The Design and Performance of Meteorological Sensors for WindBorne Global Sounding Balloons

TL;DR

The paper presents WindBorne Systems' Global Sounding Balloon (GSB) sensor payload, calibration, and processing framework for continuous global atmospheric profiling with long-duration balloon flights. The design minimizes bias and noise through a custom readout architecture, shielding, multi-sensor averaging, and calibrated corrections, and validates performance via side-by-side radiosonde comparisons and ERA5 reanalysis intercomparisons. Key findings show agreement with radiosondes within uncertainty bounds and notable consistency with ERA5 across geopotential height, pressure, temperature, wind components, and relative humidity, with quantified RMS differences (e.g., geopotential height ~14 m, pressure ~0.36 hPa, temperature ~0.91 K, wind components ~2.45–2.50 m s$^{-1}$, RH ~13%). The work demonstrates the feasibility and value of a scalable, low-cost, long-duration balloon network for near-real-time atmospheric observations, with practical impact on forecast systems (e.g., integration into GFS) and ongoing platform enhancements anticipated through 2026.

Abstract

WindBorne Systems has developed a constellation of long-duration atmospheric balloons to collect meteorological data across the globe, filling gaps in current in-situ data collection methods. Each Global Sounding Balloon (GSB) is capable of flying for weeks or months and performing dozens of soundings while measuring pressure, temperature, humidity, and GNSS-derived position, altitude, and wind velocity. This data is transmitted to ground via satellite, processed, and made available within minutes of being collected. The current meteorological sensor package has remained largely unchanged since mid-2024 and has flown on thousands of GSBs totaling over one million hours of flight time. Here we present the design and performance of this sensor package. The custom readout architecture and housing allow for data collection across nearly all in-flight conditions while minimizing sources of bias and noise. Uncertainty is characterized via sounding reproducibility studies and in-house calibration of pressure, humidity, and temperature sensors. The calibration and data processing procedures have been optimized and validated by comparison with external datasets. We present external validation in the form of 1) side-by-side radiosonde launches performed in collaboration with the Center for Western Weather and Water Extremes at the Scripps Institution of Oceanography, which show agreement within expected uncertainty limits, and 2) intercomparison studies with European Centre for Medium-Range Weather Forecasts Reanalysis v5, which show an aggregate root mean square difference of: Geopotential height -- 14 m; Pressure -- 0.36 hPa; Temperature -- 0.91 K; Wind speed u -- 2.45 m/s; Wind speed v -- 2.50 m/s; Relative humidity -- 13%.

Figures (13)

• Figure 1: Left: A GSB on a launch rig, just prior to launch. Right: A GSB after launch.
• Figure 2: Flight path (upper left) and vertical profile as a function of pressure (lower left) of a GSB that was launched from Uiseong, South Korea on 26 November 2025 and landed on 6 December 2025. Observations of temperature, dew point temperature and wind speed and direction collected by the GSB during an ascent beginning 06 UTC 1 December 2025 are shown on a skew-T, log-P diagram in the right panel.
• Figure 3: Global coverage of WindBorne balloon observations from 1 July 2024 through 30 June 2025. Observation counts are computed by binning 10 second data points onto a 5$^\circ$$\times$ 5$^\circ$ latitude-longitude grid.
• Figure 4: Left: Main electronics, which include the pressure sensors (not visible) and GNSS module, as well as solar panels, battery, communications, balloon control electronics, and shielding. Center: The complete unit attached to a balloon. The main electronics are near the top, and the temperature and humidity sensors are on the board attached to the figure-8 wire loop. After launch, this wire automatically unspools, dropping the sensors 9m below the balloon. Right: The humidity sensors, temperature sensor, and their readout electronics are enclosed in an aluminized mylar shield. The two humidity sensors, onto which an additional temperature sensor is epoxied, are located (red arrow) in a shielding configuration that allows for vertical airflow. The atmospheric temperature sensor lies 0.5m below the board on a thin wire.
• Figure 5: The predicted solar bias, which is a function of air density, ascent rate, temperature, solar elevation, and altitude. Left: Bias vs solar elevation (at sea level) at several altitudes and standard atmosphere temperatures, at a fixed ascent rate of 1m/s, typical for a profiling GSB. Right: Bias vs ascent rate at a fixed solar elevation of $45^\circ$.