X-ray Pulsar-Based Navigation Considering Spacecraft Orbital Motion and Systematic Biases.

Area of Science:

• Spacecraft navigation
• Astrodynamics
• High-energy astrophysics

Background:

• X-ray pulsar-based navigation is crucial for deep space missions.
• Orbital motion and systematic biases degrade navigation accuracy.
• Existing methods using pulse phase (PP) or PP with Doppler frequency (DF) have limitations.

Purpose of the Study:

• To develop an innovative navigation method for X-ray pulsars.
• To improve the accuracy of spacecraft navigation by mitigating Doppler effects and systematic biases.
• To enhance the reliability of X-ray pulsar-based navigation systems.

Main Methods:

• A novel method employing pulse phase (PP), difference of two neighbor PPs (DPP), and Doppler frequency (DF) as simultaneous measurements.
• Utilizing spacecraft orbital dynamics and the joint probability density function of photon arrival timestamps.
• Exploiting the near-invariance of PP systematic biases over adjacent periods, with DPP eliminating major bias components.

Main Results:

• Photon-level simulations demonstrate significantly improved navigation accuracy for Earth orbit.
• The proposed method outperforms navigation using only PP, PP with DF, or PP with DPP.
• The combined use of PP, DPP, and DF effectively mitigates systematic biases and Doppler effects.

Conclusions:

• The proposed X-ray pulsar navigation method offers superior accuracy compared to existing techniques.
• Simultaneous utilization of PP, DPP, and DF measurements enhances robustness against navigation errors.
• This approach represents a significant advancement for accurate spacecraft positioning in Earth orbit.