Acquisition is the first process of a GNSS receiver and is also the process which needs the most resources. Moreover, acquiring of weak Galileo E1 OS signals is a real challenge due to the presence of frequent (potentially at each spreading code period) bit transitions (data bit on the data component and secondary code chip on the pilot component). After a study of the effects of data modulation, two acquisition strategies, one bit transition insensitive and the other not, are developed and brought face to face on performance criteria such as: execution time, probability of detection, probability of false alarm...