On Nov. 29, 2022, Russia launched the 51st Glonass-M satellite, completing a 20-year history that began on Dec. 10, 2003, with the launch of the first one. These satellites have been providing navigation signals in two frequency bands, L1OF and L2OF, to civil users since 2011.The average orbit lifetime for this type of satellite is more than 10 years, and 13 Glonass-M satellites operate beyond their guaranteed lifetime. The last set of seven satellites has been broadcasting the first CDMA civil signal, L3OC, by means of an additional antenna and onboard transmitter.
Starting this year, the constellation will be renewed by Glonass-K and Glonass-K2 satellites, which provide CDMA signals to users. Furthermore, four Glonass-K satellites will be supplemented with additional Glonass-K satellites and the first Glonass-K2 satellite. The K2 satellite has passed all ground tests and is ready to be transported to the launch site (Figure 1). Table 1 lists the technical characteristics of GLONASS satellites.
Figure 1. Artist’s rendition of the Glonass-K2 satellite in orbit.
Table 1. The evolutions of GLONASS satellites.
The distinguishing feature of this satellite’s design is its two antenna arrays — one for CDMA signals with phase centers on the geometrical axis of the satellite, and the second for FDMA signals with phase centers shifted by 0.9 m relative to that axis.
The optical reflector panel center is also located on the satellite’s geometrical axis and passed through its mass center. It seems to be a very interesting scientific task to estimate the satellite flight model parameters by International Laser Ranging Service stations with the objective to improve the accuracy of the navigation signals for both antenna arrays.
Future GLONASS satellites will have a single antenna array for CDMA and FDMA signals (see Figure 2).
Figure 2. The evaluations of GLONASS satellites.