Comparison of Time-Domain Cross-Correlation and FFT-Based Methods for X-Ray Pulsar Phase Estimation in Spacecraft Navigation
11th International Conference on Recent Advances in Air and Space Technologies, Conference Program, RAST 2026, İstanbul, Turkey, 13 - 15 May 2026, (Full Text)
- Publication Type: Conference Paper / Full Text
- Doi Number: 10.1109/rast69551.2026.11672491
- City: İstanbul
- Country: Turkey
- Keywords: autonomous navigation, FFT, phase estimation, pulsar, XNAV
- Middle East Technical University Affiliated: Yes
Abstract
X-ray Pulsar Navigation (XNAV) is a concept in which a spacecraft equipped with a reasonably sized onboard X-ray detector collects X-ray photons and autonomously estimates its orbital state with acceptable accuracy. This concept may be very useful for space missions, especially those exploring deep space objects, planets, and comets, where ground communication may struggle due to large distances or obstruction by celestial bodies, conditions under which conventional ground-based orbit determination operations may suffer. However, utilizing the XNAV strategy depends on accurately modeling uncertainties such as ephemeris errors, pulsar direction errors, background noise, and phase estimation errors. On-board phase estimation, which then yields the calculation of the Time of Arrival (TOA) by determining the time delay and using it as a meaningful measurement, is very important for the overall accuracy of the process. In this paper, pulsar signals are modeled as a non-homogeneous Poisson process, and the epoch folding technique is used for pulsar phase estimation. The phase delay between the theoretical signature and the simulated observation data is estimated using both Time-domain cross-correlation (TDCC) and Fast Fourier Transform (FFT), and the results are compared. Signal-to-noise ratio (SNR) is also calculated to demonstrate the relationship between the phase delay estimation methods and the accuracy associated with the SNR.