Condign volumes 1 to 3

Read from the scan by GLM-OCR; expect the odd misread word.

## METEOROLOGICAL BALLOONS

1. A probable cause of UAP reports which must be considered is that of radiosondes and their lifting balloons.

2. Radiosonde Launch Sites There are eight operational upper air stations in the United Kingdom, just part of a world wide network of some 900. The stations in the UK release helium- or hydrogen-filled balloons four times a day at midnight, midday, six o'clock in the morning and evening. The transmitter, (the proper name is a radiosonde), sends back information about the temperature, pressure and the water content of the upper atmosphere. Wind speed and direction may also determine, either by using a NAVAID system or in some cases, the balloon and radiosonde are followed by radar. The distance the balloons travel away from the launch site is dependent on the wind strength, but they will quite readily reach a height of up to 15 miles (about 80,000ft) above the ground before they burst. The equipment descends on a small parachute.

3. Size and Shape The Meteorological Office currently useS balloons which are spherical and 1.5 to 2m in diameter at launch. The actual radiosonde is suspended some 30m beneath the balloon and, for visual purposes, can be ignored.

4. Location The location of radiosondes on their lifting balloons, is known from LORAN C; and could be used to eliminate suspected UAP mis-reporting.

5. The location of the release points in the United Kingdom are shown at Figure 1. The incidence of mis-reported radiosondes as 'UAPs' is likely to be higher in the vicinity of these launch sites.