Measurement of both long-wave and short-wave radiation is critical to understanding global environmental change. This is especially true in the Arctic, where the heat transfer among the ice, the atmosphere, and the ocean can alter the state of the ice pack. The transformations of thermodynamic energy in ocean-atmosphere-ice interface affect the mass balance of the sea ice and snow cover, the formation of clouds and the radiative properties of the surface. When sea ice forms, profound changes occur in local rates of air-sea interactions.

SSI's technical approach to the design of a prototype radiometer system was to protect the sensor from the harsh environment when not in use and mechanically deploy it for data acquisition. Considering the environment and the necessary functions, the system was designed with the following features:

• A 7" diameter aluminum sphere, Teflon impregnated hard coat anodized for ice release, which houses the radiometer. The sphere is mounted on top of a cylindrical housing. When the radiometer is not in use, the sphere is turned so that the radiometer is protected inside the housing while the opposite side of the sphere closes off the opening. A circumferentially mounted knife-edge seal wipes the surface of the sphere as it rotates to expose the radiometer to the environment.
• A cylindrical housing open at the bottom to maintain the radiometer at ambient temperature, and prevent heat and humidity build up by providing natural ventilation to the enclosure.
• A light or heat source (depending on the type of radiometer used) inside the housing which is energized to provide a "calibration" signal for the sensor; thus determining the condition of the dome. A decision is then made whether to clean the dome. There is no added power consumption if the dome is clean.
• A hot air blower inside the housing which clears frost or moisture from the dome if it should become contaminated.
• A fan which provides ventilation at ambient temperature when the radiometer is collecting data (similar to current commercial ventilated radiometers).
• A bi-axial inclinometer which is used in a feedback loop for leveling the radiometer. The second axis data is used for applying corrections to the data, if for example, the device is thrown off-level due to shifting of the ice.
• A low-power computer which handles the data acquisition and logic control functions of the electro-mechanical system. Operational parameters such as frequency of data collection, conditions for cleaning, motor speed control and error checking, are all controlled through the software, and can be customized depending on the user and the environment requirements.

Photographs:
(Click on the photo to enlarge it)

1 - Photographs of unprotected sensors subjected to ambient conditions: (A & B) heavy frost on a short and long wave radiometers, (C) radiometers subjected to freezing rain, (D) an anemometer in freezing rain. Needless to say, the data from all of these sensors would be erroneous in their depicted state.

2- ISPS in protected position.

3- A Long wave radiometer in deployed position. In this configuration ambient air is blown through the narrow slit around the sensor dome in order to promote mixing of the thermal boundary layer around the dome which delays the onset of frost formation on the dome.

4- A view of the "control" side of ISPS: a weather tight enclosure housing custom designed circuit boards, cables, and other electro-mechanical components.

5- Data acquisition and control module assembly.

6- A view of the "drive" side of ISPS: a weather tight enclosure housing a high torque gear motor, capable of breaking ice accumulated on the sphere during deployment.

7- Long and short wave radiometers housed in ISPS deployed on the ice at a remote site 50 km away from SHEBA. The cylindrical housing in the middle is a data buoy containing GPS, snow temperature, air temperature, and Argos satellite link. The other two buoys house batteries for the two radiometer systems. Buoys are commonly buried in the ice to keep them warm, as the surface temperature can plunge down to -40?C. The support post is plumed in a 5" diameter hole drilled all the way through the ice in order to flood it. As the water freezes in the hole, it will provide an extremely rigid support for ISPS.

8- CCGS Des Groseilliers ice breaker at dusk.

9- Site of downtown SHEBA from the deck of CCGS Luis S. Saint-Laurent ice breaker.