Autonomous orbit determination is the process by which the orbit
parameters of navigation satellites are estimated onboard using Inter-Satellite
Link (ISL) measurements. In this contribution, autonomous orbit determination
experiments using ISL measurements in a centralized mode of the new-generation
Beidou navigation satellites are conducted. The mathematical formulation
and the processing method of the dual one-way measurements are addressed
as well as the main feathers of the ISL measurements are introduced.
It is concluded that the ISL ranging data are high-precision measurements.
The centralized autonomous orbit determination is processed in a batch
mode. The average value of ISL measurements residuals is within 1.0
cm, standard deviation of ISL measurements residuals is within 10.0
cm and the standard deviation of the estimated ISL hardware delays
is within 0.2 ns. The orbital accuracy is assessed by overlap comparison,
User Equivalent Ranging Error and Satellite Laser Ranging (SLR) residuals.
The radial overlap differences of the autonomous orbits are less than
6.0 cm and 24 h predicted orbital radial overlap differences less
than 10.0 cm. The User Equivalent Ranging Error of 24 h predicted
autonomous orbits is about 0.43 m and is better than the 24 h predicted
L-band orbits at the 0.76 m level. The SLR residuals for the autonomous
orbits are less than 10.0 cm. The ground anchor station which observes
the constellation with ISL is important to maintain the Earth-Fixed-Frame
and avoid the uncertainties of the entire constellation orientation.
The influence of the ground station observation time span on autonomous
orbit accuracy is also discussed. Even if the cutoff elevation of
the ground anchor station is less than 60°, the radial accuracy of
the autonomous orbits and 24 h predicted orbits is still better than
10.0 cm and three-dimensional orbit accuracy better than 1.5 m.