A STUDY ON THE STRUCTURAL MECHANISM OF THE AUTOMATEDRADIOSONDE SYSTEM (ARS)

Yasomi OIKE, Kenji KOKUBO, Akitoshi OGURA, Makoto FUJITA, Koji SHIBATA, Shanker ManSHRESTHA

Meisei Electric Co. Ltd.,2223 Naganuma-cho, Isesaki City, Gunma, Japan

Tel: +81-270-32-9799, Fax: +81-270-32-0988ooikey@meisei.co.jp

Abstract - Meisei Electric hasdeveloped an automated radiosonde system(ARS) for upper-air sounding. It has startedits first operation at Ishigaki Island Station,Japan (WMO Station ID: 47918) in March 1,2006. The system design is based on the windsimulation to ensure that the structuralmechanism provides stable launches even atthe critical weather condition such asrainstorm, typhoon, and so on. The windtunnel tests have been performed with a modelof the launcher, which is equipped withmovable wind protector and arc bearing guidemechanism to prove the stability andreliability of the designed system. We present adetailed report on these mechanisms, windtunnel test and other case study in thefollowing section.

Keywords – Upper air observation, automatedradiosonde system (ARS), wind tunnel test.

I. INTRODUCTION

An Automated Radiosonde System (ARS)operates automatically in all weather conditionfor the measurement of meteorological variablessuch as pressure, temperature, and humidity.Generally, the radiosonde is launched manually(hand-launched), which is labor intensiveprocedure. The strong surface wind isunfavorable condition for the smooth launchingthe radiosonde. Typhoon is very common inJapan and it is considered as a sever problemfaced at the time launching the radiosonde. Inorder to alleviate these problems, we developedthe Automated Radiosonde System (ARS)equipped with movable wind protector and arc

bearing guide mechanism that is best suited forsmooth, safe, and reliable launch during thetyphoon as well. The most attractive feature ofthe system is that the wind protector (cap like astructure), which rotates automatically to protectthe wind pressure after receiving a feedback fromwind direction finder.

II. ARS2.1. System Design

MEISEI’s ARS automatically sets up theradiosonde and performs pre-flight checkfollowed by filling the gas inside the balloons. Italso launches radiosonde automatically. The ARSthen automatically receives radiosonde signal andGPS satellite signals and convert it to observedata and meteorological message to forward themto JMA and WMO. The ARS is cost effectivesystem for remote locations such as difficult towork, difficult to travel, and difficult to providemanpower.

The external outlook of ARS is demonstratedin Fig. 1 and the system design is shown inFigure 2. The ARS consists of sonde cassette, gasstorage, daisywheel, gas filling monitor andcontrol, and launching platform.

2.2 ARS Operation

ARS operation is briefly explained asfollowing. Firstly, loading the radiosonde,unwinders, parachutes, and balloons into the builtin cassettes is performed. Secondly, the cassettesare inserted in the daisywheel, which is equippedwith positing a control sensor automaticallyconnects the radiosonde cassette to the gas inletposition. Thirdly, the gas is filled inside the

balloon by carefully monitoring the amount ofloaded gas, gas filling speed and ascending force.Finally, ARS confirms the preflight test andautomatically releases the balloon with aradiosonde.

2.3 GPS radiosonde

The GPS radiosonde system consists ofgas filled balloon, parachute, suspension, andradiosonde system that is operated by battery.The sensors are the thermally sensitive resistortype thermometer, the thin film capacitancehumidity sensor, and the GPS signal sensor. The

received GPS signals are highly precise, and theaccuracy of the temperature and humidity sensoris very high.

We have developed a new GPSradiosonde for ARS to operate automatically andsafely. Parameter setting of the radiosonde isperformed remotely by software. Gas isautomatically filled and stop with the specialvalve made of plastic material because highprecaution has been taken for any possible gashazard and other accident. New radiosondesystem has provision to put the parachutes insidethe balloon so that space consumed by theballoon, parachutes, suspension is small andeasily fit to the cassette on the daisywheel.

In contrast to our previous radionsondemodel RS-01[1], the lithium battery (1.5Vx2)with high energy density has been used for thepower supply, instead of water activated battery.It has wide range of advantages, such as easilyavailable in the market, low cost, robust to all theextreme weather conditions, long life, and bestsuited for ARS. Our radiosonde unit is very lightand its weight is less than 155 gm including thebattery. Consequently, the gas filling can beremarkably saved and of course, the operatingcost will be minimized.

2.3 Ground System

The ground system consists of antennas,pre amplifier, radiosonde receiver, work station(PC), and the base line (BL) checker set as shownin Fig. 2. There are two Yagi Antennas (threeelements directional antenna), and a BrownAntenna (omni directional antenna), and thisantenna arrangement is the most effective andeconomic to receive the radiosonde signalcontinuously up to 250 KM range.

The received radiosonde signal by theantennas is fed towards the PRE AMP, whichcontains coaxial switch, band pass filter (BPF)and LNA (low noise amplifier). The antennaoperation is controlled by coaxial switch toacquire the continuous data. The telemetry signalfrom the PRE AMP is received by the UHFreceiver via coaxial cable (50 Ohm), where theRF signal will be demodulated. The FM

Fig. 1 External Structure of MEISEI ARS

Receiverunit

Antenna

Gascontrolunit

Drivedepartmen

t

Sequencer

L/Aterminal

JMA

Remotocontrol unit

AWOSGas line

PC PC

Mechanicalcontrol

Observationcontrol

Gas

W M O

Fig. 2 System design and data flow ofMEISEI ARS

demodulated signal is further transmitted to PCMdecoder at the rate of 1200 BPS via coaxial cable,where the PCM demodulation is performed. Onthe other hand, the GPS signal received via thedifferential GPS antenna is send towards the localGPS receiver via coaxial cable. Both the PCMdemodulated signal and local GPS signal arecombined in the CPU, where the error check willbe performed. Finally, the combined raw datafrom CPU is transmitted to work station(personal computer) for the post processing anddisplay the data by TCP/IP cable.

III. WIND TUNNEL EXPERIMENT

We performed the experiment inside windtunnel to examine the performance of the windprotector, which is demonstrated in Fig.7. Thewind is generated inside the wind tunnel by axialtype fan system have diameter 3.5 m operated byDC motor (400 V, 150 kw, 0-300 rpm). The totallength of the wind tunnel is 94 m and testing areahas a dimension of 2.0 m height, 2.4 m width and21 m length. It has two turn tables of diameter 2.0

m and ceiling height is adjustable. The windvelocity can be varied inside the wind tunnelfrom 0.5 to 3.3 m.

Generally, our ARS can launch theradiosonde smoothly at the wind velocity 25 m/sor less. However, it is not possible to generate thewind velocity of about 25 m/s. So we generatethe wind velocity of about 3.3 m/s and calibrate itusing Reynolds Number [2], which is expressedby the following equation.

bbaa SVSV // = (1)where, Va be an actual velocity of wind, whichis less than 25 m/s. Vb be a wind velocity inside

the tunnel, which is set to be 3.3 m/s. Sa be anactual balloon ascending speed and Sb be theascending speed of model balloon.

Actual Reynolds Number ActualeR and

Modeled Reynolds Number ModeleR can becalculated by the following equations

Fig. 3 Experimental Setup for wind tunnel test

High-speed video

Spotlight

Wind tunnel

Model

Fig. 7 MODEL-A: An ascending sequence of theballoon inside the wind tunnel

Fig.8 MODEL-B: An ascending sequence of theballoon inside the wind tunnel

Fig. 9 MODEL-C An ascending sequence of theballoon inside the wind tunnel

Fig. 6 MODELl-C Wind Protector Model having Plano-concave surface but the upper portion is plane

Fig. 5 MODEL-B Wind Protector Model havingconcavo-convex surface

Fig. 4 MODEL-A: Model without wind protector

The balloon was halted for 2 secat the launching space

No launching space forsmooth ascending balloon

6109/ ×== vULR ActualActuale (2)4109/ ×== vULR ModelModele (3)

Where,U：wind velocityL：height of the wind protectorv：dynamic viscosity

Here, the modeling scale is 1/12.5 It isfound that the discrepancy between the ActualReynolds Number and the Modeled ReynoldsNumbers is not high, which is demonstrated inEq. 2 and Eq. 3. It is concluded from thisexperiment that the proposed model can worksuccessfully in actual operation.

It is vital to know the direction and the

nature of wind for the smooth launching theballoon from the ARS. The circular wind maystop the balloon at the neck of the ARS and theballoon will not be launched smoothly. Therefore,we made several kinds of wind protector modelsas shown in Fig 4, 5 and 6. In MODEL A (Fig. 4),there is no provision of wind protector that meansthere is no launching space for the balloon. So,the launching of balloon is not smooth becausethe balloon strikes on the outlet of the ARSmodel several times. In addition, there might bechances that the balloon doesn’t come out fromthe ARS and even the balloon come out, it isflown immediately by the high velocity windstream. Consequently, slightest friction or strikeon the edge of the ARS outlet might causeballoon burst before launching, which is a severproblem of this type of model (see Fig. 7).Secondly, in MODEL B, the balloon was haltedfor 2 seconds at the launching space due to theeffect of circular wind as shown in Fig 8. Thiscircular wind (see Fig. 10) may rotate the balloonin the launching space and the ascending balloonwill not be smooth that may cause the radiosondeto strike at the inner surface of ARS.

Finally, in order to combat with suchproblems, we developed the model of the windprotector which is the best suited for successfuland smooth launching of the balloon. It isdemonstrated in Fig. 5 (MODEL C). In thismodel, the wind protector has plano-concavesurface but the upper portion is plane. The curvewill direct the wind flow in upward direction andmixed with wind profile flown above the windprotector as demonstrated in Fig.12. Thus therewas enough launching space for the balloon andthe ascending balloon was fully protected fromthe high speed wind effect and hence the balloonwas launched smoothly and safely.

IV. FIELD EXPERIMENT & OPERATION

The field experiment of ARS wassuccessfully conducted at factory premises inDecember 2005. The first operational of ARSwas performed at Ishigaki Island Station, Japan(WMO Station ID: 47918) in March 1, 2006.

Launching spaceof the balloon

Fig-11 MODEL-A: Launching space the wind flowdirection

Fig-10 MODEL-B: A: Launching space the windflow direction

Since then, it has been operating successfullyeven during the typhoon, which is demonstratedby the following data taken during Typhoon No.4 and Typhoon No. 5 [3] as shown in Table 1 and2.

V. CONCLUSIONS

Meisei has successfully developed theadvanced ARS for upper air observation. Itlaunches the radiosonde up to 16 times withoutattendant’s assistance.. The development of wind protector is amilestone towards a development of ARS. Thewind protector has ventilating system for smoothand easy outlet of balloon from the launchingspace. It is based on arch bearing guidemechanism that is best suited for smooth, safeand reliable operation during typhoon. MeiseiARS cassette pack is portable and easy to packtogether with the radiosondes, parachutes built inballoons, and the unwinders.

Other attractive features of automated radiosondesystem are use of lightest lithium battery toextend operating time, accurate GPS heightmeasurement system, environmental friendlybiodegradable material radiosonde case,temperature sensor coated with aluminum, andexternal thin film capacitance humidity sensor,pre-launch base_line check to ensure thereliability of temperature and humiditymeasurement, and so on.

Since the number of ARS and theavailable data is limited, more data acquisitionand development of advanced ARS is essentialthat can be used in challenging environmentconditions such as snow fall, change of surfacewind direction within the short span, would bethe topic for the future research.

New installation of ARS will be done inNaze, Kagoshima, Japan within this fiscal year.

VI. ACKNOWLEDGEMENT

The authors wish to express sinceregratitude to the members of the JMA (JapanMeteorological Agency) Upper Air ObservationDivision and Ishigaki MeteorologicalObservatory for valuable suggestions. Theauthors would also like to thank Dr.YoshimiSuyama of Hazama Technical Research Institute,Tsukuba, Japan for wind tunnel experimental labfacility and for his constructive suggestions.

REFERENCES

[1]. M. Fujita, H Masuyama, N. Kaneko, H.Kaneko, “Differential GPS RadiosondeObservation System”, IMOP publication, IOM-75, TECO 2002.[2] Kiyohide Takeguchi, “ Meteorology of theWind” University of Tokyo Press 1997, ISBN-4-13-064704[3] http://www.jma.go.jp/en/typh/ JapanMeteorological Agency

Table-1 Typhoon No.4

Date Time Windvelocity(m/s)

Launching

Result

2006.7.13 12Z 27.7 OK 7.13 12Z 27.0 OK 7.13 18Z 23.4 OK 7.13 18Z 22.6 OK 7.14 00Z 18.5 OK 7.14 12Z 19.9 OK 7.15 00Z 13.8 OK

Table-2 Typhoon No.5

Date Time Windvelocity(m/s)

Launching

Result

2006.7.24 00Z 7.2 OK 7.24 12Z 9.4 OK 7.25 00Z 8.2 OK 7.25 12Z 10.1 OK 7.26 00Z 8.3 OK 7.26 12Z 8.2 OK 7.27 00Z 7.2 OK 7.27 12Z 5.6 OK 7.28 00Z 3.3 OK