A $40 Sensor on a Weather Balloon Is Rewriting How We Track Airborne Particles

High above the Carpathian foothills of southeastern Poland, a weather balloon has just demonstrated that some of atmospheric science’s most stubborn measurement problems can be solved with parts that cost less than a dinner out. Researchers at the University of Warsaw have developed a balloon-borne instrument called AeroSonde, built around a low-cost optical particle sensor that retails for roughly forty dollars, and shown that it can reliably map how airborne particles are distributed through the atmosphere from the surface up to altitudes of nearly 27 kilometers. The findings, published in Atmospheric Measurement Techniques, suggest that a new generation of cheap, expendable aerosol soundings could dramatically expand the global observing system for particles that influence climate, clouds, and air quality.

The core challenge the team set out to address is one of the most consequential blind spots in atmospheric science. Aerosols, the tiny solid and liquid particles suspended in the air, are far from uniformly mixed. Their optical and microphysical properties can change dramatically with height, and particles in the planetary boundary layer often behave very differently from those in the free troposphere above. These vertical contrasts govern how aerosols scatter and absorb sunlight, how they interact with clouds, and how long they persist in the atmosphere. Yet the tools available to profile them each carry significant drawbacks. Ground-based and satellite lidars suffer from signal attenuation in dense layers and depend on retrieval assumptions about aerosol type. Research aircraft provide the most direct measurements but at operational costs that rule out routine use. UAVs and tethered balloons are limited in vertical range and payload.

AeroSonde was designed to fill that gap with an approach that is almost aggressively simple. The system pairs a standard Vaisala RS41 radiosonde with a compact add-on unit weighing just 175 grams including its housing, measuring 90 by 60 by 40 millimeters. At its heart sits a Sensirion SPS30 particulate matter sensor, a device that uses a 660-nanometer laser diode, a photodiode detector, focusing optics, and a small integrated fan to measure particle mass concentrations in the PM1, PM2.5, PM4, and PM10 fractions, along with data in five particle size bins. A Raspberry Pi RP2040 microcontroller manages data acquisition and streams measurements at one hertz to a ground station over a LoRaWAN radio link operating in the EU 863 to 870 megahertz band. The team confirmed reliable data reception even when the probe drifted more than 100 kilometers horizontally and more than 25 kilometers vertically from the receiver.

Crucially, the researchers did not simply trust the sensor out of the box. Over 22 days during the summer of 2025, five SPS30 units were run side by side in a laboratory at the Institute of Geophysics, University of Warsaw, and then calibrated against reference-grade instruments: an Aurora 4000 polar nephelometer for scattering measurements and a TSI Laser Aerosol Spectrometer 3340 for particle size. The inter-sensor agreement was strikingly tight, with average Pearson correlation coefficients of 0.97 for PM10 and PM1 when one-hour averaging was applied, and mean relative differences of less than 9 percent. Using a non-linear regression model grounded in Lorenz-Mie scattering simulations, the team converted the sensor’s mass readings into estimates of the aerosol scattering coefficient, achieving a coefficient of determination of 0.96 against the nephelometer with a root mean square error of just 5.1 inverse megameters, or 3.8 percent.

The calibration also revealed honest limits. The scattering Ångström exponent, an indicator of particle size distribution, and the effective particle radius could be estimated from the sensor’s typical particle size parameter, but with substantially larger uncertainties, limiting their use to qualitative discrimination between fine-mode and coarse-mode particles. The team also verified that the sensor’s fan maintained a stable speed of roughly 6000 revolutions per minute across pressures from 1000 down to 50 hectopascals, confirming that airflow through the measuring chamber requires no correction at altitude, and that the sensor’s response time of under five seconds supports a vertical resolution of 15 to 20 meters at typical balloon ascent rates of 3 to 4 meters per second.

The field campaigns put all of this to the test under genuinely challenging conditions. Three launches from the SolarAOT Radiative Transfer Station in Strzyżów, a rural background site on Niebylecka Hill, captured two episodes of long-range transport of biomass-burning aerosol from North America in June and August 2025, and a Saharan dust intrusion in late August. Back-trajectory modeling with the LAGRANTO tool, driven by ECMWF wind fields, traced the smoke plumes across central Canada and the Atlantic, while the ICAP multi-model ensemble indicated smoke optical depths exceeding 0.1 over Poland, accounting for 61 percent of the total column loading. During the dust event, trajectories showed air masses arriving from northern Africa, with dust contributing 58 percent of the total aerosol optical depth.

The comparison against independent remote sensing was the decisive test. Because the balloon drifts horizontally during its one-to-two-hour ascent, the team developed a spatiotemporal matching procedure that aligns each AeroSonde measurement with the lidar profile at the time the sampled air parcel passed over the station, using wind data from the co-launched radiosonde. When the resulting scattering coefficient profiles were compared with aerosol extinction profiles retrieved from a Raymetrics lidar using two variants of the Klett inversion, the Pearson correlations ranged from 0.74 to 0.81, with the agreement holding across all altitude ranges from the boundary layer up to above 8 kilometers. The positive bias between extinction and scattering was consistent with the expected contribution of aerosol absorption. Column-integrated aerosol optical depth derived from the AeroSonde profiles agreed with AERONET sun photometer values to within 0.01 to 0.05 for the biomass-burning cases and 0.11 for the dust event.

The case studies also revealed a physics-driven subtlety that the authors address candidly. During the Saharan dust sounding, both scattering and optical depth were underestimated relative to the sun photometer and lidar. Several factors conspire here: mineral dust absorbs light, the SPS30 measures at a scattering angle of roughly 90 degrees where the dust phase function reaches a minimum, and the sensor’s design is better suited to fine-mode particles than to the coarse particles above 5 micrometers that dominate dust. The team argues that aerosol-type-dependent calibration against reference instruments is essential, particularly in dust-influenced environments, and points to future upgrades including a single-channel aethalometer to retrieve absorption directly and an optical particle sizer with an extended size range.

What makes the result genuinely exciting is what it unlocks. Unlike lidar, the AeroSonde is not hampered by the geometric overlap limitations that blind ground-based systems in the lowest few hundred meters, allowing more reliable characterization of boundary-layer aerosol contributions, which the measurements showed ranged from 1 to 36 percent of total column optical depth during the transport events. Unlike drones, the passive ascent avoids flow-induced sampling artifacts and can reach into the stratosphere, opening a window on volcanic plumes and stratospheric aerosol that UAV platforms cannot access. The expendable nature of the platform, each launch sacrifices the sensor, is the trade-off, but at forty dollars per unit the economics remain compelling compared with aircraft campaigns costing orders of magnitude more.

The researchers frame the work as a proof of concept, and the limited number of profiles means broader validation across more aerosol regimes is still needed. But the implications reach well beyond one Polish hilltop. Vertical profiles of this kind provide an independent check on reanalysis products and model simulations of aerosol transport, and combining AeroSonde scattering measurements with Raman lidar extinction retrievals could eventually yield single-scattering albedo profiles, a key quantity for climate forcing calculations. If a forty-dollar sensor, a microcontroller, and a weather balloon can deliver scientifically useful profiles of the particles that shape our climate, the era of dense, affordable, three-dimensional aerosol monitoring may be closer than anyone expected.

Subject of Research: Balloon-borne aerosol profiling using calibrated low-cost optical particle sensors

Article Title: A new balloon-borne system for measuring the vertical variability of aerosol optical properties using low-cost sensors

Article References: Broda, M., Zawadzka-Mańko, O., Chiliński, M. T., Nurowska, K., Kłapiński, S., Makuch, P., & Markowicz, K. M. (2026). A new balloon-borne system for measuring the vertical variability of aerosol optical properties using low-cost sensors. Atmospheric Measurement Techniques, 19(18), 5989-6014. https://doi.org/10.5194/amt-19-5989-2026

Image Credits: AI Generated

DOI: 10.5194/amt-19-5989-2026

Keywords: aerosols, balloon-borne measurements, low-cost sensors, SPS30, lidar, atmospheric profiling, biomass burning aerosol, Saharan dust, aerosol optical depth, planetary boundary layer, radiosonde, atmospheric measurement techniques