Session
Ground Systems
Location
Salt Palace Convention Center, Salt Lake City, UT
Abstract
Loss of phase-locked loop (PLL) lock during CubeSat tracking can simultaneously eliminate both telemetry and Doppler observables, leaving operators blind during critical mission phases. While closed-loop receivers provide high-precision tracking under nominal conditions, they remain vulnerable to low signal-to-noise ratio, rapid Doppler dynamics, oscillator instability, and modeling errors. This single-point failure mode reduces operator situational awareness precisely when it is most needed. This work presents a dual-acquisition architecture that eliminates single point failure in CubeSat ground tracking. Implemented at DSS-17, Morehead State University's 21-meter deep-space antenna, the system pairs a conventional closed-loop modem with a parallel open-loop receiver implemented on a software-defined radio platform. Both receivers process the same spacecraft downlink simultaneously, providing two independent tracking paths so that loss of closed-loop lock does not result in complete loss of observability. The architecture enables graceful degradation across multiple operational scenarios. During PLL unlock, the open-loop receiver continues to detect signals and record telemetry, preserving spacecraft health monitoring and situational awareness. Under conditions of uncertainty – such as imperfect knowledge of downlink configuration or tracking dynamics – open-loop processing provides Doppler estimates that reduce the search space for closed-loop reacquisition and accelerate recovery following tracking interruptions. When higher-performance receiver hardware is deployed, the same open-loop approach additionally supports extraction of Doppler observables suitable for navigation. During nominal operations, simultaneous comparison of carrier and Doppler estimates enables independent validation of closed-loop tracking performance, detecting tracking bias, loop stress, or false lock conditions. This validation capability proves particularly valuable during commissioning, anomaly resolution, and low-margin communication passes. The system is implemented entirely within the ground segment and requires no spacecraft modifications. Operational results from DSS-17 demonstrate that commodity SDR hardware can significantly enhance tracking robustness and operational awareness when properly integrated into a complementary architecture. The approach offers an accessible, practical solution for improving data continuity and resilience in resource-constrained CubeSat missions, with potential for broader adoption across the small satellite community.
Document Type
Event
Operational Resilience in CubeSat Tracking Operations Through Complementary Architectures at DSS-17
Salt Palace Convention Center, Salt Lake City, UT
Loss of phase-locked loop (PLL) lock during CubeSat tracking can simultaneously eliminate both telemetry and Doppler observables, leaving operators blind during critical mission phases. While closed-loop receivers provide high-precision tracking under nominal conditions, they remain vulnerable to low signal-to-noise ratio, rapid Doppler dynamics, oscillator instability, and modeling errors. This single-point failure mode reduces operator situational awareness precisely when it is most needed. This work presents a dual-acquisition architecture that eliminates single point failure in CubeSat ground tracking. Implemented at DSS-17, Morehead State University's 21-meter deep-space antenna, the system pairs a conventional closed-loop modem with a parallel open-loop receiver implemented on a software-defined radio platform. Both receivers process the same spacecraft downlink simultaneously, providing two independent tracking paths so that loss of closed-loop lock does not result in complete loss of observability. The architecture enables graceful degradation across multiple operational scenarios. During PLL unlock, the open-loop receiver continues to detect signals and record telemetry, preserving spacecraft health monitoring and situational awareness. Under conditions of uncertainty – such as imperfect knowledge of downlink configuration or tracking dynamics – open-loop processing provides Doppler estimates that reduce the search space for closed-loop reacquisition and accelerate recovery following tracking interruptions. When higher-performance receiver hardware is deployed, the same open-loop approach additionally supports extraction of Doppler observables suitable for navigation. During nominal operations, simultaneous comparison of carrier and Doppler estimates enables independent validation of closed-loop tracking performance, detecting tracking bias, loop stress, or false lock conditions. This validation capability proves particularly valuable during commissioning, anomaly resolution, and low-margin communication passes. The system is implemented entirely within the ground segment and requires no spacecraft modifications. Operational results from DSS-17 demonstrate that commodity SDR hardware can significantly enhance tracking robustness and operational awareness when properly integrated into a complementary architecture. The approach offers an accessible, practical solution for improving data continuity and resilience in resource-constrained CubeSat missions, with potential for broader adoption across the small satellite community.
