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551 ' 50S' S22 : 621' :\00'9

A method of telemetering chronometric radiosonde datathrough rawin channel

L. R. '[ATHUR. N. C. DHAR a nd H . S. BHATTACHARYA

J/elooro~ical Office, New De/Ii i

(Hete ived 2:j A ug" ,! 1.9!j5)

AB..'.lT RAcr. The pIlpt't' describes 8 method of te lemetertng chronometric radiosonde data on the t' ·Mchannel of the reeeiver of the radio-theodoli te, A equeggtng oscillato r i~ ueed in conjunction with the chro nn ­metr ic radi t... md e to obta in }o' ·~1 signale from the 400 ) Iett mwin transmitter at each contac t of the met eor o­logically ecn- it tve pens with t he contaetin g hpHx of th e redioeondc. With the ground .tWlEld rawin receive r anaultiliar! electronic unit i~ u..e.:1 to work th e radiosonde recorder. whenever t he .'.~( signahl are picked up h ythe radio-theodclltc recei ver. The det ails of the balloon borne unit and auxiliary equi pment are abo described .

t . Introduction

For abo ut a decmle both C-type p[athurl!J.lfo. 19·1 S) and ~'- t)"pe (Venkiteshwaran<to nl 1948) rad iosondes have been in usent I:! stations in Iullin for the dcterminatiouof temperature and humidity aloft. Recently,0. number of th ese radiosonde stat ions ha vebeen equipped with radio-theodolites forthe (let.erminat.ion of upper winds. Themethod has generally been to attach toth e same balloon " ·100 Mes transmitteralong with t. he radiosonde instrument. Thoradiosonde transmit ter operates at 80~[cs and the signals from the moteorographuni t aTC recorded on n ground-ba sed receiversud recording equipment tuned to 80 :\(cs. Thoreceiver of the radio-theodolite works on afrequency of ,10'1 ~"" and tracks the rawintransmitter by lIU'lU18 of an antenna systemut ilising split -pattern tracking. There arefour antenna bays consisting of :l:! half-waveelements spaced half wave-lengt h apart .There are four posit ions of the antenna lobesand four pips appeor on the oscilloscope, eachpip representing one position of the lobe.When the pips are of equal height, the antennasystem is directed norma l to tho directionof propagation of the radio beam from therawin transmitter in tho balloon. Tho recei­ver of tho radio-theodolite has two channels() [etox Tech. )[anual); (I) through whichthe F-)[ radiosonde signals can pas.. and(~) in which the receiver carrier is pulse­modulated in synchronism with the antenna

ph:lXi ng. Through these two channels infor­rnation is received rrgar(UlIg radiosonde datacomprising values of pressure, temperatureund humidity and rawin data giviug the an ­gular co-ordiua tes (azimuth and elevation)of the balloon at minute intervals, The heightvalues are obtained from the pressure datafrom the radi osonde and thereby the windvelocity and its direction is measured atdifferent levels in the upper atmosphere,

For quite some time the need for obtainingboth radi osonde and rawin data from thesame t ra nsmitte r ha s been keenly felt. The uscof a single transmitter also helps in elimina­ting a separate radiosonde receiver in theground equipment. The main problem washow to ada pt the chronomet ric radiosonde toobtniu temperature, pressure Bud humiditydata on the F-M channel of the rad io-theodo­lite receiver. In the present paper a methodhas been described whereby the eoMcs rad io­Sonde transmitter has been dispensed withamI the 400 ) lcs rawin transmitter has beenmad e to give F-M signals at each contact ofth e meteorologically sensit ive pens with thecontacting helix of the meteorograph uuitof the radiosonde. This simplification hasnatura lly decreased the cost of the combinedrawin-radi osonde flight and has also climi­nated a separa te operato r for the radi osonderecorder. The method dsseribed in th e Iollow­ing paragraphs con be modified. in other waysalso to telemeter th e radi osonde data to the