Video + camera, Monitor, Board covered with black felt, Microscope, Camera, Cooler, Hexane, Petri dishes, Scalpels, Slides, Transparent oil, Test-tubes, Brake-fluid, Ice box with dry ice in, Pump, Tubing, Filters, Air collection bags, Long pipe, Surgical gloves, Clean bags, Frame for bags, Plastic viles, Guidance computer, Two way radio, Portable phone & Generator
The black felt was used to observe precipitation while waiting for the Cooler to get below freezing or when temperatures were such, that the ice crystals were melting before we could examine them.
Microscope observationIn order to observe the precipitation in greater detail, a sample must be put under the microscope. This is not an easy task! Dishes containing hexane were held outside the van, until a reasonable amount of precipitation was collected. The dish was then placed on the microscope in the cooler. Agitation of the hexane was kept to a minimum to avoid the sample clumping together.
With the video and camera running the sample was examined, with anything of interest being photographed. It was possible to separate clumped precipitation, by moving them with a scalpel. The scalpel was also useful to check the image seen was actually in the hexane and not on the underside of the dish.
Oil slidesThis primary objective of this method was to test the method itself, for use in the aircraft. Cooled slides were covered with cold oil and allowed to collect the precipitation. The slides were then placed into a test-tube containing brake-fluid situated in the ice box surrounded by dry ice. Later the slides were put into hexane and examined under the microscope.
A clean bag was placed outside supported by a frame. When there was enough precipitation to fill a plastic vile, the vile was filled and placed in the ice box (surgical gloves prevented contamination from hands).
The filter tubing was elevated above the van by a long pipe. After connecting the tubing to the pump, the system was flushed, by running it for a few minutes. A filter was connected to the end of the tube, above the van, and kept pointing downwards to avoid any precipitation being absorbed. The flow rate was checked and when enough time to pump about 100/liters had past, the filter was collected. The filters were later analyzed to provide information regarding the CCN content of the air sampled.
Using the same set up as for the filters, and after flushing, bags were filled with air. These bags were provided and their contents analyzed by C.U. To avoid degradation it was necessary to deliver the bags to CU as soon as possible.
Written by John Cardwell 3/11/94
Please don't hassle me about spelling.