The number of transmitted GNSS (Global Navigation Satellite Systems) signals has increased significantly with Galileo, Compass and QZSS constellations' ongoing deployment, GLONASS constellation maintenance and the introduction of new GPS signals. All the future GNSS civil signals are composed of two components: one being the pilot component which contains known secondary codes. In order to avoid fully exploit secondary code properties and the bit transition problem on the pilot component allowing long coherent integration for a better tracking, it is necessary to acquire the secondary code. This paper presents a mathematical model that determines the probability of correct acquisition of the secondary code once the spreading code has been acquired. The second point of the paper is the presentation of experimental results which provides some interesting results in terms of secondary code acquisition. The first one is the probability of secondary code acquisition when it is only read once. The second one corresponds to the required time to acquire the secondary code with a high probability for a given C/N0. These results, provided for four GNSS signals (GPS L1C, GPS L5, Galileo E1 OS and Galileo E5a/b) permit to compare the U.S GNSS with the European GNSS for several L band frequencies (L1 and L5).