  Low earth orbit (LEO) satellite navigation signal can be used as an
opportunity signal in case of a Global navigation satellite system (GNSS)
outage, or as an enhancement means of traditional GNSS positioning algorithms.
No matter which service mode is used, signal acquisition is the prerequisite of
providing enhanced LEO navigation service. Compared with the medium orbit
satellite, the transit time of the LEO satellite is shorter. Thus, it is of
great significance to expand the successful acquisition time range of the LEO
signal. Previous studies on LEO signal acquisition are based on simulation
data. However, signal acquisition research based on real data is very
important. In this work, the signal characteristics of LEO satellite: power
space density in free space and the Doppler shift of LEO satellite are
individually studied. The unified symbol definitions of several integration
algorithms based on the parallel search signal acquisition algorithm are given.
To verify these algorithms for LEO signal acquisition, a software-defined
receiver (SDR) is developed. The performance of those integration algorithms on
expanding the successful acquisition time range is verified by the real data
collected from the Luojia-1A satellite. The experimental results show that the
integration strategy can expand the successful acquisition time range, and it
will not expand indefinitely with the integration duration.
