Challenges of Downsizing to Micro Radiosonde (Developed for iMS-100)

Routine radiosonde soundings twice a day in the world are providing long-time and high accurate data in the upper air. Some operational stations have reduced observation to once a day or discontinued due mainly to budgetary restrictions. In addition to meet performance standards that have been established by the WMO, Easy operation, Total (initial and running) cost reduction, and Safety are needed for the valuable and sustainable upper-air observation.

We developed the world lightest-smallest radiosonde “iMS-100” (less than 40g including a battery) to solve the above problems. The lightest iMS-100 decreases risks when it falls on ground after the balloon bursts. It can fall-down quite safely even without a parachute because of the slow fall velocity. The lightweight also help reduce annual gas consumption by ~30% for one station. Since the maximum reachable height depends on the size of the balloon, the amount of gas, and the total weight, the lightest iMS-100 package can reach 100 hPa pressure level with even small 100 g balloon.

Downsizing of iMS-100 results in higher performance of measurements. One is to reduce thermal effect influenced by radiosonde box because of decreasing the volume of radiosonde package by 30% relative to RS-11G (our previous operational radiosonde). Second, pendulum motions of sonde package are reduced because the smallest package smoothly rides on the wind. Therefore, micro iMS-100 can better capture “in-situ air” in terms of temperature and winds. Besides, new relative humidity sensor mounted with iMS-100 is developed to meet an increasing requirement for accuracy of humidity measurement. The response time is within 3 and about 20 seconds at -40 degC and -60 decC, respectively, to enable more accurate measurement in the troposphere.