<p>Remote firmware updates are vital for enhancing the adaptability and functionality of satellites during their missions. This article introduces a novel framework for securely and efficiently updating the firmware of an FPGA-based Software-Defined Radio payload on a nanosatellite. By addressing challenges, such as limited bandwidth, intermittent communication, and constrained satellite pass durations, the proposed method ensures reliable in-orbit reconfiguration. The approach leverages compression, packing, and splitting techniques to optimize data transmission, enabling the firmware files to be divided into smaller, manageable chunks for secure transfer across multiple satellite passes. The framework is validated through a structured, three-phase process. In the first phase, the firmware is tested in isolation on the SDR platform, ensuring its functionality and integrity. The second phase involves integration and testing on the Engineering Model (EM) of the nanosatellite, simulating operational conditions under controlled scenarios. Finally, the third phase replicates in-orbit conditions by simulating firmware updates via S-band communication between a ground station and the EM nanosatellite. This multi-phase validation demonstrates the feasibility of overcoming the inherent challenges of in-orbit firmware updates, such as maintaining data integrity and minimizing transmission time. The results confirm that the proposed method provides a robust, secure, and efficient framework for firmware updates, contributing to the resilience and operational flexibility of nanosatellite missions in dynamic space environments.</p>