Reference radiation sensor module of the BIRDS-RPM satellite: design and functionality

Abstract

This paper presents the development of a radiation reference sensor module integrated into the BIRDS-RPM satellite platform. The system is designed to monitor ionizing radiation using two distinct sensing units: the AL54 Alpha Sensor for dose rate estimation and the VT01 RADFET for cumulative dose measurement. The AL54 sensor outputs digital pulses proportional to the radiation dose equivalent rate (mSv/h), which are counted and processed by an ATmega1284 microcontroller. The sensor operates within the temperature range of -30 °C to +60 °C and provides a typical pulse rate of 5 cpm ±15% at 1 µSv/h, with a recommended supply voltage of 5.0 V and typical current consumption of 25 µA. The second detection channel uses a VT01 RADFET, capable of measuring total ionizing dose from 1 cGy to 1 kGy. The analog output voltage, corresponding to the absorbed dose under Co-60 gamma irradiation at ~50 Gy/h, is amplified using low-noise operational amplifiers and digitized via the internal ADC of the microcontroller. The RADFET is supplied at 10 V and consumes less than 0.1 µA. All collected data from both sensors are transmitted to the main onboard computer via I²C interface for logging and telemetry. This dual-sensor approach enhances the robustness and accuracy of radiation monitoring in orbit, ensuring valuable scientific data for mission evaluation and long-term radiation impact assessment.