Performance Comparison of EKF and AKF Relative Navigation Using GPS-Based Measurement in LEO Spacecraft Rendezvous

Junghyun Kim and Sangkyung Sung

Peer Reviewed

Abstract:	This paper evaluates the performance of the Extended Kalman Filter (EKF) and Adaptive Kalman Filter (AKF) for GPS-based relative position and velocity estimation in a short baseline scenario during an autonomous rendezvous mission with the International Space Station (ISS). To improve navigation accuracy, double-differenced carrier phase, pseudorange, Doppler, and ISL measurements were used, effectively eliminating common satellite clock, receiver clock, and atmospheric delay errors. The LAMBDA method resolved integer ambiguities, and noise models were based on Gaussian white noise with standard deviations derived from carrier-to-noise density ratios (C/N0). Measurement data between GPS satellites and LEO spacecraft were collected using Matlab Simulink, and the EKF and AKF algorithms were compared under ideal space conditions. EKF achieved centimeter-level accuracy, while AKF provided improved stability and sub-centimeter accuracy in relative positioning. This study minimizes environmental effects to focus on theoretical performance. Keywords— LEO, Adaptive Kalman Filter, Carrier Phase
Published in:	2025 IEEE/ION Position, Location and Navigation Symposium (PLANS) April 28 - 1, 2025 Salt Lake Marriott Downtown at City Creek Salt Lake City, UT
Pages:	788 - 795
Cite this article:	Kim, Junghyun, Sung, Sangkyung, "Performance Comparison of EKF and AKF Relative Navigation Using GPS-Based Measurement in LEO Spacecraft Rendezvous," 2025 IEEE/ION Position, Location and Navigation Symposium (PLANS), Salt Lake City, UT, April 2025, pp. 788-795.
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