Dropsondes from the Stratosphere: Targeted Observations Over Remote Regions Using Stratospheric Platforms.
Authors: Stevens Paul 
Published: March 2024

Stratospheric platforms can navigate to remote regions and dispense tiny micro-dropsondes. These lightweight sensors safely descend, transmitting weather data in high-resolution, all the way from stratosphere to sea-level. The data is received by the dispensing platform which disseminates the data in near real-time via SATCOM. Voltitude Ltd, &#8220;Unlocking the Stratosphere&#174;&#8221;, is developing and operating two new upper air observation systems with great potential to improve the accuracy, reliability, spatial coverage and cost effectiveness of ocean and atmosphere observations in support of improving weather forecasting of extreme weather events.The StratoSonde&#174; system is a new upper air observation system, combining a long endurance balloon system with a new micro-dropsonde and dispensing system, to provide observations at low-cost from remote regions. The StratoSonde&#174; balloon has total weight less than 3kg and provides multi-day endurance in the stratosphere, navigating by selecting different wind layers to drift towards remote regions of interest. Each system supports up to 10 micro-dropsondes, each weighing ~20g. Once dispensed the dropsondes take approximately 20-minutes to descend to sea-level, measuring Temperature, Pressure, Relative Humidity, Wind speed and Wind Direction in high vertical resolution all the way from stratosphere to sea-level. Data is transmitted to the dispensing balloon, which disseminates this in near-real-time via SATCOM. The StratoSonde system is being operated out of the Cabo Verde islands, off the west coast of Africa, to support Tropical Cyclone research and forecasting, and supports many other use cases for meteorological observation data gathering over Europe.For targeted observations, the Voltitude ltd micro-dropsonde system can be implemented in an aerodynamic tubular housing for installation on other uncrewed air systems and drones. Each housing is self-contained, including dispensing system, UHF receiver and SATCOM data link, and weighs less than 1kg while full of 32 dropsondes. Under development is the StratoSat-25 solar electric stratospheric long endurance aircraft, being designed to support two dispensing pods, offering 64 targeted observations per mission. The StratoSat-25 has over 2-months endurance and is being designed to operate as part of a constellation to provide synchronous targeted observations over specific meteorological features of interest. The current generation of fixed-wing solar electric high altitude pseudo satellites (HAPS), have extremely restricted launch and recovery operating envelopes and are too vulnerable to gusts and turbulence to support missions requiring regular and routine recovery to &#8220;restock&#8221; dispensable payloads. The StratoSat-25 overcomes this challenge with great expansion of the operating envelope with enhanced resilience to gusts and turbulence, without penalising stratospheric performance.The presentation &#8220;Dropsondes from the Stratosphere&#8221; will review the global weather observation challenges, priority use cases and how new stratospheric technological innovations are impacting this field, discussing in detail the emerging capabilities offered by low-cost long endurance stratospheric platforms.