Initial Assessment of the LEO Based Navigation Signal Augmentation System from Luojia-1A Satellite

Area of Science:

• Satellite Navigation
• Geodesy
• Signal Processing

Background:

• Global Navigation Satellite Systems (GNSS) face limitations in signal power and convergence time.
• Low Earth Orbit (LEO) satellite systems offer potential for augmenting existing GNSS.
• Wuhan University developed the Luojia-1A experimental satellite for navigation signal augmentation.

Purpose of the Study:

• To assess the initial performance of the Luojia-1A LEO navigation augmentation system.
• To evaluate the system's capability to complement current GNSS.
• To determine the system's contribution to precise positioning and signal quality.

Main Methods:

• Ground tests of oscillator phase noise.
• Field ranging tests using pseudorange and carrier phase measurements.
• In-orbit tests evaluating ephemeris precision and clock stability.
• Analysis of geometry-free measurement combinations to determine noise.

Main Results:

• Oscillator phase noise meets application requirements.
• Field tests achieved 2.6 m pseudorange and 0.013 m carrier phase precision.
• In-orbit tests showed 0.1 m ephemeris precision and 3x10^-10 clock stability.
• Measurement noise was approximately 3.3 m for pseudorange and 1.8 cm for carrier phase.

Conclusions:

• The Luojia-1A system provides usable LEO navigation augmentation signals.
• Empirical User Equivalent Ranging Error (UERE) is no worse than 3.6 m.
• Integration with existing GNSS can enhance real-time navigation performance.