevation drives for the camera head are provided by 
stepper motors with gear heads,
providing a field of regard of q180 degrees in azimuth and +83 degrees 
to -72 degrees in elevation,
relative to lander coordinates. The camera system is mounted at the top 
of a deployable mast, a
continuous longeron, open-lattice type provided by Able Manufacturing, 
Inc. When deployed, the
mast provides an elevation of 1.0 m above the lander mounting surface.

The focal plane consists of a CCD mounted at the foci of two optical 
paths where it is bonded to a
small printed wiring board, which in turn is attached by a short flex 
cable to the preamplifier board.
The CCD is a front-illuminated frame transfer array with 23 micrometer 
square pixels. Its image
section is divided into two square frames, one for each half of the 
stereo FOV's. Each has 256x256
active elements. A 256x512 storage section (identical to the imaging 
section) is located under a
metal mask. The imp focal plane and electronics are nearly identical 
copies of the comparable
subsystem employed in the Huygens Probe Descent Imaging 
Spectroradiometer (DISR), using the
Loral 512X512 CCD.

The stereoscopic imager includes two imaging triplets, two fold mirrors 
separated by 150 mm for
stereo viewing, a 12-space filter wheel in each path, and a fold prism 
to place the images
side-by-side on the CCD focal plane. Fused silica windows at each path 
entrance prevent dust
intrusion. the optical triplets are an f/10 design, stopped down to 
f/18 with 23-mm effective focal
lengths and a 14.4 degree field of view. The pixel instantaneous field 
of view is one milliradian. The
filter wheel four pairs of atmospheric filters, two pairs of stero 
filters, eleven individual geologic
filters (which, when combined with the two pairs of stereo filters, 
result in thirteen distinct geologic
filters) and one diopter or close-up lens, designed to acquire images 
of magnetic, wind-blown dust
which adheres to a small magnet located on the IMP tip plate.


Full panoramas of the landing site are acquired during the mission 
using the stereo baseline provided
by the camera optics. Additionally, monoscopic panoramas are acquired 
both prior and subsequent
to the mast deployment, yielding vertically displaced stereo pairs with 
approximately 80 cm
baseline. Images of a substantial portion of the visible surface are 
acquired in multispectral images
with as many as eight spectral bands.



Figure 2. IMP Deployed On The Able Mast

A number of atmospheric imvestigations are carried out using imp 
images. aerosol opacity is
measured periodically by imaging the Sun through two narrow-band 
filters. Dust particles in the
atmosphere are characterized by observing Phobos at night. Water vapor 
abundance is measured
by imaging the Sun through filters in the water vapor absorption band 
and in the spectrally adjacent
continuum. Images of wind socks located at several heights above the 
surrounding terrain are used
to assess wind speed and direction.

A magnetic properties investigation is included as part of the IMP 
investigation. A set of magnets of
differing field strengths will be mounted to a plate and attached to 
the lander. Images taken over the
duration of the landed mission are used to determine the accumulation 
of magnetic species in the
wind-blown dust. Multispectral images of these accumulations may be 
used to differentiate among
likely magnetic minerals.

The IMP investigation also includes the observation of wind direction 
using a small wind sock
mounted above a reference grid, and a calibration and reference target 
mounted to the lander.


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