Doppler-based GNSS variometry for velocity estimation in high-dynamic sounding rocket missions

Abstract This work investigates the application of GNSS variometry for onboard velocity estimation in sounding rocket flights, with particular focus on the use of Doppler observations under high-dynamic conditions. The study assesses, for the first time, the performance of a variometric algorithm originally developed for geodetic applications based on carrier-phase observations, here extended to Doppler observables in a high-dynamic aerospace scenario. The analysis is based on data acquired during two sounding rocket launch campaigns conducted in Roccaraso, Italy (May 2025), and Texas, USA (June 2025), using a lightweight Commercial Off-The-Shelf (COTS) payload composed of a Raspberry Pi single-board computer and dual u-blox ZED-F9P chipsets. Observations from GPS, Galileo, and BeiDou constellations on the L1 frequency were recorded simultaneously at different sampling rates, allowing a comparative evaluation of observation continuity and the corresponding variometric velocity solutions under both nominal and anomalous flight conditions. The results show that carrier-phase variometry, although associated with lower nominal uncertainty, is severely affected during the boost phase, where strong accelerations lead to degraded observation quality and incomplete reconstruction of the velocity peak. Doppler observations, by contrast, maintain continuity throughout all flight phases including the most demanding ones, and yield velocity estimates capable of reproducing the main features of the flight profile. Within the limitations of the available experimental dataset, the analysis suggests that Doppler-based variometry represents a robust and practically viable approach for GNSS velocity estimation in sounding rocket applications when carrier-phase continuity or integrity is reduced.