Vertical Profiling with a Minimal Low-Cost High-Altitude Balloon: Pressure–Altitude Validation and the Separation of Altitude from Solar-Geometry Effects in Broadband UV Measurements over Kota, India

This archive accompanies the preprint "Vertical Profiling with a Minimal Low-Cost High-Altitude Balloon: Pressure–Altitude Validation and the Separation of Altitude from Solar-Geometry Effects in Broadband UV Measurements over Kota, India." It contains everything needed to reproduce and audit the study end to end: the raw measurements from a high-altitude balloon (HAB) flight over Kota, Rajasthan on 5 October 2025, auxiliary satellite/reanalysis/ground data used for context, the full analysis code, the seven regenerated manuscript figures, and the manuscript itself. A deliberately minimal two-sensor payload — a Bosch BME280 barometer and an Apogee SU-202 broadband UV sensor — was flown to 17.6 km. The study (a) validates the low-cost pressure profile against the U.S. Standard Atmosphere (Pearson r = 0.9998; median relative error 2.7%), (b) shows that the UV sensor's apparent 4.6-fold increase with altitude is a convolution of altitude and the changing solar zenith angle, and isolates a genuine altitude effect of 38.7 ± 2.9 mV/km by combining ascent and descent, and (c) documents the payload's limitations, including a failed temperature channel. The analysis is fully contained in code/Kota_HAB_audit.ipynb (or audit_kota_hab.py).