Balloon-borne software defined receiver for GNSS radio occultation measurements. ROMULUS experiment

The aim of the experiment "Radio Occultation Miniaturized Unit for Leo and Upper Stratosphere" (ROMULUS) is to test the performance of a low-cost balloon-borne Software Defined Receiver (SDR) for GNSS Radio Occultation (GNSS-RO) soundings. A small-scale unit, based on SDRs and Commercial Off-The-Shelf (COTS) components has been conceived for this purpose. By performing GNSS-RO measurements from a stratospheric balloon using SDRs, ROMULUS could demonstrate a flexible and complementary solution to the standard technique operated from Low Earth Orbit (LEO) satellites. As a matter of fact, a balloon-borne solution offers the opportunity to increase the number and density of GNSS-RO soundings in specific areas of interest. In addition, the choice of using SDRs allows to store all the raw GNSS signals recorded during the flight and to process them later with different algorithms. The ROMULUS experiment will be performed on a stratospheric balloon in September 2023. The developed concept, design, data analysis plan, simulations and expected results for the ROMULUS experiment are hereby presented.