A fast pulse time-delay estimation method for X-ray pulsars based on wavelet-bispectrum

X-ray pulsar-based navigation technology provides real-time aerospace information for spacecraft through the received X-ray photons. The time-delay estimation accuracy of the pulse integrated profile is one of the determinants of navigation accuracy. To reduce the computational complexity of the time-delay estimation algorithm for X-ray pulsar integrated pulse profile, we propose a fast time-delay estimation method based on the bispectral algorithm. This method reduces computational complexity by reducing the calculated frequency bands. Wavelet is first used to decompose the pulse profiles and obtain the low-frequency component with a high signal-to-noise ratio. Then, the low-frequency component is used to estimate the time delay of the integrated pulse profile via the bispectral method. Theoretical analysis and experimental results show that the bispectrum-based time-delay estimation method can ignore high-frequency components with considerable noise. Moreover, using only the low-frequency component can substantially reduce computational complexity whilst slightly improving estimation accuracy.