Measurements of the Middle Atmosphere Lab (M.O.M.A)
Related Faculty Dr. Charles L Croskey Dr. John D. Mitchell

Observations are needed to study the physics and chemistry of the stratosphere and mesosphere (known as the middle atmosphere).  Both remote sensing and in situ measurements are used to make these observations.
 

Remote sensing can be used to determine water vapor, ozone, and chlorine monoxide concentrations and the temperature and density in the middle atmosphere. From the surface of the Earth, an upward-looking microwave radiometer, operating at 22 GHz can observe water vapor in the upper regions of the atmosphere.   Microwave receiver used to sense water vapor in the upper regions of the atmosphere.    Spectral analysis is used to determine altitude profile of the water vapor concentration. The receiver was taken on the RV Polarstern to Antarctica.

 

From space, a millimeter wave radiometer can look into the limb of the Earth’s atmosphere.  The Millimeter wave Atmospheric Sounder (MAS) was flown three times on the Space Shuttle to observe water vapor, ozone, and chlorine monoxide concentrations and the atmosphere temperature and pressure.     Penn State was most directly involved in the FEB (Filter Electronics Box), which performed spectral analysis.   The ATLAS experiment pallet (including the MAS) being loaded into the cargo bay of the shuttle. Map of the global coverage of the MAS during the ATLAS 2 mission.

In Situ measurements of the middle atmosphere are most conveniently made from sounding rockets.  Various electrode arrangements can be used to observe the electrodynamics of the region.   Blunt probe The round circular disk is a "blunt probe" collector. A swept voltage is applied to the collector disk and surrounding guard ring and the resulting current is measured by an electrometer.  The bipolar conductivity of the region can be measured by this technique.   Nose tip The "nose tip" probe is a fixed bias Langmuir probe. Because the applied voltage is not swept, higher altitude resolution can be obtained.  The fixed bias probe is most often used to obtain relative electron concentrations.  Boom electrodes Electric fields in the region can be observed by measuring the potential difference between electrodes placed at the ends of deployed booms. Electric fields from lightning discharges are thought to produce the optical phenomena known as SPRITES, which occur at high altitudes above mesoscale thunderstorms.  http://elf.gi.alaska.edu/sprites.html Gerdien condenser By applying a swept voltage between the inner and outer electordes of the Gerdien condenser and observing the resulting currents, ion mobility and concentration can be determined. Falling sphere The temperature, density, and winds of the neutral atmosphere can also be measured in situ.  The standard falling sphere technique uses a precision ground-based radar to track the accelerations of a free falling sphere.   Active falling sphere A new-generation active falling sphere system is under devlopment at Penn State.  This enhancement uses miniature accelerometers on board the sphere to observe the changes in accelerations as the sphere falls.

Field campaigns Often sounding rocket campaigns are conducted in remote locations to obtain the proper geophysical conditions.  For example the DROPPS/MIDAS program (http://www.rocketrange.no/campaigns/completed/campaign_0699/info.html)  was conducted in northern Norway during the summer of 1999 to observe the characteristics of Noctilucent Clouds and Polar Summer Mesospheric Echoes (PMSEs).   Final assembly of the rocket instrumentation. Andoya Rocket Range provides excellent facilities for guest investigators.   DROPPS payload mounted on launch rail.   Black Brant VA   Waiting for proper science conditions.   Launch sequence during the midnight sun.

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