Chapter 9 — SPECIALIZED METEOROLOGICAL EQUIPMENT AND THEIR USES 



is an eyepiece to which a string can be tied. 

 The string may be tied to some fixed object 

 or held by another person during the release. 

 When hydrogen is used a special static free 

 shroud should be utilized. 



Train Regulator 



The radiosonde/rawinsonde train regulator 

 consists of a frame, reel, and braking mecha- 

 nism. The regulator is furnished with approxi- 

 mately 60 feet of nylon cord wound on the reel. 

 The braking mechanism permits the weight of 

 the radiosonde to unwind the cord at the nominal 

 rate of 12 feet per minute. The train regulator 

 is attached between the parachute and the radio- 

 sonde and facilitates releases during strong or 

 gusty winds. 



Parachute 



The parachute is a lightweight, expendable, 

 paper device used to slow the descent of a 

 balloon-borne radiosonde after the balloon has 

 burst. It minimizes the danger to personnel 

 and reduces or minimizes property damage 

 from the falling radiosonde. The parachute should 

 be used for ALL upper air soundings unless 

 there are specific instructions to the contrary. 



TRACKING EQUIPMENT 



Shore-Type Theodolite 



The theodolite is used in taking pibals to 

 measure elevation and azimuth angles of a pilot 

 balloon. 



The shore-type theodolite, AERO-1928-USN 

 or ML-474, is similar in many respects to 

 a surveyor's transit, with certain modifications 

 necessary to adapt it to pibal tracking. (See 

 figure 9-1.) The telescope, supported over the 

 center of the upper plate by a yoke standard, 

 is mounted for rotation in both the vertical 

 and horizontal planes. The theodolite telescope 

 differs from the transit telescope. The theodo- 

 litz's line of sight is bent through an angle 

 of 90°, placing the objective lens and eye- 

 piece at right angles to each other. A glass 

 prism conveys the image from the objective 

 lens to the eyepiece, which remains stationary 

 in the vertical plane, while the objective lens 

 moves up and down in tracking the balloon. 

 To avoid the use of two additional lenses and 

 a subsequent reduction in light, theodolites have 



nonerecting eyepieces, and the image appears 

 inverted. By rotating an internal spiral cam 

 attached to it, the eyepiece is focused on cross- 

 hairs provided for use in centering the bal- 

 loon in the field of the telescope. 



For detailed information on the operation 

 and maintenance of the shore-type theodolite 

 refer to FMH No. 5 and the handbook of over- 

 haul instructions, NA 50-30WH-1. 



Shipboard Theodolite 



The shipboard theodolite (figure 9-2) is used 

 in taking pibals at sea. This theodolite consists 

 of an enclosed optical system with an artifical 

 horizon assembly for operation at night or on 

 days when the horizon is not visible. Ray filters 

 are used to improve visibility. The vertical and 

 horizontal scales are used for obtaining eleva- 

 tion angle and azimuth angle readings. The 

 theodolite is mounted on a gimbal assembly 

 base plate which screws onto a tripod. A counter- 

 weight on the counterbalance shaft attached to 

 the gimbal assembly tends to keep the instru- 

 ment in a vertical position with minimum fol- 

 low of the ship's roll and pitch. 



For detailed operating and maintenance in- 

 structions refer to the Handbook, Operation and 

 Maintenance Instructions, Shipboard Theodolite, 

 NA 50-30FR-522. 



Radiosonde Recorders/ 

 Receptors/Receivers 



RADIOSONDE RECORDER AN/TMQ-5( ).— 

 Radiosonde Recorder AN/TMQ-5( ) records 

 weather information in graphic form that is 

 transmitted from a balloon-borne radiosonde. 

 It is normally used when taking an upper air 

 sounding with AN/GMD-1( ) equipment which 

 employs a 1680-MHz radiosonde. 



The Operator's Manual for this recorder 

 contains detailed instructions on its operation 

 and maintenance. 



RADIOSONDE RECEPTOR AN/SMQ-1( ).— 

 Radiosonde Receptor AN/SMQ-1( ) (fig. 9-3) 

 is an electronic meteorological device which 

 receives, amplifies, demodulates, and graphically 

 records signals emitted from a balloon-borne 

 403-MHz radiosonde. The receptor covers a fre- 

 quency range of 390 to 410 MHz. The radio- 

 sonde transmits data in the form of pulsed 



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