PREPARATION OF THE RADIOSONDE

Figure 1-6.—Tying the balloon neck to hold the radiosonde instrument: (A) First square knot, (B) looping the balloon neck and tying the second square knot above the first, and (C) attaching the unwinder to the balloon and tying unwinder to balloon with excess cord. Q12. Q13. Q14. Q15. Q16. Q17. Q18. U n d e r w h a t c i r c u m s t a n c e s s h o u l d a meteorological balloon be conditioned before use? What is the ideal ascension rate for a meteorological balloon? What is the purpose in using a gas regulator? How much cubic feet of helium is required to achieve a free lift of 700 grams when using a 100-gram balloon? What must be done to the balloon when conducting upper-air observations during periods of precipitation or icing? At sea, when is a parachute required to be attached to the radiosonde? What is the purpose of a balloon shroud? PREPARATION OF THE RADIOSONDE The lightweight, Vaisala RS-80 radiosondes are unpacked from the protective envelopes and readied for flight according to following the instructions provided in the operator’s manual. An 18-volt battery is activated by immersion in room-temperature tap water for 3 minutes. After lightly shaking off the excess water, the battery is then plugged into the instrument to activate the radiosonde. The radiosonde instrument is automatically set to 403 MHz, but may be tuned from 400 to 406 MHz to avoid local interference. A small screw located on the outside of the radiosonde can be turned by using a small screwdriver to adjust the frequency up or down. The radiosonde should be placed outside, out of direct sunlight and hot surfaces (decks/stacks), for five minutes. This allows the sensors in the radiosonde to stabilize prior to launch. Keep in mind that if the battery is left to sit for more than 20 minutes, it may overheat and become unstable, so time management of prelaunch procedures is essential. Be sure to remove the plastic cover from the sensor strip prior to releasing the radiosonde. ENTRY OF CALIBRATION DATA Each RS-80 radiosonde instrument is precalibrated during manufacture and is supplied with a calibration punch-tape. When each upper-air sounding is initiated, the system prompts the operator to enter the calibration punch-tape in the optical reader slot. This will ensure that the signals received from the radiosonde are properly interpreted by the system. The calibration 1-9