Tolerance constrained noise floor and thermally induced noise saturation effects of NTC thermistor 1/<i>f</i> noise differential suppression in ‘TianQin mission’

Abstract TianQin aims to detect space-based gravitational waves in the ultra-low frequency (ULF) range (10 −4 –1 Hz). This study investigates the suppression of 1/ f noise in thermistor sensors within the on-orbit temperature measurement system of the TianQin satellite, particularly in the ULF band. Theoretical analysis and simulation validation of a differential noise suppression method were performed. By integrating the thermistor 1/ f noise theoretical model with a dual-channel differential structure, a novel thermistor 1/ f noise differential model was developed. This study further examines the coupling relationships between the residual 1/ f noise limit after differential processing and factors such as thermistor resistance tolerance, temperature, and geometric length, thereby identifying the critical factors that influence the effectiveness of differential noise suppression. Results indicate that the residual 1/ f noise decreases significantly with decreasing resistance tolerance. For instance, using a 10 kΩ, 3 mm negative temperature coefficient (NTC) thermistor, a minimal residual 1/ f noise of 22.03 μΩ Hz −0.5 was achieved at a resistance tolerance of ±0.45%, demonstrating the tolerance-constrained noise floor (TCNF) effect. Furthermore, as the temperature increases, the residual 1/ f noise decreases. For three types of NTC thermistors, when the temperature rises from 289.15 K to 313.15 K, the noise initially decreases rapidly and subsequently stabilizes. The Dersonic NTC thermistor achieves the lowest noise level of 2.15 μΩ Hz −0.5 at 313.15 K, indicating the thermally-induced noise saturation (TINS) effect. Based on the TCNF and TINS effects, recommendations for optimizing NTC thermistor selection are provided to enhance 1/ f noise suppression, reduce the overall noise of the satellite temperature measurement system, and improve the thermal stability of the satellite’s internal core payload.