Orbiter Scientific Instruments

Pressure Modulator Infrared Radiometer (PMIRR)

• 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.

Mars Color Imager (MARCI)

• Combined nadir pointed pushframe Wide Angle (WA) and Medium Angle (MA) cameras, totaling 2 kg
• WA camera: FOV = 140 degrees, 7 spectral bands (5 visible, 2 UV); MA camera: FOV = 6 degrees,10 spectral channels
• Imaging: Approach imaging, daily global Mars images with WA, monitoring of surface changes with MA during intervals with high data rates

MARCI combines Wide Angle (WA) and Medium Angle (MA) cameras with individual optics but identical focal plane assemblies, data acquisition system electronics, and power supplies. Each camera is small in size (Å 6 x 6 x 12 cm, including baffle) and mass (combined mass: 2 kg). Both cameras operate in a "pushframe" mode, with their CCD detectors overlaid with spectral ("color") filter strips. The cameras are electronically shuttered at intervals timed so that the spacecraft motion spatially overlaps each filter strip view, thereby providing a "color" composite. The MARCI Principal Investigator is Dr. Michael Malin (Malin Space Science Systems, San Diego).

Near the end of the Orbiter's cruise phase, MARCI acquires approach images of Mars. Once in the mapping orbit, MARCI provides daily global images of the Mars atmosphere (and surface) with the WA camera and monitors surface changes with the MA camera during mission periods with high data rates.

The WA camera has seven spectral bands [5 visible, 2 UV] and has spatial resolutions on the planet better than 7.2 km/pixel, for nominal orbital altitude and downlink data rates. Kilometer-scale resolutions are possible, when data rates permit. Limb observations detail the atmospheric structure of clouds and hazes at Å 4 km resolution. The MA camera has a 6_ FOV covering 40 km at 40 m/pixel (nadir) and accessing all positions of the planet (except the rotational poles due to the slight inclination of the spacecraft orbit). Ten spectral channels from 425 to 1000 nm provide the ability to discriminate both atmospheric and surface features on the basis of composition.