PanX.4: A Gyrocopter-Borne Six-Band VNIR Multicamera System for Sentinel-2-Aligned Multitemporal Vegetation Monitoring

Abstract. Cross-scale vegetation monitoring of protected European grassland habitats requires sub-meter-resolution imagery that is spectrally consistent with Sentinel-2 time series. We present PanX.4, a gyrocopter-borne six-band VNIR multicamera system designed for spectral alignment with Sentinel-2 MSI bands B02–B06 and B08. The deployed system uses six monochrome 24.6 MP image sensors equipped with bandpass/interference filters spanning 8–130 nm FWHM, integrated into a tri-sensor airborne suite with RGB and VNIR–SWIR payloads on the FlugKit aerial carrier platform. Spectral band adjustment factor (SBAF) analysis quantifying the spectral harmonization quality between PanX.4 and Sentinel-2 was carried out using 1,057 ECOSTRESS spectra. All bands achieved R² > 0.99; for Sentinel-2A, RMSE values ranged from 3 × 10⁻⁴ (B06) to 9.7 × 10⁻³ (B05). Comparative filter screening identified EO560- 20 as the preferred B03 filter and confirmed an approximately 90% RMSE reduction for B06 relative to the legacy BN740 configuration. To deploy the system for multitemporal vegetation monitoring, a multi-year analysis of 86,947 first-mowing observations from 2017 to 2024 reveals substantial interannual variability, supporting a three-window multitemporal acquisition strategy synchronized with management-driven vegetation dynamics at Natura 2000 sites. Together, these results establish the sensordesign and temporal-planning basis for Sentinel-2-harmonized multitemporal airborne monitoring at spatial resolutions two orders of magnitude finer than satellite coverage.