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Pressure Modulator Infrared Radiometer (PMIRR)

The PMIRR instrument being placed
on top of the Mars Climate Orbiter spacecraft

Multispectral limb and nadir scanning atmospheric sounder
Provides vertical profiles of atmos. temp, dust, water vapor & clouds, quantifies surface radiative balance
Radiator door deployed upon achieving mapping orbit
Nominal FOV (Field of View) includes aft limb. Can also view out of spacecraft orbit plane
Vertical resolution = 5 km

PMIRR is a nine-channel limb and nadir scanning atmospheric sounder designed to vertically profile atmospheric temperature, dust, water vapor and condensate clouds and to quantify surface radiative balance. PMIRR observes in a broadband visible channel, calibrated by observations of a solar target mounted on the instrument, and in eight spectral intervals between 6 and 50 µm in the thermal infrared. High spectral discrimination in the 6.7 µm water vapor band and in two parts of the 15 µm carbon dioxide bands is achieved by employing pressure (density) modulation cells in front of selected spectral detectors. Adequate signal-to-noise in these channels is ensured through the placement of their detectors on a cold focal plane assembly cooled to 80 K by a passive radiative cooler. The PMIRR Principal Investigator is Dr. Daniel McCleese (JPL/Caltech); Vasily Moroz (IKI/Russia) is Joint Principal Investigator.


PMIRR science observations will commence only after the PMIRR radiator door is fully opened. Once PMIRR is deployed in the mapping orbit, vertical profiles of atmospheric properties are constructed from observations in three fields-of-view (FOV) stepped across the limb and onto the planet using a two-axis scan mirror in front of the primary telescope. Nominally, PMIRR views the aft limb, referenced to the spacecraft, except for the polar regions where it routinely views in and out of the plane of the spacecraft track to quantify the polar surface albedo by observing much of the bi-direction reflectance distribution function. PMIRR can also view to the side limb, acquiring observations characterized by different local times. PMIRR's vertical resolution is 5 km.

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