The Virtual Upper Air Tour Wilmington, Ohio Page: 1, 2, 3

With the flight train completed, it is now time to move back into the office and prepare the radiosonde for its journey into the sky. At Wilmington, the Sippican Mark IIA radiosonde is used. This styrofoam instrument will transmit temperature, humidity, and pressure data. It is also equipped with a Global Positioning System (GPS) receiver. The exact location of the radiosonde can be determined using the GPS, and this information is used to calculate the wind speed and direction at any point during the ascent.

The temperature sensor (known as a thermistor) is found on wire that sticks out from the top of the radiosonde. The humidity sensor (known as a hygristor) is located inside the packaging of the radiosonde, and is sealed off with masking tape. The radio transmitter sends the data to the office in the 1676-1682 MHz frequency range. The transmitter, GPS receiver, and pressure sensor are located inside of the styrofoam box.

The radiosonde is taken out of its packaging, as the Radiosonde Workstation computer software is loaded. The software will ingest all of the data received by the radiosonde, and process it into useful and readable information. The software is also used to control the tracking dish. When the software is loaded, it immediately begins warming up the components of the tracking system, so that they are ready to be used when it is time for the flight -- even on the coldest of mornings.

Each radiosonde is powered by a small battery, which must be charged immediately before the flight.

The battery is activated by submersion in water for two minutes. When fully charged, the battery can provide power to the radiosonde for up to three hours.

Back at the upper air desk, the battery is inserted into the radiosonde. After a few minutes, the radiosonde will be properly charged up.

After the radiosonde reaches a stable electrical charge, it is placed on a sytrofoam pad and run through what is known as the baseline procedure. This procedure ensures that the data the radiosonde is generating is of good quality. The data is checked against a standardized set of observing equipment installed just outside of the office. Sometimes, a radiosonde will produce erroneous data -- in such a case, the instrument must be rejected and a new radiosonde will be used.

With the radiosonde ready to go, it is time to take one last look at the surface observations before heading outside. It is rather crucial to know the wind profile of the atmosphere, in order to predict where the flight train will be directed after the launch. This is especially true in foggy situations, because the flight train may disappear from view in a very short period of time!

Finally, the last piece of the flight train is attached -- the radiosonde. The instrument will sit on the stand for a few minutes, and await the coming launch.

Continued on Page 3.

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Andrew Hatzos -- NWS Wilmington, Ohio (ILN) -- 2007